INTERESTINGLY IT’S NOT THE VITAMIN D, APPARENTLY: How Sunlight Could Fight Obesity and Heart Disease—And Why Vitamin D Supplements May Not Work. I take vitamin D supplements but I also try to get moderate sunlight, because I’ve always wondered if maybe there wasn’t some other benefit to sun exposure. I also wonder if nitric-oxide boosting supplements like citrulline, which I take, or PDE5 inhibitors that boost nitric oxide and seem to prevent heart disease and cancer, might operate via a similar mechanism.