What is the Lectin-Free Diet?

Foods high in lectins include vegetables, most notably tomatoes, peppers, and eggplant, as well as grains like quinoa and beans. Meat raised conventionally also contains lectins due to the diet fed to the livestock, although the quantities are small. Those who wish to eat meat on a lectin-free diet should only buy pasture-raised or grass-fed meat and poultry. Peanuts and cashews, high in lectin, should be avoided. One food people might have trouble eliminating is corn, which is one of the most common food additives. Most Americans eat some form of corn every day.

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If you wish to pursue a low-lectin or lectin-free diet, eat the foods that contain the least number of lectins possible. While nearly all vegetables and fruits have lectins, some have more than others. Focus on low-lectin vegetables such as onions, mushrooms, broccoli, bok choy, cauliflower, collard greens, pumpkin, squash, sweet potatoes, carrots, and asparagus. The ideal fruits include berries, citrus fruit, pineapple, cherries, and apples. Olive oil, avocado, butter, cream, and lard are low-lectin fats. Cooking high-lectin foods, especially boiling them, also reduces the lectin content. Sprouting or soaking seeds and nuts lower the lectin content as well.

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Lectins bind with carbohydrates, increasing the ability of cells to interact with other cells. In nature, lectins serve as the plant's protective properties. The protein makes insects and animals sick, which discourages them from eating the plant again. In humans, lectins can do much the same, albeit in a different way. In the human body, lectins may invoke an inflammatory response that can lead to weight gain, irritable bowel syndrome, leaky gut, and other health ailments. This is more theory than scientifically proven. Whether lectins, in the quantities found in most foods, harm the body is not clear.

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Since the body is unable to digest lectins, it produces antibodies when it senses them in the digestive system. Lectins affect the gut wall, and scientists have been studying how immune system defenses react to this perceived threat. Studies show subjects who consume foods high in lectins may experience inflammation, rashes, joint pain, nausea, vomiting, and diarrhea. But these undesirable effects occur with very high consumption of lectins, beyond the amount most people get in their diet. However, people with certain health conditions may be more sensitive to lectins. Therefore, a lectin-free diet may prove beneficial for individuals with conditions like rheumatoid arthritis, Crohn's disease, and irritable bowel syndrome.

Some research suggests lectins may not only cause weight gain but also prevent people from losing weight because they bind to sugars. A cardiologist in California first promoted the idea of cutting out lectins from the diet to aid in weight loss, adopting the diet himself and encouraging his patients to do so as well. As a result, many of the participants began to lose weight with no additional changes to lifestyle. The same number of calories were consumed, but they were no longer stored as fat. More research is needed to confirm these findings.

Diets high in lectins are hypothesized to weaken blood vessels, an early signal of heart disease. The proteins are also tied to hypertension. One study looked at 200 subjects, 72% of whom exhibited endothelial dysfunction, a condition with a well-established link to heart disease and a precursor to atherosclerosis or the deposits of fatty plaques on the inner walls of arteries. After six months on a lectin-free diet, 52% of the patients no longer showed endothelial dysfunction. This suggests a lectin-free diet might help reduce early signs of heart disease.

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Lectins are thought by some sources to cause diseases like irritable bowel syndrome or IBS. The top eight food allergens — dairy, egg, wheat, soy, peanuts, tree nuts, fish, and shellfish — are also high in lectins. In some people, blood cells react poorly to lectins, causing allergic reactions and other health issues. Some proponents of a lectin-free diet believe humans were never intended to eat foods with high numbers of lectin.

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Our ancestors only enjoyed grains when they were seasonally available, but today, we are overexposed to seasonal foods due to their unending availability. Some experts caution the human body was never intended to consume the number of grains that we do today. Though the USDA food guide has reduced their dated recommendation of six to 11 servings of grains per day, adults are still encouraged to consume three to eight servings, depending on their age and sex.

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While some experts say lectins can harm the body, especially when over-consumed, not all lectins are bad. Some may inhibit disease by acting as antioxidants, and the body uses others to carry out functions like cell-to-cell adhesion and programmed cell death. Only about 30 percent of the foods we eat contain harmful levels of lectins. There are also ways to prepare many lectin-rich foods that break down this protein before consumption, such as cooking and soaking.

A lectin-free or reduced-lectin diet may help people with specific health problems. Many people are turned off by the number of foods they must omit to follow the diet, especially the fruit and vegetable restrictions for a society that is often not eating enough of these foods. Anyone considering the lectin-free diet should speak to a dietitian or doctor when designing a meal plan, to ensure they consume enough dietary fiber, vitamins, and protein.