Vitamin D plays a well-established role in overall health, and a growing body of research has linked vitamin D status to breast cancer risk and outcomes.

However, most studies to date have relied on a single measurement to assess a person's vitamin D status, and one reading can only reveal so much (after all, it's just a snapshot in time). Now, a new study tracking vitamin D across 513 women with breast cancer found that how levels changed over the course of treatment was a stronger predictor of outcomes than any single reading alone. Here's what you need to know.

Encinitas, CA—On November 2, 2026, GrassrootsHealth will host the inaugural Baggerly-Garland Vitamin D Scientist Awards at the Goldberg Auditorium at Moores Cancer Center at UC San Diego Health. Taking place on World Vitamin D Day, the ceremony will recognize scientists whose research has helped advance understanding of vitamin D, UVB exposure, and cancer prevention. Sponsored by Solius Labs, the special press event will honor Dr. William B. Grant, Dr. Joan Lappe, and Dr. Edward D. Gorham, as well as the legacies of Carole Baggerly, founder of GrassrootsHealth, and Dr. Frank C. Garland, whose vision, persistence, and commitment helped transform the scientific conversation surrounding vitamin D and cancer prevention. The event will begin at 11 a.m. Pacific Time, with attendance available both in person and virtually.

Exposure to sunlight is associated with lower blood glucose levels and a lower likelihood of type 2 diabetes, according to a new study published in the journal Scientific Reports.

Background

Type 2 diabetes is a chronic metabolic condition in which the body either cannot produce sufficient insulin or cannot use it properly, leading to the accumulation of glucose in the blood (hyperglycemia). The condition is a major public health concern, with substantial impacts on morbidity, mortality, and healthcare expenditure.

Several observational studies have linked lower circulating vitamin D levels to a higher risk of type 2 diabetes. However, current randomized controlled trials generally do not establish low vitamin D as a causal factor or support vitamin D supplementation for preventing type 2 diabetes in the general population.

Vitamin D is primarily synthesized in the human skin following exposure to the sun’s ultraviolet B (UVB) radiation. Existing evidence suggests that exposure to UV radiation can activate nitric oxide stored in the skin, which in turn can reduce blood pressure through vasodilation. Animal studies have also linked UV exposure to reductions in metabolic syndrome markers and weight gain. These observations suggest that sunlight may confer cardiovascular and metabolic health benefits independent of vitamin D.

Most dermatologists recommend shunning the sun to protect our skin. But Dr. Steve Feldman says that is probably bad for our health.

For decades, dermatologists have warned us to stay out of the sun. Shunning the sun was supposed to protect us from premature wrinkles and skin cancer.

It is true that spending a lot of time in the sun will damage our skin. Ultraviolet radiation can indeed accelerate wrinkling and contribute to squamous and basal cell skin cancer formation. Sunburn is unquestionably harmful and worth preventing.

But Could Avoiding Sunlight Altogether Also Carry Risks?

In this brief video, eminent dermatologist Dr. Steve Feldman describes a surprising study involving nearly 30,000 Swedish women who were followed for about 20 years.