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Milk, the advertisements tell us, does a body good. The problem for literally billions of people worldwide, unfortunately, is that milk can also do a body in.
For up to 25% of people of northern European or South Asian heritage and up to 75% of people whose ancestors came from other parts of the world, a disorder called lactose intolerance can cause cramping, diarrhea, and gas after the consumption of milk, yogurt, cheese, or any foods that contain them. Even tiny amounts of dairy can cause embarrassing and uncomfortable gastric distress if they are eaten with a heavy meal.
What Is Lactose Intolerance?
Lactose is the sugar that naturally occurs in milk. Chemically, lactose is a compound known as a disaccharide. It is a sugar molecule that is made from two smaller sugar molecules combined. The digestive tracts of people who can digest milk produces an enzyme called lactase that cleaves the lactose molecule into its constituent sugars, galactose and glucose.
When the digestive tract does not secrete lactase, lactose accumulates in the gut. In the small intestine, lactose absorbs water and makes the stool runny. This accelerates the passage of digested food through the small intestine down to the colon before digested nutrients can be fully absorbed.
Undigested milk sugar and other nutrients not going into the bloodstream from the small intestine accumulate and begin to ferment in the colon, also known as the large intestine. Bacteria consume what the body cannot absorb. The bacteria emit their own waste products and gas.
What Are the Symptoms of Lactose Intolerance?
The hallmark of lactose intolerance is gas. Lactose-fermenting bacteria emit so much gas that there can be boborygmus (tummy rumbles), flatulence, and belching. If the gas can't find its way out of the rectum or up the throat because its passage is blocked, then there can be cramping. The accumulation of fluid in the small intestine to dilute the lactose causes diarrhea.
Who Gets Lactose Intolerance?
Lactose intolerance usually does not cause any symptoms until the age of 20 to 40 years. Women who develop lactose intolerance usually regain their ability to digest milk sugars when they are pregnant. Men and women are equally susceptible to the condition, but it is relatively rare among people of northern European or northern Indian descent, although up to 25% of northern Europeans and the peoples of northern India and Pakistan become lactose intolerant. Among other ethnic groups, about 75% of adults are lactose intolerant, even more in parts of Africa.
If you tend to cut the cheese after you eat cheese, or if you experience gassiness or cramping after drinking milk or eating dairy products, chances are that you have lactose intolerance. Fortunately, dealing with lactose intolerance is not difficult.