Donna Hargrove, D.O., FACOG - Nutritional Editor

Eggs have gotten a bad reputation in connection with heart disease due to cholesterol and many people have dropped them out of their diet, despite their good taste, value, convenience and nutrition. New research from the USDA shows eggs are lower in cholesterol than once thought. One large egg has 185 mg of cholesterol, a 14% decrease and 41 units of Vitamin D, a 64% increase, all for 70 calories. Many studies show that healthy adults can enjoy an egg a day without increasing their risk for heart disease.

 

Nutrition

Eggs have high-quality protein which helps active adults build muscle strength and helps prevent muscle loss in middle-aged and aging adults (1). Egg yolks are an excellent source of choline, an essential nutrient needed for health and disease prevention in all age groups. The facts are clear that Americans are not getting enough of this nutrient which is essential for most basic body functions. Choline helps maintain the structure of brain cell membranes, and is a key component of the neuro-transmitter that helps relay messages from the brain through nerves to muscles, liver metabolism and the transportation of nutrients throughout the body (2). Choline is especially important for pregnant and nursing women as it provides for brain and memory development in the fetus and newborn and can even help reduce the risk of certain birth defects, especially neural tube defects, despite folate supplementation. Two eggs provide about 250 mg of choline, or about half of the recommended daily intake for pregnant and nursing women (3, 6). Dietary choline has also been linked to a reduced risk of dementia, Alzheimer’s disease, breast cancer and heart disease. Eating foods naturally rich in choline is the best way to increase your intake. Besides egg yolks, choline is found in beef and chicken liver, soybeans, beef, milk and peanuts.

The Humble Egg?

Lutein and zeaxanthin, two antioxidants found in egg yolks, help prevent macular degeneration, a leading cause of age-related blindness. Though eggs contain a small amount of these two nutrients, research shows that the lutein from eggs may be more bioavailable than lutein from other food sources (4). One egg per day has been shown to increase the serum levels of these two antioxidants without altering serum lipid and cholesterol concentrations (5).

Conventional eggs come from hens housed in large laying facilities that use cage systems. They are fed specially formulated feed that consists of corn, cottonseed, soybean meal, and/or sorghum – depending on which grain is most affordable. Sometimes animal by-products are also added to increase protein content.

Free-range eggs come from hens that are either raised outdoors or have access to the outdoors. Due to seasonal conditions, access to outdoors can vary greatly between facilities. Cage-free eggs come from hens living in indoor facilities. These hens do not necessarily have access to the outdoors. They usually live on the floor of a barn or poultry house.

Nutrient enhanced eggs can have an increase in Omega-3 fatty acid and/or lutein. By including flax, marine algae or fish oils in the feed, or allowing for natural grazing, omega-3 fatty acid content in egg yolks can be dramatically increased, along with higher Vitamin E. Lutein is increased when hens are raised on a diet that includes marigold extract.

Organic eggs are produced from hens given feed grown without most conventional pesticides, fungicides, herbicides or commercial fertilizers. The use of growth hormones is also prohibited, which are not used commercially in the US, and the use of antibiotics is also prohibited. Vegetarian eggs means the feed for the hens is free of all animal by-products.

Brown vs white eggs

(Courtesy of eHow)

The difference in egg colors starts with the genetics of the chicken. Hens that have white feathers and white ear lobes lay white eggs. Chickens with red feathers and red ear lobes produce brown eggs.

  • The most common breed of chicken used for laying white eggs is the white leghorn. The breeds Rhode Island red and the New Hampshire, both of which are reddish brown, are the main sources of brown eggs.

  • There is no difference in the nutritional value of white and brown eggs. Both contain vitamin B12, omega-3 and omega-6 fatty acids, and folate among other nutrients.

  • The brown-colored egg tends to be more expensive than its white counterpart. This is usually because the hens laying brown eggs are larger and eat more feed than the white chickens, thus increasing costs to the farmer.

  • The white egg is favored by most people in the United States. The brown egg, however, is preferred by many consumers in the New England region.

  • It may be surprising to learn that not all eggs are brown or white. For example, some rare chicken breeds, such as the Araucana and Ameraucana, lay blue and blue-green eggs.

 

Egg Safety

The risk of purchasing an egg contaminated with salmonella bacteria is 1 in 20,000 eggs. An intact shell is the best barrier of protection. If bacteria are present at all, it will most likely be in the white where it is unable to grow due to lack of nutrients.  As the egg ages, the white thins and the yolk membrane weakens. Bacteria may then reach the nutrient rich yolk where it can grow over time if the egg is kept at warm temperatures. In a clean, non cracked, fresh shell egg, internal contamination rarely occurs. Don’t buy eggs that are cracked, leaking, or out-of-date. Two dates can appear on the carton. Egg cartons with the USDA shield must display the “pack date” or the day the eggs were washed, graded and placed in the carton. This number, called the “Julian Date”, is a three-digit code that represents the consecutive day of the year starting with January 1 as 001 and ending with December 31 as 365. The “sell by” or “expiration” date is not required by the federal government, buy may be required by the egg laws in the state where the eggs are marketed.

Eggs should be refrigerated at 45 degrees or below, in their carton, in the coldest part of the refrigerator, not the door. Eggs may be refrigerated 3-5 weeks from the day they are placed in the refrigerator. The sell-by date will probably expire by then but the eggs are perfectly safe to use.

Fresh eggs can be frozen, but not in the shell. Remove a whole egg from the shell and place in a tightly sealed container, labeled and dated. They can be stored up to one year. Defrost in the refrigerator in the sealed container and use within 3 days.

Eggs must be thoroughly cooked to destroy all bacteria. The whites will set between 144-149 degrees and the yolk between 149-158 degrees, and the whole egg between 144-158 degrees. For beaten egg food dishes, no visible liquid remains. Poached eggs should have the white completely set and the yolk firm but not hard (same for fried eggs). Hard cooked eggs should reach an internal temperature of more than 160 degrees. After cooking, cool hard boiled eggs under water or ice bath and refrigerate in the shell for up to one week.

Cooked dishes with eggs should be served promptly. If the dish is contaminated, bacteria will grow rapidly at temperatures between 40 and 140 degrees. Keep cold dishes 40 degrees or less with ice packs and hot dishes greater than 140 degrees with warmers. Whether warmed or cooled, the egg dishes should not remain left out or exposed for greater than 2 hours.

References:

(1)     Evans WJ. 2004. Protein Nutrition, Exercise and Aging. J Am Coll Nutr. 23(6)601S-609S.

(2)     Moeller SM, et al. 2000. The Potential Role of Dietary Xanthophylls in Cataract and Age-Related Macular Degeneration. J Am Coll Nutr. 19(5):522S-527S.

(3)     Zeisel SH. Choline: Critical role during fetal development and dietary requirements in adults. Annu Rev Nutr. 2006;26:229-50.

(4)     Chung HY, et al. Lutein bioavailability is higher from lutein-enriched eggs than from supplements and spinach in men. J Nutr. 2004; 134:1887-1893.

(5)     Goodrow EF, et al. Consumption of One Egg Per Day Increases Serum Lutein and Zeaxanthin Concentration in Older Adults without Altering Serum Lipid and Lipoprotein Cholesterol Concentrations. 2006. Amer Soc Nutr J. Nutr. 136:2519-2524.

(6)    Shaw GM, et al. Choline and risk of neural tube defects in a folate-fortified population. 2009. Epidemiology. Sep;20(5):714-9.

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