AHA's new Scientific Advisory finds no link between egg intake and the risk of cardiovascular disease.
This is according to a new Scientific Advisory from the AHA, which appears in the journal Circulation.
Jo Ann S. Carson, Ph.D., is its first author.
Carson is the immediate past chair and current member of the AHA's nutrition committee and a professor of clinical nutrition at the University of Texas Southwestern Medical Center in Dallas.
She and her colleagues explain in the paper that recent changes in dietary guidelines for reducing cardiovascular disease (CVD) prompted their new research.
Namely, recent recommendations from the AHA, the American College of Cardiology, and the "2015–2020 Dietary Guidelines for Americans" have no longer explicitly set a target for dietary cholesterol.
This goes against the "traditional" grain of numerically limiting dietary cholesterol to no more than 300 milligrams (mg) per day.
The Advisory includes a meta-analysis of existing research. It concludes that the studies and trials available have not managed to find a conclusive association between dietary cholesterol and higher blood levels of low-lipoprotein density (LDL) cholesterol — also known as the "bad" kind of cholesterol.
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The problem with observational studies
"Findings from observational studies have not generally supported an association between dietary cholesterol and CVD risk," write the researchers.
Furthermore, the results of the studies that did find an association were attenuated after adjusting for other dietary factors, such as fiber, saturated fat, or energy intake.
This suggests that methodological issues riddle such studies and that it is difficult to disentangle the effect of dietary cholesterol from other dietary compounds, such as saturated fats
because most foods that contain high levels of the latter are also high in the former.
Carson and colleagues conclude:
"In summary, the majority of published observational studies do not identify a significant positive association between dietary cholesterol and CVD risk."
Egg intake, cholesterol, and CVD risk
On average, egg consumption makes up a quarter of the dietary cholesterol intake in the United States, with one large egg containing approximately 185 mg of cholesterol.
However, different studies have come up with varying results in regards to the association between egg intake and CVD risk, depending on the subtype of CVD studied.
For example, several studies in populations from the U.S., Sweden, Iran, and Finland did not find an association between egg intake and the risk of coronary heart disease.
Another study even found that eating seven or more eggs per week was associated with a lower risk of stroke compared with eating less than one egg per week.
For heart failure, however, a study in the U.S. and another one in Sweden found a 20–30% higher risk in those who ate more than one egg per day, but the results only applied to men.
Overall, conclude the researchers, "For both dietary cholesterol and egg consumption, the published literature does not generally support statistically significant associations with CVD risk."
Still, they go on to note some limitations to this existing body of knowledge, such as the fact that methods in nutritional epidemiology have changed considerably over time, or that different study populations have different dietary patterns that may have influenced the results.
For instance, they write, in China, egg consumption represents a healthful addition to the diet that is already rich in fiber, vegetables, and fruit.
Clinical trials on healthful diets
The Advisory also looked at 17 randomized controlled trials that assessed the effect of high-cholesterol dietary interventions.
These trials did find a dose-dependent relationship between dietary cholesterol and high blood levels of LDL cholesterol, but only when the intervention was much higher than the levels of cholesterol that people usually eat — for instance, the equivalent of 3–7 eggs per day.
Furthermore, each of these trials had a small sample size.
Considering the above, the researchers stress the importance of an overall heart-healthy diet, as opposed to numerically limiting dietary cholesterol.
"Consideration of the relationship between dietary cholesterol and CVD risk cannot ignore two aspects of diet. First, most foods contributing cholesterol to the U.S. diet are usually high in saturated fat, which is strongly linked to an increased risk of too much LDL cholesterol," says Carson.
"Second, we know from an enormous body of scientific studies that heart-healthy dietary patterns, such as Mediterranean-style and DASH style diet (Dietary Approaches to Stop Hypertension), are inherently low in cholesterol."
The author goes on to recommend "Eating a nutrient-rich diet that emphasizes fruits, vegetables, whole grains, low-fat or fat-free dairy products, lean cuts of meat, poultry, fish or plant-based protein, nuts, and seeds."
"Saturated fats — mostly found in animal products, such as meat and full fat dairy, as well as tropical oils — should be replaced with polyunsaturated fats such as corn, canola, or soybean oils. Foods high in added sugars and sodium (salt) should be limited."
Jo Ann S. Carson