Weight-loss diets can hinder natural killer cells--an important part of the immune system--even if the diets provide healthful meals.
A new Agricultural Research Service study confirms earlier findings by other scientists about changes in killer cell activity in fasting or malnourished people. Eight healthy women, age 28 to 41, cut their calorie intake in half for 15 weeks. The researchers found about a 20 percent decrease in the activity of killer cells, which help protect the body against viruses and tumors.
They measured this activity with a standard laboratory test in which natural killer cells isolated from blood samples were mixed with target cells. Target cells successfully attacked by the killer cells released a tracer element--a special form of chromium--that the researchers could then measure.
Physicians, dietitians and other healthcare professionals could use the information to improve weight loss programs by minimizing unwanted effects on the immune system. Longer and more restrictive periods of dieting could further undermine the killer cells, scientists caution. An estimated 40 percent of American women and 25 percent of American men are trying to lose weight. Obesity increases risk of diabetes, cardiovascular disease, hypertension and other illnesses. (SOURCE: Agricultural Research Service)
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