According to emerging evidence, most Americans lack optimal blood levels of vitamin D. A major player in osteoporosis prevention, vitamin D enhances calcium absorption and prevents a process of bone breakdown known as bone resorption. There are four primary sources of vitamin D: 1) sunlight, 2) fortified foods (including some dairy products), 3) natural sources (cod liver oil, herring, mackerel, salmon, sardines, tuna, and other oily fish), and 4) supplements. While fortified foods are the leading dietary source, direct sunlight is the primary overall source of vitamin D. Only 5-10 minutes of sun exposure a few times per week (no sunscreen) can meet your vitamin D needs and replenish your stores in the spring, fall, and summer. In the winter, those living north of the latitude of 33 (imagine a horizontal line between Atlanta and Los Angeles) need vitamin D supplementation. Elderly people with limited sun exposure and dark-skinned African Americans need consistent supplementation year round.
What to Do: The current recommendation (RDA) for adults is 400 IU up to age 70, and 600 IU for those older than 70. Many researchers believe that the current RDA levels are too low. A recent study found that individuals with high normal blood levels of vitamin D (requiring 1,300 IU of supplementation for elderly populations) had a 33% lower risk of fracture compared to those with low normal blood levels. With this evidence at hand, it is advisable to strive for regular sun exposure during the summer and aim for a daily total of vitamin D intake from supplements and food of 600 IU 1000 IU the rest of the year.