Lactose intolerance is one of the most common causes of discomfort after consuming milk in adults. It is related to the function of the enzyme lactase, which is responsible for breaking down lactose in the intestine. If there is not enough lactase, symptoms such as bloating, gas, or diarrhea may occur. This is not a disease in the classical sense, but a normal variation for many people. Let’s look at how lactase works, why its levels decrease with age, and what to do about it without extremes.
There are two types of people:
those who can drink milk without problems, and those who later regret that decision.
What lactase is and how it works
Lactase is an enzyme produced in the small intestine.
Its task is simple:
to break down lactose (milk sugar) into:
- glucose
- galactose
In this form, they can already be absorbed.
If there is enough lactase — there are no problems. If not — a completely different story begins.
Symptoms of lactose intolerance
Symptoms of lactose intolerance occur because lactose is not fully broken down in the small intestine and enters the large intestine, where it is fermented by bacteria. The severity of symptoms may vary depending on individual tolerance and the amount of lactose consumed.
Most often, symptoms appear 30–120 minutes after consuming milk or dairy products:
- bloating
-
excess gas
-
gurgling in the abdomen
- discomfort or cramps
- diarrhea
- a feeling of heaviness after meals
In most cases, these symptoms do not pose a health risk, but they can affect well-being and quality of life. It is important to note that similar symptoms may also occur in other gastrointestinal conditions.
If symptoms recur regularly after consuming dairy products, it is advisable to consult a doctor to clarify the cause and receive personalized recommendations.
If you recognize these symptoms — next, let’s understand why this happens.
Why lactase decreases
And here is an interesting point.
In most people worldwide, lactase activity decreases with age. This is called “adult-type lactase deficiency.”
That is:
this is not a malfunction of the body
this is an evolutionary norm
And the ability to drink milk in adulthood is rather an exception related to genetics.
Table 1. Types of lactase activity
| Type | What happens | Who it is typical for |
|---|---|---|
| High activity | Lactose is well absorbed | Some Europeans |
| Reduced activity | Partial digestion | Most adults |
| No activity | Lactose is not broken down | Rare cases |
What happens in lactase deficiency
Undigested lactose enters the large intestine.
And there, bacteria “happily” begin to ferment it.
Result:
- bloating
- gas formation
- discomfort
- sometimes diarrhea
And this is important: this is not an allergy.
Lactose intolerance vs milk allergy
These are often confused.
Lactose intolerance:
- an enzyme issue
- unpleasant but not dangerous
Milk protein allergy:
- an immune reaction
- can be serious
These are different mechanisms and require different approaches.
How to tell if lactase is the problem
A typical scenario:
- you drank milk
- after 30–120 minutes, discomfort appeared
But it’s better not to rely on symptoms alone for diagnosis.
There are methods:
- hydrogen breath test
- elimination diet
How to live with it normally
And here’s the good news: this is not a big deal.
What helps:
- reduce the amount of milk
- choose fermented products (yogurt, cheese)
- use lactose-free options
- if needed — lactase enzyme
And there is no need to completely “eliminate” dairy if you tolerate small amounts.
Table 2. What is usually better tolerated
| Product | Why |
|---|---|
| Yogurt | Partially broken-down lactose |
| Hard cheese | Minimal lactose |
| Lactose-free milk | Lactose already broken down |
| Kefir | Bacteria help digestion |
Questions and answers
Can lactase be “restored”?
No. But the diet can be adapted.
Do you need to completely avoid milk?
Not always. It depends on tolerance.
Why was it fine before, but not now?
Because lactase activity decreases with age.
Is lactose intolerance dangerous?
No. It’s a matter of comfort, not a threat.
Conclusions
Lactase is a small enzyme with a big impact.
In short:
the problem is not the milk, but how the body processes it.
And this doesn’t need to be “treated” — it needs to be understood and adapted to.
References
- National Institutes of Health. Lactose intolerance.
- National Health Service. Lactose intolerance.
- European Food Safety Authority. Lactose digestion and tolerance.
- Misselwitz B, et al. Lactose malabsorption and intolerance. Gut. 2019.
- Swallow DM. Genetics of lactase persistence. Annual Review of Genetics. 2003.
- Deng Y, Misselwitz B, et al. Lactose intolerance in adults. BMJ. 2015.
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