What is lactose intolerance? Signs, types, and causes

Lactose intolerance is caused by a deficiency of the enzyme that helps break down lactose, the sugar present in milk. It causes digestive issues, including bloating, flatulence, and vomiting. A food intolerance is not the same as a food allergy.

People with lactose intolerance often face stomach and intestinal issues when they consume foods with regular milk. It is important to understand whether stomach distress is caused by this intolerance or not, in order to prevent discomfort and bloating.

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Signs of lactose intolerance

Stomach bloating is caused by undigested lactose (Image via Unsplash/sean S)

Common signs and symptoms may include:

• Stomach bloating
• Intestinal gas formation
• Nausea and vomiting
• Stomach pain and cramps
• Stomach unusual sounds
• Diarrhea

These symptoms are primarily caused by undigested lactose in the stomach, which irritates the stomach and intestinal lining. Since food items may take up to 24–36 hours to get digested and leave the large intestine, these symptoms may also last for a couple of days.

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Lactose intolerance causes

The main factors behind lactose intolerance are lactose malabsorption and sensitivity toward lactose. Lack of lactase enzyme deficiency leads to undigested lactose, which triggers sensitivity reactions in the intestine. Lactase production decreases as we age, and this is among the main triggers.

Gut flora also plays a major role in the processing of lactose in the intestines. If gut microbes aren't present in the right amounts, it might cause more digestive issues, as these friendly bacteria help in the digestion of food. It has to be kept in mind that a dairy allergy is different from milk intolerance.

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Types of lactose intolerance

Intolerance towards lactose can be classified in the following ways:

Primary lactose intolerance

This is the most common type of intolerance to lactose and is a normal result of aging. The enzyme lactase, responsible for the breakdown of lactose, decreases as we age. Since babies gradually start eating solid food instead of milk, lactase is no longer required in the same amounts and hence decreases. Furthermore, human mothers' milk contains lower amounts of lactose than cow's milk.

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Secondary lactose intolerance

This type of intolerance is usually caused by intestinal injury or disease, including celiac disease and inflammatory bowel disease (IBD). It can also be caused by intestinal surgeries.

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Congenital or developmental

Food sensitivities can be associated with genetic mutations. Genes pass on to the next generation and play a huge role in disease pathology. However, this is a rare condition. There is no cure for genetic disorders, and the individual must avoid dairy products containing lactose.

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Developmental intolerance toward lactose

This can be caused by premature birth, which results in the insufficient development of certain metabolic and enzymatic pathways. The underdeveloped small intestine is also highly sensitive to lactose. This condition often stays the same when the person grows up.

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What happens if you ignore lactose intolerance?

Almond milk is a popular lactose-free milk alternative (Image via Unsplash/Dhanya Purohit)

Food sensitivities are not new and have existed for a long time. Common stomach and intestinal disorders are often associated with or triggered by food intolerances or sensitivities. Ignoring intolerance towards lactose in milk can cause stomach disorders and prevent the digestion of other foods. It is always ideal to consult a doctor and substitute dairy with milk alternatives to prevent these intestinal disorders. There are some tests available to diagnose the type of intolerance, which might help in understanding the severity of the condition.

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Indranil Biswas is a nutritionist and personal trainer with a diploma in dietetics and personal training with a specialization in sports nutrition and strength training.

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