WHEN IS A VITAMIN NOT A VITAMIN?
When it’s a hormone. Such is the case with vitamin D. We produce vitamin D in our skin from sunlight and additionally absorb a little (about 10 percent) through food. Our liver and kidneys then convert it into a hormone called calcitriol, which helps increase absorption and prevent loss of calcium. In other words: It’s essential for good bone health. If you live in the southern half of the United States, you can get enough vitamin D with 15 to 30 minutes of sun exposure daily. Darker skin tones need more time as melanin protects against UV rays, which results in less vitamin D absorption. “If you live north of Atlanta, you will need other sources of vitamin D from October to April when the sun isn’t strong enough,” says Julie Stefanski, registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. “Our highest natural source of vitamin D is fatty fish, such as salmon, mackerel, and sardines.” Fortified milk, cereals, and juices are great sources, too. You can also take a vitamin D supplement, but Stefanski recommends choosing one with vitamin D3, which is absorbed more easily than D2.