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

Dear Mark: Wheat and Asthma, Minimalist Winter Shoes, High-Fat Rat Cognition Study, and Sun Exposure Timing

Today’s edition of “Dear Mark” runs the gamut. The topics will be somewhat familiar, since I tackle wheat, minimalist shoes, high-fat diets in the news, and vitamin D, but with interesting spins on each. First, I discuss the link between wheat and asthma. Next, I do a somewhat exhaustive search of the available winter minimalist shoe options, a topic that I’ve never had cause to explore for myself. Since I do this for you guys, though, I tried to help out. After that, it’s my quick but (in my mind) pretty conclusive take on the latest article to pin cognitive decline on a high-fat diet for a reader who’s dealing with a similar condition herself (or himself; the gender of the name “Jo” is somewhat ambiguous). And finally, I discuss whether or not there’s a best time of day to obtain vitamin D from the sun.

Let’s get going:


I love the website and your books. I have been eating paleo for the past 4 months and notice a huge difference in my athletic performance and general out look on life. I have suffered from asthma my entire life. After eating a sandwich made with french bread (refined wheat) or a plate of pasta (which is rarely now), I find my breathing slightly labored even while sitting. Is there any research supporting the removal of gluten and wheat help asthmatics?

I would love to know you thoughts…


I think so, yes. Something called baker’s asthma, which has been identified since at least the 1700s and is exactly as it sounds, is linked to the ingestion (this time via the clouds of airborne flour to which bakers are constantly exposed) of gliadins, the protein subfractions that make up gluten.

There’s also a related condition called wheat-dependent exercise-induced anaphylaxis where wheat-related proteins make it through the intestinal wall into the blood and cause an immune response that manifests as an asthma attack. It’s “exercise-induced” because exercise seems to speed up the rate at which the wheat gliadins make it into the blood, but even those at rest had evidence of an immune response to the gliadins.

There’s also evidence of plain-old wheat-induced asthma – no exercise necessary.

I’d say you’re on to something, Drew. You can keep experimenting if you like, but I’d suggest just staying away from the stuff myself! Good luck!

Hey Mark. I’m very addicted to my Vibrams, and with this nor’easter coming through I had to go back to my winter boots, and while they do keep me dry and warm, I’m hating it!

Tried looking through the site but didn’t find anything as far as some type of minimalist shoe for winter? Any recommendations?

Wish Vibrams made a winter type shoe. I see they used to make one that kind of looks like it would be helpful, but they don’t sell it anymore.



I share your addiction. For folks who actually have real seasons with a real winter, the minimalist winter shoe is something of a white whale – an enigma hovering just out of reach, a product that you know should exist but that you can never actually pin down. I’ve never really looked into it for my own feet, since they rarely see cold weather, but let’s see what’s out there, yeah?

First, a quick glance at the minimalist wintery offerings from the well-known companies out there:


Men – Nothing meant for winter that I could see.

Women – Barefoot Life Frost Glove: waterproof, insulated, Vibram sole.

Vivo Barefoot

Men – The Off Road Hi and Off Road Mid look to be decently protective options.

Women – They’ve got an entire winter boot collection for women, albeit a fairly small one.


Unisex – Adult Phoenix Boot: sheepskin lining, 5 mm Vibram sole, lighter and more flexible sole as of 2012, roomy toebox (very important, in my experience, for true barefoot feel), naturally water-resistant.

Now, how about the shoe options that might not be officially minimalist but are close enough?

Russel Moccasin now makes a full lineup of minimalist moccasins, some of which are winter proof. They’ve been around for decades, so they should be pretty high quality.

Otz Shoes has a Troop Boot. It’s not billed or promoted as minimalist, but as this review from Birthday Shoes suggests, it can certainly be modified to become an effective, minimalist winter boot. They’ve got ’em in women’s, too.

There’s an actual minimalist army boot out, as well – the Belleville Minimalist Training Boot. Read the review.

O’neill (yes, the surfwear company) makes a neoprene reef boot. Since it’s designed for water sports, it’s fairly water-resistant, and since it’s designed for cold ocean water, it’ll keep you warm. It’s also got good grip and the price is fantastic.

If you have a favorite barefoot shoe that isn’t quite protective or warm enough, you can always throw some overboots over your boots (or shoes). They work on hiking boots and shoes equally. Here’s another link. If you really want to stick with the FiveFingers and somehow stay warm, you could always wear them with some outdoor toe socks from Injinji.

That should do it. I hope you find something amidst all those links that works for you.

Hi Mark,

I’m an international fan — I live in Korea and have been reading your blog since February 2012. I first saw Dr. Terry Wahls’ TED talk “Minding Your Mitochondria” online, then went on vacation to Vietnam, where another tourist from Romania shared your website with me. So you have quite the far-reaching influence, and I now regularly quote you to friends from Korea, Canada, the US, and France, proselytizing as many as I can! 😉 I even try to raise primal-related questions among my students at Seoul National University, where I teach English for Academic Purposes.

Anyway, I also happen to have been diagnosed with MS (technically Clinically Isolated Syndrome), but to make a long story short, although I recovered nearly fully from my first severe attack before going primal (basically by unwittingly doing everything in the primal lifestyle except the diet bit), I have felt even better since going grain- and refined sugar-free, and my most recent MRI even indicates likely re-myelination of the lesions in my brain.

So naturally, when I saw this article on the NY Times today – Can Exercise Protect the Brain from Fatty Foods? – I was skeptical, given that I have been eating a high-fat diet and have simultaneously (if not causally) seen “improvements” in my brain. I wondered what actual foods, in both the high-fat diet and the “conventional” one, they were feeding their lab rats, and if there is a chance that a high fat diet could, in fact, damage the brain. My personal guess is that it really depends on the type of fat…I would love it if you could share your take on this study.

Thanks for all the work you do,


Browse the comment section of that NY Times article and you’ll find that one commenter (Edward Barton) contacted the study’s lead author and found out that the fat in the diet “consisted exclusively of commercially produced (soy and corn derived) lard and soy oil.” As we now know, the lard used in refined lab diets is far higher in omega-6 than previously thought due to the modern pig’s usual diet, which consists of mostly corn and soy products. If you look at the USDA nutritional database, lard is pretty high in monounsaturated and saturated fats and low in polyunsaturated, but the actual lard used in lab diets contains twice as much PUFA.

Does this matter? I think it might. Previous studies have shown that among polyunsatuturated fats, only DHA, EPA, and arachidonic acid increase membrane fluidity in the brain while linoleic acid failed to increase it, a significant finding for two reasons. First, patients with Alzheimer’s disease tend to have far less membrane fluidity than control patients, and a fluid brain is required for optimal cognition. Second, the added PUFA in the industrial lard is almost entirely linoleic acid (not arachidonic acid), which the pigs obtain from the soy and corn in their diets and incorporate directly into their adipose tissue. If these rats were on a high linoleic acid diet – which they undoubtedly were – we would expect membrane fluidity and cognition to be impaired. No real surprise there.

Besides, you’re not a rat, you’re not eating rancid refined lard and soybean oil high in omega-6 fats, and you’ve actually made progress against your condition. I wouldn’t worry. It’s not like your brain’s apparent re-myelination is merely a feint in the right direction before it begins backtracking toward progression of the disease. Even if the mice were on a rodent version of a Primal eating plan, I wouldn’t worry purely on the strength of your own response to the diet and lifestyle changes. Heck, even if you were a rat that had somehow gained the ability to send emails and compose thoughtful, cogent prose, I’d say you should stick with what is obviously working for you even if the high-fat lab diet wasn’t working for your fellow rodents. The proof is in the pudding, especially if the pudding is in your bowl.

Mark, I have read your book. What time of the day is best for the skin to create vitamin D from the sun?


Great question. The skin will make vitamin D from UVB exposure at whatever time of the day it receives it, so the real key is figuring out when UVB is out and about. That depends on where you are and what time of the year it is, of course, but for the most part, UVB peaks at solar noon, or whenever the sun is highest in the sky. If you’ve got a short shadow and the UV index is high enough, you’re probably making vitamin D.

However, there are other things to consider. Now, you may have gotten the impression that the sun is wholly our friend, that it can do no wrong, that skin cancer from too much sun is a myth. It’s not. The sun can damage our skin and, if enough accrues, it can cause cancer. Significant evidence from animal models suggests that sunning ourselves at the wrong time of day can make us more susceptible to skin cancer (PDF). To protect our skin from UV rays, we manufacture an endogenous compound called xeroderma pigmentosum group A, or XPA. XPA plays an important role in the repair of sun damaged skin, and it follows a circadian schedule. In other words, XPA isn’t just produced when you need it. It peaks at certain times of day. In mice, XPA peaked at 4 PM and dropped off at 4 AM; exposing them to UV at 4 AM gave them cancer fives times more frequently than exposing them to UV at 4 PM. For humans, XPA peaks in the morning at around 7 AM.

So, you can make vitamin D whenever the sun is strong enough, but you might want to consider your XPA levels, too. The rodents’ levels peaked at 4 PM and dipped immediately after, but they were still significantly elevated at 9 PM and totally tanked by 1 AM. If our XPA trajectory is similar, we should enjoy the most protection between 7 AM and noon, with the former time obviously offering the most protection. It’s also conceivable that all this gets thrown out the window if your circadian rhythm is messed up for whatever reason. Something to keep in mind, at the very least.

Hat tip to Jamie Scott for his excellent take on the paper.

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. Had asthma. When it went away I was eating wheat and nothing came back. I guess it could cause a problem while you have asthma but I don’t remember wheat every doing that.

    Dailytribal wrote on November 19th, 2012
  2. The asthma part of this post could have been posted by me! I had moderate asthma that would get severe when I had a cold and took me to the ER. I had no idea dropping wheat would help my asthma so it was quite a surprise when I realized that I had not used my inhaler in a while – not at all – when I used to use it sometimes numerous times a day – a good day maybe 2-3 times. It was allergy induced, exercise in the cold induced, dust induced. But that has gone away. I ate some whole-grain Dreamfields noodles a couple of days ago and not long after was wheezing and coughing up phlegm. I now SO much think it is worth it to fix a second meal when my kids have noodles – they are teens so it is hard to totally remove their noodles, especially my older daughter who was raised on them until age 7 in China. My sinus allergies are also better – I used to never be able to breathe with my mouth closed but now I can all the time, though that is not totally gone. It is so unbelievable. I second reading Wheat Belly and How We Get Fat by Gary Taubes. Life changers for me!

    Jan J. wrote on November 20th, 2012
  3. Had asthma all my life but haven’t noticed an change in my breathing after eating wheat but I’ll take a bit more notice now

    Sam wrote on November 20th, 2012
  4. When I visited Russel Moccasian,they had a link to this vintage military handbook on the soldier’s foot and military shoes.It was very interesting with lots of info on the mechanics of your feet.

    Rollo wrote on November 20th, 2012
  5. A pair of 4mm Vibram 5F KomodoSports were put aside in favor of some 6mm Merrell Trail Gloves with ankle socks and a 5k 3mi run last week in a calm -16C +3.5F went fine. Thumb and index finger got cold in light wool gloves but that’s all. Key was 4 light top layers, 2 light bottom layers, and a good hat. Will use warmer gloves or light mitts next time. Running generates a LOT of heat.

    Terry wrote on November 20th, 2012
  6. Sanuk makes a fantastic minimalist shoe for winter (not completely weather/waterproof) but they are close:,default,sc.html

    G wrote on November 20th, 2012
  7. A couple times within the last several months Dr. Mercola has sent out some articles on Vitamin D production and sun exposure. He wrote that in order for the body to produce D, sun exposure has to be when the sun is at a 50 degree angle or greater (i.e. 55 degree angle is good, 45 degree not good enough).

    He listed a web link to the U.S. Naval Observatory Sun Moon Altitude/Azimuth Table. With this table you enter in your location and it will display the angle of the sun at any given date & time. For me, in central Florida, the sun does not reach this optimal angle from about mid-October through mid-February. I interpreted this info to mean that even if it is sunny and an 80 degree temp, during this period my body will not produce D even if I sunbathe. Of course, Mercola did say the sun has other benefits so we should still get out there.

    Mercola also wrote in this article that there is an app that will provide this same sun angle info. Sorry I didn’t provide links but didn’t want my comment to get held up.

    Ellen wrote on November 20th, 2012
  8. I live in upstate NY and my solution has been Softstar RunAmoc with a trail sole for winter running. No cold toes, like with my 5 Fingers. I use their Dash shoe with a steet sole as my daily shoe at the office. Great barefoot feel and fine to be outside for short time. It’s not often that the snow is so deep I can’t get away with one of those options.

    John wrote on November 20th, 2012
  9. Malignant melanomas are created by UVA radiation, UVB is actually thought to be protective (as is vitamin D which is manufactured by UVB skin exposure). UVA is also fairly hard to block, where glass can filter out UVB. In fact until very recently nearly all sun screen formulas only blocked UVB rays, meaning that they only made the situation worse and more than likely lead to more skin cancers.

    So what is the answer? Make sure you get as high a percentage of UVB to UVA rays as possible, this means mid-day A low PUFA diet and astaxanthin both work to protect your skin from the harmful effect of UVA radiation. UVB will give you a nice surface level tan that will further block UVA rays.

    Until I discovered this about 18 months I could hardly walk from my car to a building without getting burned. I use to get terrible sun burns as a child and any time I didn’t cover up and wear sunscreen. Now I can lay out for hours in the midday sun with no sunscreen! The same applies for several other people I know, including my wife. Its truly amazing.

    From what we’ve always been told, if we don’t burn our cells aren’t being damaged.

    Astaxanthin is what gives shrimp, krill, salmon, etc. their red color and protects them from UV rays. Its thought that many insects also contain astaxanthin or similar substances. Our ancestors ate a lot of insects, crayfish, and sea food (when available). They also didn’t hide from the mid-day sun.

    If you’re already on a Paleo diet I encourage you to add astaxanthin (start taking 4mg all the time and 8-10mg in the summer) and enjoy some midday sun, our ancestors did! Just don’t burn (you’ll almost have to try to burn).

    MN_John wrote on November 20th, 2012
  10. I bought my first pair of Arrow Moccasins
    3 years ago. Now I’m ordering a second wool lined pair and having my first pair resoled. Great father son company here in the US of A.

    David (SkySpyder) wrote on November 20th, 2012
  11. I’ve had success using neoprene over injinji and heavy wool socks in my minimalist shoes. It can keep your feet dry and it keeps them relatively warm unless fully submerged. You also need to have slightly larger shoes to accomodate the bulky socks.

    Andrew Hostetler wrote on November 20th, 2012
  12. Russell Moccasins are not “pretty high quality.” They are handmade in the USA of the highest quality leathers, and are re-solable. A pair properly fitted will last a lifetime. Look at their ph line, with a soft sole – they are used for “stalking” in the woods, but were, really, minimalist way before vibram did the five fingers.

    James wrote on November 20th, 2012
  13. Oh yay, a post about wheat and asthma!
    I used to cough and clear my throat ALL THE TIME and was prescribed asthma medication for it, which reduced it to some extent…
    Well now whenever I eat wheat or gluten (not entirely sure which), that cough comes back.
    I asked my doctor if it’s even a thing… and she said it’s a rare thing, but a thing nonetheless. xD

    Audrey wrote on November 21st, 2012
  14. If you live in a climate that never requires thinking about minimalist shoes for winter its because you live where there is no winter (or hardly any). And your feet, ankles, knees, etc, are better off for it. Unless you do something about the fact that bulky boots are neseccary in very cold snowy winter areas. Like using a sauna daily to warm the lower legs (as well as the rest of the body) and then targeting the lower leg and feet area specifically with stretching (passive, active, and ballistic – in that order) and a limited amount of jumping – this makes a huge difference. People in these winter climates immobilize their ankles for a good portion of the year and those who do go out and exercise do not have the ligaments, tendons, muscles, and joint capsules warm enough. The result can often be inflexibility, improper movement patterns, and injury. Winter sports such as hockey and skiing, which use other leg muscles and immobilize the ankles, make the situation worse, because of created imbalances. In northerly climates mobility issues with age are more common and more extreme, but it does not have to be that way. Living in the north, experiencing the 4 seasons, and being in an area where it will be easier to be self-sufficient compared to the south (as things get worse) has advantages. The cold weather will keep the dependent masses at bay once financial collapse hits. In the warm south all year, night and day, they can camp out anywhere, ready to attack.

    David Marino wrote on November 21st, 2012
  15. Finding minimalist shoes a bit over-priced??? You could try making your own – a moccasin type shoe where you stitch an upper to a homemade sole and glue a Vibram sole to the bottom to protect the stitches. Stitch the upper to two sole-shaped pieces of leather (upholstery or chap leather) with a 1/8″ layer of EVA foam sandwiched in between and then glue that to 5mm or 8mm Vibram Newflex. That gives a flexible sole with a little cushioning and a midsole that won’t come unglued from the Newflex. Some good ideas here:

    David Marino wrote on November 21st, 2012
  16. I was on asthma medication for 25 years and when I took gluten out of my diet I am off all asthma related medication. On a rare occasion I will order online Einkorn wheat for my pizza fix and make my own pizza dough and have no ill effects with this type of wheat. But it is not something I eat on a regular basis more like once every 3-4 months. There is definitely a difference between modern wheat and ancient Einkorn. I am in the medical field and it drives me crazy that nutrition, diet and exercise are rarely discussed and when they do talk about it it’s always that low fat eat your grains crap!!!

    Lucy wrote on November 23rd, 2012
  17. do not forget VIVO barefoot, they now have a boot as well.

    cavejim42 wrote on November 27th, 2012
  18. I just got turned on to Vibrams and got my first pair at the site shown. I love these ugly shoes!

    j wrote on November 29th, 2012
  19. I didn’t even know about this baker’s asthma. I hate the fact that Gulten is in everything. It serves no point. This was a great post very insight full.

    Womens Fitness Program wrote on November 30th, 2012
  20. came across these PERFORMANCE SOCKS that could possibly be worn with the Vibram’s: #GA1262J Injinji Mini-Crew Performance Toesocks

    Merry wrote on December 15th, 2012
  21. I think we can hack Grok into thinking it’s getting Vitamin D on schedule by eating sardines or other fish including bones for breakfast.

    Animanarchy wrote on December 18th, 2012
  22. It wouldn’t surprise me about the link between wheat and asthma, although I think that everyone with asthma will get different symptoms from different triggers. My asthma behaves like this – noticeable laboured breathing – when I have been drinking squash.

    Sarah wrote on October 3rd, 2013

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