Yes, vitamin D is a hormone. Actually it is a secosteroid. In Latin, "seco" means to cut. This refers to the "B" ring of the pre-vitamin D molecule where it is "cut" open after exposure to UVB rays from the sun, turning it into vitamin D. If it weren't for that split in the chemical ring, it would be a steroid hormone. The importance of vitamin D being a steroid-like hormone is that it acts in the nucleus of cells on the chromosomes and genetic code! Vitamin D actually effects our genes! Genes contain the blueprint for the proper manufacture of proteins and other molecules that are important in cell function. It makes sure that cells die when they are supposed to, even cancer cells. It makes sure that the correct genes are turned on and that incorrect or damaged genes are turned off (cancer genes). This is one of the reasons that optimal vitamin D intake can reduce your risk of cancer by up to 50%! The neat thing is that vitamin D is free! You are supposed to get it from your skin, not from your diet. You would have to drink 200 glasses of milk to get the same amount of vitamin D that is generated from 20 minutes of proper sun exposure.
I am George DeFranca, DC, chiropractic physician in Central Massachusetts since 1982. I love my patients, my practice, and talking and teaching about health. I enjoy the outdoors, especially the ocean and kayakfishing.