It's a misconception that almost 75 per cent of Canadians believe to be true: The amount of cholesterol you eat boosts blood cholesterol. It's also a belief that keeps many people, especially those worried about heart disease, from eating eggs.
According to a new study from Harvard University's medical school, eating an egg a day does not increase the risk of heart attack or stroke in healthy men. But the findings suggest that if you have diabetes, you may want to swap sunny side up for a whites-only omelette.
The concern with eggs has to do with their high cholesterol content - 190 milligrams in each egg. Nutrition guidelines to keep LDL blood cholesterol in the desirable range have emphasized limiting dietary cholesterol, which is abundant in egg yolks, shrimp, liver and duck, to less than 300 mg a day. (Elevated LDL cholesterol in the bloodstream is a major risk factor for heart disease.) If you have high blood cholesterol, the American Heart Association advises consuming less than 200 mg of cholesterol a day.
The Heart and Stroke Foundation of Canada does not recommend a specific cholesterol intake for healthy people, but rather stresses the importance of limiting saturated and trans fats to help control blood cholesterol.
That's because higher intakes of saturated fat (found in meats, poultry and dairy products) and trans fats (found in baked goods, snacks and fried foods made with partially hydrogenated vegetable oil) raise LDL cholesterol much more than do higher amounts of dietary cholesterol.
While there is compelling evidence that high cholesterol intakes can cause hardening of the arteries in rabbits, pigs and mice, there's little evidence that this is so in humans. For most people, only a small amount of cholesterol in food passes into the bloodstream.
In the current study, published in this month's issue of the American Journal of Clinical Nutrition, researchers followed 21,327 male physicians for 20 years and found that consuming eggs - up to six a week - was not linked with a greater risk of heart attack, stroke or death from all causes.
The results were different for men with diabetes. Those who ate seven or more eggs a week compared with less than one had double the risk for all-cause mortality, presumably from heart disease.
This isn't the first study to find no connection between egg intake and heart disease in healthy people. An earlier study from Harvard's school of public health determined that eating one egg a day had no overall impact on the risk of heart disease or stroke in men and women.
Interestingly, that study also reported a relationship between egg consumption and risk of heart disease in people with diabetes. Among those with diabetes, egg-a-day eaters were a bit more likely to develop heart disease than those who rarely ate eggs.
Scientists speculate that individuals with diabetes absorb higher amounts of cholesterol from foods. Dietary cholesterol may also lead to the formation of smaller and denser LDL cholesterol particles in people with diabetes. (Small, dense LDL particles are more often associated with hardening of the arteries than large, "fluffy" LDL particles.)
How many eggs can a person concerned about heart disease safely eat? If you're healthy, one whole egg a day seems perfectly safe. If you're a man with diabetes, it's prudent to limit egg yolks to four a week. Instead of a three-egg omelette packed with 570 mg of cholesterol, try a whites-only omelette for a good source of protein, riboflavin and selenium.
Some eggs may actually offer protection from heart disease. Research has demonstrated that eating eggs enriched with DHA from fish oil helps lower triglycerides, a blood fat linked to heart disease.
While evidence that eating eggs boosts heart disease risk is lacking, there is plenty of scientific support for making other dietary modifications.
Numerous studies have shown that reducing saturated and trans fats, limiting sodium intake and increasing consumption of fish, whole grains and fibre guard against heart disease.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. lesliebeck.com.
Produced by Rhode Island Red hens. Egg shell colour does not affect the flavour or nutrients.
Produced by hens free to roam in open-concept barns equipped with nests and perches. Nutrient content is the same as regular eggs.
Produced by hens that have outdoor access as well as space for nesting and perching. Nutrient content is the same as regular eggs.
Contain pasteurized egg whites, a small amount of pasteurized egg yolk, beta carotene and natural flavour. Four tablespoons (50 millilitres) are equivalent to one large egg. Burnbrae Farms Naturegg Break-Free liquid eggs contain 80 per cent less cholesterol than one regular egg.
LIQUID EGG WHITES
Pasteurized egg whites that contain no fat or cholesterol. One carton (250 ml) is equivalent to eight large egg whites.
Laid by hens fed a diet enriched with flaxseed or fish oil, sources of the omega-3 fatty acids ALA and DHA, respectively. These eggs are good sources of ALA or DHA, both linked with protection from heart disease.
Laid by hens fed certified-organic grains grown without the use of synthetic chemicals or genetically modified crops. Nutrient content is the same as regular eggs.
Found in the freezer section, these products contain egg whites, corn oil, colouring, additives and preservatives.