“Previous studies on egg consumption and diseases have been contradictory because most of these studies were relatively small or moderate in size and did not include individuals from a large number of countries,” said lead study author Mahshid Dehghan of McMaster University in Hamilton, Canada.
The new study included 177,000 people from 50 countries on six continents.
“It is also possible that the health effects of eggs could depend on the background diet, with eggs providing different effects depending on the quality of protein in the diet,” Dehghan told Reuters Health by email.
Eggs are a primary source of dietary cholesterol, but they also contain high-quality lean protein and many vitamins, the researchers note in the American Journal of Clinical Nutrition. Studies investigating the link between eggs and heart disease have offered mixed results, with some pointing to a protective effect and others suggesting high cholesterol intake - whether from eggs or other foods - does increase heart disease risks.
Dehghan’s team examined data from three previous studies that tracked food intake and health outcomes. Most participants - about 146,000 people - were in a single study for about a decade starting at an average age of 51; the two smaller studies followed people for roughly half as long.
Overall, there were 12,701 deaths and 13,658 cardiovascular events. Eating eggs did not appear to influence the risk of these outcomes, or the risk of high cholesterol.
The largest study included many participants from Asia and Africa, where people typically consume high-carbohydrate diets in which eggs are least likely to be harmful to cardiovascular health, Dehghan said.
How eggs are prepared might also make a difference, and the study didn’t examine this.
The American Heart Association recommends keeping consumption to one egg a day, or two egg whites. But the AHA also advises people to scramble eggs, not fry them, to avoid adding unhealthy fats.
Many participants may have been too young and healthy to experience negative health effects of egg consumption, said Dr. J. David Spence, director of the Stroke Prevention & Atherosclerosis Research Centre at Robarts Research Institute in London, Canada.
“Because of the high lifetime risk of cardiovascular disease, the only people who could consume egg yolks with impunity would be those who know they are going to die young from another cause,” Spence, who wasn’t involved in the study, said by email.
While evidence from many smaller studies suggests infrequent egg consumption might not increase the risk of heart disease or death, the jury is still out for eating seven or more eggs a week, said Dr. Luc Djousse of the Division of Aging at Brigham and Women’s Hospital in Boston, who wasn’t involved in the study.
Eating well, exercising, not smoking and maintaining a healthy weight are all key to heart health, Djousse, who has received research funding from the American Egg Board, said by email. Rather than focusing on eggs, people should adopt an overall healthy eating pattern.
“That includes fruit and vegetables, whole grains, fatty fish, tree nuts, low-fat dairy and avoidance of fried foods, red and processed meat, carbonated beverages,” Djousse said. “In the absence of allergies, 3-5 eggs per week could provide high-quality proteins, especially in areas of the world where food security is a major issue.”