The Importance of Vitamin D: Much is not known about COVID-19 and the coronavirus that causes it. One big question is whether the big disparity in mortality between African Americans and other Americans is due simply to poorer preexisting health and worse access to health care, or if there is also something else going on. In the category of “something else going on,” a greater prevalence of Vitamin D deficiency among African Americans has to be considered as a possibility. We know that Vitamin D deficiency was historically a powerful enough evolutionary force that those who have many generations of ancestors who lived nearer the poles than the equator ended up with light skin. So Vitamin D deficiency should not be despised as a demon.

In any case given the shred of evidence we have, taking Vitamin D supplements probably has a good benefit cost ratio right now. In his April 16, 2020 Wall Street Journal article “Vitamin D and Coronavirus Disparities,” Vatsal Thakkar writes this about the importance of Vitamin D for the immune system:

Vitamin D supplementation in African-Americans reduced cancer risk 23%. How? Cancer cells develop regularly in most animals, including humans, as the result of toxic injuries or glitches in DNA replication, but a healthy immune system destroys them. There is evidence that low vitamin D levels make the immune system go blind.

…

A 2009 study examined sun exposure and fatality rates during the 1918-19 Spanish flu pandemic, which killed an estimated 50 million world-wide. Disparities in access to health care were minimal then, since treatment consisted mostly in supportive measures and convalescence. Antivirals, vaccines, intensive-care units and ventilators didn’t exist.

The U.S. erected emergency hospitals—one of which, the Camp Brooks Open Air Hospital in Massachusetts, had the unique distinction of being an outdoor recovery unit. The mortality rate for patients there fell from 40% to 13% when they were moved outside. Sunlight might have proved to be literally the best disinfectant.

How Much Vitamin D to Get: On how much Vitamin D to get, it is important to know that the minimum daily requirement was messed up by a statistical error. See:

• Carola Binder—Why You Should Get More Vitamin D: The Recommended Daily Allowance for Vitamin D Was Underestimated Due to Statistical Illiteracy

Making Sure Your Body Can Make the Active Form of Vitamin D: The Vitamin D we produce with the help of the sun or in food or supplements still needs to be turned into an active form. Contrary to what we have been taught about milk being good for Vitamin D, whatever does in terms of getting the Vitamin D raw materials, it can inhibit the production within the body of the active form of Vitamin D. See:

• Is Milk OK?

That doesn’t mean you can ever have milk or dairy. You just need to have a big enough chunk of the day when you don’t have milk or dairy to give your body a chance to make the active form of Vitamin D. That is, if you do consume dairy, don’t consume it all the time.

Caveat: I want to emphasize how little is known. It may turn out that Vitamin D does essentially nothing to reduce risk of a bad case of COVID-19. But if you take an amount of Vitamin D in line with the recommendations in line with “Carola Binder—Why You Should Get More Vitamin D: The Recommended Daily Allowance for Vitamin D Was Underestimated Due to Statistical Illiteracy,” I think the benefit/cost ratio is good. And time-restricted eating in general is a good idea, especially when so many of us are holed up at home near the refrigerator. See “Eating During the Coronavirus Lockdown.”

For annotated links to other posts on diet and health, see:

• Miles Kimball on Diet and Health: A Reader's Guide