From Our Editors
Vitamin D: Sunshine, Supplements, and Salmon
Otherwise found naturally in only a few foods, vitamin D makes its way into the body primarily through sunshine. Bask in Groupon's guide to this vital nutrient.
If you've already exhausted your excuses for taking a tropical vacation in January—Bermuda doesn't need any more packages delivered, and the doctor's margarita prescriptions have run dry—there's always a trump card: your skeleton is starving. That’s because the body’s levels of vitamin D—a substance integral to the body's ability, along with calcium, to maintain strong bones—can plummet in the winter, when sun exposure is lowest. Research has shown that up to 30 minutes of exposure to UVB rays—found in both sunlight and certain tanning beds—twice a week is enough to set the body’s vitamin D synthesis process into motion, helping prevent serious conditions such as osteoporosis and potentially multiple sclerosis, type 1 diabetes, and even the common cold.
Still, UV rays can't fulfill all the body's needs, especially since, when applied correctly, sunscreen can reduce vitamin D absorption by more than 90%. Luckily, humans can acquire it by eating fatty fish such as salmon and mackerel or from other sources such as eggs and cheese, but most Americans primarily derive vitamin D from fortified foods including milk and cereals. Supplements can also fill vitamin D gaps, staving off deficiencies that can lead to rickets in children and osteomalacia—a softening of the bones—in adults and fossilized dinosaurs.