Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
2 Jun

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.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. 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.

    Ira Satinover wrote on June 3rd, 2010
  2. 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.

    logi wrote on June 3rd, 2010
    • It’s not about living in fear, it’s about living as nature intended. Fear of the sun is preposterous.

      Brandon wrote on June 3rd, 2010
      • 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?

        Logi wrote on June 3rd, 2010
  3. 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?


    Dave wrote on June 3rd, 2010
  4. 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.

    Kristy A. wrote on June 3rd, 2010
  5. 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.

    Clack_Attack wrote on June 3rd, 2010
    • 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.

      qualia wrote on June 3rd, 2010
  6. “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

    bruce wrote on June 3rd, 2010
  7. 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!

    Jeanmarie wrote on June 27th, 2010
  8. 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.

    sunny wrote on August 3rd, 2010
    • 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.

      Stephanie wrote on October 19th, 2010
      • Love this post…very well said! :-)

        Donnersberg wrote on April 27th, 2011
  9. 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?

    sarah wrote on September 9th, 2010
  10. 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.

    Jeanmarie wrote on October 19th, 2010
  11. 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.


    Ashley wrote on October 20th, 2010
    • Disregard – found it on the Weston Price Site after all. Looks like 85 is too high, potentially harmful!

      Ashley wrote on October 20th, 2010
    • 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.

      Jeanmarie wrote on October 20th, 2010
      • 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!


        Ashley wrote on October 20th, 2010
        • 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!)

          Jeanmarie wrote on October 21st, 2010
  12. Why do the content jogs my memory of some other similar engineered so Someone said elsewhere?

    Lupe Ciriello wrote on November 7th, 2010
  13. Jeanmarie (or anyone actually) can you pls give examples of foods rich in vitamin a, based on the post two posts above me^

    bb wrote on November 20th, 2010
  14. 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.

    Jeanmarie wrote on November 20th, 2010
  15. Oi Mark,

    I’m always interested in what other countries are saying about when’s best to take vitamin D.

    According to this recent report in a leading Brazilian newspaper, the best time to get sunlight is beFORE 10am. Could they have reason? Are they wrong?



    Colin wrote on March 16th, 2011
    • 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.

      Jeanmarie wrote on March 20th, 2011
      • 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….

        Mark Sisson wrote on March 20th, 2011

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