Gut microbiota and skin health

The gut microbiota is the set of billions of microorganisms that live naturally in our intestine.

It is formed mainly of bacteria, although it also includes viruses, fungi and other microorganisms that coexist in balance with our organism.

Far from being harmful, most perform essential functions for our health.

For many years the gut and the skin were considered independent organs.

Today we know that both are closely related through what is known as the gut-skin axis.

This axis implies a continuous communication between:

• The gut microbiota.
• The immune system.
• Metabolism.
• The nervous system.
• The skin.

Therefore, intestinal alterations can influence certain skin diseases.

A balanced microbiota helps to:

• Regulate the immune system.
• Maintain the integrity of the intestinal barrier.
• Produce beneficial vitamins and metabolites.
• Favour digestion.
• Protect against pathogenic microorganisms.
• Modulate the organism's inflammation.

All this can have an indirect impact on skin health.

Dysbiosis is an alteration of the normal balance of the microbiota.

It does not simply mean having «bad bacteria», but a loss of diversity and an abnormal functioning of the intestinal ecosystem.

It can favour an exaggerated inflammatory response in predisposed people.

Research continues to advance, but there are associations described with:

• Acne.
• Rosacea.
• Atopic dermatitis.
• Psoriasis.
• Chronic urticaria.
• Alopecia areata.

It is important to remember that the microbiota is usually not the only cause of these diseases, but one of the multiple factors involved.

There are several mechanisms:

• Regulation of the immune system.
• Production of anti-inflammatory metabolites.
• Modulation of systemic inflammation.
• Influence on the intestinal barrier.
• Communication with the nervous system.

These mechanisms help to explain why some patients present skin improvement when they improve their gut health.

Numerous microbiota analyses are currently marketed.

However, most of these tests do not yet have a clearly demonstrated clinical usefulness for the diagnosis or the routine treatment of skin diseases.

Therefore, the main scientific societies do not recommend their systematic use.

Scientific evidence mainly supports:

• Mediterranean diet.
• Abundant consumption of fruits and vegetables.
• Foods rich in fibre.
• Legumes.
• Nuts.
• Whole grains.
• Regular physical activity.
• Sleeping adequately.
• Reducing stress.
• Avoiding smoking.
• Avoiding the unnecessary use of antibiotics.

There is no single «diet for the microbiota».

What matters is maintaining a varied diet rich in plant foods.

Some probiotics have shown promising results in certain diseases.

However:

• The effects depend on the strain used.
• Not all probiotics are the same.
• Not all patients respond the same.

Currently a universal probiotic cannot be recommended to improve the skin.

Prebiotics are fibres that serve as food for the beneficial bacteria.

Their consumption through a diet rich in vegetables constitutes one of the best strategies to maintain a healthy microbiota.

No.

Although the gut-skin axis is a biological reality, no skin disease should be approached exclusively by means of treatments directed at the microbiota.

The treatment must always be adapted to the diagnosis and combine the necessary measures in each patient.

• Myth: All skin diseases originate in the gut. Fact: The microbiota can influence, but skin diseases are multifactorial.
• Myth: A microbiota analysis identifies the cause of any skin problem. Fact: Currently these studies have very limited clinical indications.
• Myth: We all need probiotics. Fact: Most people obtain greater benefits through a healthy diet.
• Myth: Probiotics cure acne. Fact: Some strains could be useful as a complement, but the evidence is still limited.
• Myth: Diet does not influence the microbiota. Fact: Diet is one of the main factors that determine its composition.

• The gut microbiota plays an important role in the regulation of the immune system.
• There is a demonstrated communication between the gut and the skin, known as the gut-skin axis.
• Skin diseases are multifactorial and the microbiota is only one of the factors involved.
• The Mediterranean diet and a healthy lifestyle constitute the best tools to take care of the microbiota.
• There is no universal probiotic or microbiota analysis indicated for all patients.
• The treatment of skin diseases must always be individualised and based on scientific evidence.