December 1, 2004
Potential Weight Loss and Vision Benefits Found in Eggs
NEW YORK, Dec. 1 /PRNewswire/ -- A scientific review article published in today's Journal of the American College of Nutrition supplement reports that leucine, an essential amino acid found in high quality protein like eggs, potentially provides a weight loss advantage during dieting by helping to reduce loss of lean tissue, promote loss of body fat, and stabilize blood glucose levels.
In another paper published in the JACN supplement, research shows that two antioxidants, lutein and zeaxanthin, may significantly reduce the risk of cataract and age-related macular degeneration (AMD).
In the research, eggs are cited as an important dietary source of leucine as well as lutein and zeaxanthin and, in the case of the latter two, research shows lutein and zeaxanthin in eggs to be more bioavailable than from other food sources.
High Quality Protein Promotes Weight Loss
"We found that increasing high-quality protein in the diet, like that found in eggs, dairy products and meats, provides a metabolic advantage due to a high content of the branched chain amino acid (BCAA) leucine," says article author Donald K. Layman, Ph.D., Professor of Nutrition, Department of Food Science and Human Nutrition and Department of Internal Medicine, College of Medicine, University of Illinois at Urbana-Champaign. According to Layman, both the amount of high quality protein consumed, as well as the time of day it is consumed, may play an important role in weight loss.
Layman found that unlike other essential amino acids, leucine plays several key roles in metabolism. "Leucine is key to the metabolic advantage of a higher protein diet because of its unique roles in regulation of muscle protein synthesis and insulin signaling," says Layman. According to his research, eating more protein rich foods like eggs and limiting carbohydrates helps burn body fat and control hunger and cravings, leading to weight loss.
When limiting calories, Layman recommends daily intake of protein above 1.5 g/kg of body weight (or above 102 grams of protein daily for a 150-pound person); whereas the current Dietary Reference Intake (DRI) for protein is about half that, set at 0.8 g/kg of body weight (or 55 grams of protein daily for a 150-pound person).
Layman's research also suggests that increased use of high quality protein at breakfast, in particular, maybe important for the weight loss advantage of a higher protein diet. In a 10-week study, Layman showed that eating a high quality protein breakfast while losing weight helps maintain lean muscle mass, which is critical to long-term weight loss and maintenance.
The study, which investigated the efficacy of two 1,700-calorie weight loss diets among women aged 45 to 57 years, found that women who ate the higher protein breakfast foods including eggs, low fat dairy and lean meats (containing 10 grams leucine daily) lost slightly more weight, but of the weight lost, nearly twice as much was fat compared to those eating a carbohydrate rich breakfast (containing 5 grams leucine daily). According to Layman, the findings may provide hope to those battling obesity, which has been linked to increased risk of diabetes, heart disease and other chronic diseases.
Eggs Promote Eye Health
Also published in today's JACN supplement is a review paper discussing two antioxidants, lutein and zeaxanthin, and the protective role they play in reducing the risk of cataract and age-related macular degeneration (AMD).
"Lutein and zeaxanthin, are concentrated in the macular region of the retina and the eye lens, where they protect the eye from harmful ultraviolet light," says article author Jeffrey Blumberg, Ph.D., Professor of Nutrition and Senior Scientist at the USDA Human Nutrition Research Center on Aging at Tufts University.
Blumberg says studies have shown that diets rich in lutein may cut the risk of cataracts by up to 20 percent and age-related macular degeneration by up to 40 percent. Although broccoli, kale and other dark green leafy vegetables are good sources of lutein, one egg yolk provides approximately 200 micrograms of lutein, and studies have shown that lutein from eggs is 200 to 300 percent more bioavailable than lutein from vegetable sources.
Cataracts are the leading cause of blindness in the world and affect more than 20 million Americans age 65 and older. Age-related macular degeneration is the leading cause among seniors of irreversible blindness in the United States.
In addition, a number of preliminary studies have found that lutein is available in both breast milk and the umbilical cord plasma. This suggests that mothers transfer lutein to their fetuses and newborns, providing them with this beneficial antioxidant. Future studies should continue investigating the potential beneficial role of lutein and maternal nutrition.
The December 2004 JACN Supplement contains proceedings from the First International Scientific Symposium on Eggs and Human Health: Transition from Restrictions to Recommendations, sponsored by the Egg Nutrition Center.
Egg Nutrition Center