What role do gut bacteria play in nutrition and in human health?

Heather Campbell
 min read

What role do gut bacteria play in nutrition and in human health? They’re much more important than we think!

What role do gut bacteria play in nutrition and in human health?Choosing a good diet will lead to a good balance of the intestinal flora.

Gut bacteria are essential when considering nutritional, mental, and physical well-being. A nutritive, well-balanced diet consisting of fresh food without additives will encourage the development of good gut bacteria, thus resulting in better physical and mental health.

Intestinal flora, also called microbiota, can be defined as all the micro-organisms that evolve throughout our digestive system.

Hence, our diet plays an essential role in the health of our microbiota, which is made up of billions of bacteria, viruses, and other fungi that live in our intestines.

Read on to understand exactly how they work and what role gut bacteria play in nutrition and human health.

What role do gut bacteria play in nutrition and in human health? Introduction

Consumption of different nutrients can have a beneficial role on the microbiota and health.

To have a dense and diverse microbiota, the diet must:

  • Contain a wide variety of fibers in sufficient quantity
  • Respect the balance between saturated and unsaturated fats, while reducing the intake of saturated and trans fats and providing essential fatty acids.
  • It should not be too rich in animal proteins but provide essential amino acids.

A balanced diet is good for our health

Many bacteria found in a balanced diet can keep our bodies healthy.

For example, certain short-chain fatty acids (SCFAs) are produced by bacterial fermentation of dietary fiber.

These SCFAs reduce weight gain and improve the effectiveness of insulin secreted by the pancreas, also reducing the risk of overweight-induced diabetes.

They also reduce the risk of inflammation and allergy. In fact, a high-fiber diet can cure some respiratory allergies and strengthen the body’s defenses against intestinal infections.

Many fruits and vegetables contain anti-inflammatory and antioxidant substances.

Another beneficial element for our health is polyphenols. They are associated with the growth of akkermansia muciniphila, a bacterium that reduces inflammation and weight gain related to overeating.

Less of these bacterial populations and less diversity within the intestinal microbiota will reduce the benefit we can derive from these essential substances for our health.

Excessive dietary fat

Excessive dietary fats can lead to the proliferation of endotoxin-carrying bacteria, and this will lead to a chronic inflammation that can reach the fatty tissue in contact with the viscera inside the abdomen.

This inflammation will then promote weight gain and especially insulin resistance.

Studies have been conducted on mice where intestinal dysbiosis induced by a diet too rich in fat was transmitted to their offspring. Indeed, they had an increased risk of infections, allergies, autoimmune diseases, and fatty liver disease.

The nature of dietary fats determines the health risks to which they expose us and an excess of saturated fatty acids in the diet leads to gut dysbiosis, which can increase the risk of:

  • metabolic syndrome,
  • digestive autoimmune diseases (such as colitis), or
  • neurological diseases (such as multiple sclerosis).

Excessive consumption of red meat

Excessive consumption of red meat increases the risk of atheroma and cardiovascular disease.

Long known for its high saturated fat content, this increase is now reported due to the high L-carnitine content of the meat.

L-carnitine is transformed in two steps: in the intestine by microbiota and in the liver. The end result of these two transformations is a chemical called trimethylamine N-oxide (TMAO), which is well known in cardiology.

Numerous studies have demonstrated an increased risk of atheroma and cardiovascular disease with increasing blood levels of TMAO.

This increase is also associated with platelet hyperactivity, which increases blood coagulability (clotting) and the risk of thrombosis.

Another source of TMAO is the degradation by the intestinal microbiota of choline provided by fish and eggs.

The increase in TMAO studied after ingestion of choline-rich food disappeared under antibiotic treatment. This confirms the importance of the microbiota in the production of this metabolite. Unlike red meat, eggs and fish do not promote atheroma.

TMAO is essential for the survival of fish because it protects cells and proteins from being crushed by the enormous pressures of the water mass at great depths.

Red meat contains a lot of hemoglobin (whose role is to transport oxygen) and myoglobin (in charge of storing oxygen in the muscles).

Both of these oxygen sensors contain large amounts of hem. The latter is responsible for the multiplication of intestinal epithelial cells that increase the risk of colon cancer.

Food additives in question

Industrially processed foods contain many natural or synthetic additives.

Their actions on the intestinal microbiota are often poorly understood. Here are three examples of additives:


In cooking, it is complicated to mix water with fat. In fact, despite persistent whipping, a homogeneous paste of these two component will separate again.

Substances are often used whose molecules have one end that likes fat and the other that prefers water so as to join them.

The products that correspond to this “bipolar” structure are emulsifiers, natural or synthetic. These are widely used in the preparation of processed dishes.

The human body also uses many emulsifiers, for example, to solubilize cholesterol in the bile. People who have suffered from gallbladder stones have become aware of the importance of these natural emulsifiers.

On a daily basis, we use products other than emulsifiers that have a bipolar structure: detergents. Indeed, these have a structure close to that of emulsifiers.

Studies have focused on two emulsifiers: carboxymethylcellulose and polysorbate-80, which are widely used to facilitate mixing water and fat in the manufacture of processed foods.

In these studies, moderate amounts of either of these two emulsifiers were added to the drinking water of the mice tested. While control mice were given drinking water without the addition of an emulsifier.

After a few weeks, the two groups were compared. In the animals that received an emulsifier, the mucus layer was damaged, and many bacteria came dangerously close to the intestinal cells.

Intestinal permeability was increased, and the composition of the intestinal flora was disturbed. The consumption of emulsifiers induced a reproduction of mucus-degrading bacteria and pro-inflammatory bacteria that carried endotoxins.

In addition, the mice that had the emulsifiers gained slightly more weight than the other mice. This weight gain is the result of increased food intake. It was also associated with insulin resistance, the first symptom of type 2 diabetes.

When administered to germ-free mice, both emulsifiers did not cause any of the described abnormalities.

Indeed, this confirms that while emulsifiers were probably responsible for the initial mucus damage, the resulting dysbiosis was responsible for disturbances such as inflammation, weight gain, and metabolic disorders.

Other studies have sought to extend these results using the same experimental protocol. For example, in mice given emulsifiers, another study confirmed the appearance of abdominal fat overload associated with intestinal inflammation.

As in the previous experiment, the emulsifiers caused intestinal dysbiosis, but it appeared that this dysbiosis was different in male and female mice.

The study on behavioral abnormalities in the group of mice receiving emulsifiers also showed different results depending on the sex of the animal.

Indeed, the tests showed an increase in the signs of anxiety in male mice and abnormalities in social behavior in female mice.


Also known as substitute sugars, sweeteners are substances with a sweet taste with little or no calories. They are widely used in foods and beverages to preserve the taste of sugar while reducing their caloric intake.

In mammals, most sweeteners are excreted unchanged and are considered metabolically neutral.

Weight changes under sweetener consumption vary from study to study. Indeed, some studies show weight loss, and others, on the contrary, have shown weight gain, although these sweeteners are low in calories.

This contradiction could be linked to alterations in the intestinal microbiota favored by certain sweeteners. Indeed, these alterations could be different from one person to another depending on the previous state of their microbiota.

These results suggest that sweeteners can be consumed without weight gain and avoided in the opposite case.

Other research has shown that heavy consumption of sweetened beverages (including natural fruit juices with no added sugar) was significantly associated with an increased overall risk of cancer and breast cancer.

This risk was not observed with consuming industrial beverages artificially sweetened with sweeteners.

Nitrite salts

Fresh or processed red meat is often consumed in cold cuts, cooked and raw hams, sausages, and pâtés and can be preserved by smoking, salting, fermenting, or curing.

Many studies have published that processed meats increase the risk of colorectal cancer.

Among the probable mechanisms of this effect, the iron brought by red meat (processed or not) contributes to the triggering of oxidative stress and the production of carcinogenic substances.

Generally, nitrite salts are added to cured meats to extend their shelf life and preserve the ham’s pink color.

Nitrite salts can chemically bind to amines, substances present in meat and produced by the body. This bonding creates nitrosamines, one of the substances known for their carcinogenic effects.

The formation of nitrosamines is also accelerated by heating at high temperatures, which must be avoided when cooking sausages containing nitrite salts.

The carcinogenic effect of red meat and cold cuts is very likely in humans. Hence the emphasis on limited consumption.

It seems that marinating meat in a solution of antioxidant-rich olives and grapes may help reduce the carcinogenic effects of meat. This protective effect is also likely to be present in humans, as the marinade reduces intestinal oxidative stress.

In summary, red meat and deli meats can promote cancer development through processing, including the addition of nitrite salts in processed meats.

Ideally, nitrite salts should be eliminated from the preservation process of cold cuts, which should be a goal for the food industry. In fact some brands already market nitrite-free cold cuts.

Enriching meat with antioxidants through natural marinating may also help reduce the carcinogenic effects of these foods.

What role do gut bacteria play in nutrition and in human health? Conclusion

Having a good diet will influence the balance of our intestinal microbiota.

It is essential to promote a variety of healthy foods such as fruits and vegetables to keep our intestinal flora healthy.

We must also realize that certain food additives (such as sweeteners or nitrite salts) or excessive consumption of red meat can disturb our gut microbiota.

In fact, certain bacteria in our microbiota will help our body maintain good health. In addition to a balanced and varied diet, it is also vital to practice regular physical activity.

Therefore, adopting a healthy lifestyle is the key to a successful functional microbiota!

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About Heather Campbell

As a nutritionist, my field of specialization is science-based nutritional advice but more importantly, it is my goal to share capturing and inspiring stories, examples and solutions which can help plus-size individuals overcome their specific difficulties. Read More