Nutrition Report Reflects Race and Sex Differences

Rod Franklin

April 04, 2012

April 4, 2012 — A national survey that has aligned the concentrations of biochemicals found in blood or urine with various demographic subgroups shows that fortification of grain-based food products with folic acid (vitamin B9), required by law since 1998, continues to minimize the chances for neural tube birth defects in most American women.

Data from the latest National Health and Nutrition Examination Survey (NHANES), just released by the US Centers for Disease Control and Prevention (CDC), also suggest that ethnicity is a factor in measures of vitamin D deficiency, as well as in measures of heart-healthy polyunsaturated fatty acids at beneficial levels.

The Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population states further that iron deficiencies and excesses can be associated with age, ethnicity, and sex.

Data collected by the CDC's National Center for Health Statistics were analyzed between 2003 and 2006 for body fluid concentrations of 58 biochemical indicators that can point to healthy or unhealthy patterns in diet and nutrition. To calculate the relationship of nutritional trends with demographic variables, including age, sex, or ethnicity, analysts rendered survey statistics in the form of unadjusted geometric means, selected percentiles, and prevalence estimates. Calculations were made for blood and urine concentrations of vitamins, fatty acids, trace elements, metabolites, isoflavones, lignans, and acrylamide hemoglobin adducts.

Additional information cited in the 484-page study was drawn from an inaugural 2008 nutrition report that used earlier NHANES survey data. That document analyzed the significance of 27 biochemical indicators from body fluids that were collected in NHANES samples taken between 1999 and 2002.

Data from the combined 2 NHANES sample periods (1999 - 2006) show that unhealthy low serum (<2 ng/mL) and red blood cell folate (<95 ng/mL) levels have dropped to less than 1% of American women of childbearing age, regardless of ethnicity. This trend has continued throughout the era that began in the late 1990s, when the US Food and Drug Administration required the addition of folate supplements to food products.

Studies have demonstrated that a sufficient intake of folic acid helps prevent major birth defects, such as brain defects and spina bifida. The most recent NHANES data show that non-Hispanic whites have the highest folic acid concentrations, whereas non-Hispanic blacks have the lowest levels. Intermediate levels of folate were recorded in Mexican Americans.

In the category of fat-soluble vitamins and nutrients, the likelihood of vitamin A or E deficiencies was reported to be very low throughout the population. However, higher rates of serum 25-hydroxyvitamin D deficiency (<30 nmol/L) were reflected in 31.1% of the non-Hispanic blacks compared with 11.3% of Mexican Americans and 3.6% of non-Hispanic whites.

In the report summary, the CDC asserts that further research might be warranted to explain this observation, particularly given that greater bone density and fewer fractures have been reported for the non-Hispanic black subgroup.

Additional observations from the NHANES survey include the following:

  • B vitamins (water-soluble vitamins category): People aged 40 years or older exhibit a higher likelihood of deficiency in vitamin B6 or vitamin B12 compared with younger individuals.

  • Fatty acids (fat-soluble vitamins and nutrients category): Low (<100 μmol/L) concentrations of saturated, monounsaturated, and polyunsaturated fatty acids were more likely to be found in younger adults. Heart-healthy polyunsaturated fatty acids such as eicosapentaenoic acid or docosahexaenoic acid were found at higher concentrations in non-Hispanic black adults than in other ethnic groups. The survey included first-time measurements for 24 plasma fatty acids.

  • Iron (trace elements category): According to the assessment of a new marker for iron status, the study reports iron deficiencies in 10.9% of Mexican-American children aged 1 to 5 years, 16.0% of non-Hispanic blacks, and 13.2% of Mexican-American women aged 12 to 49 years. Adult males, however, showed a higher risk for iron excess.

  • Iodine (trace elements category): Lower urinary iodine concentrations, which can elevate the risk for disorders such as mental retardation or hypothyroidism, were observed more often in women aged 20 to 39 years than in other groups. Children generally exhibited higher iodine concentrations. Overall iodine concentrations, however, were reported to be relatively stable since the late 1980s.

Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population .

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