The Second National Report on Biochemical Indicators of Diet and Nutrition, by the Centers for Disease Control and Prevention, used data from blood and urine samples collected from participants in CDC's National Health and Nutrition Examination Survey -- 1999 to 2006, with emphasis on 2003 to 2006.
"These findings are a snapshot of our nation's overall nutrition status," Christopher Portier, director of CDC's National Center for Environmental Health, said in a statement. "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."
Although the report gave limited but generally favorable review of the nation's nutrition status, the findings didn't necessarily indicate that people consume healthy and balanced diets, Portier said.
The report found deficiency rates for vitamins and nutrients vary by age, gender or race/ethnicity, and the deficiency rate for vitamin D can be as high as 31 percent in non-Hispanic blacks.
The report found the fortification of cereal-grain products with folic acid, which began in 1998, dropped the levels of folate deficiency in women of childbearing age from 12 percent to 1 percent. Folate can help prevent major birth defects of the brain and spine in the first weeks of pregnancy, when women often don't know they are pregnant, health officials said.