Thursday, May 27, 2010

Irradiation Depletes Nutrients in Salads, Slightly

Irradiation depleted three of eight nutrients in salad greens by small amounts in a new study of the effects of the controversial food santization process.

The Agricultural Research Service study of two popular baby-leaf spinach cultivars found that irradiation decreased ascorbic acid, or Vitamin C, by 42 percent. Irradiation converted vitamin C to an oxidized form called dehydroascorbic acid, which provides the same benefits as vitamin C inside the leaf, according to the researchers.

Levels of lutein/zeaxanthin, and B-carotene, which make up 80 percent of all carotenoids in spinach, were reduced on average by 12 percent in the salad leaves.

Four nutrients -- folate, Vitamin E, Vitamin K and neoxanthin -- exhibited little or no change in concentration with increasing levels of irradiation during the study.

For the study, the two spinach cultivars were grown, harvested, sanitized and packaged according to industry practices. Each cultivar was packaged in both air or nitrogen gas as used by industry to extend shelf life. The cultivars then were exposed to up to 2.0 kiloGrays (kGy) of radiation in 0.5 kGy increments.

Irradiating salad leaves after washing has been shown to reduce harmful and non-harmful microorganisms. The U.S. Food and Drug Administration has approved up to 4 kGy of irradiation for fresh iceberg lettuce and spinach.

Source: Agricultural Research Service, USDA

Eating Nuts Improves Blood Cholesterol

Consuming more nuts appears to be associated with improvements in blood cholesterol levels, according to a pooled analysis of data from 25 trials reported in the May 10 issue of Archives of Internal Medicine.

"Dietary interventions to lower blood cholesterol concentrations and to modify blood lipoprotein levels are the cornerstone of prevention and treatment plans for coronary heart disease," the authors write as background information in the article. "Recently, consumption of nuts has been the focus of intense research because of their potential to reduce coronary heart disease risk and to lower blood lipid [fat and cholesterol] levels based on their unique nutritional attributes."

Nuts are rich in plant proteins, fats (especially unsaturated fatty acids), dietary fiber, minerals, vitamins and other compounds, such as antioxidants and phytoesterols.

Joan Sabaté, M.D., Dr.P.H., of Loma Linda University, Loma Linda, Calif., and colleagues pooled primary data from 25 nut consumption trials conducted in seven countries and involving 583 women and men with high cholesterol or normal cholesterol levels. All the studies compared a control group to a group assigned to consume nuts; participants were not taking lipid-lowering medications.

Participants in the trials consumed an average of 67 grams (about 2.4 ounces) of nuts per day. This was associated with an average 5.1 percent reduction in total cholesterol concentration, a 7.4 percent reduction in low-density lipoprotein (LDL, or "bad" cholesterol) and an 8.3 percent change in ratio of LDL cholesterol to high-density lipoprotein (HDL, or "good" cholesterol). In addition, triglyceride levels declined by 10.2 percent among individuals with high triglyceride levels (at least 150 milligrams per deciliter), although not among those with lower levels.

"The effects of nut consumption were dose related, and different types of nuts had similar effects on blood lipid levels," the authors write. "The effects of nut consumption were significantly modified by LDL-C, body mass index and diet type: the lipid-lowering effects of nut consumption were greatest among subjects with high baseline LDL-C and with low body mass index and among those consuming Western diets."

The results support the inclusion of nuts in therapeutic dietary interventions for improving blood cholesterol levels, they conclude.

"Nuts are a whole food that have been consumed by humans throughout history. Increasing the consumption of nuts as part of an otherwise prudent diet can be expected to favorably affect blood lipid levels (at least in the short term) and have the potential to lower coronary heart disease risk."

Source: Journal of the American Medical Association