Ask Gerda: Should I Take a Vitamin D
Supplement for Immunity?

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’m reading a lot about vitamin D deficiency and, of course, stressing because I’m spending most of my time inside the house right now. Can you get enough vitamin D from food? Does supplementing have any benefits for immunity? —Suzanne B.

Hi Suzanne, It’s unrealistic to get enough vitamin D from foods—even healthy ones. Getting the 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.

The major source of vitamin D for most people is sunlight. 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.

Here’s why being deficient in vitamin D is an issue: We need vitamin D for healthy immune cells. A meta-analysis of controlled clinical trials concluded that vitamin D supplements were good for respiratory tract health, especially in people with low blood levels of the vitamin. Getting adequate vitamin D is an important immune-supporting strategy, especially in the winter or anytime you are stuck inside. And as a hormone, vitamin D controls the growth of breast, prostate, and colon cells.

Vitamin D is also 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 the 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.

If you go the sunlight route, 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. (It’s not just for the vitamin D: The other thing that’s produced in the skin in response to sunlight is beta-endorphin. As an opioid, beta-endorphin reduces pain. Addiction to tanning beds is probably a real thing.)

Ideally, you want to expose a good amount of skin—say your arms and legs—to the sun regularly. The amount of time required depends on the latitude, time of year, time of day, and how dark your skin is, since the skin pigment, melanin, is a natural sunscreen. For light skin it may be sufficient to sunbathe a couple of times a week for one quarter of the time it would take to get slightly pink (about five to thirty minutes). To prevent vitamin D deficiency, those with dark brown skin may require about three times as much sun exposure as those with white skin. Researchers in the UK found that for people with dark brown skin, twenty-five minutes in direct sunlight daily at lunch time from March through September—with bare forearms and lower legs—was sufficient. Exposing only hands and face was not enough. It’s expected that people with black skin would require more exposure to sunlight, but there is unfortunately a lack of research and there should be more studies on the ideal amount.

Supplements are a great alternative for us all to consider: 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, and Hum Nutrition made the extra effort to source a rare vegan form of D3, from lichen.

1. 
   Hum Nutrition HERE COMES THE SUN HIGH-POTENCY VITAMIN D3 goop, $12

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2. 
   Genexa INFANT VITAMIN D3 goop, $11

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

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

Even easier than a softgel, the Nue Co.’s Vitamin D Spray provides a generous 3,000 IU per three sprays.

1. 
   The Nue Co. VITAMIN D SPRAY goop, $25

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2. 
   Dr. Nigma VITAMIN D SUN goop, $30

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And for even higher potency, Dr. Nigma’s capsules contain 5,000 IU (125 micrograms) of vitamin D3, together with a generous amount of vitamin K. It makes sense to combine these two fat-soluble vitamins: Vitamin D is crucial for the absorption of calcium in the gut, and vitamin K helps direct that calcium to bones.*

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.

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.