Food intolerance - Cambridge Nutritional Sciences

Food intolerance

Classic food intolerances are known as non-immune mediated reactions. This means that, unlike IgG food intolerance or a classic allergy reaction, that the immune system is not involved.  Some examples of this type of intolerance include enzyme deficiencies, such as lactose intolerance and histamine intolerance. Both these intolerances are caused by the absence of the enzymes lactase and diamine oxidase (DAO) respectively. 

Taking lactose intolerance as an example, lactase, normally secreted in the small intestine, is not produced which means that lactose (the primary sugar in milk) cannot be metabolized into its absorbable component monosaccharides, glucose and galactose. Undigested lactose cannot therefore be absorbed across the small intestinal epithelium and as a result, passes into the colon, where gut bacteria metabolize it into carbon dioxide, hydrogen and water. The characteristic symptoms of lactose intolerance are bloating, flatulence, abdominal cramping, and diarrhoea.

Most infants have sufficiently high activity levels of lactase at birth, which for most populations decreases at mid-childhood (about 5 years of age). This reduction is more pronounced in individuals from certain ethnic groups, which would explain the higher prevalence of lactose tolerance within individuals from these specific backgrounds. High lactase levels continue into adulthood in a few ethnic populations however, such as Northern European Caucasians, presumably as an adaptation to the widespread historical use of dairy products in these cultures.

It has been shown however, that individuals with lactose intolerance appear to tolerate yogurt and acidophilus milk better than other dairy products, despite these products containing substantial amounts of lactose. This may be due to fermented products having an inherent lactase activity, which is partially able to survive digestive processes and aid in the metabolism of lactose in the small intestine.

Fructose intolerance is similar in nature to lactose intolerance, in the sense that it occurs when the body’s digestive system doesn’t absorb fructose properly.  Symptoms can be quite debilitating, including abdominal pain, diarrhoea and flatulence. The cause is not due to an enzyme deficiency and rather relates to deficient carriers in the intestine, which inhibits absorption, as well as an imbalance in the bowel flora.

Additives, both natural and artificial used to flavour and preserve food, such as sodium benzoate, sulphites (a preservative found in dried fruit and vegetables) and monosodium glutamate can cause varied symptoms including asthma, hives, dizziness, sweating and even nausea/vomiting and diarrhoea. 

Other food intolerances that fall into the non-immune mediated category include chemical or pharmacological reactions.  Vasoactive amines such as histamine (see Histamine Intolerance, DAO), tyramine and phenylethylamine found in chocolate, have been found to contribute to symptoms such as migraine in some individuals.  Salicylate sensitivity, another pharmacological reaction which has been estimated to affect up to 5% of adults, can cause a variety of symptoms including stomach pain, tinnitus, fatigue, sinusitis etc. Salicylates are naturally present in fruit, vegetables, herbs, spices and condiments, nuts and seeds. Aspirin (Sodium Salicylate) is a well-known non-steroidal anti-inflammatory drug (NSAID) that may potentiate some acute allergies and causes adverse immunological reactions which have now been found to be immunological in nature are collectively referred to as aspirin intolerance. 

NB. Lactose intolerance is not something that we currently test for and will not be identified by our IgG mediated food intolerance tests. If an individual suspects that they may have lactose intolerance, then they should consult their GP to be tested for this.