Food & Nutrition

Adult Lactose Intolerance gene explained

Genetics play a pivotal role in whether you are lactose intolerance, especially as an adult. Don’t live with symptoms another day. Learn more here.

Join now & unlock 300+ unique Traits like this.

100+ are available for free


Lactose Intolerance in Adults—Is it in Your Genes? 

Lactose intolerance, an intolerance to sugar in dairy products, is incredibly common, especially as you get older, but just how likely you are to experience this intolerance might depend on your genetics! 

There’s nothing quite as satisfying as an ice cream cone on a hot summer day. I mean, who doesn’t love to indulge every once in a while? But delicious treats like ice cream can bring unforeseen consequences like stomach aches, diarrhea, or severe bloating symptoms. And if you’ve experienced these symptoms after enjoying a dairy-based food, you may be lactose intolerant. By learning more about the link between genes and lactose and intolerance, you can better understand your risk and take steps to help prevent those not so pleasant tummy aches. 

‍What is Lactose Intolerance?

Lactose is a sugar found in dairy products. People living with lactose intolerance cannot fully digest this type of sugar. Lactose intolerance means any discomfort or intolerance experienced from consuming dairy-based products such as cow’s milk, yogurt, ice cream, creamers,  and cheese. It is important to note that lactose intolerance can occur at any age. But it’s relatively common for intolerance to peak during adulthood, causing you to experience negative symptoms.

Types of Lactose intolerance

There are four main types of lactose intolerance.

  1. Primary intolerance – the most common type directly linked to the genetic predisposition of lowered lactase production. 
  2. Secondary intolerance – caused by an injury or illness to the digestive system, this type of lactose intolerance can be temporary or permanent.
  3. Developmental intolerance – is often found in babies born prematurely due to a lack of full intestinal development.
  4. Congenital intolerance – the rarest type, caused by a genetic disorder in which little to no lactase is present in the small intestine. Most often, this type is passed down from parent to child due to a genetic mutation. 

Symptoms of Lactose intolerance in adults

Lactose intolerance symptoms range from person to person, based on type and severity but often include:

Given the uncomfortableness of this condition, many people with adult lactose intolerance (ALI) tend to avoid consuming milk and dairy products altogether. For some, this purposeful avoidance may contribute to an increased risk of osteoporosis in adults for those not supplementing with other dairy-free calcium-rich alternatives.

How Common is Lactose intolerance?

ALI is a common digestive condition. 

Ranging from 2% in Sweden to 20–25% in Europe and the United States, 60–75% in South European, 80% in African-Americans, and nearly 100% in Southeast Asian populations, it is a health condition that affects millions of adults around the globe each year. 

‍How Do Genes Increase Your Risk of  Lactose Intolerance?

Lactose intolerance has been linked to both genetic and non-genetic factors. There is a tie between the genetic predisposition of the number of lactase-producing cells that line the small intestine walls and help absorb nutrients as food passes through. When a person does not have enough of these cells, lactose is broken down by bacteria inside the colon, which leads to lactose intolerance symptoms. 

The ability to tolerate lactose depends on the type of MCM6 variant a person is born with. The LCT gene follows specific instructions provided by MCM6 to either produce adequate lactase to digest dairy or not enough. This is especially true in primary lactose intolerance.

When looking at genetics, a single nucleotide polymorphism (SNP) in the lactase gene is known to be the underlying cause of adult lactose intolerance. In short, for most people living with lactose intolerance, a portion of their genes may be causing lactase reduction, which leads to dairy intolerance. 

What Is the MCM6 Gene?

The MCM6 gene is part of the MCM complex. The MCM complex is a group of proteins, or a helicase, that attaches to specific regions of DNA. Once attached, the helicase temporarily unwinds the two spiral strands of the DNA molecule to prepare the cell for duplication. MCM6 also contains code that influences production of lactase by regulating the LCT gene, resulting in decreased lactase production over time. Mutations of MCM6 affect its ability to control LCT expression. Without full function of MCM6, lactase production may continue long into a person’s life.

The Link Between Osteoporosis and ALI

In a recent study, researchers uncovered a link between osteoporosis and adult lactose intolerance when looking specifically at Turkish immigrants in Germany.1 In fact, there seems to be a higher risk for osteoporosis due to a unique and partially unknown combination of risk factors. To better understand this relationship, researchers first investigated the frequency of ALI in a gender-mixed group of Turkish immigrants living in Germany. Due to the genetic background of ALI, researchers predicted the nutritional condition would be more prevalent in Turkish immigrants than in Germans, which may influence calcium resorption and affect bone metabolism.

The study included 183 participants who completed a detailed food frequency and nutrient questionnaire on dietary calcium per week and a standardized interview covering current milk and dairy intolerance. Additionally, self-reported dislike of milk taste and aversion to dairy products assessed calcium and nutrition intake. Participants were genotyped, and it revealed that all males and 91.9% of females with the CC genotype at a specific gene location known to produce lactate reported symptoms of lactose intolerance.*

In addition, dislike of dairy products was reported in over 93% of participants with the CC genotype. 

ALI did not significantly influence calcium intake, markers of bone metabolism or bone mineral density. Therefore, ALI in Turkish immigrants does not seem to be a risk factor for osteoporosis.

How Do I Know If My Genes Play a Role in Lactose Intolerance? 

DNA analysis might be the best way to determine your genetic tendency for adult lactose intolerance. A DNA testing kit is simple to use, and your genetic DNA testing results can reveal many answers to the questions you may have about lactose intolerance or dairy-triggered symptoms. Once you’ve taken an at-home DNA test, you can use your raw DNA file to further analyze your genetic profile. Simply sign in to the Genomelink dashboard to upload your DNA file, and our experts will do the rest.

Don’t wait another day; Unlock your full genetic potential today!

*  The specific location is rs4988235 in the LCT gene.

1 Tsukamoto AS, Grosschedl R, Guzman RC, Parslow T, Varmus HE. Expression of the int-1 gene in transgenic mice is associated with mammary gland hyperplasia and adenocarcinomas in male and female mice. Cell. 1988;55(4):619-625. doi:10.1016/0092-8674(88)90220-6

Join now & unlock 300+ unique Traits like this.

100+ are available for free