Gut microbiota, omega-3s improve bacterial flora in middle-aged women

In women, supplementation with omega-3s, especially EPA, may promote the diversity of bacteria that make up the gut microbiota, independent of fiber and probiotic consumption. A higher Omega-3 Index, in fact, appears to promote the development of a high number of bacterial species in the gut, a condition associated with several health effects, including reduced risk of diabetes, obesity, and inflammatory conditions such as colitis or Crohn's disease. Omega-3 supplements could therefore be a simple strategy to improve the composition of intestinal flora. This was discovered by researchers at the University of Nottingham (UK) and published in Nature's Scientific Reports journal in recent months.

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

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

Some recent studies also suggest a positive effect of omega-3 on the gut microbiota. The gut microbiota is the collection of microorganisms, mainly bacteria, that live on the surface of the mucosa of the intestine and are 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 adhesion of pathogenic and harmful bacteria. 

The composition of intestinal flora is variable and diverse and is influenced by environmental factors such as diet, antibiotic therapy, and environmental exposure to certain microorganisms. Prebiotic foods are, by definition, non-digestible foods that specifically support the growth and activity of health-promoting bacteria that colonize the gastrointestinal tract. In this context, the role of omega-3 on the composition and diversity of gut microorganisms has yet to be well elucidated. Some studies, have in any case shown that supplementation with DHA helps combat oral and gastrointestinal diseases in which inflammation and bacterial dysbiosis play a key role. 

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

A diet high in omega-3 has also been found to alter the composition of the gut microbiota of patients with type 2 diabetes. Often the term microbiota is confused with microbiome, which instead refers to the set of genes of bacteria that populate the gut and thus allow different bacterial species to be distinguished. A diet high in omega-3 has also been found to alter the composition of the gut microbiota of patients with type 2 diabetes. Often, the term microbiota is confused with microbiome, which instead refers to the set of genes of bacteria that populate the gut and thus allow different bacterial species to be distinguished.

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

The purpose of the British study was to evaluate the association of omega-3 consumption and its level in the blood with the diversity of microbiome composition. The team of researchers found that women who had followed a diet rich in omega-3 and with a high Omega-3 Index showed a greater diversity of gut microbiome composition. 

This genetic variety of microorganisms is linked to some positive health effects, such as reduced risk of diabetes and obesity and of course inflammatory diseases of the gut itself, such as colitis and Crohn's disease. This result demonstrates that genetic variability of gut microorganisms is affected by omega-3 intake independently of fiber and probiotic consumption, particularly with regard to bacteria belonging to the Lachnospiraceae family, a group of microorganisms associated with low inflammation and lower risk of obesity. 

To further investigate this link, the researchers examined the presence of certain molecules in the feces of the people involved in the study and found, in those who had high levels of omega-3 in their blood, a higher concentration of a compound called N-carbamylglutamate (NCG), which is known for its ability to reduce oxidative status in the gut of animals. Given the beneficial effects of NCG in the mammalian gut, part of the explanation for the association between DHA and the composition of the microbiome could be that the presence of DHA that promotes the production of NCG by the intestinal flora. This in turn may improve gut function and reduce oxidative stress and thus cause the positive health effects. 

Some details of the study 

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

Statistical analysis showed that blood levels of total omega-3 and those of DHA were significantly correlated with microbiome variety, particularly between this link was evident between DHA and 38 families of bacteria, including that of Lachnospiraceae.

Omega-3 supplements could promote intestinal well-being

According to the researchers who conducted the study, these findings suggest the possibility that omega-3 supplements, combined with those of prebiotics and probiotics, may be an important strategy for improving the health of the gut microbiome. Indeed, the data suggest that the effect of omega-3s, particularly DHA, is independent of fiber intake, although their beneficial role on gut function is established. 

These data also support the hypothesis that some of the positive effects reported following omega-3 consumption may be due to their effect on the gut microbiome. In addition, omega-3 fatty acid intake tends to be associated with a healthier lifestyle in general, and thus some of the effects of DHA 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