While we’re on the subject of folate, let’s look at a few other little known facts about this nutrient and the dance it does with vitamin D in the sunshine.
Sunlight, more specifically the ultraviolet B (UVB) wavelength of sunlight, when absorbed by the skin destroys folate. The same UVB, when absorbed by the skin, stimulates the production of vitamin D. Since we need both folate and vitamin D, natural selection was presented with a real problem in dealing with both.
In Africa – from where we presumably all came – the intense equatorial sun acting through the forces of natural selection produced a race of dark skinned people. The dark skin allowed enough absorption of UVB to produce plenty of vitamin D, but prevented the absorption of enough to destroy the folate. As people migrated out of Africa into cooler, less sun-exposure intense areas, skin color got lighter allowing more absorption of UVB to produce vitamin D. UVB exposure in these areas – Northern Europe, for example – was not enough to destroy folate because the UVB rays weren’t direct as they are at the equator.
Light-skinned people who get a ton of sun exposure can destroy enough folate to cause problems, but are protected because the UVB rays burn them, driving them from the sun. Those who get progressive sun exposure develop a tan that performs the same function as the naturally dark skin of people living in high UVB exposure areas.
You can pretty much tell how much sun exposure any group of people have been exposed to over the past several thousand years by how dark their skin is. Mediterranean people, for example, are light enough to allow enough UVB absorption to make plenty of vitamin D, but dark enough to prevent enough absorption to destroy their folate. One group of people, however, are an exception to this rule: the Inuit of northern Canada. These people are pretty dark skinned, yet they live in an area with very little strong UVB exposure. But they live on a diet that is predominantly fatty fish. Fatty fish are one of the few foods containing enormous amounts of vitamin D. So, the Inuit get their vitamin D in their diets and didn’t have to evolve light skin.
Another interesting aspect to all this is how it impacts cholesterol levels. Vitamin D is made in the skin from cholesterol. People who live in areas where there isn’t much sun exposure tend to run higher cholesterol levels to trap as much of the tiny UVB exposure as they can. For this reason, if you check your cholesterol levels, they will almost always be higher in winter than in the summer.
Vitamin D is an extremely important vitamin involved in bone building, heart protection, clotting, fighting infection, warding off cancer, enhancing cognition, preventing mental illness and a host of other functions. Most of us are deficient in this vitamin because we live in northern areas, spend a lot of time indoors, and, because of the faulty advice from dermatologists, slather on sunscreen when spending much time outdoors. Sunscreens block UVB and totally prevent the formation of vitamin D. We can somewhat compensate by developing higher levels of cholesterol to trap what little UVB we get and convert it to vitamin D, but now whenever we run our cholesterol levels up a little, we are put on statin drugs to get it down.
One other factoid is that the main protein in the blood, albumin, prevents much of the UVB-induced destruction of folate. Albumin is made in the liver, and levels of it are a marker of liver function. When your liver is compromised, you don’t make as much albumin. If you go on a low-protein diet, you don’t make as much albumin.
Given all these disparate, but related, facts, what is the take home lesson?
There are several.
First, if you are a pregnant woman, be careful of too much sun exposure. If you do get a fair amount of sun exposure, make sure you take plenty of folic acid.
Second, if you don’t get much sun exposure, take a vitamin D supplement. The best are vitamin D3. Don’t take anything but vitamin D3. (I’m planning a major post on vitamin D in the near future, so you’ll know everything you need to know about this incredibly important vitamin.) Take at least 1000 units per day. In the winter, 5000 units per day isn’t too much.
Third, if you choose to take a statin, make sure you take vitamin D. If you’re worried that your cholesterol is a little high, get some good sun exposure or take vitamin D3.
Forth, eat plenty of protein so that you will make enough albumin. This albumin will protect your folate from the ravages of the sunshine that you bask in to increase your vitamin D.
Last, if your worried about your folate levels, take the newer kind of folic acid called methylfolate, which is available from most health food stores and natural food grocers. Read my previous post to learn about this supplement.


  1. Wow Dr E, that was lucid enough for a vegan. Thank you so much for all your efforts to understand and describe this information for us laypersons.
    May I ask that you consider the question of Vitamin D and cod liver oil? Specifically, the alleged checks and balances interaction between vitamins A and D that are found in that oil. Our Vitamin D winter seems to last all year here in Alaska, so I am very interested in this question.
    Thanks so much
    Hi Marilyn–
    Thanks for the kind words.  I’ll address the vitamin D question when I put up my big post on Vit D, which I hope will also be lucid enough for even a vegan to understand.

  2. Doc, you mention “One group of people, however, are an exception to this rule: the Innuit of northern Canada. These people are pretty dark skinned, yet they live in an area with very little strong UVB exposure. But they live on a diet that is predominantly fatty fish. Fatty fish are one of the few foods containing enormous amounts of vitamin D. So, the Innuit get their vitamin D in their diets and didn’t have to evolve light skin”
    Being that I am Canadian and having served with the military in the far north I am intimately familiar with this environment. I think a variable in that scientific argument as per the palour of Inuit skin may have been forgotten or ignored. It’s called wind, very, very, very cold – high speed wind. We have a similar effect on the prairies. Often I have been subjected to exercises in the dead of winter where I’ve returned a few days later with a full tan. Frankly a better tan than anything I normally get during those hot prairie summers.
    Survival in that environment requires that one must layer their clothing. As your work level increases the layers come off. As it decreases the layers go on. I’ve been in as cold as -27C/-16F with nothing more than a T-Shirt, one layer of pants, some boots and a toque on my head. Had I been wearing more the effort of carrying 80lbs on my person and helping to pull a 300lbs sled through 3 feet of snow for 10+km would have caused the considerable amount of sweat I was producing to freeze to the inside of my clothing which upon stopping would have most probably given me hypothermia.
    Welcome to Northern Canada in the dead of Winter!
    My point is that by removing layers I reduce the protection received from the wind. I always got great wind burns across my body from these activities. Indiscernible from a sun burn though this all occurred at night! We as soldiers have been wise enough to learn all of this survival skill from the Inuit who in fact teach and run our Advanced Winter Warfair Courses. Interesting stuff, at least to me!
    Let me go on a tangent here and point out one other observation. As you travel north from the equator exposure to UVB drops which results in less Vitamin D from the Sun. But here’s the kicker our environment supplies it to us via alternative means, primarily fish and animal organ meats. We Canadians have little sun exposure 8 months out of the year. Yet we have North Atlantic Cod, Bison, Moose, and venison with high levels of Vitamin D in their livers and little consumption of any of it these days. Hmmm no wonder we’re getting fatter and fatter and rates of skin cancer are going up and up. Perhaps if we lived off of and farmed what our environment provided us we would be healthier?
    Hi Pierre–
    Thanks for the interesting comment. I, too, have experienced wind burn, which, for all the world, is indistinguishable from sunburn. I’ve gotten windburned skiing at night under lights, so I know there was no sun involved. I doubt that skin pigment would afford much protection against windburn, so I don’t know if the dark skin of the Inuit help. Maybe you can let us know.
    You are correct that Canadians have a bounty of foods rich in vitamin D, but because they don’t consume them, they don’t benefit. Breast, colon, and prostate cancer and even melanoma are found at higher rates in the northern latitudes giving rise to the (I believe correct) notion that these cancers can be largely prevented by adequate vitamin D.

  3. Wow, this has to be the most interesting stuff I’ve read in months. And you had placed the bar pretty high already, doc!
    Thanks very much.

  4. Although folate is degraded by sunlight (UVR)”in vitro” (i.e., “in the glass”) it is not degraded “in vivo” (i.e., “in the body”).
    Therefore, getting enough sensible, moderate and responsible UVR exposure to stimulate an optimal level of UVR will not cause a reduction in folate.
    However, several recent studies have shown that folate levels are dropping and so women of child bearing age should make sure that they take a supplement containing folic acid.
    Hi Donosaur–
    I guess it depends on which papers one reads. There are papers showing that folate is degraded by UVL in vitro, but there are also papers showing that pregnant women who had a lot of sun exposure gave birth to a greater number of babies with NTDs, which would imply that their sun exposure reduced their folate levels. These studies, along with the in vitro studies showing UVL degrades folate are enough for me to recommend that pregnant women increase their folate intake if they plan on spending a lot of time in the sun.

  5. Wow, I disappeared for a few days and bam, a plethora of information is planted on your blog. Such a wealth of information. I learn more about low carbing with each year that I am doing this. I will have to come back for more comments. I need to get off the ‘puter and clean the living room. But, my mom was just diagnosed with low Vitamin D. Alas, a diabetic, her teeth are falling out. As a matter of fact the skeleton with the missing teeth reminded me of her. I will be back after my living room is clean.
    Loved the Pizza Party Show,
    Hi Mary–
    Stick your mom on some vitamin D3.

  6. Sir…..any idea about why we go grey ?
    Have noticed anecdotally people who use high grade EPA darken their hair so any ideas about why folks go grey ?
    Heard a very interetsing thing on the radio years back by a vet but buggered if can remember who it was and its thrust.
    Hi Simon–
    I don’t really know what makes us go gray.  I’m sure there are papers out there on why, but I haven’t read them.  I’ve heard anecdotally that people who take a fair amount of fish oil sometimes find themselves with less gray hair and more dark hair.  I’m going to take a shot in the dark as to why this may be so (If, in fact, it really is so.  I, myself, have no direct evidence.).  The only supplement that I’ve ever heard of that supposedly converts gray hair back to normal is copper.  (I’ve had one patient who swears by this, and I have no reason to doubt him.  He has light brown hair that he told me was almost totally gray until he started taking copper supplements.  He is a guy who works in the entertainment biz and thinks he needs to look perennially youthful to maintain his position.  He has copped to a face lift, an eyelid job, and a host of other cosmetic procedures, so I would think he would confess to dyeing his hair if that’s truly how he keeps in non-gray.  But he swears it’s the copper supplementation.)  Much fish oil comes from fish livers.  Fish livers contain a lot of copper.  So, if the fish oil does contains a lot of copper, and if copper does reverse the gray, then maybe that’s the answer.

  7. Sir please read the end Jan New Scientist i mentioned ref eating enormo cals.
    Afore it there’s a super duper article on how birth month, via lack of vit d/sunlight amongst other seems to switch on or off gene expression vis a whole slew of psychiatric disorders. Wonderful stuff.
    Yr take on it would be i assume as always,well hopefully pun slightly intended, enlightened
    Hi Simon–
    I read both articles when I got my issue of TNS in the mail, but neither of them really tripped my trigger as they obviously did yours.  Thy sunlight one was interesting, but didn’t really provide any useful info.  Everything was “unknown” at this time, i.e. whether what held for rodents would hold for humans.  The article was intriguing, but not particularly ‘enlightening’ to me.  Other than confirming my opinion that most people in the northern latitudes get inadequate vitamin D, I didn’t get a whole lot out of it.
    The piece on the increased calorie consumption was – to me, at least – a little more interesting.  It shows what anyone with good sense already knows: that some people can eat more than others and not have as many apparent negative effects.  It would be interesting to see what the outcome of this experiment were had it lasted a year or two instead of only a month.  The most interesting aspect of the experiment to me was in this paragraph:

    Then there is cholesterol. Over recent years it has become clear that it is very difficult to substantially change your cholesterol levels by changing your diet. Nyström’s [the director of the study] findings push that notion to the limit. Not only did many of his subjects show very little change in the amounts of cholesterol and other fatty biomolecules circulating in their bloodstream, some of them even had less low-density lipoprotein – “bad cholesterol” – and an increase in the “good” form, high-density lipoprotein. It’s not clear why a junk-food diet should improve your blood lipids, but it may be down to the precise composition of the diet. With receipts for all the food his volunteers bought, Nyström has the means to find out whether there is any correlation between certain foods and blood fat levels.

    Even a month of pigging out on a horrendous diet doesn’t seem to have much effect on cholesterol levels in a number of people.  I wonder what effect it had in the others?  I’ll be interested to see when the full study is published what specific foods – if any – have any effect.

  8. Now that I am back and had time to reread this article, I have a question. I am fortunate enough to have the darker African skin. My question is are you encouraging tanning to protect vitamin D absorption? As I told you about my mom, she is diabetic and on statins. Shen now has vitamin D deficiency. I asked her what was her cholesterol total. She had no idea nor did she feel it necessary to find out. She is 81 and in total control of her mental facilities. As a matter of fact she is a certified medical assistant. We certified together.But whatever her doctor says she follows without questioning his prognosis/diagnosis. I can see clearly that her diet and medical treatment is causing more problems than her actual disease.Being at her age she feels comfortable with the care she is given. And she probably is right but I would really like to see her using the brain that she developed in the medical assisting classes.
    Mary T.
    Hi Mary–
    No, tanning reduces the amount of vitamin D absorbed as does naturally dark skin.  You should encourage your mother to take a vitamin D supplement (make sure it’s vitamin D3).  I take from 5,000-10,000 IU daily during the winter months when I get little to no decent sun exposure.

  9. Ok, I’m a pale-skinned brunette who burns at the drop of a hat. I grew up in the AZ desert and spent my summers burnt to a crisp (ask me what the smell of summer is to me and I’ll say “Solarcaine” as I was always slathered with the stuff.) According to conventional wisdom, I’m at a high risk for melanoma so I get very little sun exposure these days per my doctor’s advice. I take cod liver oil occasionally. Now I don’t know what to think. I’m looking forward to your forth-coming post on vitamin D so that I can get all of this sorted out.
    P.S. Being fair-skinned wouldn’t have been so bad if it weren’t for the fact that both my siblings easily tanned as dark as they wanted and would sing “I’m a little moonbeam” every time I wore shorts.
    Hi Esther–
    You can get plenty of vitamin D from the sun without burning if you do it with graduated exposure.  Just a few minutes of full-body sun (what you would get in a two-piece bathing suit) in the summer will do it.   And you shouldn’t burn. It probably won’t be enough during the winter unless your in a southern clime such as Arizona.  But you can get plenty of vitamin D in supplement form now with the vitamin D3 supplements.  I take 5,000 to 10,000 IU per day, which is a perfectly safe range.
    I’ll get the post on vit D finished and up soon.


  10. Dr. Mike,
    Another great post. All the research on vit D that has come out over the past few years is very exciting. I look forward to your posting on vitamin D itself. Have you ever visited the Vitamin D Council( They have some great research there. What do you feel about testing blood levels of 25 hydroxy cholecal? I’m sure you would advocate it but do we need to be very diligent when doing 5000-10000 iu’s? I have a couple of ms people whom I want to check. Life Extension has the test for $47 which seems much cheaper than most. Sorry for all the ?’s. The only other person I have met who has been widely published and well known who has taken the time to talk to the little people is Jeffrey Bland, Ph.D. I approached him at one of the Functional Medicine symposium about 5 yrs ago and interestingly the subject was folic acid. (I found it fascinating how we learned certain nutrients could turn genes on/off, FA being one.) He talked to me like we were old college pals and I really appreciated that. Success and humility are a wonderful combination. I can now add you to that list.
    Hi Robert–
    I think blood levels are a good thing to check, but it doesn’t hurt to take vitamin D3 without them as long as the doses aren’t huge.  5000-10,000 are well tolerated and won’t cause problems.  Yes, I have visited the Vitamin D Council site–it’s a great site.  The medical literature is stacking up on the benefits of vitamin D, and the Vit D Council tries to keep up with it, but the mass is just growing too fast.

  11. Old post, but I have a question about Vit D levels. Recently I had my blood level checked (1,25 Dihydroxy, serum) and it was 33 (lab reference was 22-67). I had been taking 3000iu Vitamin D3 (oil prep, Carlson’s)every day for at least 2-3 months prior to the testing. I am also out in the sun for at least 10-15 min a day, not including driving, etc (I’m in NC).
    I increased my D to 4000iu/day, think that’s enough? Since it’s “within normal limits” my doc wont’ repeat it until my next check in 6 months.
    Hi Cindy–
    The lab test you had (1,25 dihydroxy vitamin D) is not the best test to determine vitamin D levels.  You should get a 25-hydroxy-vitamin D levels, which is more stable and a much better representation of actual vitamin D levels.
    I take 5000 IU/day of vitamin D unless I’m out in the sun.  A recent article in the American Journal of Clinical Nutrition indicated that people could safely take at least 10,000 IU per day, so I don’t worry about 5000 IU.
    Vitamin D has been an unheralded vitamin until just recently.  It needs not be ignored if one desires good health.

  12. Dr. Mike,
    (old post, but very interesting topic).
    I have question about sun exposure. During the winter months, I get almost no sun exposure (I live in New York). I am wondering about your opinion on indoor tanning. Is it an acceptable alternative to normal sunlight during the summer months, as far as stimulating production of Vitamin D?
    Is it in any way more dangerous than sun? I would think not, since the sessions are carefully timed, and during the max recommanded session at a place I have been to a few times (9 minutes) I get just a slight tan. – probably equivalent of spending 15 to 30 minutes outdoors.
    Hi Joe–
    The information I’m giving you is based on what I know about tanning beds from ten years ago. I suspect they are the same today, but I don’t know for sure. You might want to check it out yourself.
    There are two main wavelengths of sunlight: UVA and UVB. UVB is the wavelength that burns and that causes vitamin D production. UVA is the wavelength that causes tanning and the wavelength that causes melanoma, a pretty virulent cancer. The old tanning beds had lights that radiated UVA. Since UVA doesn’t stimulate the production of vitamin D, tanning beds that radiate only UVA won’t help with vitamin D deficiency. The best way to get vitamin D is to take it as a supplement in the form of vitamin D3, which is available everywhere now. I would take at least 5,000 IU per day if I lived in an area that got little sun in the winter.

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