美国鸡蛋质量提高：胆固醇减少14%，维他命D增加64%

Cholesterol in eggs has dropped in the past decade, according to a new analysis by the U.S. Department of Agriculture.

Eggs, on average, have 14% less cholesterol and 64% more vitamin D than the last time they were analyzed by the government in 2002.

"We had last sampled eggs around 9 or 10 years ago," Jacob Exler, PhD, a nutritionist with the Nutrient Data Laboratory at the USDA Agricultural Research Service tells WebMD.

For the most recent analysis, regular large-shell eggs were picked up from 12 locations across the country and then sent off to an independent lab at Virginia Tech University for evaluation.

The average amount of cholesterol found in one large egg is 186 milligrams -- a level 14% lower than recorded in the last analysis. A large egg has, on average, 41 International Units of vitamin D -- 64% higher than found last time.

However, Exler says, the message is still moderation. "It's still one egg a day," he says. He points to the Dietary Guidelines for Americans 2010, which recommend getting less than 300 mg a day of dietary cholesterol.

"Eggs are a healthy food in a diet that has a variety of foods," Exler says.

Egg Analysis: Details

The USDA has a sampling plan for retail foods nationwide, Exler tells WebMD.

For the recent egg analysis, the laboratory workers evaluated not only cholesterol and Vitamin D, but a host of other nutrients.

The new information will be updated on nutrition labels on cartons of eggs in grocery stores and on menus.

Exactly why the eggs are found to have lower cholesterol than before isn't known for sure, but may be because of improvements farmers have made to hen feed.

The vitamin D increase, Exler says, is easier to explain. "Some chickens are being supplemented with vitamin D," he says. "We think because of the interest in vitamin D that more egg producers will be changing the diet of their chickens to have more vitamin D."

Cholesterol in Eggs: Other Views

Eggs in moderation can be part of a heart-healthy diet, says David Katz, MD, MPH, director and founder of the Yale University Prevention Research Center in Derby, Conn.

In a study published in 2010 in Nutrition Journal, Katz and his colleagues found that moderate egg intake didn't adversely affect blood cholesterol in men and women with high cholesterol (although egg substitutes improved it). The study was funded by the CDC and the Egg Nutrition Center, funded by the American Egg Board, an industry group.

Moderate egg consumption doesn't appear to be linked to an increased cardiac risk, Katz and his colleagues conclude, although further testing is needed on people with established heart disease "to clarify the place of eggs in a judicious and heart-healthy diet."

When people are told to avoid or eliminate eggs from their diet, Katz says they might substitute unhealthy foods. "When we tell people not to eat eggs, what are they eating instead?" He suspects they may substitute Danish, for instance, for their breakfast eggs.

- By Kathleen Doheny，Reviewed by Laura J. Martin, MD，WebMD Health News