Saturday, June 21, 2014

The Nutrition Debate #220: “Eat protein to lower stroke risk”

“Eat protein to lower stroke risk” is the title of a recent article in The Telegraph, a British newspaper. I advocate eating protein, and who doesn’t want to lower stroke risk? But that’s not what was interesting to me about this piece. The article is drawn from a study that appeared in the scientific journal Neurology titled, “Quantitative analysis of dietary protein intake and stroke risk,” by 5 MDs/PhDs at Nanjing University School of Medicine in Nanjing, China.

The headline writer, in my opinion, did a better job in reporting on this meta-analysis of 7 prospective studies of over half a million participants than The Telegraph’s “science” correspondent. Case in point: The Telegraph’s story begins, “Eating a high protein diet [emphasis added] significantly lowers the risk of stroke and could prevent 10,000 deaths in Britain every year, a study has suggested.” High protein diet? Just a little bit of hyperbole on the part of an eager reporter, perhaps, combined with bad editing. The lesson here: stories by science journalists in the popular press are not peer reviewed.

The story quickly comes back to earth, though: “The amount of protein that led to the reduced risk was moderate – equal to 20 grams a day,” it says. That’s a small amount (by American standards). The Standard American Diet (SAD, ironically) on the Nutrition Facts Panel of manufactured and processed food packaging calls for 50 grams a day, and most Americans eat a great deal more than that. Remember, the “Dietary Guidelines for Americans” are heavily influenced by the vegan lobby who advocate a plant-based diet to save the planet from greenhouse gasses (caused by bovine flatulence), etc., etc.

The study RESULTS, from the ABSTRACT, are more specific: “The pooled RR [relative risk] of stroke for the highest compared to the lowest dietary protein intake was 0.80 (95% CI [confidence interval] 0.66-0.99).” That means the risk of stroke was 4/5s as great (0.80) for the highest compared to the lowest dietary protein intake.” Unfortunately, the full text paper is only available with a subscription to Neurology, or a big one-time payment.

The ABSTRACT had another interesting result: In addition to the 20% relative reduction in stroke risk for overall dietary protein intake, they reported that “stratifying by protein type, the (relative risk) of stroke for animal protein was 0.71 (95% CI 0.50-0.99).” For the mathematically challenged, that translates to an almost 50% greater (29% versus a 20% reduction) in relative stroke risk. In simple terms, in the words of The Telegraph’s science correspondent, “The reduced risk of stroke was stronger for animal protein than vegetable protein.” This intriguing point deserves further investigation. (100 grams of chicken at 172 calories will do the trick. Or 770 calories of potatoes.)

The study does have a bias. According to the study’s lead author, Dr. Xinfeng Liu, “people should avoid red meat,” which has been associated with increased stroke risk, according to The Telegraph. “Consuming as little as one chicken breast, or a salmon fillet, -- the equivalent of 20g – reduced the risk of stroke by 20 per cent,” The Telegraph said. And, Dr. Liu said, “These results indicate that stroke risk may be reduced by replacing red meat with other protein sources, such as fish” Hmmm. I guess the Brits have a vegan lobby too; Or, Dr. Liu was pandering to the “perceived wisdom” to get published. 

The bias deepens in the accompanying editorial in Neurology. In a long preamble, the authors review what “many experts recommend”: “…a low-fat diet such as the AHA diet, formerly the National Cholesterol Education Program or NCEP, based on the evidence for a atherogenic role for fasting cholesterol levels.” In other words, get your Total Cholesterol (TC) below 200mg/dl (with a statin) regardless of the lack of hard evidence to support lower TC in coronary care and CVD prevention.

“However,” they say, “evidence-based dietary recommendations for reduction of stroke risk are limited.” And then, interestingly: “The current recommendation for monounsaturated fat instead of saturated fat reflects the evidence that the source of dietary fat matters more than the proportion of calories from fat” (emphasis added). Very interesting, indeed! More evidence in the medical establishment’s thinking that the proportion of calories from fat now matters less than the type; still a lagging bias against saturated fat, but a green light for monounsaturated fat (olive oil, etc.) and no mention, and especially important, no advocacy for polyunsaturated fat (vegetable oils like soy bean and corn oil, e.g.).

If this sounds like the Mediterranean diet, well, it is. The editorial then swings full speed into an incestuous vortex of “validating the expectations of the perceived wisdom.” “Therefore,” it concludes, “it seems invalid to focus exclusively [?!] on protein (‘Eskimo Diet’) or what we have done with lipids in the past.” [Well, okay; that sounds like a mea culpa ON FAT]. “In other words,” they say, “eating vegetables, fruits and protein every day will help to keep stroke away!” A not very clever attempt at drollery, to be sure, but nevertheless, to this observant skeptic, some signs of transition in “the establishment.”

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