Why does thrush occur?

Thrush (candidiasis of mucous membranes) is largely related to the host's metabolism and the conditions created in the body for the growth of Candida fungi.

Excessive Carbohydrate Diet

Candida — are conditionally pathogenic fungi that normally inhabit the intestines, oral cavity, and vagina. Their growth heavily depends on the availability of substrate — and the main source of energy for them is glucose and other easily digestible sugars.

With high consumption of fast carbohydrates, the sugar level in mucous tissues and intercellular fluid increases.  Candida easily ferments glucose and fructose, producing organic acids and alcohols, which further irritate the mucosa and suppress the local immune response.

In people with insulin resistance or prediabetes, glucose is poorly utilized by cells, and its concentration in tissues is elevated, creating a nutrient-rich environment for the fungus.

Excess Free Iron

Iron — is a key microelement not only for humans but also for fungi and bacteria. Normally, in the body, iron is bound to proteins (transferrin, ferritin, lactoferrin), which limits its availability to microorganisms. This is called "nutritional immunity" — the body "hides" iron from pathogens.

If the level of free (unbound) iron in the blood or mucous membranes increases, fungi receive a powerful stimulus for reproduction.

Candida has special siderophores and transport proteins that capture iron.

When there is too much iron in free form, it destroys the natural protective barrier.  This occurs in chronic inflammation, iron overload, frequent intake of iron-containing medications without control, and hemolysis.

Conclusion

Thrush is more likely to develop where:

• there are available sugars (especially with a high-carbohydrate diet or carbohydrate metabolism disorders);
• the balance of microelements is disturbed, particularly with an excess of free iron, which removes the natural growth limitations of the fungus.

Therefore, for the prevention and therapy of candidiasis, the following are often used:

• restriction of fast carbohydrates,
• support of normal iron metabolism (binding proteins, antioxidants, control of iron medication intake),
• strengthening local immunity and microbiota (lacto- and bifidobacteria compete with fungi).