Lactose Intolerance is a deficiency of the digestive enzyme B-galactosidase (Lactase) in the human intestine and a meal containing the cow‘s milk disaccharide sugar lactose (galactose bound to glucose) will induce frothy diarrhoea, flatulence and abdominal cramps. This is caused by undigested lactose passing into the colon where it is hydrolysed by bowel bacteria producing organic acids and gas including CO2, H2 and H2O. Symptoms do not include vomiting, rashes or nasal congestion as there is no immune response, it is purely undigested lactose that results in runny poop!
So if you do indeed have Lactose Intolerance, a proper cow’s milk challenge must theoretically give you rapid onset diarrhoea. No diarrhoea equates to no Lactose Intolerance. If your nose blocks up or they get a rash on your tummy then you probably have some additional problem other than purely lactose intolerance.
Almost all people are born with sufficient lactase but with increasing age, levels drop. Most lactose intolerant individuals tolerate small amounts of lactose in the diet and usually a full glass of fresh milk is necessary to trigger symptoms. Temporary lactose intolerance may follow a bout of viral gastroenteritis due to inflammation and hence it is best to avoid cow’s milk during the recovery period.
Lactose Intolerance may be an inherited trait affecting 10% of Caucasians and up to 80% of ethnic Africans, Asians and people of Mediterranean origin. Treatment is basically lactose avoidance or supplementation with an oral Lactase enzyme preparation such as Colief. Yoghurt is often tolerated as it contains live B-galactosidase producing bacteria.
Useful tests for diagnosing Lactose Intolerance include the popular Hydrogen Breath Test (although less reliable due to false positive results from other dietary sugar intake), as well as measuring serial blood glucose levels after a lactose containing meal, or measuring Faecal Reducing Substances (Sugars) in the watery frothy diarrhoeal stool produced as a consequence of a lactose containing meal.
References:
Joneja JMV. Food Allergy & Intolerances. Mechanisms and Management. J.A.Hall publications 2003.
Metcalfe D, Sampson H, Simon R. Food Allergy: adverse reactions to food and food additives 4th Ed. Blackwell Science 2008
