The Buzz: Vitamin D and Sunscreen
- by bonappetit
What’s the buzz?
Getting “enough” vitamin D is a challenge for many.
What does the science say?
Vitamin D (aka the sunshine vitamin) has been in the spotlight in recent years due to controversy among the scientific community over the benefits of its intake. While it’s known for its role in bone and teeth health (it aids in the absorption of calcium and phosphorus), some scientists hypothesize vitamin D may also have a role in reversing or preventing diseases such as depression, heart disease, and cancer, and suggest that the current recommendation to aim for a blood level of 20 nanograms/mL of blood is outdated. But others don’t necessarily believe that the research suggesting we need more is strong enough. Either way, for such an important vitamin, it can actually be quite hard to come by.
There are three sources of vitamin D: sunlight, food, and supplements. The sun is the primary source; our bodies synthesize vitamin D from UVB rays. Researchers estimate that individuals need to spend between five and 30 minutes per day in the sun, arms and legs exposed, without sunscreen, between 10 a.m. and 3 p.m. to get enough UVB exposure to create and store adequate supplies of vitamin D for present and future needs.
But before you spend your day at the beach soaking up all the rays you can, know this: those are the same UVB rays known to cause skin cancer. Wearing sunscreen to protect against skin cancer technically blocks those rays. So, although the sun is known to be a good source of the vitamin, it’s not the safest way to get it, and likely isn’t enough to support health year round.
Although our bodies can store vitamin D in fat tissue for future use, a 2015 study showed our supplies tend to peak in September and dwindle down around March. Additionally, an average of 14-18 percent of individuals are deficient in vitamin D (based on a target blood level of 20ng/mL), with those numbers being much higher (up to 50 percent) in people who have a darker skin complexion or live above 35 degrees latitude (anyone north of Tennessee’s southern border), which is much of the United States. If you’re thinking, “isn’t everyone told they’re deficient these days?” that’s where the controversy comes in. Many doctors look for blood levels closer to 40 nanograms/mL (vs. the recommended 20 ng/mL for bone health) based on emerging research that vitamin D plays a role in much more than just bone health, and that number may be what we need to protect against things like heart disease and depression. The good news is that it’s considered safe to consume up to 4,000 international units (IU) — the unit you will see on supplements and some packaged food labels — from a mix of food and supplements. So, if your doctor suggests you need a boost, there’s a simple solution beyond the sun.
What’s the takeaway?
Sunscreen is a key to prevention of skin cancer and its importance outweighs the fear of not absorbing enough vitamin D from the sun, especially since it can be obtained other ways. Many common foods like fatty fish, fortified milk and orange juice, and egg yolks contain vitamin D. But if you’re concerned about not getting enough vitamin D, talk to your doctor about testing and, if needed, supplementation.