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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Food for Thought Food for Thought
 

Eggs -- All They're Cracked Up To Be


July 12, 2013

By Alexandra Weinstein, B.S.
Brigham and Women's Hospital

Eggs have gotten a bad rap for their relatively high fat and cholesterol contents. The average large egg has 212 milligrams of cholesterol. As foods go, that's quite a bit. However, only a small amount of the cholesterol in food passes into the blood.

Saturated and trans fats have much bigger effects on blood cholesterol levels. Recent research showed no evidence of an overall significant association between eating one egg a day and the risk of coronary heart disease or stroke.

Eggs are an excellent source of many essential and non-essential nutrients that are vital to our health. These include:

  • All nine essential amino acids that form proteins
  • Choline, an important nutrient for structure of cell membranes and brain development, especially during pregnancy
  • A low amount of unsaturated fat
  • Lutein and zeaxanthin, two carotenoids that have been associated with helping protect the eyes and decreasing the risk of macular degeneration
  • Vitamins B12, C, D, E and K
  • Iron and zinc

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What's in a Name?

Here's a guide to the different types of eggs and their nutritional value:

Type of Egg

Description

Nutrition

White, conventional
Chickens are fed grain diet; they may be given antibiotics
1 large egg has 75 calories, 5 grams fat, 1.5 grams saturated fat, 6.3 grams protein, vitamins and minerals listed above
Organic
Chickens are fed organic food
Same as white eggs
Cage-free
Produced by hens allowed to move about the floor of the barn and have access to nesting boxes or perches
Same as white eggs
Free- Range
Similar to cage free, but the hens have access to an outdoor runs as well
Same as white eggs
Brown
Egg shell color varies with the breed of the hen and has no effect on nutrition
Same as white eggs
Omega-3 enhanced
Chickens are fed flaxseed or fish oil in diet
Contain up to seven times the amount of omega-3 fatty acids as white eggs

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The Lowdown on Omega-3 Fatty Acids

Omega-3 and omega-6 are essential fatty acids that we cannot make on our own. We have to get them from our food. They are both polyunsaturated fats but have different chemical structures.

There are two types of omega-3 fatty acids: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic. EPA and DHA are the building blocks for hormones that control immune function, blood clotting, cell growth and cell membranes. Omega-3 fatty acids are mainly found in cold water fish like salmon, mackerel and black cod.

Omega-6 fatty acids are pro-inflammatory, which means that they promote inflammation throughout the body. Most Americans get far too much of the omega-6s and not enough of the omega-3s because of the amount of processed foods we eat. This imbalance may explain the rise in chronic diseases that are believed to be caused by inflammation in the body.

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Potential Health Benefits of Omega-3 Fatty Acids

  • Decrease the risk of heart disease - The American Heart Association says adults who get a daily average of 250 milligrams of omega-3 fatty acids from eating a variety of oily fish about twice a week, or through supplements, can decrease their risk of cardiovascular disease.
 
    • Relieve pain and inflammation - Omega-3s reduce the production of pro-inflammatory and pain-sensitizing messenger molecules while, at the same time, raising the levels of anti-inflammatory self-healing molecules.
    • Diminish memory loss - Eating more fish may help improve mood and memory, and protect the delicate cells of the brain and nervous systems. Low intake of DHA has been linked to an increased risk of dementia, such as Alzheimer's disease.
    • Improve skin and eyes - Omega-3s help reduce inflammation associated with ultraviolet radiation and keep eyes moist by controlling inflammation.
    • Reduce the inflammatory response in autoimmune disorders - Omega-3s have potential benefits to help manage symptoms of rheumatoid arthritis, lupus, ulcerative colitis and Crohn's disease.

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Egg-to-Egg Comparison

Here is a comparison of the fat profile of a regular large egg versus an omega-3 enriched egg:

Nutrient

Omega-3 enriched egg

Regular egg

Total fatty acids
4.9 grams
5.0 grams
Omega-6
0.7 grams
0.7 grams
Omega-3
0.4 grams
0.04 grams
Saturated fat
1.2 grams
1.5 grams
Cholesterol
185 milligrams
190 milligrams

Values based on 10% flax in the chicken's diet. Nutrient values differ by composition of feed.

Most omega-3 eggs on the market have between 200 and 300 milligrams of omega-3s. Four ounces of salmon, on the other hand, contains about two grams. While flaxseed is a good source of omega-3, it is not as easy to convert to DHA as fish sources. Thus, while these flaxseed fed eggs may contribute to our omega-3 intake, they are not as good a source of DHA as fish.

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The Take-Home Message

Eggs are a good source of protein and nutrients. They have not been proven to raise blood cholesterol. Thus, in moderation, they should be part of a healthy diet. While eating omega-3 eggs may be helpful, it is most beneficial to get these fatty acids from fish sources.

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Alexandra Weinstein, B.S. is a dietetic intern at Brigham and Women's Hospital.

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