Eating Protein Preserves Muscle, Physical Function in Postmenopausal Women
Dieting postmenopausal women who want to avoid losing muscle as they lose fat should pay attention to a new University of Illinois study. Adding protein throughout the day not only holds hunger pangs at bay so that dieters lose more weight, it keeps body composition in better proportion.
"A higher-protein weight-loss diet is more protective of muscle," says Ellen Evans, a former University of Illinois associate professor of kinesiology and community health and member of the university's division of nutritional sciences.
Researchers wanted to study the way body composition relates to physical function because older women who diet risk losing muscle as well as fat. "That loss can affect their strength, balance, and how well they perform everyday tasks, such as climbing stairs and getting up out of a chair," says Mina Mojtahedi, a researcher in Evans's laboratory.
The study shows that higher protein intake during weight loss can offset negative effects on muscle mass by maintaining more muscle relative to the amount of weight lost. Women who ate more protein lost 3.9% more weight and had a relative gain of 5.8% more thigh muscle volume than woman who did not, she says.
"When a woman has less weight to carry, even if she's lost a bit of lean mass in her legs, the effect is that she has better physical function," she says.
In the six-month double-blind study, 31 healthy, postmenopausal obese women were divided into two groups. Each group followed a 1,400-calorie weight-loss diet based on the USDA's MyPyramid, but one group received a powdered whey protein supplement in the morning and again in the afternoon or evening; the other received a placebo that contained carbohydrates.
"We believe it's important to eat protein in the morning and through the day so those amino acids are always available. Unfortunately, American women tend not to eat much protein, especially when they're trying to cut calories. But it's easy to add protein powder into a smoothie or eat a high-protein snack and incorporate a healthier diet into a busy lifestyle," she says.
Both groups were encouraged to engage in light exercise (walking and stretching) and given diet education, including examples of healthy daily menus and a scale to measure portion size.
Before and after the study, participants were assessed for strength, balance, and the ability to perform physical tasks such as walking 50 ft, standing up five times from a chair, and lifting a book 12 inches above shoulder height.
Magnetic resonance imaging was used at the beginning and end of the study to measure muscle volume of the right thigh, the amount of fat around the thigh, and the amount of fat within the thigh muscle.
In both groups, strength decreased as weight decreased. However, the study suggests that an increase in the amount of muscle relative to fat had beneficial effects on balance and performance, Evans notes.
And, even though weight loss in these older women had a negative effect on strength, their reduced weight helped with other aspects of physical function, she says. "We hypothesize that more vigorous exercise, in particular, resistance training, would preserve even more muscle."
— Source: University of Illinois College of Agricultural, Consumer, and Environmental Sciences
Cooked Green Vegetables, Dried Fruit, Legumes, Brown Rice Associated With Fewer Colon Polyps
Eating legumes at least three times per week and brown rice at least once per week was linked to a reduced risk of colon polyps by 33% and 40%, respectively, according to Loma Linda University research recently published in Nutrition and Cancer. High consumption of cooked green vegetables and dried fruit was also associated with greater protection, the study shows.
"Eating these foods is likely to decrease your risk for colon polyps, which would in turn decrease your risk for colorectal cancer," says lead author Yessenia Tantamango, MD, a postdoctoral research fellow with Adventist Health Study-2 at Loma Linda University. "While a majority of past research has focused on broad food groups, such as fruits and vegetables, in relation to colon cancer, our study focused on specific foods, as well as more narrowed food groups, in relation to colon polyps, a precursor to colon cancer. Our study confirms the results of past studies that have been done in different populations analyzing risks for colon cancer."
Results also show that consuming cooked green vegetables once per day or more, as compared with less than five times per week, was associated with a 24% reduction in the risk of rectal/colon polyps. Consuming dried fruit three times per week or more, vs. less than once per week, was associated with a 26% reduced risk.
The protective effects of these foods could be due in part to their cancer-fighting agents, the study reports.
"Legumes, dried fruits, and brown rice all have a high content of fiber, known to dilute potential carcinogens," Tantamango says. "Additionally, cruciferous vegetables, such as broccoli, contain detoxifying compounds, which would improve their protective function."
Past studies examining the effect of meat intake and legumes on colon cancer have shown that people eating meat, associated with an increased risk of colon cancer, may receive some protection when they also consume legumes. Tantamango says this suggests that besides fiber content, there may be something else present in legumes that provides a protective effect.
Researchers analyzed data from 2,818 subjects who participated in Adventist Health Study-1 (administered from 1976 to 1977) and who answered a follow-up survey 26 years later from Adventist Health Study-2. The first survey asked respondents to indicate how often, on average, they consumed specific foods. The follow-up survey asked respondents who had undergone colonoscopies to indicate physician-diagnosed colorectal polyps. During the 26-year follow-up, 441 cases of rectal/colon polyps were identified.
The study assessed several possible confounding factors, including a family history of colorectal cancer, education, physical activity level, alcohol intake, smoking, constipation, intake of sweets, pain medication, and multivitamins, as well as different food variables. The study then adjusted for those factors that were shown to distort the effect of the foods and food groups under study. About 25 foods and food groups in total were examined.
Tantamango says there is a need for future studies to examine foods shown to reduce the risk of colon polyps, since it is possible that interactions between various nutrients with anticancerous properties will be better able to explain these findings.
— Source: Loma Linda University Adventist Health Sciences Center