Thursday, November 04, 2010

Are eggs really worse than Double Downs?

For those of you who aren't familiar with the term "nutritionism", it refers to the notion that specific nutrients in foods are responsible for that food's nutritional risk or benefit regardless of whatever else may be present or absent in that food. Nutritionism is what helps to sell cookies with omega-3s, chips that are baked and not fried and what scares GI index folks away from corn.

This past week has seen a number of news stories that have covered a new article published in the Canadian Journal of Cardiology. The article, Dietary cholesterol and egg yolks: Not for patients at risk of vascular disease (free full text here) makes the case that eggs are very, very bad for you because they contain between 215 and 275mg of cholesterol per yolk - so bad for you that one newspaper ran a piece claiming that eggs were worse dietary choices than KFC Double Downs.

The study's authors' assertion is that dietary cholesterol is far worse for you than we've been led to believe and dramatically increases our risk of strokes and heart attacks.

Sadly the authors chose to make their point by resorting to cheap sound bites like this one,

"The yolk of a large egg provides more than the 210mg of cholesterol in a Hardee's Monster Thickburger, which contains two-thirds of a pound of beef, three slices of cheese and four strips of bacon."
It was this statement I'm sure which led to the Double Down angle and of course it reeks of nutritionism. Never you mind that eggs aren't simply packets of cholesterol. Who cares about their low calorie counts, high levels of protein, polyunsaturated fats, folic acid, B-vitamins and vitamin D? They've got lots of cholesterol and therefore they're worse than Monster Thickburgers (and Double Downs).

Oh, and never you mind that eggs for many represent low calorie, protein laden breakfast options which in turn may help those folks control hunger and weight and avoid the far greater nutritional risks of breakfasts consisting of highly processed carbohydrates.

You also shouldn't pay any attention to the Health Professionals Study that failed to demonstrate risk of egg consumption in healthy individuals (but did find risk in diabetics). The study looked at almost 120,000 men and women for 14 years but according to the Canadian Journal of Cardiology article's authors its,
"failure to show harm from eggs in healthy people is likely an issue of statistical power"
I guess that's also why the study published a few months ago in Public Health Nutrition that followed just over 20,000 folks from NHANES for 12 years also failed to demonstrate any increased risk of stroke or heart attack with egg consumption.

But what study did have enough statistical power for them?

A reanalysis of a much smaller subset of the very same Health Professionals Study that they previously deemed underpowered whereby the reanalysis concluded that those who were eating more than 1 egg per day had an increased risk of all cause mortality. Except that in this reanalysis of the 21,327 participants, only 8% of them reported eating eggs daily. And the results? A small increase in greater all cause mortality for folks eating 7 or more eggs a week, but not for those eating 6 or fewer eggs per week. Findings that contrasted with data from the Framingham study (with 36% daily egg eaters and no increase in risk) and the NIPPON study (37% daily egg eaters and no increase in risk).

Now I don't know what bee's in these Canadian researchers' collective bonnets, but I'd say it's a fairly safe call to suggest that if eggs do confer risk to healthy folks (this despite what seems like the majority of the literature stating otherwise) , it's pretty damn remote if 120,000 people studied for 14 years has insufficient elucidative power, and it's a risk that may well be far less than the foods a person would otherwise be consuming in eggs' stead.

I think it's also fairly safe to say that nutritionism and confirmation biases are alive and well in the Canadian Journal of Cardiology.

Spence JD, Jenkins DJ, & Davignon J (2010). Dietary cholesterol and egg yolks: Not for patients at risk of vascular disease. The Canadian Journal of Cardiology, 26 (9)

Scrafford CG, Tran NL, Barraj LM, & Mink PJ (2010). Egg consumption and CHD and stroke mortality: a prospective study of US adults. Public health nutrition, 1-10 PMID: 20633314

Hu, F. (1999). A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women JAMA: The Journal of the American Medical Association, 281 (15), 1387-1394 DOI: 10.1001/jama.281.15.1387

Dawber TR, Nickerson RJ, Brand FN, & Pool J (1982). Eggs, serum cholesterol, and coronary heart disease. The American journal of clinical nutrition, 36 (4), 617-25 PMID: 7124663

Djoussé L, & Gaziano JM (2008). Egg consumption in relation to cardiovascular disease and mortality: the Physicians' Health Study. The American journal of clinical nutrition, 87 (4), 964-9 PMID: 18400720

Nakamura Y, Okamura T, Tamaki S, Kadowaki T, Hayakawa T, Kita Y, Okayama A, Ueshima H, & NIPPON DATA80 Research Group (2004). Egg consumption, serum cholesterol, and cause-specific and all-cause mortality: the National Integrated Project for Prospective Observation of Non-communicable Disease and Its Trends in the Aged, 1980 (NIPPON DATA80). The American journal of clinical nutrition, 80 (1), 58-63 PMID: 15213028