Doctor's Note

For more on Vitamin D, check out these videos:
Is Vitamin D3 Better Than D2?
Take Vitamin D Supplements With Meals
Is Vitamin D the New Vitamin E?
Vitamin D and Mortality May Be a U-Shaped Curve

And check out my other videos on vitamin D.

For more context, also see my associated blog posts:  Aspartame: Fibromyalgia & Preterm Birth, and Vitamin D from Mushrooms, Sun, or Supplements? 

If you haven't yet, you can subscribe to my videos for free by clicking here.


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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. And check out the other videos on vitamin D. Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

  • Moss

    I live in Yukon, Canada (doesn’t show on your map). How much should I be taking? 4000 IU a day, all year long? Also, is this the amount for D2? Any thoughts on D2 vs. D3?

  • Toxins

    According to Dr. Mercola, we don’t get proper Vitamin D from the sun because we shower with soap and the oils that need to still be absorbed on top of our skin don’t have a chance to. He claims it takes 48 hours without a soapy shower for vitamin d to be used effectively. Is there any truth to this?

    • Alexandra Georgiadis

      The process by which vitamin D is synthesized by our body begins with a presence of sterol cholesterol on our skin which is converted into sterol-7dehydrocholesterol. When the skin is exposed to the sun (or ultra-violet light) for regular intervals, a photochemical conversion from sterol-7 dehydrocholesterol into Vitamin D occurs. The absorption of this newly formed vitamin D into the bloodstream is what is claimed to be disrupted by using soap. I’m not sure how strong the evidence is for this claim, and I wasn’t able to find a research publication on the topic. However, if it is true, all the more reason to take vitamin D supplements as Dr. Greger suggests! Here’s another great video that shows the association between vitamin D supplementation and longer life expectency, check it out! I hope this helps!

    • Paddycakes

      Mercola is a dolt. He also advocates eating meat and dairy which are carcinogenic.

      • Gross Bro

        Mercola also wants to sell you a $3500 tanning bed

        • Toxins

          And he sells tubs of coconut oil and advocates for raw milk.

  • evergreen517

    Now that there is a new vegan D3, (Vitashine) would you recommend this over D2? How much should we take per day? At 20$ a bottle, 4000 would be pretty expensive.

  • In New Zealand we have a problem with a hole in the ozone layer, causing a much more intense UV exposure and major problems with rates of skin cancers. My question is, does this mean the length of time for sun exposure in order to achieve sufficient vitamin D would be shorter than in the northern hemisphere?

  • kerleyc

    Very interesting…but what about sensible narrowband ultraviolet B for production of vitamin D? For example 10 minutes 3 times a week on bare skin, in conjunction with tobacco avoidance and an anti-oxidant packed, plant based diet which has been shown to be protective against skin damage including both melanoma & non-melanoma….

  • Agnete

    What about light therapy? Could this not be a way to avoid both the risk of skin cancer AND the dangers of vitamin d-supplements?

    •  I recommend sun light first in moderation. You can consider Vit D supplementation and get levels checked to make sure you are not overdoing it. Although the recent recommended blood levels have been increased levels in the 20’s are probably acceptable. Some patients even with alot of sunlight exposure can’t raise their levels above 30. It is however a confusing area but the science keeps getting better. It is also possible that somewhere down the line we will discover some other substance or effect that natural sunlight has for us that isn’t contained in a Vit D supplement. The nice thing about sun light exposure is you can often couple it with exercise. So work with your  physician(s) and keep tuned to NutritionFacts as the science keeps coming….

  • Tlfinan

    Hello Dr. Greger,
    Love your video  website.
    Can you please post more videos on melanoma.  My sister-in-law died of it last year at 48 years old.  She left behind two beautiful teenage daughters.  I want to educate them on staying healthy.  Of course I am encouraging them to eat as much raw fruits and veggies as possible.

  • Rodrigo

    What about tanning beds with electronic ballasts? instead of magnetic, or the smaller version UV lamps? that are being sold? can these also me harmfull?

    • Dan

      electronic ballasts are more energy efficient than magnetic, but I can’t see how it would have any effect on the spectrum of light put out by the fluorescent lamps.

      Same would go if they used ultraviolet LEDs instead, all that really matters is the frequency of the light, and how powerful the light source is.

  • Carsten Müller

    What about Tanning Beds with UV-B insted of UV-A ?

  • Julie

    I have read very contradictory information about sunscreen and skin cancer. Some say to always wear sunscreen to protect against skin cancer, others say non-natural sunscreens causes cancer. Of course, we also can get Vitamin D from the sun. Can you please clear this issue Up?

  • bob

    What do you think of a therapy lamp so the body can produce its own vitamin D?

    • The Vegetarian Site

      Dr. Greger points out that modern commercial vanity tanning beds are not appropriate for Vit.D production, because they produce UVA and little or no UVB. Are there any decent broader spectrum UV options that can be used lightly to simulate light/moderate exposure to the sun? Of course, UVB is more dangerous and carcinogenic than UVA, so any such product would need to be used with great care. Anyone??

  • D3forU

    “Sunbeds of course can be used to make vitamin D. It has been one of
    the ways that we have measured the amount of vitamin D that the skin has
    the capacity to make,” stated Dr. Reinhold Vieth, a professor at the
    University of Toronto in the Department of Laboratory Medicine and

    “Tanners actually have robust levels of vitamin D,” stated Dr.
    Michael Holick, Professor, School of Medicine, Endocrinology, Diabetes
    & Nutrition, Boston University.

    Here is a comparison of a typical sunbed as related to outdoor
    sunlight. The outdoor snapshot was taken on June 24, 2014 which
    coincides with the Summer Solstice in Chicago. These levels are only
    available between the hours of 12-2 PM.

    The Sunbed replicates this golden window of optimal UVB for Vitamin D
    production on demand and is not dependent on a daily schedule, time of
    the day, time of the season, weather conditions such as clouds and haze
    any day of the year in a controlled environment which can then be
    additionally adjusted by skin type for personalized exposure schedules.