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Lactose is the sugar found in milk. It occurs naturally in the milk of many animals.

Symptoms that indicate intolerance to lactose include bloating, pains in the stomach, diarrhea, and gas.

The enzyme that helps with the digestion of lactose in humans is known as lactase. It is essential in infants who feed solely on milk.

However, as a child gets older, their lactase production lessens and lessens.

By adulthood, at least 70% of people will not produce lactase that is enough to digest the lactose in milk. This causes the symptoms that you feel when you consume dairy products. Lactose intolerance is prevalent among non-Europeans.

People may also become lactose intolerant due to surgery or diseases of the gastrointestinal tract (as in the case of bacterial or viral infections).

So, how do you know if you have lactose intolerance? Here are common symptoms of the disorder.

Bloating & stomach pain

Abdominal bloating and pain are common signs of lactose intolerance. When your body is unable to digest lactose, it will run through your gut till it arrives at your colon.

The cells that line the colon cannot digest lactose, but they can be fermented by the bacteria that reside in the colon. These bacteria are known as microflora.

The fermentation of lactose triggers the release of hydrogen gas, methane, carbon dioxide, and short-chain fatty acids.stomach pain symptoms of lactose intolerance

These gases and acids cause abdominal pains and cramping. The bloating sensation is caused by excess gas and water in the colon, which stretches the wall of your gut, a process known as distention.

It is worth noting that the intensity of the pain and bloating is not associated with the amount of lactose that you ingest but by how sensitive you are to the distention. So, the severity and frequency of the symptoms vary significantly between individuals.

Finally, the distention and bloating may lead to nausea and, in some cases, vomiting. 


Diarrhea refers to an increase in the volume, liquidity, or frequency of stooling. You have diarrhea when you pass more than 200g (7 ounces) of stool within 24 hours.

How does lactose intolerance lead to diarrhea? Well, it increases the volume of water in your colon, which in turn makes your stool more voluminous and fluid. Diarrhea due to lactose intolerance is more common in children than in adults.

Microflora in your colon causes fermentation of lactose to gases and short-chain fatty acids. Most of these acids are reabsorbed into the colon. The remaining lactose and acids increase the amount of water released by the body into the colon.

milk lactose intoleranceIt is worth noting that a person must have more than 45g (1.6 ounces) of carbohydrates in his or her colon before they experience diarrhea. For lactose, this is equal to 3-4 cups of milk (assuming your body doesn’t digest any of the lactose before it reaches the colon).

However, you should note that not all carbohydrates that cause diarrhea come from lactose. Studies have shown that about 2-20% of carbs consumed at a time will reach the colon in healthy people undigested.

Finally, other factors contribute to diarrhea. These include medications, malabsorption, diarrhea, and diet. 

Other symptoms include:

  • Increased gas
  • Constipation
  • Eczema
  • Problems urinating
  • Mouth ulcers
  • Joint and muscle pain
  • Inability to concentrate
  • Headaches
  • Fatigue 

Tests for lactose intolerance

Intolerance testing will assist in diagnosis. At Global Testing Labs, we offer the following diagnostic tools or tests for lactose intolerance:

  • Blood test: Global Testing Lab conducts blood tests to screen for antibodies that may be responsible for your allergies. 
  • Food diary: Our allergy specialists will guide you on how to maintain a detailed log of your food intake, and when symptoms develop.
  • Elimination diet: You may be advised to avoid certain foods, especially those that seem to be allergic. Under the guidance of allergy specialists at Global Testing Lab, you will retain some foods gradually and observe when the symptoms show up.


The best treatment for lactose intolerance is by avoiding foods that contain lactose. Take your time to read food labels so that you will know which foods contain lactose. The market for lactose-free alternatives is rapidly expanding so, rest assured, you won’t have to go without.