The rays of the sun are a source of vitamin D. Skin converts the rays to vitamin D; however, African-Americans have extra melanin that absorbs the sun's harmful ultraviolet rays, offering them greater protection against skin cancer. At the same time, however, this also decreases production of vitamin D in the skin, causing a higher prevalence of vitamin D deficiency among African-Americans. Blood levels of vitamin D above 50 nmol per liter are necessary for proper bone growth in nearly all people.
Food Sources of Vitamin D
Fatty fish such as salmon, tuna and mackerel and fish liver oils are among the best sources of vitamin D. Cod liver oil has 1,360 IUs of vitamin D per tbsp. Small amounts of vitamin D are also found in beef liver, cheese and egg yolks. Milk and infant formula as well as some breakfast cereals, orange juice, yogurt and margarine are fortified with vitamin D. African-Americans are not less likely to ingest these foods than other Americans, with the exception of milk, since many blacks are lactose-intolerant.
Health Effects
Vitamin D aids absorption of calcium, a mineral that strengthens the bones. Vitamin D deficiency leads to less calcium absorption and weaker bones. Vitamin D-deficient African-Americans are at risk for diseases such as rickets, osteomalacia or adult rickets and osteoporosis. This deficiency also increases their risk for muscle weakness and psoriasis or skin plaques. Scientists are beginning to discover the role that vitamin D plays in protecting against chronic conditions including cardiovascular disease, diabetes, and some cancers which are as prevalent or more prevalent among blacks than whites.
Recommendations - Dietary
Recommended dietary allowances for vitamin D are 400 IUs, international units, per day for children 12 months and under and 600 IUs for ages one to 70. Adults over 70 should get 800 IUs of vitamin D daily from supplements or food sources Dr. Rick Kittles, a geneticist studying the effects of vitamin D on prostate cancer in African-Americans, suggests that people who live in gloomy climates take at least 1,000 IUs of vitamin D daily.
Recommendations - Sun exposure
Sunlight exposure recommendations are debated in the scientific community because of the potential increase in skin cancer risk. As little as 10 minutes of sun exposure per day is thought to be enough to prevent vitamin D deficiencies. The lack of concrete sun exposure recommendations implies that African-Americans should focus on getting most of their vitamin D from dietary sources. African-Americans should also ask their physicians to check their blood levels of vitamin D and make lifestyle adjustments based on their results.
References
- The Journal of Nutrition: Vitamin D and African Americans
- National Institutes of Health: Vitamin D
- Northwestern University: Vitamin D deficiency poses added risks for African-Americans
- MayoClinic: Vitamin D
- MedlinePlus: Do low vitamin D levels matter during pregnancy?
- University of Pennsylvania: Vitamin D and Human Skin Color
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