Recently, headlines have proclaimed that vitamin D is ineffective, that we shouldn’t bother testing for it, and that most people shouldn’t bother taking it. Pushing back on those assertions is Dr. William Grant, one of the world’s foremost vitamin D researchers with over 60 published studies. His latest paper explains why research on vitamin D is plagued by methodological errors and colored by bias against nutritional supplements that might supplant pharmaceutical drugs. Dr. Grant explains how vitamin D, far from being just a “bone vitamin”, can impact a wide range of conditions ranging from dementia and Alzheimer’s, cardiovascular disease, diabetes, mood disorders, and cancer; studies have shown it improves pregnancy outcomes and extends life; the latest research suggests a benefit for respiratory infections and Covid. We also discuss the important role sunlight exposure plays in vitamin D synthesis, and how wrong-headed health authorities have stigmatized sun exposure to great detriment. What levels are best? How much to take? Is there an upper limit? Dr. Grant is currently the director of the Sunlight, Nutrition, and Health Resource Center.