Proteins in boiled and fried eggs may reduce blood pressure and potentially reduce the risk of cardiovascular disease, suggests new research from Canada.
Traditional views on eggs, and particularly their cholesterol content, has led to some recommendations to avoid eggs in order to boost heart health, but new research published in the Journal of Agricultural and Food Chemistry, suggests that proteins from eggs may benefit cardiovascular health.
According to findings by Jianping Wu and Kaustav Majumder, proteins in fried and boiled eggs can be converted by enzymes in the stomach and small intestine to produce peptides with angiotensin converting enzyme (ACE)-inhibitory activity.
ACE inhibitors work by inhibiting the conversion of angiotensin I to the potent vasoconstrictor, angiotensin II, thereby improving blood flow and blood pressure.
“Our results showed that in vitro digestion of cooked eggs could generate a number of potent ACE inhibitory peptides which may have implications for cardiovascular disease prevention, including hypertension,” wrote the researchers from the University of Alberta.
High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
“Findings from this study provided further evidence that eggs are an excellent source of health-promoting food,” added Majumder and Wu.
The effects are specific to the proteins in the eggs, and the effect of the fat and oil content of fried eggs was not considered.
The Edmonton-based researchers used a model system of the stomach and small intestine to simulate human gut conditions. Fried and boiled eggs were passed through the model gut and the peptide products measured.
Protein from fried egg showed greater ACE-inhibition than proteins from boiled egg, said the researchers. This disparity could have been due to differences in cooking temperatures (170 versus 100 degrees Celsius for fried and boiled respectively), or from a difference in heating rate – fried eggs have a “nearly identical thermal treatment”, said Majumder and Wu, while the boiling process produces a gradient from the shell inwards to the core of the egg.
“The core of the egg where the yolk proteins or the white protein part close to the yolk may have not been extensively denatured, result[ing] in a lower digestibility and weaker ACE inhibitory activity of boiled egg samples,” they added.
The results also should that the proteins would be absorbed by the body, allowing the in vivo antihypertensive activity to occur. However, Majumder and Wu stressed that an in vivo study would be needed to confirm this assumption.
The study was funded by the Alberta Livestock Industry Development Fund (ALIDF) and the Poultry Research Centre.
Debunking the cholesterol ‘myth’
British researchers reported recently that concerns over egg consumption and cholesterol increases are unfounded, after reviewing up-to-date evidence.
Writing in Nutrition Bulletin (March 2009, Vol. 34, pp. 66-70), Professor Bruce Griffin from the University of Surrey said that the link between eggs consumption and raised cholesterol levels (hypercholesterolaemia), which ultimately could lead to cardiovascular disease, was based on out-of-date information.
“It is high time that we dispelled the mythology surrounding eggs and heart disease and restored them to their rightful place on our menus where they can make a valuable contribution to healthy balanced diets,” concluded the Surrey researchers.
Source: Journal of Agricultural and Food Chemistry
2009, Volume 57, Issue 2, Pages 471-477
"Angiotensin I Converting Enzyme Inhibitory Peptides from Simulated in Vitro Gastrointestinal Digestion of Cooked Eggs"
Authors: K. Majumder, J. Wu