The best advice is to avoid diets that recommend avoiding whole food groups without published scientific evidence. Photo/Getty Images
Question: Seeking dietary advice, I was referred to Dr. Steven Gundry The plant paradox. It claims to have transformed countless lives, but its list of foods to avoid includes a multitude of vegetables, grains, legumes,
dairy products and vegetable oils. This seems to go against many other advisors.
Respond: Steven Gundry’s book recommends a lectin-free diet for health. But despite the claimed benefits, no clear scientific evidence shows that lectin-free diets can cure chronic health conditions or autoimmune diseases. Indeed, Gundry’s diet has been called a fad by many health authorities, who have advised consumers to avoid it. But is there any truth to what Gundry, a former cardiothoracic surgeon turned nutritionist, writes about lectins? He recommends avoiding foods high in this carbohydrate-binding plant protein. He claims that they disrupt cell communication and cause inflammation, harm the gut, and lead to various health issues and weight gain. However, because they’re found in a wide range of food groups — such as beans, legumes, vegetables, dairy, seeds, and nuts — avoiding lectins means severely restricting your food intake.
We know that plants use lectins to protect themselves against external pathogens such as fungi and other organisms. And these same characteristics of lectins can cause digestive problems in humans if consumed in their active state. A prime example is the high concentrations of lectins found in kidney beans. Eating raw or undercooked beans can cause food poisoning, with symptoms including nausea, vomiting, and diarrhea. But no such problem occurs if the grains are properly soaked and boiled, thus inactivating the lectins, before consumption.
Indeed, varying levels of lectins exist within food groups. Those with higher levels tend to be foods we cook before eating, such as wheat and legumes, thereby inactivating many lectins.
From a research perspective, most of the evidence on lectins and health comes from animal studies, which have shown that they can survive transit through the gut and impair the absorption of essential nutrients such as calcium. , iron, phosphorus and zinc. Therefore, their effects have been termed “anti-nutritional”. They can also bind to the cells that line the digestive tract, interfering with the proper functioning of the digestive system and its microflora. Because they can bind to these cells for a long time, they have been theorized to play a role in inflammatory autoimmune diseases such as rheumatoid arthritis and type 1 diabetes.
However, a review published in 2021 in the American Journal of Biomedical Science and Research concluded that there are more questions than answers regarding dietary lectins and disease. Specifically, the foods that contain the highest concentrations of lectins are the same foods that improve our health, such as vegetables, legumes, fruits, and nuts. The Mediterranean diet, for example, is rich in lectins, with its high intake of plant foods. Yet those who follow a Mediterranean diet have a lower risk of cardiovascular disease and type 2 diabetes.
The fact that lectin-rich foods are associated with better health highlights a key point in nutritional science: we cannot consider the health impact of a compound in a food without also considering the matrix of other beneficial compounds in that same food. So the overall effect of the food, rather than a component, is what ultimately matters. More research is needed to understand which lectins are harmful — as not all appear to be harmful — and what effects occur with a specific dose and duration of intake.
Given the current lack of evidence to support the lectin-free diet, there’s not much to recommend following it. The best advice is to avoid diets that recommend avoiding or severely limiting an entire food group or staple without strong, published scientific evidence to support that recommendation.