Food Intolerance Research Paper

Causes of food intolerance

By Dr. Liji Thomas, MD

Food intolerance is a functional or structural intolerance to food, which is non-immunologic and non-toxic in origin, but is chemically based instead. A third type of food intolerance involves the effects produced by pharmacologically active amines and other compounds present in foods.

Thus, food intolerance describes a range of food-related symptoms that are not immunologically-mediated. These account for the majority of food reactions.

Functional intolerance

Functional food intolerance is not associated with structural abnormalities of the digestive tract, but may be due to an isolated enzyme deficiency. A prime example of functional food intolerance is lactose intolerance.

Enzymatic

Lactase deficiency is the best known and is the cause of intolerance to milk and other dairy products, which contain lactose, also known as milk sugar.

Other examples include the isolated or combined disaccharide malabsorption syndrome, which prevents the absorption of sucrose, lactose and other disaccharides, either one in particular or all together. In addition to this, there is isolated maltase, galactase or saccharase deficiency.

When these sugars are not absorbed properly, they reach the large intestine in increased amounts, resulting in excessive fermentation and bacterial overgrowth. The production of osmotic sugars and their fermentation products in larger quantities causes symptoms, such as meteorism (i.e. the accumulation of excess gas in the gastrointestinal tract), flatulence and diarrhea, as described below.

Diamine oxidase deficiency may cause histamine intolerance.

Transport

This leads to symptoms of food intolerance following ingestion of a number of foods, due to the release of excessive bacterial decomposition products in the gut.

Active compounds in foods

Many foods contain compounds with intrinsic biologic activity, such as:

• Salicylates, as in curries, peppers and some spices, as well as fruits like raisins, sultanas, oranges and pears.

• Biogenic amines, such as histamine, serotonin or tyramine, as in chocolates, may lead to intolerance due to enzyme deficiencies, such as diamine oxidase or histamine N-methyl transferase. Foods which are rich in histamine include fermented foods, such as sauerkraut, aged cheese and red wine.

Other foods release histamine, such as citrus fruits or nuts. Black tea and some colorants actually inhibit diamine oxidase. In addition, factors that increase histamine release may precipitate intolerance, such as sports activity, some infections or emotional upsets.

Idiosyncratic intolerances

Some substances evoke individual intolerances, such