Flavour of the Week

The Yolk – A Burden or a Blessing?


Over Easter it’s impossible to ignore the omnipresent Easter Egg – while the majority seem to be in chocolate form, the traditional egg can still be found. Did the Easter Bunny bring you a low-calorie, nutrient-rich present or a cholesterol-laden, unwanted gift?

The healthfulness of eggs is a controversial topic with experts weighing in on both sides. Although most would agree that egg whites provide an excellent source of complete protein and are low in calories, cholesterol and fat, the debate rages furiously about the yolk. The yolk provides several nutrients including the much needed: vitamin D, choline, lutein, zeaxanthin and protein; however, it is also relatively high in cholesterol. Are those who frequently consume whole eggs making a nutritious choice or walking on proverbial egg shells?

Cholesterol
It cannot be denied that egg yolks are relatively high in cholesterol; however, different sources will cite different amounts of cholesterol. For example an anti-egg article from the Canadian Journal of Cardiology (1) states that a single large egg yolk will contain approximately 275 mg cholesterol, however, my package of Vita Eggs Omega-3 large size contains only 195 mg per egg according to the nutrition label. Recommendations for dietary limits vary: the United States recommends healthy people should not exceed 200-300 mg/day (it changes depending on the source), while many other Western countries have a vague “limit cholesterol intake” as their official recommendation (2). You can check out Health Canada’s report on cholesterol levels in Canadians. Hint: it’s not good that at least 40% of Canadians have total serum cholesterol levels that are too high!

Recommendation discrepancies aside, could the cholesterol found in egg yolks negatively impact health? This is a tricky question because of individual variances. For those who have or are at risk for vascular disease and/or type 2 diabetes, it seems prudent to recommend they limit consumption of egg yolks (1), although a more recent study calls even this into question (2).

Diets high in cholesterol do have the potential to increase blood levels of the harmful LDL cholesterol, however, the impact of dietary cholesterol on serum cholesterol levels is strongly influenced by other factors, such as saturated fat (3). In healthy people, the story might be different. A recent study in the United States found that consuming eggs seven or more times per week as compared to less than once per week did not increase risk of mortality from heart disease or stroke (2); and this is certainly not the first time research results have vindicated the egg (4,5).

Of course, studies using self-reported data to correlate dietary intakes to disease risk are messy at best and there are always limitations. In summary, eggs contain cholesterol and this has the potential to be harmful in at-risk individuals (maybe). It is important to realize that cholesterol is found in *all* animal products, not just egg yolks and to regulate your egg consumption in relation to your overall diet.

Beyond Cholesterol
Egg yolks are one of the richest sources of choline containing 125 mg/egg (6). Choline is an essential nutrient (some say the next vitamin) with many roles in the body including fetal brain and memory development and the prevention of fatty liver disease and muscle damage in adulthood. It is needed for energy metabolism, to maintain cell structure and form neurotransmitters (6). The Institute of Medicine, Food and Nutrition Board has set the daily recommended intake at 425 mg/d for adult females and 550 mg/d for adult males, but many individuals do not meet these recommendations (7).

The egg yolk also contains 40% of the egg’s total protein, thus, eating only the egg whites will not provide you with the full 6 g of protein. The yolk provides lutein and zeaxanthin too. These two carotenoids have antioxidant properties and are thought to promote eye health (8). With 15% of the daily value for Vitamin D, in addition to a variety of other nutrients, these eggs pack a lot into 70 calories!

No Baloney’s advice? The inclusion of eggs, yolk included, in the diet of healthy individuals will provide a variety of nutrients, many of which are not commonly found in other foods. When consuming eggs, the method of cooking is important, as it is the oxidized form of cholesterol that is most harmful (9). When you expose the yolks to air or heat them, the cholesterol becomes oxidized; soft boiling your eggs will minimize oxidation. Finally, hold the butter, bacon, ham, and sausages to minimize the calories, saturated fat and additional cholesterol!

* Nutrition information from Vita Eggs Omega-3 organic large size.

References

  1. Spence JD, et al. Dietary cholesterol and egg yolks: not for patients at risk of vascular disease. Can J Cardiol 2010; 26: e336-9.
  2. Scrafford CG. Egg consumption and CHD and stroke mortality: a prospective study of US adults. Public Health Nutr 2011; 14:261-70.
  3. Ginsberg HN, et al. A dose-response study of the effects of dietary cholesterol on fasting and postprandial lipid and lipoprotein metabolism in healthy young men. Arterioscler Thromb 1994; 14:576–86.
  4. Zazpe I, et al. Egg consumption and risk of cardiovascular disease in the SUN project. Eur J Clin Nutr 2011; 65:676-82.
  5. Quershi AI, et al. Regular egg consumption does not increase the risk of stroke and cardiovascular disease. Med Sci Monit 207; 13: CR1-CR8.
  6. Zeisel SH & da Costa K. Choline: an essential nutrient for public health. Nutr Rev 2009;  67: 615-623.
  7. Jensen H et al. Choline in the diets of the U.S. population: NHANES, 2003-2004; Presented at the National Nutrient Data Bank Conference, 2007.
  8. Fernandez ML. Effects of eggs on plasma lipoproteins in healthy populations. Food Func 2010; 1:156-60.
  9. Staprans I, et al. Oxidized cholesterol in the diet is a source of oxidized lipoproteins in human serum. J Lipid Res 2003; 44:705-15.
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2 thoughts on “The Yolk – A Burden or a Blessing?

  1. Pingback: Nutrition 180s and Consumer Confusion | No Baloney

  2. Pingback: Again with the Egg Yolks! | No Baloney

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