August 20, 2010

Does the average American diet provide adequate nutrition?

"Nearly the entire U.S. population consumes a diet that is not on par with recommendations," is the conclusion of a report published online on August 11, 2010 in the Journal of Nutrition.

Susan M. Krebs Smith and her colleagues at the National Cancer Institute evaluated data from 16,338 individuals aged 2 and older who participated in the 2001-2004 National Health and Nutrition Examination Survey (NHANES). Quantities of foods reported in 24 hour dietary recall interviews were categorized into groups included in the USDA's food pyramid, which diagrams the recommended dietary intake of total fruits, whole fruits, total vegetables, dark green vegetables orange vegetables, legumes, starchy vegetables, other vegetables, milk, total grains, whole grains, meat and beans, and oils.

With the exception of total grains, and meat and beans, the majority of the sample surveyed failed to consume the minimum recommendations for each food group. Of 14 groups analyzed according to age and gender, two to three year olds had the least inadequate intake of total fruit, whole fruit, orange vegetables, legumes and milk. Almost all participants failed to consume enough dark green vegetables, orange vegetables, legumes and whole grains. Total vegetable and milk recommendations were unmet by most people in over half of the groups. Empty calories, including solid fats, added sugars and alcoholic beverages were overconsumed by more than 90 percent of those aged 70 and younger. Even though the recommended limit for alcoholic beverages for men is twice that of women, more men than women exceeded their limit, particularly those aged 31 to 50. Women aged 19 to 30 consumed less than the recommended intake in 8 of the 14 groups.

"This analysis indicates that nearly the entire U.S. population consumes a diet with fewer vegetables and whole grains than recommended and that a large majority underconsume fruits, milk, and oils relative to recommendations," the authors write.

"The stark contrasts observed between the diets of Americans as well as the U.S. food supply and current dietary guidance underscore the need for individual- and environmental-level interventions to facilitate healthier dietary intake patterns. Without such interventions, the diets of most U.S. adults and children will continue to be markedly divergent from recommendations, a worrisome state in the context of the obesity epidemic and alarming rates of other diet-related chronic diseases."

Blood disorders

Red blood cells are manufactured in the bone marrow. This process relies on various nutrients, including iron, vitamin B12, and folic acid, as well as smaller amounts of vitamin C, riboflavin, and copper. Also, the production of red blood cells is stimulated by a hormone called erythropoietin. Deficiencies in any of these nutrients or in erythropoietin can result in anemia. Besides iron deficiency anemia caused by bleeding, other forms of anemia include:

• Pernicious anemia (vitamin B12 deficiency)—It is estimated that 300,000 to 3 million people in the United States have a vitamin B12 (cobalamin) deficiency (Diamond AL et al 2004). Vitamin B12 deficiency is rarely related to a dietary deficiency. Rather, vitamin B12 relies on intrinsic factor, a protein generated by cells in the stomach, to be bound to vitamin B12 and then absorbed in the ileum, the last segment of the small intestine. People who lack intrinsic factor cannot use the available vitamin B12, meaning that anemia can develop even if large amounts of vitamin B12 are consumed. Besides a lack of intrinsic factor, pernicious anemia can be caused by Crohn's disease, stomach surgery, or a strict vegetarian diet. Breast-fed infants of vegan mothers are particularly at risk of vitamin B12 deficiency.
• Folic acid deficiency anemia—Folic acid is abundant in green leafy vegetables. Because many people in industrialized countries don't eat enough vegetables, folic acid deficiency is more common than pernicious anemia. Folate deficiency is found in malnourished individuals (especially alcoholics), infants who are fed only cows’ milk, pregnant women, and adults over age 60. It can also be caused by diseases that affect absorption in the small intestine, including Crohn's disease.
• Anemia of chronic disease—Anemia is associated with various chronic diseases and conditions, including infections, inflammatory diseases, and cancers that affect the ability of the body to produce red blood cells (Brill JR et al 2000; Bron D et al 2001). Diseases or conditions that are associated with anemia include cancer (Gillespie TW 2003; Knight K et al 2004), HIV/AIDS (Sullivan PS et al 1998), and testosterone deficiency (Bain J 2001; Zitzmann M et al 2000). In patients with cancer or HIV/AIDS, anemia is associated with increased mortality (Buskin SE et al 2004; Caro JJ et al 2001). Testosterone deficiency can cause anemia because the hormone helps stimulate kidneys and bone marrow to produce erythropoietin and stem cells.

Life Extension Update

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