“Cod liver and other fish liver oils, swordfish, salmon, egg yolks, and mushrooms that have been exposed to sunlight are some of the richest food sources of vitamin D,” says Pittsburgh-based nutritionist and dietitian Leslie Bonci. Aim for a serving or two of these foods a day. Fortified cereals and milks are another option.
Only a blood test can reveal a deficiency. “Don’t supplement before you know your levels,” says Bonci, as vitamin D toxicity is dangerous. Follow your doctor’s instructions. D3 may be more readily absorptive than D2 at higher doses to treat serious deficiencies.