New Food Fad: Lectin-Free Diet

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There have been a few articles written in recent days discussing lectins (proteins found in plants and animals), how they are damaging to your health, and why you should avoid them. *Insert eye roll*.

These articles are based on information found in a popular book recently released, in which a doctor claims that lectins are the cause of serious health conditions and “incite a chemical warfare on our bodies.” Lectins are components found naturally in many common foods we eat including grains, beans, and fruits and vegetables. According to the author of the book, we should avoid these foods. Specifically, we should avoid whole grains, legumes, seeds, nightshade vegetables such as tomatoes, peppers, eggplant, and potatoes, out-of-season fruit, dairy, and eggs. So, the real question seems to be: “what can we eat?”  

There are many kinds of lectins and each food has different concentrations of them. In animal studies, lectins have shown to be resistant to digestion, and remain partially undigested in the gut. Additionally, studies have shown that some lectins can bind to the cells of the digestive tract and cause disruptions of cell membranes. It’s important to note that the majority of these studies have been conducted in vitro, on animals, and with isolated lectins, meaning that the studies have been done with cells in a test tube or culture dish, not in actual humans, and with lectins that have been removed from a food and purified. In fact, dietary lectins and their role on human health remain largely unstudied.

Let’s look at some of the claims about lectins.

1. They make you gain weight

Not exactly. Systematic reviews of multiple studies have shown that increased fruit and vegetable intake does not have an effect body weight. In a study looking at whole grain consumption over 12 years, increased whole grain consumption was associated with lower body mass index (BMI) and waist circumference in both children and adults, with both populations being significantly less overweight or obese compared to those who did not consume whole grains. Additionally, in a systematic review of the effect of dietary pulses (legumes such as chickpeas and lentils) on body weight, researchers found that people that included these foods in their diet experienced weight loss.

2. They cause inflammation.

Questionable. There is limited research on the effect of nightshade vegetables on inflammation. What we do know is that fruit and vegetable consumption has been shown to decrease inflammatory markers and possibly lower the risk for certain chronic diseases associated with inflammation. The lectin found in wheat has been shown to induce inflammatory responses in vitro, but data on the effect of this lectin in human studies is lacking

3. They are toxic.

“Toxic” is a quite the overstatement. Kidney beans, when eaten raw  seem to induce gastrointestinal issues such as nausea, vomiting, and diarrhea. But really, who eats raw kidney beans on purpose? Cooking beans destroys the lectin, and makes them completely safe to eat. The Food and Drug Administration (FDA) recommends boiling beans for at least 30 minutes to ensure that they are cooked at a high enough temperature with adequate time.  Slow cookers should not be used to cook the beans because the temperature does not get high enough.

Are there any consequences of removing lectin-containing foods from your diet? Well, you may be missing out on important nutrients. Fruit and vegetable intake has been associated with reduced risk of all-cause mortality, cardiovascular disease (CVD), hypertension, etc. Nightshade vegetables are particularly targeted as “bad” in the book due to their lectin content, but they provide many nutrients as well. Tomatoes contain lycopene, a carotenoid which has been associated with decreased risk of different cancers, decreased triglyceride levels, and decreased risk of CVD. Eggplants contain phytonutrients that improve memory function, urinary tract health, and heart health. Whole grains and beans? Cutting whole grains and beans from your diet would limit intake of B vitamins, protein, iron and fiber. The benefits of these foods seem to outweigh the (understudied and over exaggerated) negatives.

Bottom line, be sure to look at the facts before you jump on the bandwagon or you may be depriving yourself of your favorite foods and the health benefits they provide. Be wary of food criminalization and diets that tell you to stop consuming specific foods (unless you have a diagnosed medical need). But if, after reading this article, you still believe that lectins are bad for you, you can purchase supplements to shield yourself from lectins for the cheap price of $79.96. *Insert second eye roll*. 

This blog was written by Paula Karamihas, MS, a dietetic intern at the University of Maryland.