Vitamin D is rarely listed on food labels. Most of us remember it as the sunshine vitamin we learned about long ago in high school biology class. And, few of us think about this vitamin daily. Maybe we should. Vitamin D may be more important to your health than you realize.
Vitamin D protects your bones and may prevent osteoporosis (adult bone thinning). It also helps maintain a healthy immune system and protects you against cancer, especially colon, prostate, and breast cancer. Most of us don’t get enough of this important vitamin. There are few strong food sources – salmon, mackerel, tuna, and sardines – that we eat regularly. Milk is a good, but not great source of the vitamin.
Our best source of vitamin D may well be sunshine. When your skin is exposed to ultraviolet (UV) light it triggers vitamin D production. This is one of the few vitamins our bodies can make and the only one where we can get our full complement of the vitamin from sun exposure. The problem is most of us do not get enough sun and when we do we slather on sunscreen which blocks UV rays. Sunscreens with an SPF (sun protection factor) of 8 or greater will block enough UV rays to diminish vitamin D production.
In addition to sunscreen, the season, area of the country, time of day, cloud cover, smog, skin color, clothing, and your age all interfere with vitamin D production. Living in New England between November and February, you are unlikely to get enough sun exposure to provide adequate vitamin D. living in a smoggy city, such as Los Angeles, will also cut down on D production. Women who wear full robes and head covering for religious reason, night shift workers who sleep during daylight hours, homebound elderly, and children who spent long hours inside in daycare may all get too little vitamin D.
Melanin is the pigment that gives our skin color. People from Asia, Africa and the Middle East have more melanin and darker skin. This higher melanin content interferes with the body’s natural ability to produce vitamin D from sunlight. Over 40% of African American women have low blood levels of vitamin D.
The vitamin is converted to its active hormone form in the liver and kidneys. Active vitamin D sends a message to the intestines to increase the absorption of calcium and phosphorus, two mineral vital to bone health. Too little D, and bones become thin, brittle and misshapen. In children this deformity is called rickets. Prolonged low levels of vitamin D contribute to osteoporosis (adult bone thinning). In a review of women hospitalized with hip fracture, 50% had signs of vitamin D deficiency.
If you are over 50, your skin produces vitamin D less efficiently and your liver and kidneys are less able to convert D to its active form. It’s tough to get enough vitamin D daily through food. Most adults need a supplement. The easiest way to get enough is to buy a calcium supplement plus vitamin D. Many experts now feel a blood test to check levels of vitamin D should be part of routine physical check-ups.