Find out how nutrition science has evolved in the past decade. Here's what we know now—and didn’t then.
"Such a well sourced article Karen! It's very interesting to see how the common-knowledge assumptions change over time, thanks for the read! "
5. We need more vitamin D than we thought
Thanks to our obsession with sunscreen, a short list of vitamin D-rich foods and hours spent indoors, three out of four Americans don’t get enough vitamin D. While we once thought vitamin D deficiency was only a problem for people living in northern latitudes, a 2010 Pediatrics study found that 56 percent of teens living in the sunny South were vitamin D-insufficient, meaning they didn’t soak up enough rays to produce the amount of D required for optimal health.
No wonder the Institute of Medicine (IOM) recently tripled its recommendation for the “sunshine vitamin” to 600 IU daily (800 if you’re over 71). The new quota is critical for strong bones, but many experts say you may need even more to lower risk of heart disease, type 2 diabetes, multiple sclerosis and many kinds of cancer (the upper limit is 4,000 IU). Moreover, it’s nearly impossible to get enough D from foods, especially when “vitamin D-fortified foods, such as milk and some orange juices, usually only have about 100 IU per serving,” says Michael F. Holick, Ph.D., M.D., director of the vitamin D, skin and bone laboratory at Boston University School of Medicine. The amount of vitamin D you make from sun exposure depends on several factors, such as the color of your skin, where you live and even how old you are. Because of that Holick recommends a three-pronged approach for everyone: eat D-rich foods (namely wild-caught salmon, which delivers more D than farmed salmon, UV-exposed mushrooms and fortified dairy and orange juice), get 10 to 15 minutes of sun on your arms and legs (and abdomen and back when possible) sans sunscreen three times a week during spring, summer and fall (when you can get enough UV rays to produce sufficient vitamin D) and take a supplement of 1,500 to 2,000 IU of vitamin D3 each day.