Visual guide: what is lactose intolerance and how to know if you are lactose intolerant?

Do you feel bloated, gassy or sick after consuming products such as milk, cheese, yoghurts, ...? You are not alone.

Many people experience digestive discomfort without suspecting that dairy might be the culprit. Lactose intolerance affects more than 30% of the population in some regions of the world, and its prevalence is even higher in Asia and South America. Despite its frequency, it remains under-diagnosed due to lack of awareness or confusion with other gastrointestinal conditions.

In this visual guide, we explain clearly what lactose intolerance is, how to recognise its most common symptoms and what steps to take to confirm it reliably.

What is lactose intolerance?

Lactose intolerance is the difficulty in digesting lactose, the natural sugar found in milk and milk products. This occurs when the small intestine does not produce enough lactase, the enzyme responsible for breaking down lactose into glucose and galactose.

It is important not to confuse it with cow's milk protein allergy, which is an immune system reaction to milk proteins, such as casein or whey, and not an enzyme problem.

Most common symptoms of lactose intolerance

Symptoms usually appear between 30 minutes and 2 hours after consuming foods containing lactose (milk and dairy products, biscuits, sausages, etc.). They vary according to the amount ingested and the degree of lactase deficiency.

Abdominal bloating in lactose intolerance

This is one of the most common symptoms. Lactose that is not digested reaches the colon, where it is fermented by intestinal bacteria. As a result, gas accumulates and bloats the abdomen, creating a «balloon» sensation.

What you feel: hard belly, abdominal pressure, discomfort when sitting or buttoning trousers.

 

 

Gas or flatulence after consuming dairy products

Bacterial fermentation of lactose generates gases such as hydrogen, methane and carbon dioxide. This results in frequent and often foul-smelling flatulence.

What you feel: a strong urge to pass gas, discomfort in social situations, pressure in the lower abdomen.

 

 

Diarrhoea or intestinal urgency in lactose intolerance

Unabsorbed lactose acts as an osmotic: it draws water into the colon, which can cause liquid or loose stools. In some cases there is intestinal urgency, especially in the morning.

What you feel: sudden need to go to the toilet, watery stools, fear of eating outside the home.

 

 

Abdominal pain or cramping in lactose intolerance

Colic can be sharp and stabbing, due to increased intestinal motility and bloating caused by gas.

What you feel: cramps, knot-like pain, localised cramps in the lower abdomen.

 

 

Mild nausea after eating milk, cheese or yoghurt in lactose intolerance

Although less common, some people experience nausea, especially if they consume lactose on an empty stomach or in combination with other digestive irritants.

What you feel: upset stomach, mild disgust, loss of appetite after eating dairy products.

 

 

Sound familiar? It could be intolerance. We tell you about it below.

How do you know if you are lactose intolerant?

The most reliable method: lactose intolerance test at home. The hydrogen breath test is the most widely used and scientifically validated procedure to confirm this condition.

How does it work?

1. You receive a kit at home with detailed instructions.
2. You perform the breath test after ingesting a solution containing lactose.
3. You receive a clear report of your exhaled hydrogen and methane levels.

A significant increase indicates poor lactose digestion, which confirms the diagnosis.

Unreliable alternatives:

• Undiagnosed dairy elimination can lead to unnecessary calcium deficiencies.
• Self-diagnosis based only on symptoms that can be confused with irritable bowel syndrome or other intolerances.
• Trying enzyme supplements without knowing whether they are necessary may be ineffective or costly.

What do I do if I am lactose intolerant?

Having this intolerance does not mean giving up dairy completely.

• Lactose-free versions: Today there are many lactose-free milk, cheese and yoghurt alternatives that retain the taste and nutritional value.
• Food adaptation: reading labels, identifying ingredients with hidden lactose and portion control can make a difference.
• Medical consultation: After the test, a professional can help you personalise your diet and avoid long-term nutritional deficits.

Your body is already warning you

If you've been feeling digestive discomfort for some time, your body may be trying to tell you something. Validating those symptoms is the first step towards a better quality of life.

Don't ignore discomfort. Understanding what you eat and how your body reacts is key to your wellbeing.

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