Intestinal microbiota, omega-3 improves bacterial flora in middle-aged women

In women, supplementation with omega-3s, especially EPA, may promote the diversity of bacteria composing the gut microbiota, independently of fiber and probiotic intake. A higher Omega-3 Index appears to favor the development of a greater number of bacterial species in the gut, a condition associated with various health benefits, including reduced risk of diabetes, obesity, and inflammatory conditions such as colitis or Crohn’s disease. Omega-3 supplements could therefore represent a simple strategy to improve the composition of the intestinal bacterial flora. This was discovered by researchers at the University of Nottingham (UK) and published recently in Nature’s Scientific Reports.

Gut microbiota and omega-3: a link yet to be fully defined

Dietary supplementation with omega-3s can improve human health, particularly cardiovascular health. Some of the mechanisms through which omega-3 fatty acids act are directly related to their anti-inflammatory actions since both EPA and DHA reduce the synthesis of molecules that promote inflammation.

Recent studies also suggest a positive effect of omega-3s on the gut microbiota. The gut microbiota consists of microorganisms, mainly bacteria, living on the surface of the intestinal mucosa and is now known to actively influence various aspects of human health. The relationship between the gut microbiota and its host organism plays a key role in several physiological processes such as immune system maturation, food digestion, drug metabolism, detoxification, vitamin production, and prevention of pathogenic and harmful bacterial adhesion.

The composition of the intestinal bacterial flora is variable and diverse and is influenced by environmental factors such as diet, antibiotic therapies, and environmental exposure to certain microorganisms. Prebiotic foods are, by definition, indigestible foods that specifically support the growth and activity of health-promoting bacteria colonizing the gastrointestinal tract. In this context, the role of omega-3s on the composition and diversity of intestinal microorganisms is still not fully clear. However, some studies have shown that DHA supplementation helps combat oral and gastrointestinal diseases where inflammation and bacterial dysbiosis play a fundamental role.

Some research has revealed that high levels of omega-3 increase the production and secretion in the intestine of a molecule called intestinal alkaline phosphatase, which induces changes in bacterial composition resulting in reduced inflammation. A recent clinical study in an Indian population also showed that omega-3 and probiotic supplementation had a greater beneficial effect on insulin sensitivity, lipid profile, and atherogenic index compared to probiotics alone.

It has also been found that a diet high in omega-3 alters the gut microbiota composition of patients with type 2 diabetes. Often, the term microbiota is confused with microbiome, which instead refers to the collection of genes of the bacteria populating the intestine, allowing differentiation of bacterial species.

A high Omega-3 Index is associated with greater bacterial species diversity in the gut

The aim of the UK study was to evaluate the association between omega-3 consumption and blood levels with the diversity of the microbiome composition. The research team found that women who followed a diet rich in omega-3 and had a high Omega-3 Index showed greater diversity in their gut microbiome composition.

This genetic diversity of microorganisms is linked to positive health effects, such as reduced risk of diabetes and obesity and, of course, inflammatory diseases of the intestine itself, such as colitis and Crohn’s disease. This result shows that the genetic variability of intestinal microorganisms is influenced by omega-3 intake independently of fiber and probiotic consumption, particularly concerning bacteria belonging to the Lachnospiraceae family, a group associated with low inflammation levels and reduced obesity risk.

To further investigate this link, researchers examined the presence of certain molecules in the stool samples of study participants, finding that those with high omega-3 blood levels had higher concentrations of a compound called N-carbamylglutamate (NCG), known for its ability to reduce oxidative stress in the intestines of animals. Given NCG’s beneficial effects in mammalian intestines, part of the explanation for the association between DHA and microbiome composition might be that the presence of DHA promotes NCG production by the gut bacterial flora. This, in turn, can improve intestinal function and reduce oxidative stress, thus producing positive health effects.

Study details

To conduct the study, researchers analyzed microbiome data collected from a previous study involving 876 middle-aged twin women and related it to blood levels of DHA, total omega-3s, omega-6s, and other circulating fatty acids. The estimated consumption of omega-3-rich foods was obtained through specific food frequency questionnaires.

Statistical analyses showed that blood levels of total omega-3s and DHA were significantly correlated with microbiome diversity, with a particularly strong link between DHA and 38 bacterial families, including the Lachnospiraceae.

Omega-3 supplements may promote gut health

According to the researchers, these results suggest that omega-3 supplements, combined with prebiotic and probiotic supplements, could represent an important strategy to improve gut microbiome health. The data indicate that the effect of omega-3s, particularly DHA, is independent of fiber intake, although the beneficial role of fiber on intestinal function is well established.

These findings also support the hypothesis that some of the positive effects reported following omega-3 consumption may be due to their impact on the gut microbiome. Furthermore, omega-3 fatty acid intake tends to be associated with a generally healthier lifestyle, so some of DHA’s effects on the gut may be indirect.

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Source: Menni C. et al., “Omega-3 fatty acids correlate with gut microbiome diversity and production of N-carbamylglutamate in middle aged and elderly women” Scientific Reports