What is a Food Intolerance?

What is a Food Intolerance?

September 01, 2015

Food intolerance can be defined as an adverse reaction to food that results in clinical symptoms but is not caused by a reaction of the immune system. The physiological mechanisms responsible for these reactions can be diverse and complex, and many are poorly understood.

Examples of substances involved in non-immune mechanisms of food intolerance are:

  • Lactose
  • Other diasaccharides
  • Biogenic amines (histamine, tyramine)
  • Artificial colors
  • Salicylates
  • Preservatives (BHA, BHT, sulfites)
  • Monosodium Glutamate (MSG) and other artificial flavors

Food intolerance and Digestive Enzymes:

Digestive enzymes for proteins, carbohydrates and fats are released by the pancreas and work best when mixed with bile from the liver. Anything impairing pancreatic or liver function can result in an adverse food
reaction. Abnormal bacteria levels in the gut can impair digestion. Undigested food is fermented resulting in abdominal pain, bloating, gas, and diarrhea.

Food additives and food intolerance or sensitivity:

Some foods and food additives have a direct toxic effect on the gastrointestinal tract. Additives such as MSG and sulfites can cause symptoms, including flushing and diarrhea or the “Chinese restaurant” or “salad bar” syndromes.

Lectins and adverse food reactions:


All foods contain proteins linked to carbohydrates known as lectins. Some are highly resistant to digestion or are lethal in humans. Others are highly toxic to the humans unless the food is soaked and then cooked well. An
excellent example is inadequately soaked and cooked kidney beans. Kidney bean lectins will cause a food poisoning like illness if the beans are not soaked a prolonged period and cooked thoroughly.

Symptoms commonly associated with food sensitivity or intolerance:

There are numerous symptoms commonly associated with food sensitivity. The symptoms can be both gastrointestinal and outside the gut. They include digestive symptoms such bloating, gas, diarrhea (and sometimes constipation), abdominal pain, nausea and vomiting. Non-digestive symptoms include severe fatigue, headaches, joint and muscle pains, skin rashes, weight loss or gain, anemia or nutritional deficiencies,
irritability, depression, mental fogginess, and nerve pain (neuropathy). These symptoms may be misdiagnosed or mislabeled as irritable bowel syndrome, chronic fatigue syndrome, reflux, ulcer, and fibromyalgia. Food sensitivity is treated simply by elimination of the offending food.

(information obtained from "Food Allergies and Intolerances" by Jancie Joneja, PhD, RDN and Dr. Scot Lewey www.foodoc.com)

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Food Allergies Intolerances/Sensitivities