Wednesday, November 3, 2010

The Cholesterol in Egg Yolk

There's been a widespread misconception developing among the public and even health practitioners, that consumption of dietary cholesterol and egg yolks is harmless. Much of this has to do with effective egg marketing

Stroke prevention expert, Dr. David Spence of The University of Western Ontario, nutrition expert Dr. David Jenkins of the Risk Factor Modification Centre at St. Michael's Hospital in Toronto, and cholesterol expert Dr. Jean Davignon of the Clinique de nutrition métabolisme et athérosclérose in Montreal have published a review in the Canadian Journal of Cardiology to put cholesterol back into perspective.

There are good reasons for long- standing recommendations that dietary cholesterol should be limited to less than 200 mg/day; a single large egg yolk contains approximately 275 mg of cholesterol (more than a day’s worth of cholesterol). Although two studies showed no harm from consumption of eggs in healthy people, this outcome may have been due to lack of power to detect clinically relevant increases in a low-risk population. However, the authors point out that in both studies, those who developed diabetes while consuming an egg a day doubled their risk of cardiovascular disease compared to those eating less than an egg a week. The studies also showed a significant increase of new onset diabetes with regular egg consumption.

Diet, the authors say, is not just about fasting cholesterol; it is mainly about the postprandial effects of cholesterol, saturated fats, oxidative stress and inflammation. A misplaced focus on fasting lipids obscures three key issues. Dietary cholesterol increases the susceptibility of low-density lipoprotein to oxidation, increases postprandial lipemia and potentiates the adverse effects of dietary saturated fat. Dietary cholesterol, including egg yolks, is harmful to the arteries.

Egg yolks are not something that should be eaten indiscriminately by adults without regard to their global cardiovascular risk, genetic predisposition to heart attacks and overall food habits.

Journal Reference:

JD Spence, DJ Jenkins, J Davignon. Dietary cholesterol and egg yolks: Not for patients at risk of vascular disease. Canadian Journal of Cardiology, 2010; 26 (9): e336-e339

What about Omega 3 enriched eggs?

Omega-3 enriched eggs are the same as the classic egg we all know, except they contain higher levels of the polyunsaturated fatty acid called omega-3. Omega-3 fatty acids are commonly found in fish and fish oils as well as canola oil, soybean and flaxseed.

Omega-3 enriched eggs are produced by altering the diet of laying hens. Hens are fed a special diet which contains 10-20% ground flaxseed. Flaxseed is higher in omega-3 fatty acids and lower in saturated fatty acids than other grains. As a result, the eggs produced from hens on this feed formula are higher in omega-3 fatty acids.

Comparison of Fat Profile*

Omega-3 Enriched** Classic Egg**
Total Fatty Acids 4.9 g 5.0 g
Omega-6 0.7 g 0.7 g
Omega-3 0.4 g 0.04 g
Monounsaturated 1.6 g 2.0 g
Saturated 1.2 g 1.5 g
Cholesterol 185 mg 190 mg
**based on 1 whole large egg
*Values are based on 10% flax in the diet. Nutrient values vary depending on the composition of the feed.

However, the total fat content and cholesterol level of the egg remain very similar.

When deciding whether to include eggs (including Omega-3 enriched eggs) in your diet, Mayo Clinic’s Dr Thomas Behrenbeck recommends

  • If you are healthy, limit your dietary cholesterol intake to less than 300 milligrams (mg) a day.
  • If you have cardiovascular disease, diabetes or a high low-density lipoprotein (LDL, or "bad") blood cholesterol level, you should limit your dietary cholesterol intake to less than 200 mg a day.

One large egg has about 213 mg of cholesterol — all of which is found in the yolk. Therefore, if you eat an egg on a given day, it's important to limit other sources of cholesterol for the rest of that day. Consider substituting servings of vegetables for servings of meat, or avoid high-fat dairy products for that day.

If you like eggs but don't want the extra cholesterol, use only the egg whites. Egg whites contain no cholesterol. You may also use cholesterol-free egg substitutes, which are made with egg whites. If you want to reduce cholesterol in a recipe that calls for eggs, use two egg whites or 1/4 cup (59 milliliters) cholesterol-free egg substitute in place of one whole egg.

Picture Credit : Malaysia's all-time favourite hawker-food, char-koay-teow, best with duck egg, but, which alone will contribute at least 425mg of cholesterol to your 'health'.

NB You will notice the three different figures quoted for the cholesterol content of eggs, from 190mg used by the Canadian Egg Marketing Agency, to 213mg by Mayo Clinic and 275mg by Spence, Jenkins and Davignon - these can be attributed to the size of the yolk and the breed of chicken.

1 comment:

  1.'s very informative.i'm a heart patient and wanted to know the benefits/harms of an egg yolk.