Diet type or diversity of foods: Which has a greater impact on gut health?

As we’ve been learning the last few years, the gut microbiome has a vital role in our overall health. A study recently published in the journal Nature Microbiology suggests that a particular dietary pattern (vegan, vegetarian or omnivorous) is less important to the makeup of your gut microbiome and its effects on overall health than the quality and diversity of the food you eat.

The gut microbiome is a community of trillions of microorganisms, including bacteria, fungi, viruses, and other microbes that live within the digestive tract. Its key functions include digestion, immune system support, and metabolism. It is active in mental health via the gut-brain axis – a working relationship of sorts between the gut and the brain, potentially affecting mood and other aspects of mental health.

We know from previous research that an unfavorable population of gut microbes may lead to health issues, such as inflammatory bowel disease (IBD), Type 2 diabetes, cardiovascular disease, and depression.

The gut microbiome participates in the effects of diet on the body. Thus, understanding how diet impacts the microbiome and how the combination of diet and microbiome affects metabolism and general health is essential.

Nicola Segata, PhD, the principal investigator at the Universita di Trento in Italy and author of the new study explains the findings. They suggest, he states, that whether you follow a vegan, vegetarian, or omnivorous eating pattern, it’s the quality and diversity of the food choices you make that have the greater impact on the composition of the gut microbiome.

Segata’s team of scientists analyzed the gut microbiomes of 21,000 people in the U.S. and the U.K. All the subjects followed either a vegan, vegetarian, or omnivorous diet. The study found that people with an omnivorous diet had microbiomes with higher concentrations of bacteria associated with meat digestion, along with bacteria associated with IBD and an increased risk of colon cancer.

The researchers found less diversity among the species of microbes in the gut microbiomes of people who followed vegan and vegetarian diets. Although that could be of concern, Segata speculated that diversity of species may not be the best measure of microbiome health because it doesn’t consider the microbe types.

The gut microbiomes of vegans included helpful bacteria which are associated with beneficial effects on gut health, including reducing inflammation. The vegans and vegetarians also had greater numbers of microbes associated with cardiometabolic health than those with omnivorous diets.

Segata said these findings confirm that plant-based foods boost microbes that produce immunomodulary metabolites (substances that affect immune function).

Segata also discusses the importance of fiber to the gut microbiome. In a news release he states, “The greater the variety of plant-based foods we consume, the greater the diversity of beneficial microbes in our gut. This is because different plant-based foods contain diverse types of fiber, and each fiber can stimulate the growth of diverse types of health-promoting microbes,” he says. “These microbes work together to improve our gut health, so the more diversity of health-associated microbes in our gut microbiome, the better our chances of good gut health.”

The findings and their interpretations presented above are those of Segata and associates. As always, StudyFinds encourages readers to use their own judgment regarding the merits of the research presented but does not interject its own agenda or bias.

Reading with discriminating eyes

Reading medical research papers with discernment is an acquired skill. This article is good practice. The following are just two of the features of research papers to consider when scrutinizing a report’s validity.

• Funding. Look for how any study is funded, for potential conflicts of interest. Segata’s study was partly funded by the personalized nutrition program company ZOE Limited. Segata is on its advisory board and is a consultant. Several other study authors have affiliations with or monetary interests in the company, while others declare no competing interests. A conflict of interest is a situation in which the researchers have a stake in the outcome of an investigation, favoring a particular result over another. Conflicts of interest call into question the objectivity of the researchers and the credibility of their findings and interpretations. A study may lose value when there are potential conflicts of interest affecting it.

• Internal consistency. Findings should be consistent within an individual paper. A key claim of this study was that quality and diversity of foods chosen was more important to gut microbiome health than a particular diet plan. Yet, when they found less diversity in the gut microbiomes of people eating strictly plant-based foods, Segata stated that diversity of species may not be the best measure of microbiome health. Later, Segata again writes that the more diversity among health-associated microbes in the gut microbiome, the better the chances of good gut health.

Sometimes you just have to ask, “Does this even make sense?”