Doctor's Note

This is the eighth video in a nine-part series on vitamin D. Be sure to check out yesterday’s video: How the Institute of Medicine arrived at their vitamin D recommendation.

For more context, check out my associated blog posts: Vitamin D: Shedding some light on the new recommendationsEating To Extend Our Lifespan; and Vitamin D from Mushrooms, Sun, or Supplements? 

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. This is the 8th video in a nine day series on vitamin D. Be sure to check out yesterday’s video-of-the-day How the Institute of Medicine arrived at their vitamin D recommendation.

  • dgmusselman

    Thanks for the comprehensive info. re: vit. D. I’m still unsure, however, about which form of D supplement is effective–D3(nonvegan) or D2(vegan). I’ve even seen ads for vegan D3. Over the last 3 years I’ve seen conflicting reports about the effectiveness of D2? Can you clarify?

    • Michael Greger M.D.

      Taken daily in doses at 2000IU or less, vitamin D2 (ergocalciferol) and D3 (cholecalciferol) appear bioequivalent (meaning they both work just as well in your body). However if your physician suggests you take large intermittent doses (such as 50,000IU weekly, then D3 is probably superior).

      • Toxins

        I take 2400 daily, is this too much?

        • Michael Greger M.D.

          Nope, the current upper daily limit is 4,000 (though more likely 10,000).

          • I’ve found a affordable supplement, however the dosage is 5000 IU per capsule. Would you consider this as too much, Michael? 

          • DrDons

            If you decide you should take a supplement remember that Vitamin D is stored so if you were to take your 5000 IU every other day you would average 2500/d. I think caution is in order especially with supplements which can be toxic. Also cautionary is the study showing that taking isolated supplements Beta Carotene, Vitamin A & E lead to increase morbiditiy and mortality see The best recommendation is to get your Vitamin D from sunlight. It would not surprise me if future studies show that there are other factors that our bodies make with exposure to sunlight that are helpful… time will tell. So I would recommend factoring in your location and amount of sun exposure you get to your decision whether to take supplements and how much to take see Keep tuned as new scientific studies shed light on these complex issues.

      • Charma1ne

        Dr Greger thank you for the information. Could I please ask about D2 and amyloid plaque based on this research: . Thank you.

    • henk

      There are vegan d3 supplements.. check: it’s taken out of lichen.


    Thanks for the awesome website!
    So I’m assuming that the suggestion of 2000 IUs/d to hit the “sweet spot” are the total IUs of vitamin D/d, meaning from all sources such as supplements, food, and sun. Is there a correction factor to apply to 2000 IU/d to account for sun at various latitudes and times of the year? (For example, Denver, CO — Summer versus Winter.)


      So I watched the videos in reverse order a saw that there’s no “one-size-fits-all” correction factor. Guess I’ll just shoot for 2000 IU/d in the Winter and less if I’m getting some sun.

  • JoyZakarian

    Hi Dr. Greger,

    Is the 2,000 IU/day recommendation the same for vegan Vitamin D2? I thought one of your articles in a previous video explained that they aren’t exactly equivalent. Thank you!

    • Michael Greger M.D.

      Same recommendation Joy–see my response to dgmusselman above.

  • dave23

    Thanks for the this informative video. Aren’t there other health benefits from the sun that we can’t get from supplements?

    Also, if I live on the east coast and get pretty much zero sun during the winter should I just take vitamin d or should I get tested because perhaps I have enough stored from previous sun and/ or from mushrooms?

  • Michael Greger M.D.

    For some context, please check out my associated blog post Vitamin D: Shedding Some Light on the New Recommendations!

  • Sheri O

    Are your recommended levels the same for children as they are for adults?  

    • beccadoggie10

      I’ve read that adult dosages given to children are toxic. Any comment on this?

      I’m worried about the source of vitamin D3 CHOLECALCIFEROL, coming from cod liver oil or the liver of other fish. That also depends upon the waters from where those fish live, but all waters are increasingly toxic with chlorinated pesticides, PCBs, Dioxins. Don’t those also contaminate the liver?

      I would feel more comfortable about a vegan vitamin D2 supplement, but my local health food store only carries vitamin D3 from cod liver oils. I desperately need vitamin D to keep my bones strong especially with osteoporosis but need a brand name for security.

  • Marek Záda

    I have read a number of articles on vitamin D and dundruff. I suffer from dundruff for over 10 years, no shampoo really cured my scalp. However, when I go for vacation – usually nearby sea during summer time, dandruff almost disappears within a week. I never thought of vit. D deficiency as I never had a broken bone (yet live an active lifestyle). I live in central Europe and am an office rat, lack of sun exposure is quite common in my case. I concluded that a weekly safe tube tanning might be a good way how to get D3 they way we are supposed to. Your opinion on the matter?

  • Julia

    I just discovered that Magnesium supplement helps/cures not only my newly revived muscle cramps, but also longstanding insomnia. Foot cramps (usually at night) arose after taking 2000IU/d Vitamin D for a few weeks. I read a story about a woman whose serum D levels didn’t go up with supplementation until she also took magnesium. Apparently it takes a good bit of Mg to convert the D to its usable form. Did any of the research on optimal D supplementation levels take Mg levels or intake into account? BTW, I’ve been eating nutrient dense whole plant food, lots of greens, for going on 6 years. Still I noticed if I skipped more than a day or two eating spinach, I’d get the leg and toe cramps. Wondering if i need less D when i get enough Mg. I am 61y.o. female. Thanks!

  • Celia Ready

    Hi Dr Greger please answer my question. ???? Last year I had 1/2 my thyroid removed due to a undiagnosed nodule, which was benign. So I could have left it there. Very frustrated about that. Seeing my parathyroid glands have been interferred with during the operation and always keeping a check on my thyroid levels, due to having OSTEOPENIA, degenerative discs in my cervical spine. I would like to know which is the best way to avoid more bone loss seeing I am only 49. Should I eat more mushrooms and magnesium rich food. Is it only certain mushroom that have a high level of vitamin D OR do all mushrooms have vitamin D. Should I be taking vitamin D and magnesium supplements and vitamin K supplements and BORON supplements, Because don’t you need all of those vitamins working together to absorb enough calcium for your bones and other organs to keep healthy. Please explain. Should you be getting more vitamins from eating real food, or topping up on supplements. I would like to be able to educate my children as well. So this would really be appreciated. Advice from you.

  • Celia Ready

    I will be having more surgery shortly a hysterectomy so more recuperating, not a lot of exercise happening for a few weeks after that operation. So not much sun around during winter. So do you take supps or not.???

  • Noboa

    can I take vitamin D 50,000 IU D2 one time a week along with my reg dosis of Donepezil 5 mg

  • Anna Kathrine Fløistad

    Thank you. I am a woman (from Norway) with ms- and are quite confused of how high level of D vitamin I should have and the best way to take it. There are not much sun here in Norway. At the same time, it could reduce attacks, so I’ve heard. I am confused, because there are several ways of measure the vit D level.. Is solarium the best mean or should one take substitudes? And are there other factors that lowen the leven of vit D? f.ex in food etc.

    • JacquieRN

      Hi Anna, you may want to check out all the other videos on Vit D:

    • Dr Colin Walsh

      Hi Anna – even more important than vitamin D is eating the right kind of diet. An American neurologist called Swank used a very low fat diet for recently-diagnosed cases of MS and got excellent results which were published in the Lancet around 1990. A 30 year follow-up revealed that all his patients who stayed on the diet were alive and well, with little or no disability. Another study is being done at the centre where Swank worked (Oregon USA), with Dr John McDougall acting as the advisor on diet. See the Dr McDougall website By the way, Dr McDougall is happy to answer emails. Good luck. Dr Colin Walsh

  • techomaniac

    why not just take 60,000 once every month since the body regulated the mega dose down to that sweet spot level?

  • Beate

    My husband had 4stage liver cancer 2 years ago. He is healing himself with nutrition supplements and cannabis oil. My question is, his vitamin D3 levels have been way to low, around 27. He is taking daily 10000 D3 in liquid form. He feels healthy, gets plenty of sunshine also. Why aren’t his levels coming up? His cancer shrunk 2/3 and tumor markers are normal

    • Lokesh Soni

      Hi Beate. This is a remarkable comment to read. I wonder if there is any chance i could speak with you by phone / email? I have family who is treating their tumor naturally and would love to be able to speak with you if possible. I can be reached on or +34 674552214(Spain). Thanks, Lokesh

    • dogulas

      Way low? 27 is pretty close to the supposed ideal of about 30 ng/ml. He’s healthy, and he should be. Why try to assume his body needs to be in a place it is apparently fighting hard to stay at? The body knows what it needs, and his needs what everyone else’s does: around 30 ng/ml. I bet if he tested again it wouldn’t be 27, it would be different. Levels fluctuate.

  • Edith

    Dr. Greger, my (young) doctor has just given me a prescription for Ergocalciferol 50000 Unit Oral Capsule (**8** Capsule) to take one/week for eight week and then retest. I have sarcoidosis (currently no symptoms) and have been told in the past not to take Vitamin D supplements. I’ve just moved to Florida from Michigan. Blood test results were 26 ng/mL. Do you consider this a reasonable course of action?
    By the way, Sunday cup of tea is always enjoyed reading your email.

    • Nicole Jaja

      My mom has sarcoidosis too. So if i understand your post correctly, vitamin D supplementation is not advised for people with sarcoidosis? And if i could ask, how are your vit.D levels now and do you still supplement with 50000 IU?

      • Edith Andersen

        The last blood test shows it to be normal. I took the supplement for one week.

        • Joseph Gonzales R.D.

          Glad to hear numbers improved! I suggest more Florida sun :-) and continuing having levels checked by your doctor.

  • davidbala

    I have read recommendations that all of us–whether one is diabetic/pre-diabetic or not–would benefit from taking Metformin. Life Extension has been recommending it for 20 years. Metformin is the only drug they recommend. It appears to have positive impacts on cell function and longevity, decreasing cancer rates and increasing cellular metabolism, specifically by increasing the production of AMPK. I am interested in your perspective of Metformin use for non-diabetics.

  • Joe Tilman

    Are there any studies regarding eczema and vitamin D? Looking at medically prescribed eczema treatments such as UV treatments, and anecdotal evidence regarding vitamin D, it seems like a promising path…from a layperson’s viewpoint. Would love to see if there is anything more than anecdotal evidence.

  • dogulas

    If a human living far enough away from the equator supposedly cannot expose themselves to enough sunlight during certain months of the winter to sufficiently make vitamin D naturally, how is it that they can still get a sunburn during those winter months?

    • As we moved away from the equator we tended to lose our pigment to allow for more production of Vitamin D and the other beneficial aspects of sun exposure. Losing our pigment, however, makes us more susceptible to sun damage so we have to be careful not to get too much exposure.

      • dogulas

        Thank you!

        I found some more helpful information elsewhere that explains the paradox as well: Vitamin D synthesis is enabled by UVB absorption, which the atmosphere scatters more. Sunburns are mostly from UVA, which the atmosphere doesn’t scatter much, even at the north pole.So even a sunburn doesn’t mean getting enough UVB in winter months at certain distances from the equator.

        • Good point. Thanks. Interestingly the UVA seems to be responsible for liberating nitrate like compounds into our blood and helping our arterial system.

  • C Hamel

    Is the 2000 U/day recommendation based on an oral or sublingual dose?

    • C Hamel

      Ooops! I meant to ask this question under a Vit B12 thread (@ 2.5 mg/wk).

      • It is recommended as sublingual but oral would most likely work as well. The Vitamin B12 needs to be absorbed in the upper part of your GI tract. Be well.

  • nicolasmainella

    I’m only able to find 10.000 IU capsules where i live, is it ok for me to consume this dosage every 5 days, reaching this way the 2.000 IU sweet spot?

    • Joseph Gonzales R.D.

      Hi Nicolasmainella, I think there are too many factors to say for certain. (age, skin color, dietary Vit. D intake, location, etc) I would ask your doctor the best dosage for vitamin D supplementation right for you. As I understand it needs are very personalized. Quick thought can you order lower doses of Vitamin D online?

      Best to you,

      • nicolasmainella

        Ok, thanks i’ll check it with my doctor!

  • Dr. Greger, I’m a mom of two little ones under 3, and am having a really hard time losing ANY weight (I still have about 10 pounds from my first baby to lose, and about 20 additional to go to my optimal weight). I have been on a diet and exercise program for the last 6 weeks, and have not lost a single pound; in fact, the scale is going UP! I’ve read that Vitamin D can help with weight loss, but I’m also wondering how hormone levels affect weight loss. From what I can find, there is very little information about mothers and weight loss, except the old “It takes 9 months to put it on, give your body time, bla bla bla.” I can’t be the only mother who can’t get rid of this belly! Any insights would help!

    • Patience. There have been studies that show that exercise plus diet can result in “weight” gain. Exercises can often put “muscle” weight on…. fat loss is slower since each pound of fat has 3500 calories… so in the early stages weight can go up. Exercise suppresses appetite and raises metabolism. Fat loss is a function of calorie density as well. Calorie density scale courtesy of Jeff Novick RD(his CD can be purchased on Engine 2 website): vegetables(100 cal/#), fruits (300 cal/#), starches-corn, potatoes, rice(500 cal/#), fatty protein sources (1000); bread(1400), sugar & cheese (1800), junk food (2400), nuts (2800), oils (4000). There are of course some tricks… pasta is like bread when dry but since it is cooked in water it drops. Nuts seem not to put on quite as much weight as one would expect based on calories. Be careful of oils since leading source of calorie intake for women since 1980 is salad oils. You can calculate the calorie density of foods at select food, change servings to g for grams and enter 454(grams/pound) and it will give you the calories/pound). Keep in mind that you can spot build muscles but can’t spot lose fat. Faces get thinner, arms get thinner, breasts get smaller… sometime later belly and hips reduce… sorry… sometimes the truth hurts. Of course some folks short cut out the fat via liposuction to spot reduce but it is better to go the CD with exercise route. The other resource in addition to Jeff Novick’s CD is available free on YouTube… Doug Lisle PhD’s presentation… How to Lose Weight Without Losing your Mind!. Realistic fat loss goals are 1/2 to 1 pound per week. Best to track over time as younger women have to consider menstrual cycles with accompanying fluctuations. You are interested in lowering body fat and the scale can be misleading. Estrogen tends to result is weight gain and testosterone in muscle gain… no one said life is fair. I would not supplement with anything other than Vitamin B12 unless you have a deficiency. Jeff Novick’s other suggestions based on studies are preload with low fat salad and/or soup, don’t drink your calories and avoid Calorie dense, Refined And Processed foods. Whole foods don’t typically come with labels whereas processed foods do. Hope this has been helpful. Enjoy parenthood… my wife and I are beyond that at this point and am enjoying grandparenthood. Happy holidays.

  • Gail VH

    I’ve read that Vit D supplements are a synthetic Vit D that is not good to take. Vit D should be taken in whole foods or via the sun. Is this correct? After I read that I stopped taking Vit D.

  • Brux

    I love math …. and I have wondered about just this question … what can a reasonable person do to ensure they are getting enough, but not too much to build up toxicity? Great video!

    Now … are there videos like this for other or all the vitamins ? Do all vitamins follow the same paradigm ?

  • Annetha

    Epilepsy Behav. 2012 May;24(1):131-3. Epub 2012 Apr 11.
    Correction of vitamin D deficiency improves seizure control in epilepsy: a pilot study.
    Holló A, Clemens Z, Kamondi A, Lakatos P, Szűcs A.

    … Although vitamin D deficiency is known to be highly prevalent among epilepsy patients, only a single study, published nearly forty years ago, assessed the effect of vitamin D on seizure control. Here, we measured serum 25-hydroxy-vitamin D (25(OH)D) levels and normalized it by administration of vitamin D3 in 13 patients with pharmacoresistant epilepsy. To see if vitamin D3 has an impact on seizure frequency, we compared seizure numbers during a 90-day period before and after treatment onset. We found that seizure numbers significantly decreased upon vitamin D3 supplementation. Median seizure reduction was 40%. We conclude that the normalization of serum vitamin 25(OH)D level has an anticonvulsant effect.

    (Apologies if I posted this previously, but 40% reduction in seizures among patients for whom drugs did not work sounds pretty significant!)

  • JH

    I think you have to be aware of the source of your Vit D supplements. I don’t like to think of lanolin (wool grease) as edible.

    According to Wikipedia:

    Vitamin D2

    Main article: Ergocalciferol


    Mushrooms are a good dietary source of vitamin D2. They contain high concentrations of ergosterol (provitamin D2), and sunlight or ultraviolet radiation triggers its conversion to viosterol (previtamin D2), which then turns into vitamin D2. Low values in mushrooms for vitamin D2 below indicate no or only incidental exposure to sunlight. When fresh mushrooms or dried powders are purposely exposed to artificial sunlight by use of an industrial ultraviolet lamp, vitamin D2levels can be controlled at much higher levels.[154][157][158]

    Content of vitamin D2 per 100g:[159]

    • Mushrooms, portobello, exposed to ultraviolet light, raw: Vitamin D2: 11.2 μg (446 IU)

    • Mushrooms, portobello, exposed to ultraviolet light, grilled: Vitamin D2: 13.1 μg (524 IU)

    • Mushrooms, shiitake, dried: Vitamin D2: 3.9 μg (154 IU)

    • Mushrooms, shiitake, raw: Vitamin D2: 0.4 μg (18 IU)

    • Mushrooms, portobello, raw: Vitamin D2: 0.3 μg (10 IU)

    Human bioavailability of vitamin D2 from vitamin D2-enhanced button mushrooms via UV-B irradiation is effective in improving vitamin D status and not different from a vitamin D2 supplement.[154][160] Vitamin D2 from UV-irradiated yeast baked into bread or mushrooms is bioavailable and increases blood levels of 25(OH)D.[154]

    By visual assessment or using a chromometer, no significant discoloration of irradiated mushrooms, as measured by the degree of “whiteness”, was observed.[161] Claims have been made that a normal serving (approx. 3 oz or 1/2 cup, or 60 grams) of fresh mushrooms treated with ultraviolet light have increased vitamin D content to levels up to 80 micrograms or 2700 IU if exposed to just 5 minutes of UV light after being harvested.[157]


    • Alfalfa (Medicago sativa subsp. sativa), shoot: 4.8 μg (192 IU) vitamin D2, 0.1 μg (4 IU) vitamin D3 (per 100 g).[162]

    Vitamin D3[edit]

    Main article: Cholecalciferol

    In some countries, staple foods are artificially fortified with vitamin D.[163]

    • Vegan sources

    • Lichen

    • Cladina arbuscula specimens grown under different natural conditions: The contents of vitamin D3 range from 0.67 to 2.04 μg g⁻¹ dry matter in the thalli of C. arbuscula specimens grown under different natural conditions.[164]

    • Animal sources[159]

    • Fish liver oils, such as cod liver oil, 4.5 g (1 teaspoon) provides 450 IU (100 IU/g)

    • Fatty fish species, such as:

    • Salmon, pink, cooked, dry heat, 100 grams (3.5 oz): 522 IU (5.2 IU/g)

    • Mackerel, Pacific and jack, mixed species, cooked, dry heat, 100 grams (3.5 oz): 457 IU (4.6 IU/g)

    • Tuna, canned in oil, 100 grams (3.5 oz): 269 IU (2.7 IU/g)

    • Sardines, canned in oil, drained, 100 grams (3.5 oz): 193 IU (1.9 IU/g)

    • Cooked egg yolk: 44 IU for a 61 g egg (0.7 IU/g)

    • Beef liver, cooked, braised, 100 grams (3.5 oz): 49 IU (0.5 IU/g)

    Industrial production[edit]

    Vitamin D3 (cholecalciferol) is produced industrially by exposing 7-dehydrocholesterol to UVB light, followed by purification.[165] The 7-dehydrocholesterol is a natural substance in fish organs, especially the liver,[166] or in wool grease (lanolin) from sheep. Vitamin D2 (ergocalciferol) is produced in a similar way using ergosterol from yeast or mushrooms as a starting material.[154][165]

  • lydia trom

    This is probably too hard to answer, considering all of the variables, but if my diet consists of the recommended daily allowance of Vitamin D and I walk outside approx 10 house a week, mid day, should I still take the current recommended daily allowance of vitamin D in supplement form? I am having bloodwork done to determine my vitamin D level. If it is normal, should I avoid supplements? I am not a big fan or believer in supplements, in general…

  • Cole Magbanua

    Here is a recent video from Dr McDougall. I would appreciate it if one of the moderators or Dr Greger could comment on this new information. I have been recommending D to my patients, and will change my tune if the evidence is clear…. Thanks

  • Jcardozo723

    When taking D3, what is the ratio of vitamin K2 to D3, as well as calcium, magnesium, zinc?

  • Zazzels

    I used 2400 IU over the winter and got now my blood work done. 21.7 ng/ml but it should be over 30ng/ml (30-100) to have enough. Weird that it didn’t do it for me. Next winter I’m going for 5600IU and see how this works with blood work before winter and after.