DR ROHAN BADAVE
In India, almost 60-65 per cent population is not able to digest lactose properly. Lactose is a disaccharide, a principal carbohydrate found in the milk and milk products. Lactose is hydrolyzed by lactase enzyme in the small intestine into D-glucose and D galactose before it can be absorbed. Deficiency of lactase enzyme is the most common cause for lactose intolerance.
Physiologically, amount of lactase declines as people age. Adult lactase activity constitutes approximately 10 per cent of that of newborns. Secondary lactase deficiency occurs due to small bowel mucosal injury in conditions like Crohn's disease, celiac disease, radiation induced injury or giardiasis.
The typical symptoms of lactose intolerance include abdominal pain, bloating, flatus, diarrhea, borborygmi, and less frequently as constipation. 30 per cent people with lactose intolerance suffer from constipation.
Constipation is characterised by infrequent bowel movements, hard and/or large stools, painful defecation, and fecal incontinence, and is often accompanied by abdominal pain. Among organic causes of constipation, celiac disease and food intolerance are mentioned. In the course of celiac disease, secondary lactose intolerance may occur because of damage to the brush border and transient dysfunction of lactase.
Lactose intolerance symptoms are mainly produced as undigested lactose gets processed by colonic bacteria leading to formation of gas and byproducts.
Owing to the low oxygen concentration in the large intestine, 90 per cent of the gut bacteria are anaerobes. In the low-oxygenated environment, lactose becomes a source of hydrogen (H2), methane (CH4), and hydrogen sulfide (H2S).
The H2 produced can act as the substrate for the reaction carried out by methanogenic archaebacteria. Produced methane possibly acts as a neuromuscular transmitter and delays intestinal transit.
It causes the augmentation of contractile activity of the gut and slows the peristalsis down. Studies have shown that patients with chronic constipation have more methanogenic bacteria than healthy subject.
Diagnosis of this condition is challenging. Hydrogen breath tests are required to detect lactose malabsorption. Additionally, a methane breath test should be performed to support the diagnosis and establish the ratio of H2 and CH4 in exhaled air.
The lactose tolerance test is non-complex and inexpensive. It involves ingestion of 50 g of lactose and measuring blood glucose at different times.
Restricting carbohydrates intake may alleviate the symptoms of constipation, depending on its etiology. Restricting lactose in the diet can be helpful in some cases, although its presence in the everyday diet is crucial for the proper absorption of nutrients from food and should not be eliminated completely.
Most clinical trials indicate that 12g of lactose per serving is still well-tolerated by lactose intolerant individuals. The composition of gut microbiota plays a crucial role in the clinical manifestation of both lactose intolerance and constipation.
The recent RCT study shows that use of selected probiotics (Bifidobacterium longum and lactobacillus rhamnosus) and vitamin B6 can alleviate symptoms and gut dysbiosis in lactose-intolerant patients. Yet, it requires further research.
(The author Dr Rohan Badave, is a Consultant - Medical Gastroenterology at Manipal Hospital, Goa.)