Tuesday, September 24, 2019

Retrospective #220: “Eat protein to lower stroke risk”

“Eat protein to lower stroke risk” is the title of a piece in The Telegraph. The article is based on a study in Neurology, “Quantitative analysis of dietary protein intake and stroke risk,” from the Nanjing School of Medicine in China.
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.” A high protein diet? Maybe some hyperbole by an eager reporter, combined with bad editing. The lesson here: stories in the popular press are not peer reviewed.
“The (total) amount of protein that led to the reduced risk was moderate – equal to 20 grams a day,” it says. Moderate? 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 (10 percent of total calories), and most Americans eat a diet of more than 15 percent protein. Remember, the lower minimum percentage in the “Dietary Guidelines for Americans” only survives because they writers 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, however, 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 [range]).” That means the risk of stroke was 4/5s as great (0.80) for the highest compared to the lowest dietary protein intake.”
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.
“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. The study analysis does have a bias, however. According to the study’s lead author, “people should avoid red meat,” which has been associated with increased stroke risk, according to The Telegraph. “These results indicate that stroke risk may be reduced by replacing red meat with other protein sources, such as fish” Hmmm. Isn’t pork the “other white meat”? In any case, it appears the Brits have a vegan lobby too; Or, if this was part of the study’s conclusions, perhaps the lead author was pandering to the “perceived wisdom” to get published. 
The bias deepens, however, in the accompanying editorial in Neurology. The authors review what “many experts recommend”: “…a low-fat diet such as the AHA diet, formerly the National Cholesterol Education Program diet, based on the evidence for an atherogenic role for fasting cholesterol levels.” That means, you need to get Total Cholesterol (TC) below 200mg/dl (with a statin) regardless of the lack of hard evidence to support lower TC in 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). The worm turns (in 2014) in the UK. 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 fats (vegetable oils like soy bean and corn oil), which the American dietary establishment strongly advocated for in the 2015 Dietary Guidelines.
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.” [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 to this skeptic, a sure sign of transition in the UK’s dietary establishment.

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