TUESDAY, Jan. 24, 2023 (HealthDay News) -- Vitamin D is widely promoted for better health, but if you're overweight, you might not reap the benefits.In a new study, researchers found a 30% to 40% reduction in cancer, cancer deaths and autoimmune diseases among people with a lower body mass index (BMI) who took vitamin D supplements, but only a small benefit among those with higher BMIs."Patients with obesity, despite taking the same amount of supplement, had a lower response," said lead researcher Deirdre Tobias, an assistant professor in the department of nutrition at the Harvard School of Public Health, in Boston.The cutoff was a BMI of less than 25, which is considered a healthy weight, the study authors noted. It's not known why being overweight or obese affects levels of the...