No, You Probably Shouldn't Follow Kelly Clarkson's 'Lectin-Free' Diet
Singer Kelly Clarkson performs on NBC's "Today" at Rockefeller Plaza on June 8, 2018. During an interview on the show, Clarkson revealed the secret to her 37-lb. weight loss: a lectin-free diet.
Credit: Mark Sagliocco/WireImage

In a recent interview with NBC's Today show, singer Kelly Clarkson said her 37-lb. (17 kilograms) weight loss was a happy side effect of a diet she followed primarily to overcome her thyroid problem.  

"I literally read this book, and I did it for this autoimmune disease that I had, and I had a thyroid issue," Clarkson said. "I'm not on medicine anymore because of this book." And along the way, she also lost weight, she said.

Clarkson was referring to the book "The Plant Paradox" (Harper Wave, 2017) by Dr. Steven Gundry, which was published last year and was followed by a cookbook this April.

The book comes with a big, controversial claim: Gundry says a broad group of plant proteins called lectins — found in grains; beans and legumes; nuts; fruits; nightshade vegetables such as eggplant, tomatoes and potatoes; and dairy — are the root of modern illnesses, ranging from obesity and gastrointestinal issues to autoimmune disorders and allergies. Lectins, according to Gundry, bind to sugar molecules in cells throughout the body, altering their function.

"Kelly Clarkson is a great example," Gundry told Live Science. "All she did was to remove these foods from her diet, and her thyroid problem went away."

But Gundry's dietary recommendations have baffled other doctors. "This is against every dietary recommendation represented by the American Cancer Society, American Heart Association, American Diabetes Association and so on," said Dr. Robert Eckel, a professor of medicine at the University of Colorado and a past president of the American Heart Association. [7 Biggest Diet Myths]

Gundry said the idea is based on ample research, but other scientists strongly disagree.

"It's kind of controversial. There are some studies on lectins since the 1970s, but they are very inconsistent, and a lot of them are in very isolated environments like in test tubes or animals," said Ariana Cucuzza, a dietitian nutritionist at the Cleveland Clinic in Ohio. "So, translating [the results of those studies] to humans can be very confusing, and people don't really know how it affects us."

In the absence of conclusive research, Gundry uses data from his own patients as evidence. (Gundry, a former heart surgeon, now works in private practice.) Recently, at an American Heart Association conference, Gundry presented the results of his study of 102 people on a lectin-free diet. After nine months, 95 of the people showed a reduction in biomarkers of inflammation and autoimmune diseases.

But scientific presentations that are not yet peer-reviewed and published are inadequate evidence, Eckel said. Moreover, Gundry's study does not include a control group, and it is impossible to make any conclusions based on limited data in a presented abstract, he said.

"I'm not saying this is definitely wrong. I'm saying, at this point, there's not adequate research to make any conclusions," Eckel told Live Science. "At the same time, it opens up the door to do controlled studies that may lead to finding something novel and applicable."

Lectins are found in almost all foods. These proteins bind to carbohydrate molecules (such as sugars) and have a variety of important functions in plants, animals and humans. There are many types of lectins, and a few are toxic at high levels, according to the U.S. Food and Drug Administration. "High levels" is a key phrase here; because lectins bind to carbohydrates available around them, the idea is that if there are a lot more lectins than carbs in the body, the leftover lectins may attach to the body's cell membranes and alter the cells' functions.

The most well-known toxic type of lectin is called phytohaemagglutinin, which is found at relatively high levels in raw beans. Eating as few as four raw kidney beans can cause vomiting and a host of other gastrointestinal symptoms, according to the FDA.

So, yes, you should not eat raw beans. You have to fully cook them to reduce their lectins.

"Most lectins are found in legumes. If you are cooking beans, grains and vegetables, the lectins are pretty much wiped out, and they are not going to affect your body," Cucuzza told Live Science.

But you might ask why you should take any chances with lectins. Why not just avoid anything containing these proteins?

There are several pieces of evidence hinting that we may need some lectins in our diet.

The sugar-binding activity of these proteins means that in ordinary amounts, lectins may even be necessary for normal digestion and absorption of foods. [11 Surprising Facts About the Digestive System]

"It is true that lectins can be toxic — purified lectins may cause problems," said Dr. David Jenkins, a professor of nutritional sciences and medicine at the University of Toronto. "However, we have also evolved to eat foods that contain lectins. Lectins in modest concentrations in otherwise-healthy people may have advantages in reducing too-rapid nutrient absorption."

In other words, adopting a diet that eliminates lectins may alter nutrient absorption and result in severe nutrient fluxes, Jenkins told Live Science.

There are also serious concerns about whether a lectin-free diet provides all the essential nutrients, Cucuzza said. "Any time you are cutting out groups of foods, there's a possibility that you cut out things that are also good for you," she said. "Lectin, especially, is in so many fruits and vegetables that have disease-preventing characteristics. Tomatoes, for example, have a strong antioxidant called lycopene that can actually have a number of positive effects on the cardiovascular system."

Moreover, many studies looking at many thousands of people have documented the importance of plant-heavy diets for living a long, healthy life. And these diets would contain an abundance of lectin-containing foods.

"When you are eating [a] plant-based [diet], you are getting all of those anti-toxins and the variety of nutrients that are important for the gut microbiome to flourish and [for you] to live a long, healthy life," Cucuzza said.

Is a lectin-free diet responsible for Clarkson's great results?

Her weight loss may have more to do with eliminating carb-heavy foods and processed foods, Cucuzza said. If you are lectin-free, you wouldn't eat pizza, for example.

"A lot of lectin-containing foods, like grains and legumes, are also high in carbohydrates, so I would anticipate that people following a lectin-free diet are probably eating less of the foods high in carbs and high-glycemic foods," Cucuzza said.

What about Clarkson's thyroid problem? We don't have any details about her issue, but thyroid problems are relatively common among women. One in 8 women will develop a thyroid disorder during their lifetime. (The rate for men is five to eight times lower.) Thyroid disorders cause hormonal problems in the body, and they can be caused by a range of factors, including an autoimmune disease.

In some cases, it's plausible that a bad reaction to something in the diet could cause inflammation in the body and lead to an autoimmune disorder, Cucuzza said.

"What I've found in my patients with autoimmune issues or hormonal deregulation is that it really comes down to inflammation," Cucuzza said. "Usually, a good first step is to review your diet … making sure you are eliminating processed food — high-glycemic choices like white flour and pasta — and focusing more on a variety of fruits and vegetables, lean meat and healthy fats." [11 Ways Processed Food is Different from Real Food]

Typically, to find out whether a particular ingredient in the diet is causing a reaction, dietitians start eliminating foods and then reintroduce them one by one to check for a reaction to each item.

"Lectins can come later as part of the process of elimination, but I don't think it's an appropriate first step for most people," Cucuzza said. But judging from the sales numbers for Gundry's "The Plant Paradox" (listed on Amazon as the No. 1 best seller in the "Diet & Weight Loss" category) and associated cookbook (which sold more than 20,000 copies in its first week), thousands and thousands of people are looking into a diet that might be good for only a few people.

"Unless nothing else has worked for you, I don't think it should be something you consider, especially not without consulting with a dietitian," Cucuzza said.

Original article on Live Science.