Nutrition researchers at Kansas State University have published the first evidence that the absorption of cholesterol is reduced by another compound in the egg, a lecithin.
The research by Sung I. Koo, Yonghzhi Jiang and Sang K. Noh has resulted in the issue of U.S. Patent No. 6,248,728, "Compositions and methods for lowering intestinal absorption and plasma levels of cholesterol." The patent was issued June 19 to the KSU Foundation.
A peer-reviewed research paper by the three researchers, "Egg phosphatidylcholine decreases the lymphatic absorption of cholesterol in rats," appears in the September issue of Journal of Nutrition.
Many people believe that dietary cholesterol directly contributes to raising blood cholesterol. Because eggs provide about half the dietary cholesterol in a typical Western diet, the public has been advised to limit its egg consumption.
Under the experimental conditions using an animal model that closely mimics human physiology, Koo and his associates found that a particular egg phospholipid interferes with the absorption of egg cholesterol and markedly lowers its uptake by the intestine. When the phospholipid is saturated, its inhibitory effect is further enhanced.
The researchers controlled experimental conditions to specifically look at egg phospholipid and its effect on cholesterol absorption. Even though a good amount of cholesterol is consumed when an egg is eaten, much of the cholesterol becomes "unavailable for absorption" in the presence of the phospholipid, Koo said.
"This may be a reason why so many studies found no association between egg intake and blood cholesterol," he said. The phospholipid, or lecithin, found in egg markedly inhibits the cholesterol absorption. The inhibition is not 100 percent, he said. Some cholesterol is absorbed but the amount is significantly reduced in the presence of this phospholipid.
"Less absorption means less cholesterol introduced into the blood," Koo said. "We were able to determine experimentally that a substantial amount of the egg cholesterol is not going into the blood stream."
The compounds are naturally occurring or derived from their natural precursors which could lead directly to development of new compounds for lowering cholesterol. Koo anticipates that regulatory barriers to such development will be low.
Koo says people with normal cholesterol levels and no family history of cardiovascular disease should not worry about eating one to two eggs a day. There's more overall nutritional benefit than harm to be gained from eating "nutrient-dense" eggs -- in moderation, he said.
Egg contains a higher quality protein than protein found in meat, milk or fish.
Furthermore, egg is a significant source of vitamins A and E, and B vitamins, B-6, B-12 and folate, which are known to lower blood levels of homocyst(e)ine, an independent risk factor for heart disease.
Koo's research has received support from the Kansas Agricultural Experiment Station and the USDA National Research Initiative Competitive Grants Program.
Koo is a professor of human nutrition at K-State; Jiang received a master's degree in nutrition from K-State; and Noh is a postdoctoral researcher at K-State who is continuing research with Koo.