The scientific debate over eggs continues. One side touts them as nutritionally dense, low in saturated fat and trans fat-free, while the other insists that high levels of dietary cholesterol mean this common food is a serious danger to heart health.
However, a new study published in the American Journal of Clinical Nutrition – and notably funded by the science unit of the American Egg Board – suggests that high consumption of saturated fats, not cholesterol-rich eggs, is what drives increased risk of heart disease.
The study, conducted by researchers at the University of South Australia, tackles the effects of cholesterol and saturated fats on blood lipids to distinguish how each contributes to increased cardiovascular disease (CVD) risk. By looking at three different dietary mixes, the researchers found that saturated fats are what drive higher levels of LDL cholesterol – not eggs. Often referred to as the “bad” cholesterol, high levels of LDL can lead to buildup of cholesterol in the arteries, raising the risk of CVD.
Participants were assigned to three diets: a control diet, high in saturated fat and cholesterol; an egg rich diet, low in saturated fat but high in cholesterol; and an egg-free diet high in saturated fat but low in cholesterol. After five weeks on one diet, they were switched to another one, with each group completing all three in different orders.
[See more: How to make sure your boiled eggs are easy to peel, according to science]
In addition to lipid levels, the researchers measured the impact of lutein and zeaxanthin – pigments concentrated in leafy green vegetables but more bioavailable in eggs – on brain function and physical activity, which could in turn affect lipid levels. Participants were not informed of this potential influence to avoid biasing their habits and muddying the data.
Researchers found that consuming two eggs daily – double the one egg broadly considered safe for most healthy people – as part of a low-saturated fat diet lowered LDL concentrations, which may reduce CVD risk, compared to both the control and low-cholesterol diets.
Researchers did note, however, that the positive effect of high egg consumption may be mitigated somewhat by the shift from larger LDL particles to smaller ones, which are more likely to deposit along artery walls.Taken together, the findings offer more evidence for cutting saturated fats than increasing egg consumption. The shift to smaller, more sticky particles suggests that the current recommended levels – three to seven per week, depending on health – remain wise, balancing the nutrition benefits of eggs with the potential risks of over consumption.
