Vitamin D
Fat-soluble vitamin that corrects low vitamin D status and supports bone and immune health in adults with low sun exposure.
Vitamin D
Fat-soluble vitamin that corrects low vitamin D status and supports bone and immune health in adults with low sun exposure.
Worth it if you get little sun or test low — strong for deficiency correction, modest beyond that.
Vitamin D is a fat-soluble vitamin made in skin after sun exposure and found in fatty fish, egg yolks, fortified dairy, and UV-exposed mushrooms. In the body it is converted to calcitriol, a hormone-like compound that regulates calcium and phosphorus balance and gene signaling in bone, muscle, and immune cells. Best-supported uses are correcting low vitamin D status, supporting bone and muscle function, and modestly lowering respiratory infection risk. It helps most people with low sun exposure or low blood levels.
Proven Benefits
Protocol
Onset Time
Who Should Consider
Food Sources
- Salmon or sardines (~300-600 IU per 100 g)
- Cod liver oil (~1300 IU per teaspoon)
- Egg yolks (~40 IU each)
- Fortified milk (~100-120 IU per cup)
- Fortified plant milk (~100-150 IU per cup)
- UV-exposed mushrooms (~400 IU per 100 g, mostly D2)
How It Works
Vitamin D is converted in the liver to 25(OH)D and then in the kidney and other tissues to calcitriol. Calcitriol binds the vitamin D receptor to increase intestinal calcium and phosphorus absorption and alter gene expression in bone, muscle, and immune cells.