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Why are so many people are lactose intolerant?

Naturally, milk is a substance only consumed by a baby until the child is weaned. Lactase, the compound used to break down lactose in milk, is generally only produced during childhood. Around half of the world's population is unknowingly lactose intolerant and are unable to effectively digest & consume milk.

What is lactose intolerance?

Lactose intolerance is the inability to digest lactose, the primary sugar found in milk and dairy products. Normally when a person eats something containing lactose, an enzyme in the small intestine called lactase breaks down lactose into simpler sugar forms called glucose and galactose. These simple sugars are then easily absorbed into the bloodstream and turned into energy — fuel for our bodies. People with lactose intolerance do not produce enough of the lactase enzyme to break down lactose.

Lactose intolerance is natural

Unknowingly to most people, a vast majority of us are lactose intolerant. In fact, it is perfectly natural to be lactose intolerant, since our bodies are genetically designed to consume milk (specifically human breast milk) only until we have been weaned off milk. Naturally, all animals reduce / stop producing the lactase enzyme post weaning, since they no longer have a requirement to consume milk.

Certain communities have been more intolerant to lactose than others. Asians are the most lactose intolerant – studies indicate that as much as 90% of Asians are lactose intolerant, which is reflected in the very low usage of dairy products in their traditional cuisines. South Indian have an intolerance to lactose similar to Asian averages (again reflected in absence of dairy products in traditional cuisine), while North Indian's may have slightly higher tolerance levels (linked to the Aryan race). African Americans, Jews, Mexicans and Native Americans are other communities where the vast majority of people are intolerant to lactose and should avoid consumption of dairy products.

Symptoms of lactose intolerance

Symptoms of lactose intolerance can be mild or severe, depending on how much lactase your body makes. Sometimes people who have never had problems with milk or dairy products suddenly develop lactose intolerance. This is more common as you get older. Symptoms usually begin 30 minutes to 2 hours after eating or drinking milk or milk products.

Symptoms of lactose intolerance

  • Bloating
  • Pain or cramps in the lower belly
  • Gurgling or rumbling sounds in the lower belly
  • Gas
  • Loose stools or diarrhoea
  • Nausea and vomiting

Symptoms occur because the unabsorbed lactose passes through the small intestine and into the colon. In the colon, one type of normal bacterium contains lactase and is able to split the lactose and use the resulting glucose and galactose for its own purposes.

Unfortunately, when they use the glucose and galactose, these bacteria also release hydrogen gas. Some of the gas is absorbed from the colon and into the body and is then expelled by the lungs in the breath. Most of the hydrogen, however, is used up in the colon by other bacteria. A small proportion of the hydrogen gas is expelled and is responsible for the increased passing gas.

Not all of the lactose that reaches the colon is split and used by colonic bacteria. The unsplit lactose in the colon draws water into the colon (by osmosis). This leads to loose, diarrheal stools.