Food Contaminants That Disrupt the Intestinal Bacterial Balance

Heather Campbell
 min read

Are you aware of food contaminants that disrupt the intestinal bacterial balance?

Marine Plastic Pollution And Microplastics Negatively Impact Food Chain And Our MicrobiomeThere is a worldwide increase in the frequency of inflammatory disorders in the intestine and the whole body. Food contaminants are part of the problem, so let’s hereby discuss these in more detail.

Food contaminants that disrupt the intestinal bacterial balance: Introduction

The human (Western) diet has seen an increase in the use of protein, sugary foods, saturated fats, and food additives.

Most importantly, our food is often contaminated with unwanted and potentially harmful chemical residues.

Our gastrointestinal tract is the first organ to come into contact with foreign substances in the food we eat and drink.

Fortunately, the intestinal microbiota and the intestinal mucosal barrier defend us from external agents that can be potentially harmful.

However, our gut will also be the first to be disrupted by these external agents. This can sometimes have severe consequences for our whole body.

This article will discuss the different food contaminants that can alter our intestinal microbiome.

The danger of food contaminants in food production

Every year, about four billion tons of food are produced for human consumption, fueled by the increased demand from an ever-growing world population.

To meet this ever-increasing need for food, agriculture and industry use many strategies to increase productivity and expand food storage.

In addition, land, water, and air are often contaminated by substances produced by various human activities, sometimes even from decades ago.

Unfortunately, all this will weigh heavily on human health and may also have significant consequences:

  • On the one hand, there is a production of foods with low nutritional value.
  • On the other hand, foods can contain traces of contaminants and additives that are often harmful to our health.

Good to know: Studies have shown that more than 1,000 xenobiotics can be intentionally or accidentally added to processed food products.

Food can also be contaminated at any stage of processing. For example, foreign substances can be absorbed during cultivation, harvesting, breeding, or even during cooking.

When ingesting our food, we introduce these xenobiotics into our intestinal tract, where they can endanger the balance of our intestinal microbiota.

Many of them can alter our intestinal flora, causing inflammation of the intestine and the whole body, with severe consequences for our health.

For example, these food contaminants can contribute to the development of disorders:

The danger of food contaminants is increased because the exposure is continuous in time but also by their high number. Furthermore, it is tough to predict the effect of the simultaneous ingestion of several substances.

The primary contaminants found in our food can have different origins. They can be classified as:

  • physical, such as microplastics;
  • biological, such as viruses, bacteria, and parasites; and
  • chemical, such as pesticides and other agricultural chemicals, antibiotics, heavy metals, and persistent organic pollutants, from thermal processes.

This article will focus on physical and chemical contaminants.

Physical contaminants: Microplastics

We are constantly surrounded by plastic objects in our daily lives, and we have all seen images of islands of plastic waste floating in the oceans.

Millions of tons of plastic are produced each year to meet world demand. Unfortunately, some of these end up as waste in aquatic environments around the world and constitute a significant public health problem.

Studies have estimated that since the 1950s, about 7 billion tons of plastic waste have been produced worldwide. If this trend continues, it will increase to over 25 billion tons by 2050.

Of course, some of this waste is recycled correctly. However, a good amount is still dispersed in the environment and pollutes the water, air, and soil. All of this is accumulating at an increasing rate in all marine ecosystems.

Particles smaller than 0.20 inches, also known as microplastics, are particularly dangerous. They can be accidentally ingested by marine fauna and accumulate in the food chain until they enter our food.

Microplastics have been found worldwide in marine and terrestrial environments, including rivers, oceans, air, drinking water, and food.

They have even been found in human stool samples, confirming that humans are also exposed to these substances through food.

Apart from in fish and drinking water, these microplastics have also been detected more indirectly in other types of food, such as:

  • honey,
  • salt,
  • sugar,
  • beer, and
  • tea bags.

In addition, bottled water is a significant source of microplastics that should not be underestimated.

Research has shown that microplastics can carry many other harmful chemical molecules, added during manufacturing processes.

For example, they can carry dangerous environmental contaminants on their surfaces, such as polychlorinated biphenyls, other persistent organic pollutants, and heavy metals.

Studies conducted on mice have shown that, once ingested, microplastics can significantly damage the intestinal environment.

In fact, they decrease mucus secretion and cause inflammation and dysfunction of the intestinal barrier. As a result, this generates dysbiosis and oxidative stress, with harmful effects on the whole body and our psycho-physical balance.

Chemical contaminants: Heavy metals

It is important to know that heavy metals are naturally present in the environment. However, their concentration has increased considerably due to human activities.

Several scientific studies have found that exposure to certain heavy metals, especially if prolonged, can negatively affect the gut microbiota and human mood and behavior.

Heavy metal residues have been found in many foods, fish, and drinking water.

The most common heavy metals that are most dangerous to the gut microbiota are:

  • mercury,
  • lead,
  • cadmium,
  • copper, and
  • arsenic.

Approximately 40 to 60% of ingested heavy metals pass through the intestinal barrier and are spread throughout the body. This can cause:

  • inflammation,
  • tissue damage,
  • oxidative stress, and
  • dysbiosis, combined with:
    • a decrease in the richness and diversity of the intestinal flora, and
    • an increase in pathogenic bacteria.

Now let’s look at the most dangerous metals for our gut microbiota.

Mercury (Hg)

Mercury is one of the most toxic metals humans can be exposed to through food.

Mercury is often found in the form of “methylmercury,” a contaminant found in many foods, especially fish, shellfish, and marine mammals. Moreover, it is highly neurotoxic.

Some experts are particularly concerned about the negative impact of methylmercury on pregnant women and newborns.

High levels of prenatal exposure in humans have been shown to result in severe neurological problems, such as cerebral palsy and severe mental retardation.

For this reason, it is strongly recommended to limit the consumption of fish species with a high risk of containing methylmercury for children and pregnant mothers. In addition, it is also advisable to pay special attention to the origin of the fish consumed.

In addition to being neurotoxic, mercury can also seriously harm the intestine, causing injury, dysbiosis, and consequent metabolic disorders.

Research has shown that Lactobacillus Brevis can protect us from the harmful effects of mercury. Selenium also has a protective function against mercury. It helps to restore intestinal balance and promote the excretion of the metal.

Lead (Pb)

Lead is a common pollutant and was once used as an additive in gasoline and paint. It was also used in the construction of car batteries.

As a result, lead is found as a pollutant in the air, soil, drinking water, and food in various parts of the world.

Cadmium (Cd)

For non-smokers, cadmium enters our bodies primarily through contaminated food and water.

It is derived from both natural and human processes and can come from:

  • pesticides and fertilizers,
  • batteries,
  • photovoltaic devices,
  • waste incineration, and
  • galvanization processes.

According to some food studies, it is present as a residue in cereals and their derivatives, fish, and offal.

The consequences of cadmium in our intestines are multiple:

  • It induces an inflammatory response.
  • It alters the permeability of the membrane and the microbiota.
  • It damages the mucus layer (lining the intestinal mucosa), reducing its thickness and causing a decrease in beneficial bifidobacteria, lactobacilli, and short-chain fatty acids.

Good to know: The decrease in lactobacilli and short-chain fatty acids is linked to mood disorders.

It seems that the administration of bifidobacterium longum would be able to restore the mucus layer, thus rebalancing the intestinal balance.

Copper (Cu)

Although copper is an essential element for humans, excessive exposure to it is associated with hepatotoxicity and intestinal dysbiosis.

This metal can increase intestinal permeability and cause intestinal inflammation.

Arsenic (As)

Arsenic is everywhere in the environment and is found in many foods such as fish, shellfish, and rice.

The consequences of chronic exposure to this metal are multiple:

  • It is associated with the development of tumors.
  • It also alters the intestinal microbiota and its metabolites.
  • It induces the production of pro-inflammatory substances and decreases the secretion of compounds that defend us from inflammation.

Effects of food contaminants on our gut microbiota

Let us now discuss:

  • the different effects of heavy metals and microplastics on our intestinal microbiota,
  • the consequences that this will have on our health, and
  • the foods where we can find them.


Effects on the microbiota

  • Increased risk of dysbiosis
  • Decrease in the diversity of the microbiota
  • Reduction of mucus

Health consequences

Microplastics will cause intestinal barrier dysfunction and inflammation and provoke metabolic disorders and oxidative stress.

Foods where microplastics are most often detected

  • Drinking and bottled water
  • Beer
  • Honey
  • Salt
  • Sugar
  • Fish


Effects on the microbiota

  • Increased risk of dysbiosis

Health consequences

Mercury causes systemic inflammation and metabolic disorders.

Foods where mercury is most often detected

  • Crustaceans
  • Fish such as tuna, pike, swordfish, and hake


Effects on the microbiota

  • Increased risk of dysbiosis
  • Decrease in the diversity of the microbiota

Health consequences

Lead causes systemic toxicity and nerve damage.

Foods where lead is most often detected

  • Water
  • Vegetables
  • Canned food
  • Crustaceans
  • Cereals


Effects on the microbiota

  • Increased risk of dysbiosis
  • Decrease in the diversity of the microbiota
  • Decreased synthesis of short-chain acids

Health consequences

Cadmium causes metabolic disorders, dysregulation of the immune system, and intestinal barrier dysfunction.

Foods where cadmium is most often detected

  • Meat and offal
  • Chocolate
  • Seaweed
  • Nuts
  • Cereals and derivatives
  • Legumes
  • Vegetables
  • Mushrooms
  • Potatoes
  • Fish


Effects on the microbiota

  • Increased risk of dysbiosis
  • Increase in antibiotic resistance genes

Health consequences

Copper causes intestinal barrier dysfunction and systemic inflammation.

Foods where copper is most often detected

  • Water
  • Foods of animal origin
  • Fatty fruits


Effects on the microbiota

  • Increased risk of dysbiosis
  • Decrease in the diversity of the microbiota
  • Increase in antibiotic resistance genes

Health consequences

Arsenic causes systemic toxicity and immune system dysregulation.

Foods where arsenic is most often detected

  • Bottled water
  • Beer
  • Milk
  • Coffee
  • Vegetables
  • Rice
  • Fish
  • Seaweed
  • Cereals and derivatives

Food contaminants that disrupt the intestinal bacterial balance: Conclusion

The various physical and chemical contaminants, introduced accidentally or intentionally into food by human activities, have consequences on our intestinal microbiota.

Indeed, they can alter the balance of the gut microbiota and, consequently, cause inflammation and imbalances in human mood and behavior.

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