Food Lectins in Health and Disease: An Introduction
In recent years it appears there is a rising epidemic of people suffering from chronic digestive and autoimmune conditions. Food intolerance or sensitivities may lie at the root of the problem. Most people, including doctors, have little clue how foods they eat may be contributing to their chronic illness, fatigue and digestive symptoms.
There are, however, a lot of clues in the medical literature and the lay public’s experience about how foods are causing and/or contributing to the current epidemic of chronic illness and autoimmune disease. There are several diets being used by many people with varying success to improve their health despite a general lack of iron clad scientific proof for their effectiveness. One of the clues to the cause and relief of food induced illness may lie in proteins known as lectins that are present in all foods.
Animal and plant sources of food both contain complex proteins known as lectins. These proteins typically have the ability to attach to sugars or carbohydrates on the surface of human cells. Some of these proteins can cause clumping of human red blood cells, a process that is called agglutination. The process of agglutination occurs when someone receives the wrong blood type during a blood transfusion. In fact, red blood cell agglutination specific to each person or groups of people is the basis for testing for blood types. There is some data that blood types may influence how people respond to certain foods though a blood type specific diet appears to have been disproven. The attachment or binding of certain food lectins can initiate a variety of cell specific effects. These reactions may mimic hormones or cause changes in cells. This is termed molecular mimicry.
Most plants contain lectins, some of which are toxic, inflammatory, or both. Many of these plant and dairy lectin are resistant to cooking and digestive enzymes. Grain lectins, for example, are quite resistant to human digestion but well suited for ruminants like cattle who have multi-chambered stomachs. Therefore, lectins are present in our food and are often resistant to our digestion and some have been scientifically shown to have significant GI toxicity in humans. Others have been shown to be beneficial and maybe even cancer protecting. Either way plant and animal proteins are foreign proteins to the body and are dealt with by digestion and our immune system in a positive or negative manner.
The human digestive system was created to handle a variety of plant and animal proteins through the process of digestion and elimination. Some plant and animal proteins or lectins are severely toxic to humans and cannot be eaten without causing death like those in Castor beans and some mushrooms. Other foods must be prepared before they are safe to be eaten. Preparations may include pealing, prolonged soaking and cooking like kidney beans. Other foods may be poorly tolerated because of a genetic predisposition or underlying pre-existing food allergy or intolerance. Others are tolerated to some degree or quantity but not in large amounts or on a frequent basis. People who are intolerant to the milk sugar lactose, because of inherited or acquired deficiency in lactase enzyme, may tolerate small amounts but may have severe bloating, gas, abdominal pain and cramps with explosive diarrhea when a large amount of lactose containing foods are eaten. Foods can become intolerable to some people after their immune system changes or gut is injured from another cause.
Of the food lectins, grain/cereal lectins; dairy lectins; and legume lectins (especially peanut lectin and soybean lectin) are the most common ones associated with reports of aggravation of inflammatory and digestive diseases in the body and improvement of those diseases and/or symptoms when avoided. Recent research by Loren Cordain PhD., has suggested that these lectins may effectively serve as a “Trojan horse” allowing intact or nearly intact foreign proteins to invade our natural gut defenses and enter behind the lines to cause damage well beyond the gut, commonly in joints, brain, and skin of affected individuals. Once damage occurs to the gut and the defense system is breached the result is what some refer to as a “leaky gut”. Moreover, many people who develop a “leaky gut” not only have gut symptoms such as bloating, gas, diarrhea, and abdominal pain but also other symptoms beyond the gut, or extra-intestinal symptoms. Commonly affected areas are the brain or peripheral nerves, skin, joints, and various body glands. With continued exposure of the gut by these toxic food lectins a persistent stimulation of the body’s defense mechanism in a dysfunctional manner, occurs, i.e. autoimmune disease.
Wrong types or levels of good and bad bacteria in the gut, or intestinal dysbiosis, may contribute to this process of abnormal stimulation of the immune system. Research supports the strong possibility that such stimulation may be accentuated by interaction of the bacteria with food lectins. It is believed by some that this may further worsen gut injury and autoimmune disease. This latter concept is gaining acceptance and recognition by doctors in one form as the hygiene theory. It is speculated that our gut bacteria have become altered by increased hygiene and over use of antibiotics and that this phenomenon may be playing a significant role in the rising incidence of autoimmune diseases such as diabetes, arthritis, and chronic intestinal diseases like Crohn’s disease and irritable bowel syndrome.
Lectins as a cause however are largely being ignored in the U.S. though the field of lectinology and lectins role in disease is more accepted internationally. Avoidance of certain food lectins may be helpful in achieving health and healing of chronic gut injury. Healing of a “leaky gut” and avoidance of ongoing abnormal stimulation of the immune system by toxic food lectins and bacteria in the gut is the basis for ongoing research and probable success of several popular diets such as the paleo diet, carbohydrate specific diet and gluten-free/casein-free diet. More research is needed in this exciting but often neglected area. The Food Doc, LLC features a website http://www.thefooddoc.com that will provide physician authored information on food intolerance, sensitivity and allergy such as lectin, gluten, casein, and lactose intolerance with dietary guidance that will feature in the near future an online symptom assessment and diet-diary.
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