Can a DNA Test for Allergies? What We Know About Genes and Lactose Intolerance

Written by: 
Jeanne Conradie

When it comes to humans drinking milk, opinions vary. On the one hand, it is a part of our very class as Mammalia, or mammals. Mammals are defined as vertebrates that nourish their young with milk from the mammary glands. Then there are those that are of the opinion that human beings have no business drinking cow’s milk because it can cause allergic reactions like eczema, colic and other gastrointestinal discomforts, or what has become collectively known as lactose intolerance.

Our Early Dependence on Milk

Humans are reliant on their mother’s milk as soon as we are born for at least four to six months to ensure we gain weight and grow at a healthy pace. Babies are weaned from breastmilk (or whatever alternative was used) early on in life. They are quickly introduced to dairy in early childhood once they are no longer dependent on breastmilk. People that have no problem digesting lactose (the complex sugar in milk) go on drinking milk and consuming dairy products without any issues.

What is Lactose Intolerance?

Lactose intolerance is known as the inability to digest lactose in milk. Milk is made up of water, fats, proteins and sugars known as lactose. If milk is consumed by such an individual they will experience nausea, cramps, diarrhea and gastrointestinal discomfort shortly after consuming dairy products, usually within about half an hour and for up to two hours afterwards. The more dairy a lactose intolerant person has consumed, the more discomfort and symptoms they are likely to experience.

Those suffering from lactose intolerance do not produce enough (or at all) lactase which is the enzyme in human bodies responsible for breaking down lactose into its smaller molecules: glucose and galactose. The cells responsible for creating the LCT gene which allows humans to digest milk comes from your DNA, which means, technically speaking, lactose intolerance can be genetic.

What Has Genetic Testing Revealed About Lactose Intolerance?

Lactose intolerance has been identified as a recessive disorder. This means that both alleles, copies of the gene, must be identical. Individuals who have a cytosine (C) remaining on both alleles the information for creating lactase will be carried through by their DNA, these people are lactose tolerant.

Genetic Testing Can Identify Variants of the MCM6 gene:

CC Variant – This is the variant of the MCM6 gene that allows individuals to enjoy dairy without adverse symptoms, even in adulthood.

Carriers of the T variant (CT) – are also able to enjoy dairy without adverse symptoms.

TT Variant – The recessive TT variant of the MCM6 gene means the person is likely to be unable to produce lactase and so unable to digest dairy, making them lactose intolerant.

Should I Take a DNA Test for Lactose Intolerance?

You could always have this tested, but genetic testing can reveal much more than just whether you are lactose intolerant or not. Symptomatic testing is quick and effective. Simply eat or drink dairy, wait thirty minutes to two hours afterwards and if you experience any of the following symptoms there is a high chance you are lactose intolerant:

  • Cramps
  • Nausea
  • Vomiting
  • Bloating
  • Diarrhea

Genetic testing available at GENEWAY™ can give you invaluable insight into your own genetic makeup to better understand how to better care for yourself. Contact us at GENEWAY™ for more information and find out how it works.


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