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CDC report examines vitamin levels in U.S. population

Monday April 2, 2012
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The U.S. population overall has sufficient levels of vitamins A and D and folate in the body, but some groups need to increase their levels of vitamin D and iron, according to a report by the Centers for Disease Control and Prevention.

Deficiency rates for vitamins and nutrients vary by age, gender and race/ethnicity, according to the report, and can be as high as 31% for vitamin D deficiency in non-Hispanic blacks.

"Research shows that good nutrition can help lower peopleís risk for many chronic diseases," Christine Pfeiffer, PhD, lead researcher in the Division of Laboratory Sciences in the CDCís National Center for Environmental Health, said in a news release. "For most nutrients, the low deficiency rates — less than 1% to 10% — are encouraging, but higher deficiency rates in certain age and race/ethnic groups are a concern and need additional attention."

The CDC said its "Second National Report on Biochemical Indicators of Diet and Nutrition" offers a limited but generally favorable review of the nationís nutrition status, although the findings do not necessarily indicate that people consume healthy and balanced diets.

CDC researchers measured indicators in blood and urine samples collected from participants in the agencyís National Health and Nutrition Examination Survey. The report presents data for 1999 through 2006, with an emphasis on newly available data for 2003 through 2006.

Folic acid fortification

The report found that the fortification of cereal-grain products with folic acid beginning in 1998 has had a sustained positive impact on blood folate levels, with folate deficiency dropping to less than 1% after fortification. Blood folate levels in all race/ethnic groups are 50% higher since fortification began.

Before fortification began, approximately 12% of women of childbearing age were deficient in folate, which is essential during periods when cells rapidly divide and grow and thus is particularly important for women prior to and during pregnancy and for children during infancy. Folic acid can help prevent certain major birth defects of the babyís brain and spine, such as spina bifida.

Vitamin D deficiency

The report found the highest rates of vitamin D deficiency in non-Hispanic blacks (31%) despite clinical data showing greater bone density and fewer fractures in this group. Further research is needed to explain why non-Hispanic blacks have better bone health but a higher rate of vitamin D deficiency, the report's authors said. According to the report, the vitamin D deficiency rate was 12% for Mexican-Americans and 3% for non-Hispanic whites.

Vitamin D is essential for good bone health and may also improve muscle strength and protect against cancer and type 2 diabetes, the CDC noted. Researchers are investigating these potential benefits and the vitamin D requirements for various groups.

Iodine levels

Findings were not as encouraging regarding iodine levels in women ages 20 to 39. This age group had iodine levels that were slightly above iodine insufficiency. Young women had the lowest iodine levels among any age group of women.

Iodine is an essential component of thyroid hormones that regulate human growth and development, the report's authors noted. Iodine deficiency disorders include mental retardation, hypothyroidism, goiter, cretinism and varying degrees of other growth and developmental abnormalities. Iodine is especially important in women during childbearing years to ensure the best possible brain development of the fetus during pregnancy.

New data categories

Using a new marker of iron status, the report indicates higher rates of iron deficiency in Mexican-American children ages 1 to 5 (11%) and in non-Hispanic black (16%) and Mexican-American (13%) women of childbearing age (12 to 49) when compared to other race/ethnic groups. The new iron marker measurements will help clinicians better interpret iron status in individuals, especially in those with chronic disease that includes inflammation, such as certain cancers.

The report also provides first-time data on blood levels of fatty acids in the U.S. population. These include heart-healthy polyunsaturated fatty acids and saturated fatty acids, the latter of which increase risk of heart disease. The report found heart-healthy polyunsaturated fatty acid levels in plasma differ by race/ethnicity. These first-time measurements provide a baseline that will allow CDC to track fatty acid levels over time, which will evaluate the nationís progress toward heart-healthy diets.

To read the report, visit www.cdc.gov/nutritionreport.

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