The term vitamin D refers to several forms of this bone-supporting vitamin.† Vitamin D—which is actually a hormone—is critical for strong, healthy bones and may help prevent osteoporosis.†† Vitamin D must also be present for the body to fully absorb calcium and can actually increase calcium absorption twofold or more depending on the individual.
Unfortunately, 70% of women ages 51-70 and 90% of women over 70 don’t get enough vitamin D from food and supplements. Others at high risk for vitamin D deficiency include the elderly, the obese, exclusively breast-fed infants and those with limited sun exposure. Low levels of vitamin D are linked to osteoporosis, reduced calcium absorption, bone loss and increased fracture risk.
Two forms of vitamin D are especially important to human health: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is made in plants—thanks to the help of sunlight. Similarly, vitamin D3 is made in humans when a form of cholesterol found in our skin cells reacts with sunlight.
In fact, 15-20 minutes of sunshine each day, in the nude, helps your body manufacture 10,000 to 15,000IU of vitamin D3—but that probably isn’t going to occur on a daily basis for most of us, so we should consider alternate sources of vitamin D3.
Excellent sources of vitamin D3 include: wild, coldwater fish like salmon, cod, mackerel and sardines; egg yolks; beef liver; whole milk and other dairy foods.