Lactose Intolerance: Do Genes have a role to Play?

Lactose intolerance is a digestive disorder caused by inability of the body to breakdown & digest lactose, the main carbohydrate in dairy products. It can happen at any age. There can be many reasons for people becoming lactose intolerant & genetics do play a role. According to the U.S. National Library of Medicine, about 65 % of the world population is Lactose Intolerant. In eastern part of Asia, the number is 90%.

Lactose Intolerance usually occurs when the body doesn’t produce enough Lactase, an enzyme found in the small intestine, responsible for breaking down sugar found in dairy products into simple glucose & galactose which are absorbed in bloodstream as fuel. In other words, the bodies of Lactose intolerant people do not produce enough lactase. With low lactase production, the undigested lactose passes into the colon where it interacts with bacteria. This interaction causes lactose intolerance with symptoms such as stomach bloating, cramping , nausea, gas & diarrhoea after consuming dairy products. Milk allergies are similar to lactose intolerance, but not common. However milk allergies have potential to be far more severe with symptoms as vomiting & blood stools.

Vector medical poster lactose intolerance. Symptoms of the disease. Illustration of a cute girl with milk.

Types of Lactose Intolerance

There are four types of Lactose Intolerance. Two are genetically disposed, one is temporary & rest occurs due to illness or injury. Let us discuss these in detail:

1. Primary Lactose Intolerance: This is the most common type & people with primary lactose intolerance are genetically predisposed to reduce Lactase (enzyme) production in the age group of 2 to 5. As enzyme levels decrease, dairy becomes hard to digest. There is a possibility that you may not see symptoms until adulthood.
2. Secondary Lactose Intolerance: This is caused by injury or illness. Any negative impact on the small intestine can result in reduced lactase production. Diseases such as Celiac are commonly linked to this type of Intolerance. Surgery, medication, or chemotherapy can also reduce Lactase production. This can be temporary or permanent.
3. Developmental Lactose Intolerance: This occur in babies who are born prematurely. It usually resolves when babies’ small intestines are fully developed.
4. Congenital Lactose Intolerance: This occurs when a baby is born with little or no lactase production in the small intestine. This genetic disorder can only be passed on to the baby when parents have mutated gene.

Primary Lactose Intolerance is an inherited genetic trait that runs in families. When a baby stops breastfeeding, the genetic response is to decrease the expression of the LCT gene which provides instruction for making Lactase in the small intestine. When lactase producing cells lines the wall of small intestines, they help absorb nutrients as foods pass through. Without this enzyme, lactose is broken down by bacteria in the colon which causes symptoms of lactose intolerance.

So do genetics play a role in Lactose Intolerance?

The type of lactose tolerance a person suffers from determines whether genetics play a role. For primary lactose intolerance, genetics do play a role. Located within chromosome 2, MCM6 gene help control the expression of LCT gene. The ability of a person to tolerate lactose depends upon the type of MCM6 variant the person has. The LCT gene follows the instruction of MCM6 to produce enough lactase to digest milk or not enough. For babies with Congenital intolerance, MCM6 gene is responsible for little to no lactase production. Primary lactose intolerance is generally set later in life once people attain adulthood.

Lactose intolerance can happen any time for a number of reasons. For instance, taking antibiotics can interfere with the small intestine’s ability to produce lactase. Some of common risk factors include:

1. Celiac disease
2. Diarrhea
3. Injury
4. Surgery
5. Ageing
6. Medication
7. Chemotherapy

Although there is no cure for Lactose tolerance, there are successful ways to manage the condition. People with primary lactose intolerance should avoid consuming milk products altogether. Besides, people can combine small amounts of dairy products with other non-lactose foods that can sometimes help you successfully deal with side effects. The type of lactose rich food you choose can have a profound impact on the health of those suffering from lactose intolerance. Yogurt is easily digestible as compared to milk.

PS: Originally published on www.thesushantkumar.com