The truth about eggs and cholesterol
Thursday, March 29, 2018. Author Dr. Haran Sivapalan
Thursday, March 29, 2018. Author Dr. Haran Sivapalan
Are you eating eggs this Easter?
Alas, I don't mean the chocolate kind, but the ones laid by hens.
Mention eggs in the context of fitness and the image of Sylvester Stallone downing a glassful of raw eggs, immortalized in the first Rocky movie, invariably springs to mind.
High in protein and a good source of Vitamin D, folate, and selenium, eggs have long been considered an ideal pre- or post-workout food.
But eggs haven't always benefitted from such positive PR.
In the 1970s, several health organizations warned against the consumption of eggs. "The public should be encouraged to avoid egg yolk consumption," pronounced the Inter-Society Commission for Heart Disease Resources in 1970. Three years later, the American Heart Association proclaimed, "that individuals eat no more than three egg yolks per week."
What was the reason for these health warnings?
Eggs are rich in cholesterol: a waxy, fat-like substance found in certain foods and also produced by our bodies, where it is used to build cell membranes, produce bile and make steroid hormones such as testosterone, estrogen and aldosterone.
Cholesterol is also a major component of atherosclerotic plaques, the fatty deposits that narrow and clog the coronary arteries supplying the heart. Indeed, it's well established that high blood levels of one type of cholesterol, LDL cholesterol (often known as ‘bad cholesterol'), increases the risk of (coronary) heart disease.
Unfortunately, eggs also became unduly embroiled in this link between cholesterol and heart disease. The argument was as follows: 1) eggs are rich in cholesterol; 2) eating eggs causes high levels of LDL cholesterol in the blood; 3) high blood cholesterol is linked to heart disease; 4) therefore, eating eggs increases the risk of heart disease.
If reading the above has just made you spit out your breakfast omelet, you needn't worry. In the decades following the 1970s, several studies have debunked the second and fourth claims – eating eggs neither elevates the levels of bad cholesterol in your blood nor increases your risk of heart disease.
Analysis of the Framingham Heart Study (a large-scale project investigating lifestyle factors and cardiovascular health) found no relationship between egg consumption and blood cholesterol levels. Upping egg intake by an average of 9.2 eggs per week did not appear to change serum cholesterol.
In fact, the NHANES III study, which examined egg consumption in 20,000 people, found that people putting away more than 4 eggs per week actually had lower cholesterol levels than those eating less than 1 per week!
Furthermore, in studies where eggs have been shown to raise blood cholesterol levels, the increases were invariably very small and therefore unlikely to significantly affect the risk of heart disease.
The egg, it seems, has been well and truly exonerated.
While the above studies looked at total cholesterol, it's also important to distinguish between the different subtypes of cholesterol in the blood.
As you may know, cholesterol is transported in the blood in particles called lipoproteins. High-density lipoproteins (HDL) transport cholesterol away from tissues, including the walls of arteries, to the liver. It's for this reason that HDL cholesterol is called ‘good cholesterol.'
Conversely, low-density lipoproteins (LDL) carry cholesterol away from the liver to be used by tissues. When levels of cholesterol transported in LDL are too high, it (cholesterol) gets deposited on blood vessel walls, clogging arteries and increasing risk of heart disease – hence the name ‘bad cholesterol.'
It's worth noting that there are also other types of ‘bad cholesterols'. Cholesterol bound to very low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and lipoprotein A (Lp[a] have all been linked to heart disease. Collectively, these are known as non-HDL cholesterol.
Anyway, back to eggs. Evidence suggests that eggs selectively increase the level of ‘good' HDL cholesterol, while not affecting or even reducing levels of ‘bad' LDL cholesterol. In other words, as part of a healthy diet, eggs favorably alter your blood lipid profile.
There's more good news when it comes to the risk of cardiovascular disease. A comprehensive meta-analysis found that egg intake did not affect coronary heart disease risk. On the contrary, eating one egg per day may in fact reduce your risk of stroke.
In line with these revelations, egg lovers will be happy to learn that organizations such as the American Heart Association and the British Heart Foundation no longer put an upper limit on the number of eggs you should eat.
As well as cutting your risk of stroke, there's evidence that eggs can also help cut your waistline. Eggs are high in protein, with a medium egg (weighing 58g) containing about 6-7 grams of protein. As we've mentioned before, high protein foods can promote satiety (feelings of fullness) and therefore reduce your risk of overeating.
Indeed, a study of obese and overweight women found that having eggs with breakfast significantly reduced food intake over the following 36 hours.
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