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food for thought

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.

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OZIER MUHAMMAD/The New York Times News Service

Talk about a major dietary flip-flop. Findings published this week in the Annals of Internal Medicine concluded that there’s no need for adults to cut back on red and processed meat intake to stay healthy.

The controversial advice, issued by a self-selected 14 member panel, is in stark contrast to current guidelines from authoritative organizations including the World Health Organization, the Canadian Cancer Society, the American Institute for Cancer Research and the American Heart Association. Canada’s new Food Guide advises choosing plant protein more often than animal sources.

Existing recommendations to eat less red and processed meat are based on a large body of scientific evidence, gathered over decades, that has tied higher intakes to a greater risk of heart disease, Type 2 diabetes, certain cancers, especially colorectal, and premature death.

Confused? I don’t blame you. Before you include steak and bacon on your regular menu, here’s what you need to know.

About the latest study

Led by researchers from Dalhousie and McMaster Universities, the study team performed five systematic reviews of previously published studies on red and processed meat. The findings were then used to craft intake guidance for consumers.

Three of the reviews analyzed more than 100 observational studies involving more than six million participants. These types of studies uncover associations by following people for decades to see if participants who became ill or died adhered more or less to a certain diet or consumed more or less of a certain food than those who stayed healthy.

The data found that dietary patterns lower in red and processed meat were associated with statistically significant lower risks of coronary heart disease, heart attack, Type 2 diabetes, cardiovascular death and all-cause mortality. These findings were ignored in the final recommendations because they were deemed low- or very-low quality by the grading method used to rate the evidence.

Another review analyzed randomized controlled trials, studies that show cause and effect, comparing diets lower in red meat with ones higher in red meat.

The researchers found “low- to very-low-certainty evidence” that diets lower in red meat have little or no effect on risk of cardiovascular disease, cardiovascular mortality, cancer, including colorectal cancer, and cancer mortality.

Yet, one trial that involved almost 49,000 women dominated the analysis; it was a trial designed to cut dietary fat intake not to reduce meat intake.

The authors’ concluding recommendation – that adults can continue eating red and processed meat at current levels – was based on their lack of confidence in their data. They acknowledged that their recommendation was weak.

Swift reaction, criticisms

Major health groups including the American Institute for Cancer Research, the American Heart Association, the American College of Cardiology and the Physicians Committee for Responsible Medicine pushed back quickly reiterating recommendations to limit red and processed meat and calling the recommendations “reckless” and a “major disservice to public health.”

Renowned nutrition researchers cited numerous criticisms, including the fact that major relevant studies linking significant cardiovascular benefits to eating less meat were omitted from the analyses.

The research results did not separate red meat from processed meat, suggesting that eating four servings of processed meat a week does not affect cancer risk, which isn’t supported by scientific evidence.

Experts also contend that while the methodology that was used to grade the studies is rigorous, it was developed for drug trials, not for observational studies on diet.

Dietary studies are difficult to do

Randomized controlled trials assign participants to one diet or another. But adhering to a diet for long enough to know if it influences the risk of disease is incredibly hard, if not impossible.

And it can be unethical to ask people to change their diets. For instance, you can’t tell people to eat lots of processed meat or lots of sugar for years.

Most nutritional research is observational, meaning it relies on people to remember what they ate, so findings can be prone to error.

It’s also possible that a factor that wasn’t measured was responsible for the observed association.

So, now what?

This new research is not a major scientific breakthrough. It does not change my advice to reduce intake of red and processed meat and to eat more protein from plants.

A large body of evidence suggests that a high intake of red and processed meat increases the risk of ill health. I acknowledge that the risk on an individual level may be small, and that it’s your overall diet that matters most when it comes to health, not one food.

But it goes beyond human health. Raising livestock and producing meat takes a large environmental toll affecting land degradation and water use, while releasing greenhouse gases and chemicals.

Today, it’s narrow-minded to not consider environmental sustainability, as well as animal welfare, when making recommendations about meat intake.

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