Nearly one-third of Americans take a vitamin D supplement. In an industry whose market value is currently around $1.3B, there has been a considerable increase in vitamin D supplementation in the past two decades. But a landmark study in 2019 and then an ancillary study in 2022 have called this into question—and created a lot of controversy in the field.

The study, called "The Vitamin D and Omega-3 Trial," or VITAL, randomized 25,871 women 55 years or older and men 50 years or older to one of four conditions: vitamin D plus omega-3 fatty acids, vitamin D plus placebo, omega-3 fatty acids plus placebo, or double placebo. The researchers collected annual questionnaires on health outcomes and ultimately concluded that there was no impact of vitamin D supplementation on the risk for cancer or cardiovascular disease. An ancillary study in 2022 that randomized participants to vitamin D and omega-3 conditions found that there was no benefit of vitamin D supplementation for the prevention of fractures.

In the........

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