Why is fiber harmful in case of constipation and what to do?

Constipation — is not always a result of a lack of fiber. On the contrary, an excess of it with insufficient fluid intake often exacerbates the situation.

The fact is that fiber (especially insoluble) absorbs water, swells, and increases the volume of stool. If there is little water in the intestines, the stool becomes hard, moves slowly, and causes a feeling of heaviness and pain. Therefore, mechanically adding fiber without replenishing fluids can lead to even greater stagnation.

Constipation — is a signal that:

• The body is experiencing a water deficit. With insufficient hydration, the intestines "withdraw" liquid from the stool to maintain the water balance of blood and tissues. This makes the stool dry and hard.
• Peristalsis is insufficient. The muscle contractions of the intestines depend on the electrolyte balance, especially the levels of magnesium and potassium.
• There may be a disruption in the microbiota. Without a sufficient amount of beneficial bacteria, fiber is not processed into short-chain fatty acids, which stimulate peristalsis.

Therefore, to eliminate constipation, it is important to:

1. Increase water intake — it is usually recommended to consume 30–35 ml per kg of body weight.
2. Add magnesium (for example, magnesium citrate) — it attracts water into the intestinal lumen (osmotic action) and simultaneously relaxes smooth muscles, facilitating the movement of contents.
3. Monitor fiber balance — prefer soluble fiber (vegetables, berries, chia seeds, flaxseeds) rather than coarse insoluble fiber (bran in large amounts).
4. Support the microbiota — fermented products (sauerkraut, yogurt, kefir) help fiber to be processed into active metabolites.
5. Stay active — physical activity enhances peristalsis and speeds up intestinal motility.

Thus, the key point in constipation — is water and magnesium, not "let's add more fiber." Without fluids, fiber turns into a plug, but with water and magnesium, it begins to perform its natural function — gently stimulating the intestines.