How common are adverse reactions to certain foods?

20% of individuals report unpleasant symptoms after eating specific foods.

How are adverse reactions to food classified?

These are classified as either immune-mediated (true food allergy) or non-immunologic. The latter are more common and synonymous with food intolerance.

What foods are most commonly implicated in true immune-mediated food allergy?

Cow’s milk, eggs, peanuts, shellfish, and seafood.

What symptoms can result from exposure to a food allergen?

Only 50% of individuals with food allergies have GI symptoms at exposure. The skin, respiratory tract, and cardiovascular system can also be involved, either in isolation or together with the GI tract.

What is the most common food intolerance?

Lactose. It results when an individual lacks specific small intestine enzymes which allow breakdown of lactose in dairy products. It is more common in those with African, Native American, or Mediterranean descent. Lactose intolerance can result in bloating, gas, and diarrhea on lactose exposure.

Do all dairy products result in symptoms in those with lactose intolerance?

No. Some dairy products such as yogurt are low in lactose and should not cause symptoms in lactose intolerant individuals. Severe symptoms from these are more suggestive of irritable bowel syndrome.

Can other carbohydrates cause similar problems?

Sorbitol and fructose are commonly found in processed food and juices are fermented by bacteria in the colon and can cause identical symptoms when ingested in large quantities.