Eggs are one of the richest sources of dietary cholesterol, but they also contain a wide variety of essential nutrients for the body, such as high-quality proteins, vitamins and minerals. For this reason, researchers have been trying for years to understand what its real effects are on the risk of cardiovascular disease, the leading cause of death and disability worldwide. To date, the association still remains controversial, with a positive association reported in some studies and others not finding a significant correlation. In particular, a 2018 study, published in the journal Heart, carried out on about half a million adults in China, found that those who ate about one egg per day had a substantially lower risk of heart disease and stroke than those who ate fewer eggs. frequently.
Now, to better clarify this relationship, researchers from the Department of Epidemiology and Biostatistics of Peking University (China), have conducted a new study, published in the journal scietifica eLife which investigates how egg consumption specifically affects LDL (also known as ‘bad cholesterol’), a form of circulating fat in the blood that can accumulate in the arterial wall, gradually form atherosclerotic plaques and block the corresponding artery, increasing the risk of ischemic heart disease, ischemic stroke and intracerebral hemorrhage. “Few studies – explained the first author Lang Pan – examined the role that plasma (blood) cholesterol metabolism plays in the association between egg consumption and cardiovascular disease risk, so we wanted to help fill this gap ”.
The Chinese study
The researchers selected 4,778 subjects aged 30 to 79 from the China Kadoorie Biobank, of whom 3,401 had cardiovascular disease and 1,377 did not. They used the innovative nuclear magnetic resonance (NMR) technique to measure 225 metabolites in plasma samples taken from the participants’ blood. Of the metabolites, they identified 24 associated with levels of egg consumption, reported by participants through a questionnaire. Possible answers were “never / rarely, monthly, 1–3 days a week, 4–6 days a week and every day”. The frequency was then converted into egg consumption days per week, with each option corresponding to 0, 0.5, 2, 5 and 7 days per week, respectively.
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The results of the study showed that subjects who ate a moderate amount of eggs (2/3 times a week) had higher levels of a protein in the blood called apolipoprotein A1, a building block of high-density lipoprotein (HDL). also known as “good cholesterol.” Specifically, these subjects had larger HDL molecules in their blood, which help release cholesterol from blood vessels and thereby protect them from atherosclerotic plaques that can lead to heart attacks and strokes. also identified 14 metabolites that are linked to heart disease, and found that participants who ate fewer eggs had lower levels of beneficial metabolites and higher levels of harmful ones in their blood, compared to those who ate eggs more regularly.
Thus, it is evident that egg consumption is associated with several metabolic markers, which may partly explain the protective effect of moderate egg consumption on cardiovascular disease. “Our findings – said Canqing Yu, another author of the study – provide a potential explanation of how eating moderate amounts of eggs can help protect against heart disease. However, further studies will be needed to verify the causal roles that lipid metabolites play in the association between egg consumption and the risk of cardiovascular disease “.
What the Italian Dietary Guidelines say
The current Italian dietary guidelines underline how eggs have numerous positive nutritional connotations, such as the high density of nutrients, among which the high quality protein kit with a low energy content, the richness of functional components, the practicality, the versatility, low cost, and the advantage of promoting satiety by virtue of the protein content. For these reasons it is no longer considered appropriate to set clear limits on the actual number of eggs to be consumed, but to impose as the only limit the general balance of the diet, the presence of other sources of cholesterol (remember that an average egg contains approximately 220 mg of cholesterol, about 80% of the recommended daily requirement) and that of all other foods in the right proportions.
“Therefore – clarifies the document” Italian Dietary Guidelines “- the inclusion of eggs in a balanced diet must be evaluated, even for those with hypercholesterolemia problems, focusing more than on the number, on the overall composition of the diet, on the way in which they are cooked and to foods with which they are accompanied. Net of these considerations and taking into account that the egg is also present as an ingredient in many industrial preparations, we recommend a consumption of 2-4 eggs per week to be distributed over several days “.