Wellness

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Ask Gerda: Should I Take a
Vitamin D Supplement?

Gerda Endemann

Gerda Endemann, our senior director of science and research, has a BS in nutrition from UC Berkeley, a PhD in nutritional biochemistry from MIT, and a passion for cherry-picking from our wellness shop. She spends a lot of her time interpreting research—established and emerging. And our wellness routines thank her for this. (Yours will, too. Send us your own questions for Gerda: [email protected].)

Dear goop, I hear so much about vitamin D deficiency, and everyone seems to use supplements, but I hate taking pills. If I eat a relatively healthy diet, am I okay? —Kelly M.

Hi Kelly, It’s unrealistic to get enough vitamin D from foods—even healthy ones. Getting the recommended Daily Value of 800 international units (IU), which is twenty micrograms, would require drinking six cups of milk every day. And a three-ounce serving of fatty fish provides only around 500 IU of vitamin D.

So whether or not you’re okay depends on something you didn’t mention: Do you get any sun? Just as plants need sunlight to grow, people need sunlight so that their skin can make vitamin D, which is actually a hormone. With all the fear of skin cancer, we tend to forget that we’re like plants in that way. And if you always cover up when you’re outside, always use sunblock, or have dark skin (which acts as a natural sunscreen), you may be low in vitamin D.

The reason so many people have suboptimal levels of vitamin D these days is that we’re either inside or we’re using sunblock, which blocks vitamin D production. Our bodies haven’t had nearly enough time to evolve strategies to deal with these recent developments in lifestyle. Also, as we get older, our skin becomes less efficient at turning sunlight into vitamin D.

There is absolutely no need to risk sunburn or skin cancer or to prematurely age your skin. Good health is all about moderation, and sun in moderation is healthy. Ideally, you want to expose a good amount of skin—say your arms and legs—to the sun a couple of times a week for one quarter of the time it would take to get slightly pink (about five to thirty minutes). Depending on latitude, cloud cover, skin pigmentation, and time of day—10 a.m. to 3 p.m. is best—this may take care of your vitamin D needs, including storing extra for the winter.

Of course, we don’t all live in places or have lifestyles that allow for this kind of consistent sun intake. My mother grew up in Fannystelle, Canada, where vitamin D deficiency is a major concern because there are only a few sunny months to go sleeveless. (She took an old-fashioned approach to vitamin D with her kids: giving us baths in the sun as infants and then giving us cod liver oil throughout childhood.) And again, if you have dark skin, it’s harder to get all the vitamin D you need; it ups the time required in the sun.

Here’s why being deficient in vitamin D is an issue: As a hormone, vitamin D controls the growth of breast, prostate, and colon cells. We also need vitamin D for healthy immune cells. Getting adequate vitamin D is an important immune-supporting strategy, especially in the winter. Additionally, vitamin D is needed to build and maintain healthy bones all year long, because without it, we don’t absorb the calcium we eat. While this may seem like something to worry about after retirement, the opposite is true. Incorporate as much calcium into your bones as you can in your teens and twenties, while it’s possible to build denser, stronger bones. By your thirties, it’s all about being consistent with vitamin D and calcium to minimize ongoing loss of bone.

It’s relatively simple to find out what your vitamin D status is. Any doctor or lab can do the test on a blood sample and report your level of 25-hydroxy-vitamin D. If your level is lower than you and your doctor are happy with, the simple solution is to take a supplement. Functional medicine doctors often like to see higher numbers, but twenty to fifty nanograms per milliliter (50 to 125 nanomolar) is considered good by the Office of Dietary Supplements in the National Institutes of Health.

Vitamin D comes in small softgels that are easy to take, and drops can be used for infants.

Hum Nutrition makes a softgel with 2,000 IU of vitamin D3 per serving. D3 is the same form that’s made in the skin.

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The American Academy of Pediatrics (AAP) recommends giving all infants a daily supplement with 400 IU (ten micrograms) of vitamin D, unless they are drinking a liter of fortified formula. Genexa makes drops for infants that provide 400 IU of D3 in one serving. The formula is organic, non-GMO, and free of common allergens and additives.

And the AAP also recommends giving all children and adolescents a vitamin D supplement unless they consume plenty of fortified foods.


This article is for informational purposes only. It is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. To the extent that this article features the advice of physicians or medical practitioners, the views expressed are the views of the cited expert and do not necessarily represent the views of goop.

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