Lactose is a sugar (disaccharide) which consists of monosaccharaides such as galactose and glucose and is the main source of calories of all mammal milk. Intestinal absorption of lactose requires hydrolysis to its component monosaccharaides namely galactose and glucose by the brush-border enzyme lactase. The ability to digest lactose during the period of breast-feeding is essential to the health of the infant. Therefore, during the eighth week of gestation, lactase activity can be detected at the mucosal surface in the human intestine while activity increases until 34th week. Lactase expression is at its peak by birth. However in some individuals, lactase activity begins to decrease after the first few months of life. This is due to stopping a genetic programme which reduces the lactase synthesis and as a result a very low lactase activity occurs in some adults. This condition is known as a lactase non-persistence while it results in incomplete digestion of an ingested load of lactose. Therefore, lactose is malabsorbed and undigested lactose reaches the colon and consequently, lead to certain symptoms. This condition is known as lactose intolerance and nearly 70% of the world’s population suffer from this clinical syndrome. This condition is high in northern European populations, and has decreased in frequency across southern Europe and the Middle East and is low in Asia and most of Africa.
Some beneficial components of dairy foods such as calcium, vitamin D, conjugated linoleic acid, sphingolipids, etc; have been shown experimentally to have protective effects against colon cancer
Biological mechanism
Lactase deficiency results in unabsorbed lactose being present in the colon which is a part of the large intestine. First, the increased osmotic load increases the intestinal water content by absorbing water from stool and changes it from a liquid to a solid form. Then, lactose is readily fermented by the colonic microbiome leading to production of short chain fatty acids and gas mainly hydrogen (H2), carbon dioxide (CO2), and methane (CH4)). These biological processes are present also for other poorly-absorbed, fermentable oligosaccharides, disaccharides, monosaccharides and polyols that are abundant in the diet. As a result of that some symptoms such as abdominal pain, bloating, excess flatulence, and diarrhoea occur.
Risk Factors
Factors that can make people more prone to lactose intolerance include;
- Age: As people get older, their bodies usually stop producing the lactase enzyme, and most people would naturally become lactose intolerant over time. Lactose intolerance usually appears in adulthood.
- Ethnicity: Lactose intolerance is most common in people of African, Asian, Hispanic and American Indian descent.
- Premature birth: Infants born prematurely may have reduced levels of lactase because the small intestine doesn’t develop lactase-producing cells until late in the third trimester.
- Intestinal injury: Small Bowel Injury from gastroenteritis, persistent diarrhoea, small bowel overgrowth, Giardiasis and other injuries to small intestinal mucosa can result in temporary lactose intolerance.
- Diseases of small intestine: Small intestine problems that can cause lactose intolerance include bacterial overgrowth, celiac disease (an immune disease in which people can’t eat gluten because it will damage their small intestine) and Crohn’s disease (an inflammatory bowel disease and causes inflammation of digestive tract).
- Certain cancer treatments: Receiving chemo therapy for cancer in abdomen or intestinal complications have an increased risk of lactose intolerance.
- Medicines : Certain antibiotics can trigger temporary lactose intolerance by interfering with the intestine’s ability to produce the lactase enzyme.
Types of Lactose Intolerance
There are four types of Lactase deficiencies and categorization is based on the origin of deficiency.
- Primary lactase deficiency
Also known as a lactase non-persistence, this is the most common type of lactase deficiency. In people with this condition, lactase production declines over time. This decline often begins at about age two. However, the decline may begin later too. Children who have lactase deficiency may not experience symptoms of lactose intolerance until late adolescence or adulthood. Research studies have discovered that some people inherit genes from their parents that may cause a primary lactase deficiency.
- Secondary lactase deficiency
It results from injury to the small intestine by infection, diseases, or other problems. Treating the underlying cause usually improves lactose tolerance.
- Developmental lactase deficiency
This type may occur in infants born prematurely. This condition usually lasts for for a short time after birth.
- Congenital lactase deficiency
Is an extremely rare disorder in which the small intestine produce little or no lactase enzyme from birth. Genes inherited from parents cause this disorder.
- Long-term effects of Lactose restriction
Restricting dietary lactose may improve gastrointestinal complaints since dairy products are the major source of calcium in many individuals. Other than that, dairy products might exert a protective or adverse effect in different physiological abnormalities because of differences in certain bioactive functions between lactose-intolerance and normal subjects.
- Lactose intolerance and osteoporosis
One of the primary risk factors for developing osteoporosis is lack of calcium in the diet. People with lactose intolerance, who avoid dairy products, could be at increased risk of developing osteoporosis since dairy products are a major source of calcium. However, research exploring the role of lactose intolerance in calcium intake and bone health has produced conflicting results. Some studies have found that people with lactose intolerance are at higher risk of low bone density, while other studies have not. Regardless, people with lactose intolerance should follow the same basic strategies to build and maintain healthy bones and should pay extra attention to getting enough calcium through other food or supplements.
- Lactose intolerance and vitamin D deficiency
The researchers have found those who are lactose intolerant had lower levels of vitamin D since dairy products are fortified with vitamin D, and most people don’t get enough of this vitamin from the sun or other foods. Vitamin D is considered essential for the absorption of calcium in the gut, which is important for good bone health. Vitamin D also aids nerve functioning and helps the body to stave off bacteria and viruses.
- Lactose intolerance and colorectal cancer risk
Diet has great effects on the incidence and progression of colorectal cancer. Some beneficial components of dairy foods such as calcium, vitamin D, conjugated linoleic acid, sphingolipids, etc; have experimentally shown to have protective effects against colon cancer. Moreover, some short chain fatty acids, such as butyric acid, which are produced through milk products, and fermented by colonic lactobacilli are important for the epithelial stability. These beneficial normal flora, lactobacilli and bifidus bacilli are also increased with the consumption of dairy foods. Calcium and vitamin D regulate cell growth and promote cell differentiation by stimulating calcium-sensing receptors, and calcium itself forms nontoxic insoluble compounds by binding with vulnerable free fatty acid and free bile acids.
In addition to that, intestinal galactose produced by lactase hydrolysis has a protective effect against colon cancer by binding lectins with inhibiting mucosal proliferation. Thus, lower amount of galactose in decreased activity of galactase leads to the pathogenetic process of developing cancer. One of the most common glycosylation abnormalities in colon cancer is the increased mucosal expression of the galactose β-1,3-N- acetylgalactosamine, which is known as the Thomsen-Friedenreich blood-group antigen while this compound adversely affects the ability of intestinal galactose to bind with lectins, which are known to stimulate colon epithelial proliferation.
Lactase deficiency results in unabsorbed lactose being present in the colon which is a part of the large intestine. First, the increased osmotic load increases the intestinal water content by absorbing water from stool and changes it from a liquid to a solid form
Treatment for Lactose intolerance
Lactase containing milk products and calcium supplements are recommended. Limit dietary intake of lactose by avoiding intake of lactose containing dairy products such as soft and processed cheese, buttermilk, cream, milk, ice cream etc.
- Lactase supplements
Lactase enzyme supplements contain lactase which breaks down lactose in milk and milk containing products. They are available as lactase enzyme tablets or drops.
Probiotics alter the intestinal flora and may have beneficial effects on inflammatory bowel disease patients. According to research, four-week consumption of a probiotic combination of Lactobacillus casei Shirota and Bifidobacterium breve Yakult improved symptoms and decreased hydrogen production in lactose intolerant patients and these effects appeared to persist for at least three months after suspension of probiotic consumption.
Conclusion
Lactose intolerance is a digestion disorder which is common in our society. People who are suffering from this syndrome need to have appropriate supplements in adequate doses in order to prevent specific nutrition disorders such as calcium and Vitamin D deficiencies which are nutrients mainly associated with dietary products.
The writer is a medical laboratory technologist at a private hospital and holds a MSc. Degree in Industrial and Environmental Chemistry from the University of Kelaniya and BSc.
Food Production and Technology Management degree from the
Wayamba University of Sri Lanka.
