MISSOULA - We've all heard the phrase "Got milk?" and know that milk and dairy products are a staple of our diet. But people are the exception when consuming milk.
Milk is the first food of newborn mammals. It’s rich in lactose (roughly 40 grams/liter for cow's milk), which serves as a major energy source in the initial phase of baby mammals’ lives.
The list of benefits goes on from a rich source of vitamins and minerals to cardiovascular health.
Lactose is a sugar found in milk, and it needs to be broken down into simpler sugars for our body to absorb.
To do this, we need an enzyme called lactase which is found in the small intestine. Mammals produce lactase so they can have their mother’s milk.
But most mammals become lactose intolerant after weaning.
That means they lose the ability to digest lactose as they grow older because their body stops making the enzyme lactase.
So, let’s cut to the cheese. If all mammals become lactose intolerant after weaning, why are people the exception?
Scientists believe it's due to a genetic mutation that occurred in some human populations about 10,000 years ago.
As we evolved and started domesticating animals like cows and goats and drinking their milk, people simultaneously started to develop a genetic mutation that allowed them to digest lactose even as adults.
This was very beneficial. You see before these genes evolved, people resorted to fermenting cow milk to extract sugar, resulting in a loss of up to 50% of its caloric content.
The ability to digest milk provided humans with access to this previously untapped source of energy.
Wildlife never had the opportunity to evolve this mutation since they never consumed milk beyond childhood.
Today, around 68% of the world's population is lactose intolerant according to the U.S. Department of Health & Human Services.
This means they experience symptoms like bloating, gas, and loose stools when they consume dairy products - while the others can enjoy all the products dairy has to offer without the grumbles in their stomachs.
This ability to keep drinking milk by producing the enzyme lactase throughout their lives is called lactase persistence or lactose tolerance.
According to Colorado State University, lactose tolerance is seen predominantly in people with northern European ancestry, especially Scandinavian.
Lactose intolerance is observed in a majority of the world's population, including most of those with Asian or African ancestors.
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