Sunday, October 12, 2014

1588. Food: How Meat Advocates Skewer Science

By The Physicians Committee for Responsible Medicine, Good Medicine, Autumn 2014

In 1974, a new book titled We Never Went to the Moon: America’s Thirty Billion Dollar Swindle alleged that NASA faked the lunar landing. In 2001, the Fox network broadcasted a documentary on the subject, and a follow-up survey showed that as many as one in five Americans doubted that Neil Armstrong’s boots had ever touched the moon’s surface.
Fast-forward to June 23, 2014. Time magazine’s cover proclaimed in large type “Eat Butter” and featured a big artistic swirl of the stuff. Several other publications—the New York Times, the Wall Street Journal, the New Scientist, and others—ran similar stories. The experts have been wrong all this time, the articles exclaimed. Fat isn’t unhealthy after all. Steak and pork chops won’t hurt you. Go ahead, dig in!
Of course, meat and dairy products are strongly linked to all manner of health problems, from heart disease to cancer, diabetes, obesity, and hypertension. So what is behind the contrarian stories?
Eskimos and Maasai
Some of the articles were based on a new book called The Big Fat Surprise: Why Butter, Meat, and Cheese Belong in a Healthy Diet. Its author, Nina Teicholz, aimed to rehabilitate meat’s image, starting with Eskimo and Inuit populations of the far north. They have almost no heart disease, she held, despite a diet heavy on fish and blubber. Was she right or wrong? 
Wrong. A study from the University of Ottawa Heart Institute published in the Canadian Journal of Cardiology showed that cardiovascular disease has been at least as frequent among northern native populations as for others.1 Strokes have been particularly common, and life expectancy overall was found to be about a decade shorter. Heart disease seemed rare among northern native populations mainly because reporting of medical problems has been spotty.
Teicholz then invoked the Maasai, an African population who are supposedly free of heart disease, despite a diet of meat, milk, and blood. Right or wrong? 
Wrong. Researcher George V. Mann wrote in 1978, “We have collected hearts and aortae from 50 authenticated Maasai men who died of trauma and we found extensive atherosclerosis.”2
Okay, so the Maasai’s arteries are clogged with atherosclerotic plaques. But they don’t have heart attacks, Teicholz maintained; so meat and milk must be safe. Right or wrong? 
Wrong. Plaques that form in arteries can rupture, sparking the formation of a clot that blocks blood flow like a cork in an artery, causing a heart attack. Teicholz’s notion was that the Maasai have plaques, but the plaques somehow never rupture, like time bombs that never explode. This is highly unlikely. A better explanation for the lack of reported heart attacks among the Maasai comes from their tragically short life expectancy. If life is cut short in one’s 40s by an accident or an infection, plaques have not had enough time to produce a heart attack. Moreover, in a rural population with limited medical care and poor medical records, heart attacks may not be recognized or reported.
Ancel Keys and the Seven Countries Study 
Teicholz and other fat-backers zeroed in especially on Ancel Keys, the University of Minnesota researcher who identified the dangers of fatty foods in the 1950s. Looking at six countries with reliable dietary and medical records, Keys found a clear association between fat intake and heart disease deaths.3
But as Teicholz tells it, the rug was pulled out from under Ancel Keys by University of California at Berkeley statistician Jacob Yerushalmy.4 If Keys had zeroed in on more countries than just six, Yerushalmy held, the relationship between saturated fat and heart disease would have been weakened. In Teicholz’s words, it “nearly disappeared.” Right or wrong? 
Wrong. Including additional countries, as Yerushalmy suggested, did muddy the correlation between fat and heart disease deaths, because many of these countries had poor data on diet or medical care at that time. Even so, the correlation between fat and heart deaths remained high, and the correlation between animal protein and heart deaths was even higher.
What really grabbed the headlines, however, was a meta-analysis published in early 2014 by the Annals of Internal Medicine.5 The meta-analysis combined 72 smaller studies, finding no overall effect of saturated fat on heart risks. According to the fat lobby, that proved that “bad” fat isn’t bad for your heart after all. Right or wrong?
Wrong. The Annals meta-analysis combined data from many studies. Some were designed to accurately show the dangerous effects of saturated fat. The designs of other studies did not make the hazards of saturated fat readily apparent. The net result was that the two types of studies canceled each other out, showing no risks. For example, take these two studies the Annals meta-analysis included:
The Oxford Vegetarian Study6 included 11,000 people whose diets ranged from vegan to ovolactovegetarian to nonvegetarian, with saturated fat intake ranging from a low of 6 percent of calories to more than 13 percent of calories. The study found that the fattiest diets tripled the risk of dying of heart disease, compared with diets that had very little saturated fat.
But in a Swedish study, no groups were on lower-fat diets. All of the study groups averaged more than 13 percent of their calories from saturated fat. Not surprisingly, the study could not identify any effect of avoiding saturated fat, because no groups in the study had a low fat intake.
Is Meat Safe or Not? 
Of course, no one orders saturated fat at a restaurant or puts it on a shopping list. This fat is hidden in meat, dairy products, and other foods. And here, the evidence is crystal clear. Meat-eaters are heavier than people who avoid meat. They have higher blood pressure, higher risk of diabetes, cancer, heart disease, and many other problems. And in carefully controlled studies, when people take meat out of their diets, they lose weight, and cholesterol, diabetes, and heart disease all improve. So while researchers debate the statistics on saturated fat, it pays to remember that getting away from meat is a healthy choice. 
So how could the media have been duped? As John McDougall, M.D., said, people are always looking for good news about bad habits.

1. Fodor GJ, Helis E, Yazdekhasti N, Vohnout B. “Fishing” for the origins of the “Eskimos and heart disease” story: facts or wishful thinking? Can J Cardiol. 2014;30:864-868.
2. Mann GV. The Masai, milk, and the yogurt factor: an alternative explanation. Atherosclerosis. 1978;29:265.
3. Keys A. Atherosclerosis: a problem in newer public health. J Mt Sinai Hosp NY. 1953;20:118-139.
4. Yerushalmy J, Hilleboe HE. Fat in the diet and mortality from heart disease: a methodologic note. NY State J Med. 1957;57:2343-2354.
5. Chowdhury R, Warnakula S, Kunutsor S, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160:398-406.
6. Appleby PN, Thorogood M, Mann JI, Key TJA. The Oxford Vegetarian Study: an overview. Am J Clin Nutr. 1999;70:525S-531S.
7. Wallstrom P, Sonestedt E, Hlebowicz J, et al. Dietary fiber and saturated fat intake associations with cardiovascular disease differ by sex in the Malmo Diet and Cancer Cohort: a prospective study. PLoS One. 2012;7:e31637.

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