To protect myself, I use sunscreen everyday and try to limit my sun exposure during the afternoon hours. However, I heard that sunscreen prevents vitamin d absorption. Is this true? How much vitamin D do I need, anyway?
Basking in the sun helps make the active form of vitamin D in your body. In fact, the major source of vitamin D is exposure of our skin to sunlight.
While using sunscreen is encouraged because it helps reduce your risk of skin cancer (sunscreen protects your skin from the sun’s damaging ultraviolet rays), sunscreen with sun protection factors (SPF) of 8 cause a 95 percent reduction of the vitamin D activation process, according to Dr. Michael F. Holick, PhD, MD, Professor at Boston University Medical Center. This sounds like one of those “darned if you do and darned if you don’t” situations.
But here’s the good news, according to Dr. Holick: “In general, five to 15 minutes of exposure of hands, face, and arms to sunlight, two to three times a week, should be adequate to satisfy a person’s vitamin D requirement. This, however, is dependent on the person’s sensitivity to sunlight. For example, if you get a sunburn after 30 minutes of sun exposure, then five to 10 minutes would be more than adequate. This practice would provide the benefits of sunlight while limiting the damaging effects,” says Holick.
But take note: People who live above latitudes of approximately 40 degrees north (Boston or Chicago) and below 40 degrees south (Melbourne, Australia) won’t be exposed to strong enough sunshine to make vitamin D during most of the winter. This period of sunlight deficiency is even longer for those in far northern and southern spots. Also, more time is needed to make the same amount of vitamin D in people with an increased amount of melanin, which are the darker pigments that occur in the skin, compared to individuals with lighter skin.
Adults aged 19 through 50 need 200 international units (IU) daily. That number doubles to 400 IU for ages 51 through 70 and triples to 600 IU after age 70. As you get older, your skin’s capacity to produce vitamin D decreases.
While there are very few foods that contain a good amount of vitamin D, fortified milk products can be a big-ticket vitamin D item. A cup of fortified milk has 100 IU. Consequently, two cups of milk will do it for many adults, but may not even come close to the needs of older folks.
Fortified foods, such as cereals, can provide around 40 IU per serving, and some fatty fish, such as three ounces of salmon with bones, provides 10 IU per serving. Although some is good, more is not better. Too much vitamin D can be toxic. If you think you may need to take a supplement, check with your doctor. A registered dietitian can assess your diet and help you meet your vitamin D needs.