How eggs became healthy again
You may not have noticed, but last February the scientists behind the official dietary guidelines walked back a 50-year-old article of faith.
They said eating cholesterol was OK.
The Dietary Guidelines Advisory Committee (DGAC), a panel of experts assembled every five years to update what we are told about a healthy diet, did away with its decades-old recommendation that Americans limit their consumption of cholesterol to no more than 300 milligrams a day. Their move awaits approval by the final vote of the USDA, but appears likely to pass.
The admission was three sentences long.
"The 2015 DGAC will not bring forward this recommendation," was how the committee worded its news making reversal. It said "available evidence shows no appreciable relationship between consumption of dietary cholesterol and serum cholesterol." (That's the term for the amount of cholesterol in your blood). "Cholesterol," it concluded, "is not a nutrient of concern for overconsumption."
When it comes to cholesterol, in other words, you aren't what you eat.
"If somebody is consuming a couple eggs every other day, for most individuals it won't be a problem," said Alice Lichtenstein, senior scientist and director at Tufts University in Boston and vice chairwoman of the DGAC. Lichtenstein believes eggs may still matter for people at high risk of heart disease, but it's a tepid warning for a food that was once considered verboten.
Cholesterol in the blood has long been a bio-marker of concern for cardiologists, so it seems natural to assume eating cholesterol from egg yolks, shrimp, organ meats, cheese and other high cholesterol foods would cause blood levels of the waxy substance to rise. Doing so has caused the loss of sources for valuable dietary nutrients ranging from lutein to iron and folate.
Early ideas against dietary cholesterol were generated after a Russian researcher fed rabbits copious amounts of cholesterol, then found plaques in their arteries. "But they were feeding them oxidized cholesterol, which causes arteriosclerosis, plus they are herbivores." says Nina Teicholz, a science writer and author of "The Big Fat Surprise, Why Butter Meat & Cheese Belong in a Healthy Diet." (The dietary guidelines committee did not change its advice to limit consumption of saturated fat.)
The body makes cholesterol, well over 1,000 milligrams a day on average. Cholesterol is critical for a host of functions — it helps to insulate cells and synthesize vitamin D and important hormones. The amount we make, in fact, far exceeds the amount of cholesterol you can take in through a plate of eggs, which contain roughly 180 to 200 milligrams an egg.
Once your body senses the presence of too much dietary cholesterol, moreover, it dials back its own production and increases its excretion of cholesterol. It may sound like a sophisticated finding, but we've known this for years.
"This isn't really anything new," said Dr. Donald Hensrud, MD, Medical Director of the Mayo Clinic Healthy Living Program. In fact, Ancel Keys, the noted University of Minnesota physiologist whose work in the 1960's and 1970's pioneered today's advice to avoid saturated fat concluded in 1955 that dietary cholesterol had little effect on blood cholesterol. Hensrud says change in official advice came because "the American Heart Association found insufficient evidence that cholesterol we eat is related to cardiovascular disease."
"In most patients the synthesis of cholesterol was indeed suppressed by the feeding of dietary cholesterol." That was from a feeding study of eight patients at Rockefeller Hospital in 1971. It found some patients did accumulate excess cholesterol after eating eggs in excess, "but these accumulations were not necessarily reflected in plasma cholesterol; that increased only slightly or not at all." Other studies have found that for some people, LDL or "bad cholesterol" does indeed rise after eating extra eggs, but so does their HDL or "good cholesterol," making it a wash in terms of harm.
Hensrud believes there remain other concerns about eggs, including a paper linking their consumption with diabetes, but says other pieces of dietary advice take precedence over dietary cholesterol, like the limitations on red meat and saturated fat. "Whenever you try to simplify something you lose a little context."
Lichtenstein believes there are individual differences in our ability to tolerate dietary cholesterol. She says some people are "hyper-responders" who can't down-regulate their own cholesterol after a plate of eggs, and that the problem is we don't know who they are or even how many of them exist.
A 2003 study in the journal Human Nutrition and Metabolism found that hyper-repsonders did see a rise in LDL after eating cholesterol, but saw most of that increase in the form of the benign, large form of LDL. This might explain the 2013 conclusion of an article in the International Journal of Clinical Practice:
"It is evident that the dynamics of cholesterol homeostasis, and of development of (heart disease), are extremely complex and multifactorial." It added that "the earlier purported adverse relationship between dietary cholesterol and heart disease risk was likely largely over-exaggerated."
"Every other western country has backed off their dietary cholesterol guidelines years ago," Teicholz said. "But here it just developed its own momentum."
In other words, you will likely still be offered egg white omelets for a long time to come.