Can Vitamin D Replace Sunlight? A Stunning Discovery

Primal Girl is a stay-at-home mom. I met her at the Ancestral Health Symposium. Her sleep was bad. I made recommendations. One of them was to get an hour of sunlight soon after you wake up. She can’t do that — too busy being a mom. So she decided to take Vitamin D early in the morning. After all, sunlight exposure produces Vitamin D. Here’s what happened:

One day as I was taking my supplements, I was thinking about how many units of Vitamin D your skin produces in 30 minutes of sun (20,000 I believe). I looked aghast at the 10,000 units of Vitamin D I was taking. It was 7 o’clock at night! I was essentially giving my body 15 minutes worth of bright sunlight energy. No wonder I was waking up in the middle of the night! I was telling my body that it wasn’t really time for bed, it was still the middle of the day. I wondered what would happen if I only took my Vitamin D first thing in the morning. It wouldn’t be an hour naked in the sun, but 15 minutes is better than nothing. That night I slept like shit. Worse than normal.

I usually took my supplements mid-afternoon. I vowed to take them first thing every morning. If I forgot, I would not take the Vitamin D at all that day. I tried it the next day and that night I slept like a rock. And the next night. And the next. Days I forgot and skipped the D3, I still slept great. That was the only change I made to my lifestyle and my sleep issues completely resolved. [emphasis added]

OMG! Double OMG! Like Primal Girl, I have never heard anything like this. Even I am stunned that such a simple safe easy change could have such a positive effect. (Taking Vitamin D at sunrise is a lot easier than standing on one leg four times!) I’ve read lots about circadian rhythms. Many studies showed that a drug would be much more powerful at certain times of day. Most of these studies were with rats. It never occurred to me that the time you take a vitamin could matter so much.

46 Responses to “Can Vitamin D Replace Sunlight? A Stunning Discovery”

  1. Matt Says:

    I had heard of this somewhere as well, and I too don’t take Vitamin D later in the day – if I forget my vitamins one morning/early afternoon then I skip the D that day. I’ve always tried to take my magnesium at bedtime.

  2. JG Says:

    Chrissake man, this is so embarrassing to read early in the am — this is a revelation? With a study of ONE person? My VAST experience with D3 (many more years than “Busy Primal Momz”, whatevs) does not support this theory. There…does that make you think twice about making broad generalizations?

    I cannot believe that this passes as science in your version of self-quantification. Where is the testing before jumping to conclusions?

    I know this is your blog and you’re free to publish what you want, but I’ve seen less and less self-editing from you and more pruning to fit the message…and everything you write seems to be framed as some MASSIVE REVELATION that required your genius and eye to solve it — further positioning yourself vs. the mainstream, etc.

    It’s clear to me that, while it’s cool to rail against mainstream researchers, you have not spent any time in the lab or actually talking with QS peers and bouncing these ideas off of them. This stuff — this STUNNING REVELATION — is old weak sauce. This is not so far removed from what actual doctors know. Seriously, this is medicine 101. It’s so obvious that I can’t believe this is a revelation to you.

    HEY, DO YOU THINK THERE WILL BE SOME EFFECT IF YOU TAKE MELATONIN IN THE MORNING…of course! Let’s see if you don’t fall asleep! Same with Magnesium Citrate — see how long you can go without feeling sleepy. I dare you to take Melatonin and Magnesium today with your yoghurt…and when you wake up eight hours later, perhaps you can write another post about another stunning timing revelation! TRIPLE OMG!

    D3 is TECHNICALLY a hormone…just like MELATONIN. OF COURSE timing is everything when it comes to HORMONES.

    I think you’re really stretching the scope of discoveries here. Please, kind sir, as an admirer of yours, I ask that you get yourself an editor. Or bounce these ideas off a REAL PRACTITIONER before you go declaring some discoveries as though you’re in Mendel’s company. TALK TO MORE PEOPLE. You are big and respected enough now to have to face the heat for half-digested posts.

  3. Seth Roberts Says:

    “this is a revelation?” To me, yes. “required my genius…to solve it”? My contribution to this was minimal. The notion that morning sunlight might help you sleep is pretty obvious. “This is not so far removed from what actual doctors know. . . . It’s so obvious.” I have never heard a sleep doctor (or any doctor except Nephropal) say this. Many things that are “obvious” are wrong.

    The Wikipedia entry for Vitamin D says nothing about time of day effects.

  4. john Says:

    Nephropal has mentioned this before.

  5. Seth Roberts Says:

    Thanks, Aaron & John. Gotta start reading Nephropal. However, there are important differences between what Nephropal said and what Paleogirl says. I will discuss this in tomorrow’s post.

  6. Tim Beneke Says:

    Fascinating. I’ve been recently trying to reset my circadian rhythms by getting more morning sunlight. I’ll add some morning Vitamin D to the mix and see what happens…. It sounds unlikely that it’s just “placebo” — the effect seems pretty striking…

  7. dearieme Says:

    If you breakfast on smoked salmon and scrambled eggs, or on kipper, would you get some of this effect?

  8. Seth Roberts Says:

    “If you breakfast on .. ” No, they have little or no Vitamin D.

  9. gwern Says:

    Hm, interesting. I always take my vitamin D with my other capped pills, which include caffeine and sulbutiamine so I never take them after 7 PM. I also never noticed any effects on my sleep when I got fresh supplies on vitamin D. (I probably don’t care enough to test this with my Zeo and see whether taking vitamin D right before bedtime makes a difference, though – bad sleep is nasty.)

  10. jpb Says:

    That is a amazing! I never thought about the effects of taking D3 at night. I have been doing that for a long time and it always takes me hours to fall asleep. I will try the new schedule today and see how things go tonight!

  11. Joseph Buchignani Says:

    You the man, Seth! And she’s the woman! THanks for the awesome tip.

    Never liked melatonin. This is much better.

    Call Tim Ferriss. He’ll give you a guest post or something. He NEEDS this.

  12. Chuck Currie Says:

    I always take my D3 5000 (along with 400 mg magnesium citrate) right before going to bed, but only if I don’t get a good dose of natural sun exposure during the day. I have no problems with sleep either way. I sleep at least 8 hours with maybe one bathroom break and wake naturally – no alarms.

    I’ve also found that I become drowsy and fall asleep earlier if have more carbs with dinner (potato/sweet potato/rice) or a small bowl of ice cream for dessert (usually an hour or two after dinner).

    I have also postponed my first meal of the day for about 3 to 4 hours after awakening. I have found that I awaken later than I did when I ate 1 hour after awakening. I only eat two meals a day – usually bacon & eggs with a little sweet potato/plantain/or berries for breakfast and meat and veggies for dinner. I also have two or three glasses of cold tea with heavy cream though out the day. Plus 1/4 stick of butter and two tbls of flax oil, some souerkraut and/or kombucha.

    Just for reference, I’m 65, male and have been practicing a paleo/primal life style for a year and a half.

    I know this is a long comment on D3, but I think context is important.

  13. Aaron Blaisdell Says:

    Like John, I also read about this on Neohropal blog. That’s why for the past couple of years I have been taking it in the morning with my coffee.

  14. Greg Biggers Says:

    This is a provocative and probably helpful observation! I would love to see some people turn it into a group study over at Genomera. We (or Seth, for that matter) can help you with study design if you wish.

  15. Rachael Says:

    Other supplements that will keep you up if you take them at bed time are B vitamins, and calcium. Magnesium at bed time will help you sleep. I suspect everyone has varying levels reaction to supplements, perhaps if one is replete in vit D one responds to it less?

  16. Jazi yechezkel zilber Says:

    This book discusses the effects of time of time on ANYTHING! Drugs sex all you can dream of

    I gained a lot from it. Because, I learned that what matters is not the exact time you wake up, but the rythm. So I started sleeping late and waking late an exact timing, which wass good.

  17. Seth Roberts Says:

    Jazi, you have convinced me I should have titled the post Can Vitamin D Replace Sunlight? A Stunning Discovery.

  18. Jazi yechezkel zilber Says:

    Btw, in another book of the author

    See the chapter rythms and depression, where she says – like you – that rythm disruption and depression are ddeeply linked

  19. Jim Purdy Says:

    Seth, I hope you’ll forgive me for asking a very off-topic question, but at least it’s about self-experimentation, sort of.

    I am a binge eater with type 2 diabetes, but I refuse to take any medications of any kind, not even over the counter stuff like aspirin or vitamins. (My doctors call me everything from “non-compliant” to “crazy and suicidal.”) And I really struggle to get my blood sugar readings out of the stratosphere. However, something happened today that really surprised me.

    This morning, my blood sugar was very high (I don’t want to admit how high, but it was high). And then I went on a binge, eating 30 (yeah, 30!) fast food chicken wings deep-fried in peanut oil. I checked my blood sugar several times over the next 9 hours, and my blood sugar plummeted rapidly, just as if I had taken a huge dose of insulin.

    Does that make any sense to you? Could chicken wings — and/or peanut oil — help control diabetes? I’m thinking about buying a bunch of plain chicken wings and microwaving them, without any oil or other ingredients.

    A chicken-wing binge diet for diabetes? Will I die tomorrow?

  20. Seth Roberts Says:

    Jim, I’m afraid I have no insight about your plummeted blood sugar. I suggest seeing if you can repeat the original observation before trying to figure out what caused it. If you manage to figure anything out about the cause, please let me know.

  21. Jim Purdy Says:

    oops … I think I mis-typed my email address in a comment a moment ago. The correct address is

  22. Jim Purdy Says:

    Seth, I will repeat my chicken-and-peanut-oil binges … I mean experiment … in the name of good science. But at least one of my lacto-vegetarian sons reads your blog, so I may get a severe scolding from them (and my doctors) about my super-binges. I hope you appreciate my big sacrifice here for science.

    Of course, I am familiar with the Atkins Diet, and how it should have a minimal effect on blood sugar. However, my blood sugar numbers yesterday seemed to go far beyond any Atkins Diet effect that I would have expected. The numbers, seem amazing to me, considering that I take no medications.

    About 1145 am yesterday, I ate the first batch of 15 chicken wings, deep-fried in peanut oil. I didn’t record the other times that I ate chicken wings, but I did eat a second batch of 15 several hours later, and a third batch of 15 another few hours later. I don’t know if it’s relevant, but I had a can of Diet Coke with each batch of 15 wings.

    Yesterday, 1010 am (before any chicken wings): 347 blood sugar
    1225 pm (after 15 wings): 263
    350 pm: 213
    650 pm 210
    1005 pm: 164 (down 200 in 12 hours. despite 45 deep-fried chicken wings, and no meds)
    Today, 130 am: 245 (the wing effect fading?)
    Today, 325 am: 261. Then I drank 8 ounces of apple juice.
    Today, 720 am: 256

    I’ve never seen changes of this magnitude before without medications. I will do this again, keeping more detailed records … unless I die of a heart attack first. To do it right, I should eat the same wings deep-fried in peanut oil, but I think I’ll just microwave them, with no oil or anything else. Maybe it’s the peanut oil and not the chicken?

    I hope my cardiologists never see this. My doctors already call me crazy and suicidal because I won’t take any of their drugs.

    Incidentally, I asked Jenny at Diabetes Update about this same experience yesterday, and she replied with some real skepticism here. I will repeat this to see what happens.

  23. Seth Roberts Says:

    If someone is scolding you about binging once or five times on deep fried chicken wings they are missing the point. I believe a much bigger problem for you is your very high blood sugar score. If you can find a way to get them way down (and keep them down) you will be helping yourself immensely.

    You might also want to try large amounts of walking. Perhaps tolerable amounts of walking will reduce your blood sugar substantially. I found that was true.

  24. John W Says:

    Just to clarify, the D3 you take as a supplement (25-dihydroxy-vitamin D3) is NOT a technically hormone, it is a prohormone. The hormone form (1,25-dihydroxy-vitamin D3) is made from the prohormone form and is tightly regulated. Furthermore, the prohormone has a half-life of a couple of weeks. So it is, in fact, a little surprising that the dose timing can have such an effect.

    By the way, I noticed this myself a couple years ago – I never take vitamin D in the evening, so n>1.

  25. Nancy Lebovitz Says:

    Jim, just to check– did you do a significant amount of walking before your blood sugar went down? From what I’ve heard, doing a lot of mild exercise can make a big difference.

  26. nile Says:

    Mr. Purdy-
    In addition to walking, as Seth suggested, you might try, depending on your tolerance for exercise, HIIT or High Intensity Interval Training. A fair amount of research has been done on this in the last 10 years or so. Just go to pubmed ( and you can search for HIIT studies. About 10 minutes per day of exercise above your aerobic capacity will help a lot. I think it will have the same effect as large amounts of walking. A good protocol to start is “P.A.C.E.” by Dr. Al Sears. The book is poorly written but the protocol works fine. Out of shape, unconditioned individuals can use this method to get started. Start slowly and work up to 10 minutes. I think you will find your cravings for carbs and sweets will diminish with exercise – either long walking or HIIT.
    I hope you can get your blood sugar down. Good luck.

  27. Jim Purdy Says:

    I hope Seth doesn’t get upset with me for going off topic with his blog, but I really appreciate everybody’s input. And, actually, I only gave a very short version of my situation. Here are a few more details:

    In early 2010, doctors told me that my right foot had a very bad diabetic ulcer, and that the leg had to be amputated. Being non-compliant, I did not have the amputation, and I went to work on exercise, especially walking up stairs. RESULT: I still have my leg, and it has healed just fine.

    In the summer of 2010, cardiologists rushed me straight to a heart hospital because they said I needed emergency quadruple bypasses for had badly blocked coronary arteries and that I could die of a heart attack at any moment. I did not have the bypasses, and I relied on exercise and diet changes. RESULT: I exercise regularly now, and I no longer have any chest pains at all.

    For a few years, doctors have said my kidneys were failing and that I would eventually need dialysis unless I too lots of BigPharma chemicals. I felt that the chemicals would actually be more of a burden on my kidneys and liver, and I didn’t take any of them. RESULT: On my most recent lab work, my kidneys are just fine.

    Since all my other health issues have improved greatly with lifestyle changes, I am fully confident that the right lifestyle adjustments can control my diabetes. Interestingly, when I asked for advice from Seth Roberts and Jenny Ruhl (of Diabetes Update), they gave me very different responses. Seth recommended exercise, which is indeed what I am working on now in a brand-new exercise room in my apartment building. Jenny had only one suggestion: insulin. I ‘m going to go with Seth over Jenny. Exercise has worked for our evolutionary ancestors for many millions of years, but BigPharma’s injected insulin has only been around since 1921. I’ll take my chances with millions of years of evolution, over 90 years of BigPharma lab products.

    Sorry for the distraction, Seth, but I really appreciate the input here.

  28. Seth Roberts Says:

    #1-3 are great and powerful stories, Jim. I am very pleased to have them on this blog.

  29. Matt B Says:

    @Jim, have you written the very long versions of your stories yet? #2, “cardiologists …said I needed emergency quadruple bypasses for had badly blocked coronary arteries and that I could die of a heart attack at any moment” is a common refrain that could use some alternate thought.

  30. grace Says:

    Hi Seth!

    It is my personal experience as well as observations that vitamin D in the evening disrupts awakening or sleep for some, so I generally always take it < 12-3pm unless I am sick (in which case if I am coming down with a cold, it doesn't matter and I sleep well despite the timing of the dosage).

    Is this story from Tara at The link above didn't work right for me?

    Jim Purdy,

    Awesome story and biohacking! Do you check your BGs frequently (20, 40, 60, 120 min after meals and fasting)? Protein/amino acids and their timing make profound changes on hormones, growth hormone, sex hormones, insulin/glucagon and leptin.

    Sounds like to me that you have lingering insulin resistance issues. Do the food cravings persist despite eating 50 grams protein in the AM + 15-30 grams carbs in the morning? Have you considered the value of 5HTP or L-tryptophan in the morning for cravings? Often these are deficient with leaky gut/intestinal permeability. Would love to hear your progress.


  31. Seth Roberts Says:

    Yes, this story is from Tara at

  32. Perfect Health Diet » Around the Web; Wise Traditions & CrossFit NYC Pre-Talk Edition Says:

    […] Seth Roberts reports “a stunning discovery”: it’s better to take vitamin D in the morning. […]

  33. Dan Says:

    Vit D, when produced on the skin, is absorbed over a period of days. Hard to square that with this anecdote.

  34. Seth Roberts Says:

    Dan, several others have reported that Vitamin D at night causes sleep problems. Which supports the idea that it really does affect circadian rhythms. No matter how slowly it is absorbed.

  35. Harpoinseoul Says:

    Hi Seth,

    Thank you for your interesting blog. Myself, before going to bed I take Magnesium, and Vitamin B12. I personally find it helps me sleep well.
    BTW, any thoughts on sulfure? Just wondering.

  36. Seth Roberts Says:

    I don’t know what sulfure is, sorry.

  37. Erin Says:

    Jim, I’m confused as to if you’ve made huge lifestyle changes before and gotten miraculous results through them why you still can’t kick the binge eating!

    You should check out Tim Ferris’ book 4-Hour Body. His plan is very close to a paleolithic diet, but with very low glycemic index foods, and will lower your blood sugar – and you can still eat wings, just not fried in peanut oil! I think that book would be a good one for you because there is one set binge day a week.

    Check out the book by Eric Braverman, The Edge Effect. There’s a test in there for your neurotransmitter balance. Supplementing certain amino acids can help balance your brain chemistry and help curb your desire to eat compulsively.

  38. Don’t take Vitamin D at night | Aquatic Ape Diet Says:

    […] should’ve remembered Seth Roberts’ advice – don’t take it at night or […]

  39. Henk Poley Says:

    View this lecture by Stasha Gominak, where she explains her findings about vitamin D (and B12) in relation to sleep.

  40. Seth Roberts Says:

    Thanks, Henk. A fascinating and informative lecture. Curiously she says nothing about the time of day one takes Vitamin D.

  41. Joseph Buchignani Says:

    Dan, the chemical mechanism for absorption of Vit-D from skin is different than ingested Vit-D. See the Mayo clinic vitamin D page.

  42. jscott Says:

    I’ve been having massive insomnia, but it has been sporadic…or so I thought.

    Within the past month there have been 5 cases of insomnia. Onset of sleep has varied. Waking time has remained constant.

    D3 late at night (one hour prior bed) has been the only tracked variable that I have to point to and test. The D3 dosage has also been varied. I have yet to test but found it interesting to say the least.

  43. Seth Roberts Says:

    I’ve been having massive insomnia, but it has been sporadic…or so I thought.

    Within the past month there have been 5 cases of insomnia. Onset of sleep has varied. Waking time has remained constant.

    D3 late at night (one hour prior bed) has been the only tracked variable that I have to point to and test. The D3 dosage has also been varied. I have yet to test but found it interesting to say the least.

    I hope you will comment here to say what happens when you change the time you take your Vitamin D.

  44. Sceptically Fit Says:

    […] an ongoing look at the effects of Vitamin D3 supplementation and its role on sleep. A month ago I blogged about a “stunning discovery”: Primal Girl’s sleep got much better when she took Vitamin D3 in the early morning instead of […]

  45. jeanine Says:

    Jim Purdy,
    I was diagnosed with gestational diabetes. I tested my blood sugar levels constantly during the day and I found that beans of any sort (chili, refried, etc.) always dramatically lowered my blood sugar levels. Just an fyi.

  46. Pennyjeans Says:

    Is anyone here a bit concerned that no one has heard from this person Jim Purdy since November 3rd and his last post was that he would continue eating 50 fried chicken wings a day and tell how that worked out for his glucose levels…?