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Studie bringt hochverarbeitete Lebensmittel mit Risiken für die Darmgesundheit in Verbindung

von NFI Redaktion

A recent review published in the journal Nature Reviews Gastroenterology and Hepatology summarized the current knowledge on the impacts of food additives and ultra-processed foods (UPFs) on gut health.

With UPFs and food additives becoming more prevalent in diets worldwide, they are associated with negative effects on gut health such as changes in microbial communities and gut permeability, leading to chronic inflammation or diseases like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) and colorectal cancer. However, there is limited human intervention studies on this topic.

Study: Ultra-processed foods and food additives on gut health and diseases. Image credit: Lightspring / Shutterstock

Identification of UPFs

To classify foods as UPFs, nutrition scientists use criteria related to how different an item is from its original unprocessed ingredient, how it is processed, whether additives were used, whether it is commercially produced instead of homemade, and whether it is used for optical or practical reasons.

However, different classification systems complicate comparisons; the most widespread variant has been adopted by the Food and Agriculture Organization of the United Nations and includes powdered and packaged foods, carbonated soft drinks, and sugary breakfast cereals as UPFs. However, some foods, such as whole grain bread and plant-based meat alternatives, are generally considered healthy but meet the criteria for UPFs.

UPF Consumption and Gut Health

Although UPFs are widespread, there are large variations among individuals and countries. In the United States, UPF consumption accounts for 59.7% and 67% of energy intake in American adults and young people, respectively.

Individual characteristics associated with consuming more UPFs include female gender, younger age, lower income, lower education, living alone, overweight or obesity, lower physical activity, and screen use during meals.

People who consume more UPFs have more free sugars, saturated fats, and energy in their diet but less fiber, proteins, and many micronutrients. Vegetarians and vegans more frequently consume UPFs, while those adhering to a Mediterranean diet consume less.

Controlling for dietary quality and nutrient intake shows associations between UPF consumption and diseases. However, UPF intake from fruit yogurt, fortified breakfast cereals, and whole grain bread is healthier than the same UPF intake from ready meals, burgers, and pastries.

Cohort studies have found that UPF consumption is associated with higher mortality and morbidity from cancer, cardiovascular diseases, and type 2 diabetes mellitus. Observational studies show associations with depression, metabolic syndrome, overweight, and obesity. These effects are likely due to processing rather than the nutrient and energy content of UPFs.

Cohort studies investigating UPF consumption and IBD (ulcerative colitis and Crohn’s disease) found that those consuming more UPFs were at the highest risk. Similar results were found when looking specifically at Crohn’s disease, but not ulcerative colitis. Significant associations between UPF consumption and irritable bowel syndrome and functional dyspepsia were found in a cohort study, but not with functional diarrhea or constipation. UPF intake is also associated with distal colon cancer in men and colorectal adenomas.

Due to methodological inconsistencies, including the use of self-reported dietary data, there may be biases in the results and comparisons between studies and the use of meta-analytic methods are limited. The adverse health effects associated with UPFs could be attributed to their effects on the gut microbiome, but this has only been studied in two studies.

Effects of Food Additives

Food additives include sweeteners, colorants, stabilizers, emulsifiers, thickeners, and gelling agents. There is significant overlap between UPFs and food additives, as an item containing a commercial food additive is considered a UPF. Mechanistic studies on the effects of food additives on the microbiome have included animal and in vitro studies, with few studies conducted in human populations.

In vitro studies show that emulsifiers like polysorbate 80 can cause excessive growth of small intestinal bacteria, while carboxymethylcellulose (CMC) can shift bacteria across the in vitro epithelia. This could lead to chronic inflammatory diseases, as shown in studies in mice. Consumption of CMC and polysorbate 80 was also associated with tumor development and anxiety-like behaviors in mice.

Artificial sweeteners that pass through the gastrointestinal tract but are not digested come into direct contact with the gut flora, although this has not been well studied in humans. However, in vitro and animal studies suggest that sweeteners like aspartame, sucralose, and saccharin alter the microbiome, disrupt gut permeability, decrease colon length, and increase mortality.

These were short-term studies with much higher doses than those used in humans. An observational study in humans found no differences in microbiota consumption after four days of sweetener consumption, but did not control for background diet and dose-response relationships.

A randomized controlled study found that constipation, diarrhea, burning, and postprandial discomfort increased after five weeks of sweetener consumption, while upper abdominal pain, early satiety, and abdominal pain were lower in a control group with a reduced-sweetener diet.

Conclusions

There is clear evidence that UPFs and food additives lead to health-damaging consequences, but methodological inconsistencies and gaps in human studies need to be addressed. The authors emphasize the need for high-quality evidence to interpret the effects of dietary interventions. As the availability and consumption of UPFs increase, public health policy should focus on reformulating UPFs and targeting consumer behavior.

Journal Reference:

  • Ultra-processed foods and food additives for gut health and diseases. Whelan, K., Bancil, AS, Lindsay, JO, Chassain, B. Nature Reviews Gastroenterology and Hepatology (2024). DOI: 10.1038/s41575-024-00893-5, https://www.nature.com/articles/s41575-024-00893-5

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