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Why no fruits and vegetables?

The theory is that lectins, gluten and phytic acid found in many plants are toxic to humans. Lectins, in particular, were singled out as demons in the 2017 book The Plant Paradox, by U.S. cardiologist Steven Gundry. Found in seeds, grains, skins, rinds and leaves, lectins protect plants from predators, but, according to Gundry, once ingested by humans they cause inflammatory reactions leading to weight gain and serious health problems.

However, Heidi Bates, director of the Integrated Dietetic Internship at the University of Alberta, told McGill’s Jarry that, while people can experience gas or stomach upset if they eat a lot of beans or other high-lectin foods, “there is no research to suggest that we should avoid all of these nutrient-rich foods.”

Celiac disease is caused by an immune reaction to gluten, but only one per cent of the Canadian population has this condition.

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What about the evolutionary argument?

Modern meat isn’t like the meat our Stone Age ancestors ate, said Lisa Sasson, a clinical professor in nutrition at New York University. “When was the last time a woolly mammoth was in Whole Foods?” Meat from prehistoric times was very lean, unlike the processed, salty and high-fat meats many people eat today.

Our Palaeolithic ancestors also consumed a high-fibre diet from a variety of plant foods — wild plants, berries, or whatever they could forage. Their calorie needs were also very high (perhaps more than 4,000 calories per day) and they moved a lot more. They also died a lot sooner, with a life expectancy of around 30.