Eggs and cardiovascular health: an important update
For years, public health experts have been faced with the dilemma of recommending eggs for their excellent nutritional profile or restricting their consumption because of their cholesterol content. Several recent studies by highly reputed researchers have finally shed light on this question.
Eggs: an exceptional nutritional profile
Eggs are among the most nutritious foods we have. With only 71 calories, a large egg contains more than 6 g of high quality protein and a large number of essential nutrients. A large egg provides, for example, 29% of the daily recommended intake of vitamin B12, as well as 15% of folacin and pantothenic acid, 14% of the riboflavin and 9% of the vitamin E our body needs everyday. In addition, eggs are a source of zinc, phosphorus, niacin, and vitamins A and D.
Nature has also given eggs a great fat profile, most of it in the form of unsaturated fatty acids (i.e. 48% monounsaturated fat and 15% polyunsaturated fat, for a total of 63%). Unsaturated fatty acids play a beneficial role in cardiovascular health.
There is increasing recognition that saturated and trans fatty acids are fats which, when consumed in excessive quantities, increase the risk of cardiovascular disease. However, an egg contains only 1.5 g of saturated fat and virtually no trans fatty acids.
Yes, but what about cholesterol?
Until recently, the cholesterol content of an egg was a concern for health professionals. But in the past few years, genetic selection and improved feeding of hens have made it possible to lower the cholesterol content of eggs. According to the latest analyses (1999), a large egg today contains 190 mg of cholesterol.
It should also be remembered that cholesterol is essential for health, namely for healthy growth and hormone production. The cholesterol in our bloodstream is a combination of cholesterol that the body produces on its own and the cholesterol we ingest. The liver regulates the production and elimination of cholesterol. Despite this, the body sometimes produces too much cholesterol, for a number of reasons that include heredity, illness, certain medication, excessive body weight or excessive consumption of fats, particularly saturated fat and trans fatty acids.
Blood cholesterol does not circulate on its own – it is always bound to carriers. Some carry it from the liver into the bloodstream; this is the case with low density lipoprotein (LDL). Others recover it from the bloodstream and return it to the liver for elimination, which is the case with high density lipoprotein (HDL). A high blood cholesterol level, particularly LDL-cholesterol, increases the risk of cardiovascular disease. This is why health professionals recommend diet modifications and sometimes medication to normalize their patient’s elevated cholesterol levels.
How important is the cholesterol we ingest?
The effect of egg consumption on the level of blood cholesterol has been the subject of many studies over the past decade. In one such study aimed at measuring the effect of various doses of dietary cholesterol, young men ate 0, 1, 2 or 4 eggs per day over 8-week periods. Their blood cholesterol level varied very little despite the increase in the number of eggs. Another study showed that adding two eggs per day to the diet did not change the ratio of total blood cholesterol to HDL-cholesterol. It should be noted that this ratio illustrates the body’s capacity to get rid of excess cholesterol.
Experts have noted that egg consumption may raise blood cholesterol in individuals also suffering from a high level of blood triglycerides. Individuals with moderate hypercholesterolemia seem to have no more reaction to eggs than normal individuals.
In recent years, the correlation between cholesterol consumption and cardiovascular risk has been thoroughly studied. Epidemiological studies in which large groups of men and women were followed for several years have shown that this link is not significant (or very low, in the case of one study only) when the impact of cholesterol is isolated from the impact of saturated fat, trans fatty acids, total fat and lack of fibre.
Eggs and cardiovascular health
Now that light has been shed on the effect of eggs on blood cholesterol and the impact of dietary cholesterol on cardiovascular disease, let us take a look at the effect of eggs on the risk of cardiovascular disease. A prospective study, whose findings were published in spring 1999, addressed the concerns of health professionals and public health experts by measuring the risk of coronary incidents on heavy consumers of eggs and those who only eat them rarely. By analyzing the food intake of nearly 118 000 men and women, and by following them over a period from 8 to 14 years, the Harvard School of Public Health researchers came to the conclusion that this risk is the same whether a person eats less than one egg per week or more than one per day.
Once again, researchers were careful to isolate the effect of eggs from that of other risk factors presented by some study participants. The authors observed that several individuals were already suffering from obesity, that they were smokers and sedentary or that their diet was too rich in fat. It is these factors, not egg consumption in itself, that explains the higher frequency of coronary incidents in these individuals.
The Harvard study authors clearly state that eating one egg a day does not increase the risk of coronary disease except in people with diabetes. Current egg consumption in Canada is therefore far from worrisome. In fact, according to the latest Statistics Canada data, average egg consumption per capita is only 3.5 a week.
In conclusion, what did we learn from the most recent research?
- Eggs are among the most nutritious foods around. They are affordable and provide high quality protein plus several essential nutrients.
- A large egg contains virtually no trans fatty acids and only 1.5 g of saturated fat. It is these types of fats which, when consumed in excessive quantities, increase the risk of cardiovascular disease.
- Cholesterol which comes from the diet, or from eggs in particular, does not influence cardiovascular risk in the majority of people.
- Research has shown that healthy individuals can eat up to 7 eggs a week, in contrast to the current consumption, which is only 3.5.
-  Canadian Egg Marketing Agency. Nutrient Values of Canadian Eggs, January 1999.
-  Ginsberg HN et al. A dose-response study of the effects of dietary cholesterol on fasting and post prandial lipid and lipoprotein metabolism in healthy young men. Arterioscler Thromb 1994; 14:576-86.
-  Schnohr P et al. Egg consumption and high-density-lipoprotein cholesterol. J Intern Med 1994; 235:249-51.
-  Knopp RH et al. A double-blind, randomized, controlled trial of the effects of two eggs per day in moderately hypercholesterolemic and combined hyperlipidemic subjects taught the NCEP step I diet. J Am Coll Nutr 1997; 16(6):551-61.
-  Hu FB et al. Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med 1997; 337:1491-9.
-  Millen BE et al. Macronutrients and plasma total and low-density lipoprotein cholesterol in women: the Framingham Nutrition Studies. J Clin Epidemiol 1996; 49(6):657-63.
-  Pietinen P et al. Intake of fatty acids and risk of coronary heart disease in a cohort of Finnish men. Am J Epidemiol 1997; 145:876-87.
-  Ascherio A et al. Dietary fat and risk of coronary heart disease in men: cohort follow up study in the United States. BMJ 1996; 313:84-90.
-  Hu FB et al. A prospective study of egg consumption and risk of cardiovascular disease in men and women. JAMA, 21 avril 1999; 281(15):1387-94.