How highly processed foods affect the gut microbiome and health

Several studies have shown a possible link between ultra-processed foods (UPF) and severe inflammation. A recent review was published in Lancet Gastroenterology and Hepatology It describes a mechanistic link between UPF consumption and chronic medical conditions, particularly those involving the gut microbiome.

Research: Ultra-processed foods and human health: from epidemiological evidence to mechanistic insights. Image credit: Dawid Rojek / Shutterstock.com

Introduction

Many methods of food preparation have been developed over the past several centuries to preserve food and improve its taste and digestion. Modern industrially processed foods use a supply of salt, sugar, vegetable oil, animal fat and flour.

Typically, the production of these products uses mechanical and physical techniques such as roller milling, extrusion and pressure rendering, as well as chemical methods such as hydrogenation. Artificial flavoring agents and preservatives, anticaking agents and other additives are also used to achieve the final desired texture, color and taste of these food products.

“These techniques allowed for the production and mass production of mass-produced foods, making them available year-round.He said.

Such highly processed foods are typically hygienic, convenient, affordable and accessible, making them ideal products for many high-income countries (HIC). More recently, low- and middle-income countries (LMIC) have become increasingly dependent on these food products.

Along with this trend, the number of chronic pain cases including metabolic syndrome and inflammatory bowel disease (IBD) has increased. The current paper explores the evidence for a link between modern UPF and gut microbiota-mediated chronic disease.

Types of prepared foods

There are several classification systems used to describe foods based on their composition. The most commonly used is NOVA, which classifies foods from groups 1 to 4.

Group 1 includes unprocessed or minimally processed foods such as fresh, frozen, dried, frozen, fermented or pasteurized products. Group 2 includes added ingredients such as vegetable oil, sugar, salt, butter or other food ingredients added to Group 1 foods.

Group 3 includes all common processed foods such as salty canned foods, canned dried fruit, salted meats, cheese, and fresh bread. In short, group 3 describes group 2 products added to group 1 products.

Group 4 includes UPFs that undergo one or more of the above industrial processes. These may include non-domestic ingredients, including those used for flavoring, coloring, flavoring or emulsification.

UPF intake increased in HICs, accounting for up to 30%, 50%, and 60% of caloric intake in France, the United Kingdom, and the United States, respectively.

Research findings

Of the 100 prospective studies analyzed in the present study, 50% examined the relationship between UPFs and various health or mortality outcomes.

Mortality

Seven studies reported an association between UPFs and all-cause mortality, with a 20% to 60% increased risk in the highest UPF intake category compared with the lowest. Five studies showed an increased risk of cardiovascular disease or stroke. Four studies found an increased risk of type 2 diabetes, and one found an increased risk of gestational diabetes.

blood pressure

Four studies have shown an increase in blood pressure of up to 30%, one with cancer risk, and several with overweight and obesity. Many of these studies reported associations with increased weight, waist circumference, and serum lipid levels in children.

IBD

In the year In the 2021 Prospective Urban Rural Epidemiology (PURE) study, UPF intake was associated with an increased risk of IBD, particularly for Crohn’s disease but not ulcerative colitis. Other studies have linked UPF consumption to increased risk of depression, abnormal lipid levels, decreased kidney function, and fatty liver disease.

Weight gain

Short-term randomized intervention trials are currently underway, in which UPFs and unprocessed foods are assigned to different groups for a short period of time. Following this, the researchers observed an average increase in energy consumption of more than 500 kcal per day and an average weight gain of 0.8 kg in the UPF group. Conversely, an average weight loss of less than 1 kg was reported in the unprocessed food group.

The mechanisms behind long-term inflammation with UPFs

There are many mechanisms that can contribute to weight gain and chronic inflammation with increased UPF consumption. One example involves the poor nutritional quality of many UPFs.

According to the French Open Food Facts database, only one in five UPFs had a high nutritional value. Even when energy intake from UPFs was compared to non-standardized foods, negative health outcomes continued to show a strong association, thus “Factors beyond nutritional aspects play a roleHe said.

Another issue is the presence of potentially toxic ingredients in UPFs, such as polycyclic aromatic hydrocarbons, flavonoids, advanced glycation end products, trans fatty acids from fat hydrogenation, and acrylamide from cooking starchy foods at high temperatures. The latter chemical can be found in common foods such as French fries, fries, and crackers, both domestically and industrially; However, the amount of acrylamide in these industrial products is usually high.

Other contaminants such as phthalates, bisphenols, mineral oils and microplastics can leach into foods from packaging, especially when the food has been in contact for long periods of time. This may happen to food products that have been kept on the shelf for a long time.

Ready-to-eat foods are typically UPF and require microwave heating, which can increase bisphenol leaching from the polycarbonate packaging or increase acrylamide formation.

The effect of such exposure is unknown; However, previous studies suggest a link to cancer, cardiovascular disease, insulin resistance, type 2 diabetes, obesity, and endocrine disruption.

Another issue is the process-induced structural changes in different parts of the food product, which can affect bioavailability through variable digestion, satiety, eating rate, and chewing, all of which contribute to the energy gain of UPFs. . This area is largely unstudied.

More than 300 food additives are approved in Europe, many of which may be implicated in chronic inflammation, possibly through their effects on the gut microbiome. Landmark studies indicate that dietary patterns influence gut microbiota profiles, which subsequently alter host metabolism and promote obesity.

Gut bacteria can often eat and process simple sugars when exposed to high dietary fat. Intestinal irritants include certain food dyes, emulsifiers, artificial sweeteners and nanoparticles such as E171 (titanium dioxide).

These supplements alter the ratio of key bacterial species in the gut, thereby affecting the protective mucosal layer and the expression of important defense molecules such as β-defensins, allowing microbes to reach the mucosal sterile zone. This induces the accumulation of endotoxin, leading to metainflammation and IBD.

At the same time, the changes in the molecular profile promote the extraction of energy from processed foods, thereby causing metabolic disorders and obesity.

This links calorie intake from food intake to diet-induced metabolic abnormalities. This regulated metabolism is characterized by lower levels of inflammation and changes in the gut microbiome. The result is the leakage of bacterial products such as lipopolysaccharide (LPS) from the gut into the host system.

LPS contains lipid A from Gram-negative bacterial cell walls, which is a molecule that crosses the intestinal mucosa. Once lipid A enters the bloodstream, it can cause inflammation in various target tissues, such as the liver and body fat.

This cycle is called “metainflammation”. Metainflammation can be defined as a metabolic inflammatory condition characterized by low-grade chronic inflammation caused by metabolic cells and stress sensors.

This suggests the need to interfere with UPF intake to induce beneficial changes in the intestinal microbiome, leading to the production of ‘good’ bacterial metabolites through appropriate gene expression by intestinal mucosal cells. These include anti-inflammatory short-chain fatty acids (SCFAs).

Conclusions

The findings of the study emphasized the need to improve the current understanding of how food processing affects human health. Larger scale studies are needed to identify factors associated with metainflammation and obesity.

Public education is critical to support eating healthy foods, especially those that are minimally processed and free of additives. Such dietary choices are emphasized by the recommendations of the United Nations Food and Agriculture Organization (FAO) as well as several national dietary guidelines.

Federal policies should shift toward the production and distribution of healthy, high-quality food products, using measures such as financial incentives, legislation, and mobile phone applications that ensure food choices.

Governments and the food industry must join efforts to establish policies that promote a healthy food environment for consumers to effectively combat the growing number of chronic inflammatory conditions.He said.