Vitamin D: Sun Exposure, Supplementation and Doses

From the presence of vitamin D receptors in our cells and vitamin D factories in our epidermis, along with the central role vitamin D plays in calcium metabolism, immunity, and gene expression, it’s pretty clear that having adequate vitamin D is an essential component of being a healthy, successful homo sapien. And yet, many health practitioners suggest that vitamin D deficiency is one of the biggest nutrient deficiencies in modern society. The question, then, arises: What’s the best way to get enough vitamin D – via oral supplementation or sunlight?

To determine that, let’s examine a few common questions surrounding the various modes of intake.

Is it natural?

This is a big one. We obviously care about how nature shaped human evolution. Shouldn’t then our mode of obtaining vitamin D also be “natural”?

For us humans, getting vitamin D from sunlight is the clear winner if judged by this standard alone. We are basically hairless, upright apes for a reason, with hefty D3 requirements, and before oral supplements appeared, dietary vitamin D was not a very reliable source. We had to get it from the sun. Today, we’re still those same hairless, upright apes (albeit with different fashion trends and hygiene sensibilities), and we can still obtain vitamin D from UV-B radiation. Personally, I prefer getting my D3 from sunlight, simply because it’s enjoyable to spend time in the sun and it’s an effortless way to get something that’s critical to my health. But I don’t think it’s necessarily “better” than getting it through supplements. Nature’s way is quite often better, or at least more congruent with how we’re “intended” to work, but that doesn’t always preclude the effectiveness of modern methods.

Additionally, as a little added factoid, this is essentially the way fur-bearing mammals and birds obtain the bulk of their D3: orally. The oils in their fur/feathers produce D3, and preening/self-grooming results in oral intake, with diet rounding out the rest. Skin production is either inadequate or nonexistent. Now, we aren’t dogs or sparrows, but the mechanism for oral intake clearly exists across a wide variation of species.

Yet another question arises: Does oral D3 differ – qualitatively – from solar D3?

Let’s examine the pathways – let’s see what happens when you produce or swallow vitamin D3.

When UV-B reacts with the 7-Dehydrocholesterol in your skin, cholecalciferol (D3) is produced and ends up in your liver, where it’s hydroxilated into calcidiol, also known as 25-hydroxyvitamin D or 25(OH)D.

When you swallow cholecalciferol (either in food or supplement), it ends up in your liver, where it’s hydroxilated into calcidiol, also known as 25-hydroxyvitamin D or 25(OH)D.

From that point onward, it’s all the same. It’s all calcidiol, ready for storage in fat tissue or dispersal to the kidneys for conversion into calcitriol, also known as 1,25(OH)D. Calcitriol is the active hormonal form whose primary role is to regulate blood calcium levels. If there’s enough calcidiol left in the tank after the calcium duties, it gets sent to other tissues in the body to be converted into more calcitriol to fulfill even more roles. That’s where all the immune system/cancer cell/heart health/insulin sensitivity benefits begin to kick in, and it explains why having plenty of vitamin D available – beyond what’s only required to avoid rickets and monitor blood calcium – is so beneficial.

Both oral supplements/dietary sources and sunlight can get you there. Qualitatively, they are identical. The only difference is in the dosage. With oral D3, dosage can be consciously controlled, but it’s also subject to human error (or foolishness). You could conceivably keep popping capsule after capsule and end up with toxic blood levels. It’s difficult to do (one official site suggests the level might be in the millions of IUs), but it’s technically possible. When you sunbathe, on the other hand, you don’t consciously flip a mental switch that shuts down D3 production. Instead, you burn, or you grow uncomfortably hot. You – quite naturally – opt out of sun exposure before it gets too intense. As your skin darkens and you begin to tan, it produces less vitamin D, and you can stay out longer without burning, but it’s generally true that sun exposure up to the brink of turning pink is safe and will net you plenty of D3. In addition, it’s interesting to note that once you have produced enough vitamin D through sun exposure, those same UVB rays will begin to prevent excess vitamin D production by degrading existing cholecalciferol. Ain’t homeostasis grand?

So – sun or supplement? What should I do?

Take stock of your living situation. If the sun is available regularly where you live, go that route whenever possible. It’s free, it’s safe, it’s easy, and it’s enjoyable. Avoid burning, of course, and you’ll be safe. I find it inconceivable that the amount of sun exposure necessary to produce 10,000 IU of D3 (about 20-30 minutes of afternoon sun for light skinned folks; a few times that for dark skinned folks) will also kill you and give you skin cancer.

As with anything, though, ease into the sun. The pasty, mostly interior set will want to treat full sunbathing like learning to barefoot sprint after a lifetime of dress shoes – they’re coming from a position of weakness, of sheltered living. Five minutes of unfiltered rays can turn a freckled redhead lobster-pink, sore, and resigned to indoor living. Just be careful. Ease into things. Learn your limits, and throw on a shirt or find some shade before you burn.

Eating the right foods seems to confer greater natural skin protection against the sun, at least anecdotally. I’m not exactly the best case subject to determine this, as I’ve spent much of my life fairly tan with regular sun exposure, but you hear time and time again about folks who cut the grains, sugar, and industrial vegetable oils, replaced them with veggies, meat, and animal fats, and have never had any issues with the sun again. Nutritional deficiencies do have the tendency to potentiate existing problems or jumpstart/trigger health maladies, so I wouldn’t be surprised. Besides, we’re eating this way regardless. We might as well pick up a few additional theoretical health benefits along the way.

We can’t all bask in the midday sun (if such a thing even exists in our neck of the woods), nor can we even reliably count on there being adequate sunlight on a regular basis. For those of us unable to run shirtless and shoeless through a sun kissed meadow, the last of its residual morning dew having finally evaporated, from noon to 12:45, our option is oral intake.

Certain foods get touted as vitamin D powerhouses: wild salmon, mackerel, herring, cat fish, cod liver oil, eggs. Eat these, but don’t expect to increase your 25(OH)D levels much. Don’t eat the fortified, processed junk which, in the case of cereal grains, actually reduces calcium absorption. It’s a good thing they’re usually fortified with meager amounts of vitamin D, just enough to avoid rickets and keep blood calcium relatively under control. Remember, the body preferentially uses available D for calcium regulation, so it’ll mobilize every last scrap when it comes to matters of the bones – but that is far from optimal. When you eat grains and other junk, you’re increasing your D requirements.

No, food will help, but it won’t suffice. You need something stronger. Might I suggest licking the nearest sunbathing dog? (Would that actually work? I know that most vitamin D3 supplements are isolated and extracted from the fat in lamb’s wool; perhaps a similar concoction could be devised from oily dog fur).

In all seriousness, take a good D3 supplement if you can’t get real sunlight. As long as you don’t go overboard on the dosage, you’re good to go. If it’s not in an oil-based capsule, just take it with a bit of fatty food (not a stretch for an Primal eater). It travels the same pathway and results in the same benefits. It’s always easier to just let nature take its course, but it’s not always realistic.

A good general rule is 4000 IU per day supplemented. That’s what I take during winter time and when I go a few days trapped indoors and without sun (as I was last weekend while at the Book Expo of America in New York). Get your 25(OH)D levels tested before you start supplementation, take the 4k IU daily, and get them tested again after two months. Aim to get your levels up around 50-60 ng/mL, which is where most of the big benefits seem to kick in. If you don’t respond well to 4000 IU, feel free to increase the dosage. Given that we can make around 10,000 IU in well under an hour, supplementation up to that level is well tolerated.

I’ll end it here for now, with more coming tomorrow. It’s a big topic and there’s a lot to cover.

TAGS:  prevention

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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162 thoughts on “Vitamin D: Sun Exposure, Supplementation and Doses”

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  1. Mark,
    Thank you so much for this!!

    Living in Naples, I get my sun. But I also do supplement as I’m not retired…yet 😉 So during the week when I’m in the office for most of the day, I take 4,000 a day. I have not had a cold or bug in 3 years. (not bad with 4 kids in grade, middle and high school,)

    Can you talk a bit more about taking higher doses perhaps? ie; air travel, cold coming on etc?

    Thank you Mark.



  2. Mark, I have read about recommendations on taking 2 large bolus doses a week of oral D3 versus 5000 IU per day. For example, take 25000 IU twice a week for better D3 levels in your body. Any comments?

    1. D is fat soluble. You could take your D once a week if you want to and be fine.

  3. Thank you for this series of very informative posts. I have been wrestling with the Vitamin D, K, Calciun, and Magnesium connection for a while.

    Any thoughts about how much UVB absorbtion is compromised by an overcast day?

  4. I actually just got my vitamin D levels tested last week. The results came back as 30ng/mL (this labs ref range was 30-80) and I was told taking a supplement was “optional”. I’m now taking a loading dose of D3 for 1 month every day (10,000 IU) and then I’ll drop back to taking that every other day. I think I will have them retest in 2 months just to see.

    1. It may take a lot longer than a month or two to see a big increase in your D levels. After discovering my low levels, my doctor recommended 10,000 IU of D3 per day. On that dosage, it took me a year to increase my levels from 32 to 70. Now, I take 5,000 IU as a maintenance dose daily. That was also with a completely gluten free and 80% paleo diet.

  5. Mark,

    Nice article. Question about the “big benefits” chart you posted near the end:

    –If a person has a serum level higher than the max optimum benefit for say, heart attacks (~35ng/ml) and supplemented to maintain a level to avoid fractures (~45ng/ml) is there then a negative effect on the incidence prevention for heart attack?

    –And do you know what the “X” indicates for a given incidence of disease and serum concentration?

  6. Mark, all of my friends teeth are breaking, she is a vegatarian that eats a diet very high is carbs and a lot of grain based foods, but no vegtables (funny), her dentist is telling her it is because her fillings are expanding, this sounds like bull shit to me, could low vitamin D be the cause of this, please let me know what you think, and if there any thing that will help, please don’t say eat meat because i am already trying to get her to do that.

    1. If she has silver (mercury) amalgam fillings, they do corrode and expand, causing teeth to fracture. One good reason, along with getting mercury out of your mouth, to have them safely removed and replaced with a composite material. BTW, it’t touted as a benefit that they “expand” aka corrode over time, since the filling to tooth seal becomes better. Causing your teeth to crack apart – not so good.

    2. apart from the fact that amalgam fillings indeed can expand with the applied chewing pressure and time, it is possible that your friend has a vitamin D and/or vitamin K2 deficiency. both are needed to properly deposit calcium into the teeth. considering that K2 mainly occurs in meat, that could be one factor. google vitamin K2 for more information.
      considering her lacking diet, i’d recommend that she takes a high-quality multivitamin incl. a calcium/magnesium supplement plus a specific vitamin D+K2 supplement, at least for the time being. you can find the D+K2 combo at the usual online shops. also, if not meat, at least make her eat wild fish and eggs regularly 😉

      1. The best sources of vitamin K2 are fermented foods, especially cheeses (the most plausible explanation of French paradox) and natto (a soy dish popular in Japan). Natto contains the highest concentration of K2 of any food measured; nearly all of it is present as MK-7, which research has shown to be a highly effective form.

  7. Any recommendations on what supplements to take? Brand? Type? (capsules, drops, etc?)

  8. Vitamin D is the new Vitamin C. I had my levels tested just a few months ago and was at 24ng. Anything below 25 is considered “deficient” or so my physician says.

    The benefits of Vitamin D are MASSIVE and definitely shouldn’t be ignored. Thanks for covering, Mark!

  9. Interesting about the sun/skin tolerance.

    I am very fair-skinned and used to burn very easily. After 3 years of eating primally and supplementing vitD, I assumed it was something about the supplementation that caused a marked reduction in burning. It didn’t occur to me that the increase in nutrient quality might be the difference.

    After decades of burning, it’s lovely to be out in the garden for hours soaking in the natural vitD, without suffering the after-effects.

    1. Same story here, I assumed it was d3 but didn’t think of the highly nutritious food I was eating making me less succeptable to burning. Being fair skinned and getting tan and not burning is a whole new experience for me this year….it’s exciting!

      1. So eating better has helped your skin protect from burning or are you saying proper supplement is. I’m fair skinned the Rays literally can be felt burning my skin… Although they don’t exactly. But I hate the sun it just hurts. Plus my genetics is high for cerebrocaratosis. I need d and so there I sit. Twiddling my thumbs.

      2. I’m going to conclude that it has a lot to do with to higher protein intake, more specifically the higher intake of an amino acid called Tyrosine. I experimentally took L-Tyrosine supplements all winter one year to help with mood and winter blues, and that summer I found that from the very first time I laid out in the sun I did not burn or peel AT ALL for the first time in my entire life- and I actually got a good dark tan FOR THE FIRST TIME in my life. I’ve always struggled with being able to tan and with burning, so I was extremely surprised and curious when this happened to me. I began researching and found that your body uses Tyrosine to create melanin in your skin. So, high protein intake= more tyrosine intake=more melanin. So one could say that a high protein diet is very protective to the skin as well! Ahhh the benefits of being primal!

  10. Susceptibility to sunburn is caused by excessive linoleic acid in the diet. AKA, those vegetable oils that the Primal Blueprint tells you to avoid.

    I attended one of Barefoot Ted’s classes, and my dark-skinned Colombian wife and blonde, blue-eyed me stood side by side in the sun in Central Park for 2.5 hours. For the first time ever, she burned and I did not.

    That was the day she adopted the Primal diet. 😉

    She still can’t believe what a difference it has made for me. I used to roast after an hour or two in the sun. Now, 5 days in Florida with no sunscreen and no sun burn. It’s pretty unbelievable.

    So now I’m getting my Vit-D the old fashioned way, and with a big smile on my face.

  11. Living in Los Angeles, I am lucky enough to be able to get much of my Vitamin D from sunlight all year round. I still take an oral D3 supplement when I’m traveling, too busy to spend much time outside, feel a sniffle coming on, etc. I take 4-10k IU D3 from Carlson’s drops (2k IU per drop). I prefer to get my D3 from the sun, however. It is not what I know I’m missing that concerns me, but what I don’t know that I may be missing. Sunlight may yield other health benefits beyond just Vitamin D production. Oral dosing with D3 won’t give you these other possible benefits.

    And I’ve also noticed that switching from a SAD to a primal diet has dramatically improved my sun tolerance (and put a metabolic disorder–porphyria–into remission). I think

    1. “It is not what I know I’m missing that concerns me, but what I don’t know that I may be missing. Sunlight may yield other health benefits beyond just Vitamin D production.
      Aaron, you’ve summmed up the supplements fallacy in two sentences. You’re so right.
      Mother Nature has it’s own agenda, we need to respect it and not try to “improve” it and “optimize” it… We’re fools if we think we can take shortcuts to our health…

  12. I have found that taking cod liver oil and eating lots of butter has helped me tolerate more sun exposure. I don’t burn as easily and recover faster from a light burn than I used to. So taking cod liver oil is not just good for its content of vitamin D but also for being able to stay out in the sun without burning.

    Also coconut oil is by far the best topical sunburn recovery method I’ve tried.

    1. I lived in Central Otago New Zealand when I was a kid. Extremes of temperature and very dry. Our mother always treated sunburn (that usually only happened late spring) with sour cream. Stank a lot and the dogs loved us. It was an almost instantaneous relief from the burning and next day the red was gone. We always had plenty of cream as we kept a house cow.

      1. Hey that is very interesting! I heard of using milk to relieve burns from hot peppers but never tried it on a sunburn. I think my cats would love that too.

        1. Since hot peppers don’t actually burn anything, it’s difficult to compare in this manner.

          They irritate nerve endings, creating a burning sensation, no actual tissue damage like a radiation burn (sunburn).

          Milk (fat) tends to take away the sensation caused by capsaicin (chemical that ‘burns’ in hot peppers) as it is attracted to the fat and carried away from the nerve endings.

  13. Since going primal in February, I’ve spent almost every lunch break with even a little sunlight at the park – either napping with my shirt off or sprinting in shorts and T-shirt. It’s hard to say how much of my improved health is attributable to the diet and how much is the sunlight (vitamin D), but it all works together. One thing is certain: I’ve gone from pasty and doughy, to tanned and slim. I like it a lot better!

  14. if one comes from a severe deficiency, 4’000IU/d will not get you far. i took 5’000 for 3 month and barely reached 40ng. everything <=40ng is *not* enough to re-saturate all bodily tissues with D3 (from 40-50ng, the 2nd metabolic pathway begins to kick in). therefore, depending on your initial level, you should aim rather high for the first few weeks (like 10-20kIU) to be sure to overcome the 40ng bump. then retest, and adjust down to like 4-10kIU. up to 20kIU/200ng, no harm is to be expected according to the research i know.

  15. Mark, just curious if you know anything about idiopathic guttate hypomelanosis. Is it sun related and can it be reversed. Not much on the web about it and since CW is out, what the go with this?

    1. Rob, I have this condition and my dermatologist didn’t seem too freaked out about me getting some sun. I’m just worried that if the white spots have no pigment, is it safe for them to get sun exposure? Let me know if you find any answers. I’d appreciate it.

  16. How can tanning beds be effectively utilized?

    I know that UVB rays are the “burn rays” and higher-end tanning beds don’t have them. So going for the cheap beds appears to be the best option.

    But what about lotion? The stuff you get specifically for beds has an ingredients list that looks like a commercial salad dressing ingredient list. (Now that’s scary!) Should I use coconut oil as others have mentioned?

    Or should I just start taking an hour-long lunch break and head out to the nude beach? Haha.

  17. Why is there only 800IU of Vit D3 in the daily dosage of the Master Formula? I’ve been supplementing with 1,000IU daily + trying to get 10 minutes of sunshine daily.

    1. those higher vitamin D recommendations are of rather recent date, so i guess mark first needs to sell of his existing stock before he can request a new, reformulated batch from his supplier.. but it certainly would not do harm to give a free bottle of 2000IU D3 with each order as long as this is the case.. right, mark? 😉

      1. @Qualia and @kathy,

        I update the DCMF every year based on new science. This year we have increased to 2,000 IU per dose to reflect the latest science – including the requisite safety analyses. The new formula is in production now (based on the exceptionally high standards of GMP production, it takes at least 16 weeks from start to finish for most of my products now).

        I am also introducing (very soon) a separate vitamin D supplement, which will allow anyone to adjust D levels day-to-day or beyond the DCMF dosage.

        1. My doctor just told me to stop taking most supplements, except for Vit D and fish oil. He said to stop taking calcium. I was using Garden of Life GrowBone Calcium blend that included stronthium. He feels taking supplemental calcium can be dangerous and deposit in the arteries and elsewhere.
          I live in Phoenix and after spending all summer in the blazing noon sun and dosing with approx. 2K of Vit D capsules, my September level of VitD was only 37.5. Weird huh?
          My question is..would it be dangerous to just take D alone without taking supplemental calcium and relying on my food source for it?

        2. Is there a reason Vitamin D is included in DCMF and not just as a separate supplement? I feel I am more anxious when I take too much Vitamin D, and for this reason I haven’t been taking recommended amounts of DCMF like I would like to. I’ve been looking into other multivitamins for this reason.

  18. also, it it worth noting that according to the literature, a small percentage of people seem to react unusually sensitive to vit D supplementation. those people will show an unexpected rise of the blood calcium levels together with the D supplementation. for this, it is recommendable to also measure the calcium level before and during supplementation, to be sure to exclude even the slightest risk of overdosing.

    1. Nope, no mention of sensitive reactions in some people.

      But I have read in in numerous blogs.

  19. I think it is very good idea to get your vitamin D levels tested. Working clinically with clients I have found that even when people are getting sufficient sunlight and/or supplementation, Vitamin D levels are often still in the 20-30 range.

    Their are quite a few factors that can effect the conversion of Vitamin D in the liver to 25(OH)D.

    Things like the amount of body fat, activity of the enzymes in 25-hydroxylase activity, malnutrition and the effects of aging and disease.

    I think this probably explains why many people are able to tolerate sun exposure better once they improve their overall health.

  20. Thanks qualia for the note about sensitivity to D3 Supplements The first time I ever experienced angina was after my doctor prescribed the 50K IU vit D capsules 2x times a week. (I was at 11.8 ng! in March 08) I can tolerate the 400 IU’s that are in the kids multivitamins and try to keep up the gardening! I’m rocking at 31 and my new PCM is still on me for an upward trend or he’s putting me on supplements. I’m not perfectly primal, but everything is better when I stick to the plan!

    1. personally, i’m also a bit sceptic of the usual megadoses that doctors use to give their patients in a single day. although D3 is fat soluble, and therefore could *theoretically* be absorbed and stored rather rapidly, the human body normally does not produce more than 10-20kIU max. from sun. also, the body has some additional metabolic security measures for D3 to be regulated within a certain limit which indeed can be overwhelmed by doses not normally occurring. personally, i try to stay under 20kIU per day. for additional information see chapter: “Dose-response curve of 25(OH)D concentration versus vitamin D intake”

    2. Thanks Christine,

      I’m interested in exploring this further as I myself only seem to tolerate a dose of D3 under 2000 IU. Anything above instantly causes angina and a running nose. I’ve tested it numerous times and it always does. Sunbathing all day (which would produce MUCH more D3) does not have that effect.

      What supplement did you take ?

  21. If we can produce up to 10,000 IU via sunlight, why is the daily recommended dose found on the back of vitamin supplements so low?

    1. I believe 400IU was the minimum amount to prevent rickets, which is the reason for the low amount on supplements. I agree that it’s stupid.

    2. All of the recommended doses are completely out of whack. I simply use them as a guide.

      Take Vitamin A for example… 1 carrot has all the Vitamin A you need in a day. One sweet potato has 600-700% of the vitamin A you need in a day… Kale has like 10,000%, or maybe its spinach?

      Basically, the numbers mean nothing. 400 IU for vitamin D3 means what I say it means. Spend time outdoors – get a tan, just don’t burn to the point where it hurts!

      1. Toad, carrots and sweet potatoes have beta carotene (and other carotenoids, I imagine), NOT true, pre-formed vitamin A, which comes exclusively from animal sources. The conversion rate of carotene to Vit. A is as high as 10 or 20 to 1, in other words, a given amount of beta carotene is worth 1/10th or 1/20th the amount of Vit. A. And many people, such as the very young, those with diabetes, etc., can’t make the conversion at all, according to WAPF articles. The carotenoids are *also* useful as antioxidants and possibly for other reasons we don’t know yet, but they aren’t useful as a substitute for true Vitamin A (retinol).

        1. I second that. The conversion is very difficult…true vitamin A = retinol is only found in animals, such as their eyes. (e.g. fish eyes)

          Also without having enough D3 the ‘fake’ vitamin A’s in supplements quickly turn toxic. A has to be taken in conjunction with D. (WAPF)

  22. With all the sun topics around: Does anyone know if all the “get out into the sun stuff” is OK for people with many (as in: a lot) naevi, too?
    My doctor always told me those probably increase the risk of getting skin cancer a lot when exposing them to the sun, which is why I mostly go out in protective clothing and LSF 50+ when the sun is shining a lot. I’m not sure how much of a risk it really is, because I’ve read many different opinions about it, and I’m not sure who’s right anymore.

    1. i’m no doctor, but all i heard/read so far about this is indeed that the cancer risk is directly proportional to the total number and size of the birthmarks. so, personally, i wouldn’t take the (unnecessary) risk, and simply supplement the D3 with pills while still protecting the skin as usual (and let them get checked regularly by a dermatologist).

      1. Thanks. Yeah, I guess you’re right; With the possibility to supplement Vitamin D3 it’s probably the best thing not to take any risk.

        Oh, by the way: LSF of course should’ve been SPF. LSF is the German word for it (Lichtschutzfaktor).

  23. As a long time owner of various pets, what about a UVB reptile lamp aimed at a non-tan portion of my body while I am at home for ~15min? I feel that the tan that I am developing and my genetics will require me to stay out longer than I have time for before and/or after work. I’m having outdoorsly fun every weekend, but was just thinking of an alternative to taking supplements on a June gloom (Ahhh! it’s back!) weekday. Just trying to think outside the box…the boyfriend thinks it’s nuts but the thought of me reading the paper with a lamp on my bum got some good laughs. What do you think?

    1. Hi PRana


      “In 1939, Dr. Abraham Myerson measured initial levels of circulating testosterone in men and exposed their various body parts to UVB light.

      After five days of chest exposure sufficient to cause reddening, circulating testosterone increased by 120%. After eight days without additional UV exposure, testosterone returned to initial levels. When the genital area was exposed, testosterone levels increased by 200%!”

      As a 52 yo male, I have my UVB reptile lamp aimed to maximize my T levels.

      My wife has not made any comments yet,
      but she considers me crazy.

      1. That’s enough to convince me to give it a try. Hey, it’s working for the vast number of pet reptiles out there too…

        Thanks Mat, very cool article!

  24. For those who want to get their Vitamin D levels tested, D*Action is a great way to do it (

    It is an ongoing epidemiological study on Vitamin D, so the cost of a test is subsidized. They mail you a kit, you prick your finger and send back a blood dot, and they send you your results. Prices have changed but I think a test is about $50 right now.

    As someone who lives in a sunny climate, spends some time outdoors every day, and takes cod liver oil every day, I was very surprised to find my Vitamin D levels extremely low before I started supplementing at ~4000IU/day. Test!

  25. I love these sunlight articles. Perfect timing for them too Mark! You obviously planned it.

    Over memorial day weekend I played 45 holes of golf. I put on zero sunscreen even though I was in mid 80 degree weather. I just stayed in the shade when possible and, well, I eat primal!

    I got a slight pink that has not turned into a “hot” tan. I feel great and continue to be more energized then ever on 6-7 hours of sleep a night (was 8-8.5 before going primal).

  26. Hi Mark,

    It may be worth pointing out that for some people, (depending on latitude), it may be impossible to make vitamin D via sunlight during the winter months. This article says above 37 degrees North or below 37 degrees South:

    On the sunburn front, perhaps related to the dietary changes you mention, I have seen some articles that indicate that omega 3’s may be helpful:

    Finally, the Vitamin D council website has some speculation that vitamin D itself may have a protective effect relative to sunburn, (you’ll need to scroll toward the bottom):

    This is my first post so I hope the links work…

  27. Hi Mark,

    Just curious. You recommend 4000IU of vit D however your own damage control master formula only has 800IU. Is there any reason for this?

  28. Great article Mark… I was hoping you’d cover this subject in a major way.

    I recently started supplementing both Vit D and B12 in a major way (Mercola Health brand), and have never felt better in my life.

    ..breathing very freely now, even though we’re in winter down here… and I’m a mild asthmatic. No brain fog either, although this all but disappeared when I’d gotten to 75% primal. This is the best investment I’ve ever made in myself.

    Looking forward to the second installment.

  29. This is great stuff.

    Hey Mark, if we are taking the damage control master formula with the 800 IU should we be supplementing to get more vitamin D as well?

  30. Unfortunately, my skin/body is not smart enough to inform me I am sunburning the bejeesus out of my skin until after it is too late. It doesn’t hurt until later! Of course, if I was living a thousand years ago with a completely different life style, perhaps many factors would render such a warning mechanism unneeded. It could be that skin cancer becomes more of a danger when other factors are out of balance as well. It’s hard to make perfect decisions on how much sun to get without knowing exactly what factors are coming in to play with both vit D and cancer. We just don’t know that yet so you just have to make a best guess. Plus it will also depend on your genetics (dark skin, light skin, etc) All that being said, a friend of mine who suffers from seasonal affective disorder loves his sun lamp. It’s a smaller one and he uses it as a reading lamp. Apparently, you have to be careful about sunburn with some lamps though, but they can be another option for helping get sun/vit D and combating winter doldrums.

  31. I have a 21 month old son and his mom never lets him go outside without lathering him up with sunblock when I am over at her house seeing him. We have a great working relationship with him but aren’t together. Anyways, I have tried giving her the speech of the necessity of the natural sunlight and its benefits. I’m looking for some advice on how to get it across to her. My mother died of skin cancer, her father has had a cancerous mole removed, but I’m not one to believe sun is the culprit. Excess exposure coupled with our dietary deficiencies, the crap they add to the our food, exposure to chemicals, pollution and majority of peoples inactive lives is the true cause. I’ve even given her the PB book and she is not open to reading it. Any advice?

    1. If he’s healthy, let it go, bro. Get him some time outside without burning when he’s with you and let her do it her way when he is with her. Coparenting has it’s limits. Being overcontrolling will look bad for you. She’s his primary, she makes the decisions.

  32. @Mark

    Does your “Advanced Health Formula” cover most of one’s Vitamin D requirements? (assuming that’s with a good diet and ‘occasional’ sunlight)

    Thank you.

  33. Mark, thanks for the informative article. However, when publishing a chart such as the “big benefits” chart, it would be much more persuasive if you gave a reference in the scientific literature to substantiate the data. The data is, after all, very quantitative. Please provide a reference. Thanks. (And, by the way, just to stipulate, I am not a primal routine skeptic. I’ve been on a primal routine now for 2 months. But I am a health care professional, and need data confirmation.) Thanks.

  34. There is a direct link between UV exposure and skin cancer.

    I find it funny, that people on this site worry about tiny amounts of chemicals in non-organic food but recommend that you go out in the sun – a KNOWN CARCINOGEN! Use vitamin D supplementation. Just because in your mind it’s “natural” doesn’t mean it’s good for you.

    1. It’s not about living in fear, it’s about living as nature intended. Fear of the sun is preposterous.

      1. I’m not claiming you should fear the sun, I’m just pointing out the contradictions between these two points:

        1) we should avoid any kind of trace chemical contaminants in food such as (hormones, antibiotics, etc.) at all costs — they should be avoided 100% of the time.


        2) going into the sun is perfectly fine and should not be avoided at all, other than not burning.

        Are chemicals in food “bad” and can they presumably cause cancer? Yes, so avoid them as much as possible.

        Does getting UV dose cause cancer? Yes, so avoid it as much as reasonably possible (as long as you have enough vit D)

        Nature has no “intentions”. Either things are good for us or they are not.

        Uranium is naturally present in all soil. Is it good for us? Did nature “intend” us to eat small amounts of Uranium?

  35. Hi, great post, whats the concessus of opinion on exposing areas of the skin with moles to the sun? I have read all the links, sun is good, but dont burn etc. but nowhere does it mention it’s ok to expose areas of skin that has moles to the sun, any thoughts on this?


  36. I’ve been researching vitamin D myself for a series of posts on my website. Your article is a great resource and I am anxious to read more, because like you said this is a HUGE topic!

    I would add that skin color, latitude, time of year, time of day, age, and exposure duration are very important factors to take into account when you try to get your vitamin D from the sun alone. For many, year round sun exposure is not adequate and even in sunny locations, people are still vitamin D deficient.

    And I know you are going to get to it in your subsequent articles, but to anyone thinking of supplementation: use vitamin D3–NOT D2! You need an animal source or don’t bother.

  37. The typical “serving” of vitamin D in supplement form is 400 IU and it says that’s the 100% daily value. So to get 4000 IU’s I’d have to take 10 pills? There’s only 100 to a bottle and each bottle is about 10 bucks. A dollar a day definitely adds up overtime.

    1. not at all. you can buy D3 in all the different dosages you can think of. for example, 1000, 2000, 5000, and even 10000IU per pill, for very cheap. so, no problemo.

  38. “But I don’t think it’s necessarily “better” than getting it through supplements”

    You’re bypassing natures own method of producing this essential pre-hormone by not using moderate exposure to ultraviolet. UV exposure converts 7-dehydrocholesterol in the skin into previtamin D(3)

    “For those of us unable to run shirtless … our option is oral intake.”

    Moderate and controlled non-burning exposure in a tanning bed is also a good way to get UV exposure in higher latitudes and when outdoor sunshine is not available.

    Typically 1/3 to 1/2 session of full body exposure will make upwards of 10,000 IU with 1 MED adjusted for skin type (just less than slightly pink after 24 hours) PubMed link

    Another study shows that tanners have upwards of 90% higher levels of Vitamin D than those that do not. PubMed link

  39. I got my first Vit. D blood test back from and found my 25 (OH)D level is 55 ng/dl, woohoo! I supplement irregularly, 4-7 times a week with vit. D caps, couple times a week with fermented cod liver oil (whenever I remember, basically) and eat lots of eggs, butter, grass-fed meats, greens, etc. My diet’s not perfect (having trouble totally kicking sugar and grains, but my consumption is way down most of the time), but I have the Vit. D down!

  40. People, you don’t want to have an advanced case of Vitamin D deficiency: pain everywhere (it affects the bones,) severe weakness, severe fatigue. I felt like I was 90 years old. I needed help to stand up or get out of a car, could not rise from a crouching position, spent most of my time indoors sleeping, which obviously exacerbated the situation. I used to be energetic and robust and was considering getting a cane. I wonder how many confined people would be doing a lot better if someone took them out in the sunshine for a while. I am a lot better since I have been sunbathing daily at noon.

    1. I went through this too…I was totally falling apart!
      Unfortunately and somewhat mysteriously for me, I am almost totally unable to respond to oral dosing of Vit D and I live in Seattle, WA where we don’t get enough sun exposure to make up for Vit D deficiency…I have to go tanning year round but when I do, I see immediate results with my levels brought right up!
      And before anyone comments on my inability to respond to oral dosages…OTC’s do not work for me and I was on a doctor’s prescription strength D therapy for over two years which is a massive weekly dose, and was never even able to get within normal limits.
      During Summer months, I can tan much less but I still have to go periodically.
      Lastly, to people who have posted about how we are so concerned about a few chemicals in our food yet would expose ourselves to the SUN, a KNOWN carcinogen.
      Here’s the deal.
      Vitamin D is actually a very essential hormone that helps with so many things the list grows longer each day but for the sake of this conversation, it fights against most types of cancer, as well as SKIN CANCER.
      You get Vitamin D from the SUN.
      Yes, there are other avenues that support big business to get Vitamin D but ultimately..look at the big picture.
      Vitamin D comes from the SUN. It prevents SKIN CANCER and other cancers.
      It prevents depression.
      Many other things too.

      We are not the only creature on this ENTIRE PLANET, including plantlife, not made to be in the sun daily!

      This is highly illogical.

      Unless you want to scare people into thinking they need the following every day, frequently or regularly:

      Sunblock, LOTS of it! And special kinds for your face so it doesn’t break out!

      Cancer screening tests regularly whether there is reason to check or not.

      Cancer treatments brought on by the very screening tests supposedly used to ‘look’ for cancer.

      Acne products to clear up your skin after sunblock chemicals have caused rampant breakouts.

      Moisturizing specialty products to cure the stripping caused by the acne products.

      Trips to the dermatologist to figure out the cause of various and sundry skin abnormalities caused by the cheap petroleum products in the moisturizing, sunblocking and acne products.

      Trips to the rheumatologist to figure out why your joints hurt SO bad you can hardly move anymore! You are only (insert absurdly young age here)!
      Why are you SO tired with muscle weakness that just doesn’t make sense?

      Trips to the psychologist to figure out why you are SO depressed?
      Just what did mommy and daddy do to you back all those years ago?

      And on and on and on and on and on it goes…

      Oh, and don’t kid yourself Big Pharmaceutical is sitting there pretty making money from you hand over fist.

      Don’t just take MY word for it…WAIT, yeah…you can take my word for it.
      I am a licensed pharmacy technician, a licensed aesthetician and a formerly suffering, still recovering severely Vitmin D deficient, severely bipolar, fibromyalgia, arthritic, diabetic nightmare who is no longer any of those things.
      I nearly lost my entire life because of this stupidity. In the end, rock bottom, I was suicidal, my marriage was in ruins, I could barely move…when all it took was literally the basics:

      The love of my family
      A new and deeply real attitude
      Vitamin D
      Complete food reform

      Sure, throw in exercise too and a few other spices of life:)

      The Sun, along with common sense (don’t fry), is healthy.

      Lining greedy pockets who have no interest in your well being is disaster.

  41. all you lucky gits! I’ll be lucky to see the sun once or twice until about March. :- (

    Just lots of grey, miserable, rainy days.

    So! My vitamin D supps come with calcium. I take it i need to find one with vit d alone?

  42. It’s good to remember that Vitamins A and D work together and both are needed in much higher doses than found in the SAD standard american diet. Dr. Weston A. Price found that the diets of healthy native peoples eating their traditional diet (in the 1920s and 1930s) were getting 10 times the level of A and D in Western society at the time…and that was probably higher than today, because people still drank raw milk and had pastured eggs and butter, though margarine and processed foods were becoming more common.
    The Weston A. Price Foundation has lots of good, in-depth articles about A and D that I urge you to read. The recommended ratio of A to D is 5 to 1, so, for example, a good dose might be 25,000 iu of A to 5,000 iu of D. Taking both vitamins together in the proper ratio also is protective against any toxicity from being too high in one or the other (and toxic doses are way, way higher than this anyway, but it is still best to take these nutrients in the proper ratio).
    An excellent source of both nutrients in the right ratio is fermented cod liver oil, available from several places online but made by only one company (Blue Ice is the brand).

    Most commercial CLO brands have *reduced* the Vit. D levels (so they can make more money selling separate capsules??) and they are way inadequate. Take a look at some CLO labels and you’ll see what I mean.

  43. People who are on statins or who have low cholesterol have a harder time producing vitamin D.

    I wonder about what is “too much” – my blood vitamin D is 84.9 ng/mL, which seems awfully high. Anyone know of any research on what might be too much? I didn’t see anything on the Weston Price site but I’ll go back and make sure I wasn’t missing something.

    I only supplement with 2000 per day. It’s hard to find a vitamin d capsule without soybean oil, but for those of you looking, SourceNaturals makes one, and I think that Now Foods does as well.


    1. Disregard – found it on the Weston Price Site after all. Looks like 85 is too high, potentially harmful!

    2. I believe the “too high” level is way over 100, you should be fine at 84.9. (I have read it from an authoritative source, I just don’t remember more specifically than that, but it is definitely way over 100 before it’s a problem.) Some would say that’s a very desirable place to be. The Vitamin D Council has lots of info on desirable levels and supplementation, as does Grassroots Health (Google both for links). Neither of them writes about the need for A along with D, however. The Weston A. Price Foundation and many WAPF-friendly bloggers including Chris Masterjohn have ample documentation on that.

      1. Thanks Jeanmarie! I love your website!

        The weston price website concerned me about this, but it seems that some people say that levels between 50-80 are good. I’m just wondering if I should continue supplementing with 2000 IU a day (as I am now). Well, it’s 2500 IU a day if we count the two citrical pills I’m taking as well. I do live in the desert (Tucson) so sun is aplenty. Thoughts on that? I don’t take Vitamin A, I feel that as primal people we get plenty of that from vegetables.

        I’d love to hear more of your thoughts!


        1. Thanks, Ashley! I need to update my blog…
          I can’t advise you on how much to take for your particular situation of course, but I can tell you many researchers think the minimum daily recommended level should be something like 2,000 international units to 5,000 iu a day of Vitamin D — way above the U.S. government recommended level of 400 units! Pathetic. That’s enough to keep you from getting rickets but that’s about it. As Mark has written, there are other reasons to get sun exposure besides just vitamin D — it feels good, for one!

          On Vitamin A, what you find in fruits and vegetables is actually beta-carotene, not Vitamin A, and not all f&v are good sources of even beta-carotene (and there are other caroteinoids, and they’re all needed for other reasons, as anti-oxidants for example). In most vitamin pills, if you read the fine print, it will say “Vitamin A” x number of units in bigger letters, followed by “as beta-carotene” in tiny letters. These are NOT the same thing. The conversion to vitamin A is inefficient at best, so you have to eat 10-20 times as much betacarotene as Vitamin A to end up with the same amount of A. And infants, children, the elderly, diabetics, and people with certain other disorders can’t convert betacarotene as well or at all. That’s why WAPF refers to “pre-formed Vitamin A.” It’s better to eat real Vitamin A, not its precursor, beta-carotene (you need both probably, but the latter isn’t a good substitute for the former, is my point). Again, A and D work synergistically, and each protects us against toxicity in the other — if they are both present in sufficient quantities and in the right ratio. My personal feeling is, if you’re supplementing with D, you probably need A also. (And both need to be taken with fat or as a gelcap in an oil base for assimilation. Of course, if you’re eating primally, you’re probably getting plenty of fat!)

  44. Jeanmarie (or anyone actually) can you pls give examples of foods rich in vitamin a, based on the post two posts above me^

  45. Short answer: Animal foods, especially organ meats like liver are the only sources of preformed vitamin A. Eggs, butter and cream, shellfish are also good. It’s interesting that A and D tend to occur together in nature. Used to be cod liver oil was a generally good source, but most retail brands remove the vitamins during processing and add back artificial ones. I *believe* that Garden of Life’s Olde Icelandic Cod Liver Oil is an exception to that, and Green Pastures’ Blue Ice Fermented Cod Liver Oil is reputed to be the best available and doesn’t remove or add back vitamins. It’s only sold online through various marketers such as Azure Standard. That’s the one I use now.

    1. While awaiting Mark’s response… the first thing that comes to mind is that parts of Brasil are near the equator and the sun is very strong there, so to avoid burning, don’t get mid-day exposure. If there’s another reason, I’d also like to know. Not that I have a chance to go to Brasil, though I’d love to.

      1. That’s probably the reason (the equatorial spin). Also, just FYI, I rarely comment here after a post is more than a few days old. With 2200 posts and thousands of comments coming in, it’s impossible to answer them all. Wish I could….

  46. I live in UAE(Dubai) . What would b the best time for sun exposure?? wont it b early morning sun? Its usually 45deg celcius here after 9 am. Will uvb will have required frequency after 11am as per US ?UK norm? Let me know.

  47. Hi Mark,
    Any topical ointments or creams one can use for D defficiency? What make of UV lamps would you recommend if any?

  48. After living in the highest uv city in the world, I developed a D deficiency. Crazy right!

    Got the supplements and working on it. However, in Australia for a pale creature like me it’s a really bad idea to be out in the midday sun. For me, and it seems for the Brazilians in that article the best time is in the morning, before ten am or in the arv after 3. The UV is lower and it makes it easier to control the burn factor if your skin reacts in under 7 minutes…. so I will get out in the bare minimum and cycle in the sunshine. Hopefully this will work for me long term. Still in the early stages of supplementation.

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  51. I think people would be doing a lot better if someone took them out in the sunshine for a while. I am a lot better since I have been sunbathing daily at noon.

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  59. Thanks qualia for the note about sensitivity to D3 Supplements The first time I ever experienced angina was after my doctor prescribed the 50K IU vit D capsules 2x times a week. (I was at 11.8 ng! in March 08) I can tolerate the 400 IU’s that are in the kids multivitamins and try to keep up the gardening! I’m rocking at 31 and my new PCM is still on me for an upward trend or he’s putting me on supplements. I’m not perfectly primal, but everything is better when I stick to the plan!

    Read more:

  60. Vitamin D is very important to functionality of body, specially you can get vitamin D from sunlight in early morning.

  61. I was very happy to uncover this page. I wanted to thank you for your time for this particularly fantastic read!! I definitely liked every little bit of it and i also have you saved as a favorite to see new information in your web site.

  62. Thats why i love hiking in the morning and expose to the sun so that i can get more vitamins thanks for the helpful information.

  63. I have noticed my dog lying in the hot sun sometimes and he looks very content. I think it’s too hot for him and call him in and he’s reluctant to leave his sunny spot. Now, I’ll let him stay as long as he wants. I was wondering if the dog and cats sunning was a healthy thing like it is for me.

    Thanks Mar, for all your work.

  64. I know I’m way late, but is it possible that we need those times of the year when we don’t get much sun due to temperatures? It just seems that we adapted to live on the planet with periods of time where there is little to no sunlight.

  65. Hi Mark,

    I am so glad I found your site, thank you for all the great reading material. I just did a Vitamin D level blood test for the first time – and it is 5! My doc put me on 50,000 UI once per week but he gave me Vitamin D2 not D3. I am not sure why and read on other sites that you need to take Vitamin D3 NOT Vitamin D2. Of course, my Doctor is off on vacation and I was wondering what your take on this is. I am young, healthy, I do sports and actually spend at least 25 to 30 min outside running around, even though I live in NYC. Many thanks!

  66. The ultraviolet light in sunlight is ionizing radiation, which directly mutates DNA – that’s how it causes cancer. Humans are not all that well optimized to deal with cancer in our old age because over our evolutionary lifespan, we were much more likely to be killed by an infection or predator than we currently are. If you plan to die at 35, I wouldn’t worry about the cancer risk of sunlight, but if you intend on living into your 60s or 70s or later, then cumulative sunlight exposure should be a concern.

    Given the tremendously better availability of healthy foods in modern times, most people now can get sufficient vitamin D from their diet, and if that works for you, there is no downside to doing that. There is certainly a strong upside to eating your leafy vegetables. Whether or not it makes anyone any money, getting vitamin D from diet or supplements is certainly safer, regardless of whether or not it’s more “natural”. Advising people that sunlight is the safest way to get vitamin D is clearly wrong and potentially quite harmful!

  67. I live in Dallas, Texas. I’m curious to know if I can get enough Vitamin D from the sun exposure during the winter months here in Dallas ( Nov – March)
    My level is at 24 right now and I’m pregnant. I am taking 2000 IU D3 supplements daily. will that be enough?

  68. Mark, my vitamin D3 fish oil capsuke contains saflower oil. I take 1,000 Iu’s per day. Is it safe to keep takin with safflower oil?

  69. I’m surprised that this article didn’t touch on the role that melanin plays in the production of vitamin D in the body. The more melanin someone has, the less vitamin D their body is going to produce because melanin protects the skin against ultra violet light. The darker your skin, the longer you would have to stay in the sun to produce vitamin D. That includes those donning temporary tans. Therefore, it is advisable to get quality vitamin D through the diet with fatty fish, liver, eggs and cod liver oil. Twenty minutes of sun exposure is too much for a fair skinned person; only a few minutes of sunbathing is needed for the body to begin making vitamin D because it is directly related to the amount of melanin.

  70. I’m taking 50000 ui vit. D. I’ve also been. In the sun due to sudden weather changes mid 60 and 70 degree temps. I have been sick off and on for at least a week. Today is the worst. Nauseated vomiting some and abdomina
    Pain. Wondering if I’m getting toxic. I take one per week for 7 weeks and am almost done. I was at a 18 on my blood test. Any comments?

  71. Dear mark,

    It has taken a year starting with 30 to get to 49 for me! I am taking vit D3 2000 to 5000 according to sun exposure availability. I am also completely primal!
    I have recently read Wheat Belly and there is a recommendation for shiratki noodles made with some kind of vegetable root with potato starch and calcium hydroxy. That doesn’t sound primal to me! Anyone who has tried them here?

  72. If one has sun allergy, is it possible to get necessary dose od vitamin D with supplements and food? or is there any other source to keep vitamized?

  73. Wow…talk about an eye opener! My bottle of Vit D is 400iu. I actually had to go get the bottle as surely I must have misread it.

    You’d mentioned at the end of the post “…if you don’t respond well to 4000iu, feel free to increase”. Im assuming the only way to tell how you are responding is through lab work, correct? If I bump my 400iu to 4000iu…I wont physically be noticing any difference?

    GREAT article…thank you!

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  75. Mark, you need to cite some science in this. I got in a fight with the Stuff You Should Know guys defending you and I can’t refute them.

  76. Personally, I prefer toward getting my D3 from daylight, essentially in light of the fact that it’s agreeable to invest energy in the sun and it’s an easy approach to get something that is basic to my wellbeing. Be that as it may, I don’t believe it’s fundamentally “better” than getting it through supplements.

  77. Do you have a supplement recommendation? I have been taking liquid Vitamin D3 for about 2 months and just had my levels checked and am at 40. I have been taking about 4000 IUs per day. Is there a better form of Vitamin D to take? I will take more, but if it’s not bioavailable in my body it won’t do good.

  78. What happen if you take too much vit d , can it affect your mental status . Im menopausal now ???