According to the “Second National Report on Biochemical Indicators of Diet and Nutrition,” released by the Centers for Disease Control and Prevention (CDC), the U.S. population has good levels of vitamins A and D and folate in the body, but some groups still need to increase their levels of vitamin D and iron. The report offered a limited but generally favorable review of the nation’s nutrition status although the findings did not necessarily indicate that people consume healthy and balanced diets.
CDC’s Division of Laboratory Sciences in the National Center for Environmental Health measured indicators in blood and urine samples collected from participants in CDC’s National Health and Nutrition Examination Survey. Data were processed for the years 1999-2006, with emphasis on newly available data for 2003-2006.
“These findings are a snapshot of our nation’s overall nutrition status,” said Christopher Portier, PhD, director of CDC’s National Center for Environmental Health. “Measurements of blood and urine levels of these nutrients are critical because they show us whether the sum of nutrient intakes from foods and vitamin supplements is too low, too high or sufficient.”
The report also found that deficiency rates for vitamins and nutrients vary by age, gender or race/ethnicity and can be as high as 31% for vitamin D deficiency in non-Hispanic blacks.
“Research shows that good nutrition can help lower people’s risk for many chronic diseases. For most nutrients, the low deficiency rates, less than one to 10%, are encouraging, but higher deficiency rates in certain age and race/ethnic groups are a concern and need additional attention,” said Christine Pfeiffer, PhD, lead researcher in the Division of Laboratory Sciences in CDC's National Center for Environmental Health.
CDC’s Second Nutrition Report establishes blood and urine reference levels for 58 biochemical indicators; more than twice as many indicators as its first report, published in 2008. The report includes first-time data for a new indicator of iron deficiency and for 24 healthy and unhealthy fatty acids.
Ingredients were also singled out and assessed individually.
Folic acid: The report credited the ongoing fortification of foods “a sustained public health success.” Before fortification began, approximately 12% of women of childbearing age were deficient in folate, as determined by blood folate levels. The report found that the fortification of cereal-grain products with folic acid, which began in 1998, has had a sustained positive impact on blood folate levels. Folate deficiency dropped to less than 1% after fortification. The report also showed that blood folate levels in all race/ethnic groups are 50% higher since fortification began.
Vitamin D: 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 yet have a higher rate of vitamin D deficiency. According to the report, the vitamin D deficiency rate for Mexican-Americans was 12% and for non-Hispanic whites it was 3%.
Iodine: Findings were not as encouraging with regard to the iodine status in young women (20-39 years of age), as this age group had iodine levels that were just above iodine insufficiency. Young women also had the lowest iodine levels among any age group of women.
Iron: Using a new marker of iron status, the report indicated higher rates of iron deficiency in Mexican-American children aged one to five years (11%) and in non-Hispanic black (16%) and Mexican-American women (13%) of childbearing age (12-49 years) when compared to other race/ethnic groups. The new iron marker measurements will help clinicians better interpret iron status in individuals, especially in persons with chronic disease that includes inflammation, such as certain cancers.
Healthy and unhealthy fatty acids: Using information gleaned from a new deficiency marker, the report provided first-time data on blood levels of fatty acids in the U.S. population. These included heart healthy polyunsaturated fatty acids as well as saturated fatty acids, which increase risk of heart disease. The report found that 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 nation’s progress toward heart healthy diets.