Healthiest gut bacteria with plant-based or Mediterranean diet

By Dr. Liji Thomas, MDOct 21 2019

A new study shows that specific foods that are supplied by either a plant-based or a Mediterranean-type diet can protect the gut against inflammatory disorders, by selectively promoting the growth of anti-inflammatory bacteria.

The researchers looked at individual fecal samples from participants in four different groups: one representing the general population while the other three represented people with three different inflammatory gut disorders. The resulting pattern of microbial populations was compared with the dietary habits, to establish strong correlations between what they ate and the resulting structure of the gut microbial population.

Image Credit: Marian Weyo / Shutterstock

The gut microbiome

The gut microbiome is a term which denotes the entire population of multiple and diverse microbes living in the intestine. The pattern formed by relative numbers of various bacterial strains is different between different groups of people. The differences are dictated by dietary variations, in part.

The gut microbes play a big part in many human physiological functions, including immune system development and function, the body’s metabolism, and neurological function as well as behavioral traits. The gut microbiome has also been found to lack the usual diversity in inflammatory and allergic disorders, such as celiac disease and inflammatory bowel disease (IBD), atopic dermatitis (eczema), diabetes, atherosclerosis and psoriatic arthritis.

Intestinal disorders are quite common in many developed countries in Europe, with IBD alone affecting about 3 million people. They take a significant toll on the economy. They also pose a burden on healthcare, with a direct expenditure of about 5.6 billion euros on just IBD. Obesity is another condition which is rife in the developed world. Over half of Europe is overweight or obese, and the resulting healthcare costs go up to about 81 billion euros each year.

These diseases have been found to be more common in people who habitually eat certain types of foods, which means that diet is a risk factor for these conditions. The present study focused on finding which type of food intake pattern is linked to the most beneficial gut microbiome structure, and thus explains how diet affects our health.

The study

The study included four different groups of people: the population at large; people suffering from the chronic intestinal inflammatory disorder called Crohn’s disease; people with another similar gut disorder called ulcerative colitis; and people with irritable bowel syndrome (IBS). This helped them describe the individual’s microbial pattern. This was then correlated with the results of the food frequency questionnaire administered to the same group.

The findings

The analysis showed a link between 61 different food items and changes in specific bacterial populations. It also highlighted the link between 49 types of eating patterns and groups of bacteria.

The research presented at UEG Week 2019 pointed out that foods like pulses, fish, nuts, bread and wine increase the levels of gut-friendly microbes in the colon. These bacterial strains are responsible for synthesizing a range of helpful nutrients including short-chain fatty acids (SCFA) which are the main source of energy for colonic bacteria. Many of the bacterial metabolites also participate in a variety of biological reactions. The scientists feel that this validates a dietary approach to dealing with a spectrum of intestinal disorders – fine-tuning the gut bacteria by supplying the right food types.

Some of the highlights included:

• People who ate more bread, legumes, fish and nuts had fewer aerobic bacteria which could potentially turn harmful.
• The same eating pattern was linked to a lower level of inflammatory markers in feces, which in turn reflects less intestinal inflammation
• A higher percentage of meat, refined carbohydrates, and fast foods was linked to lower numbers of helpful bacteria and an increase in molecules which are found in inflammation
• More anti-inflammatory bacteria are found in those who included red wine, legumes, fruits and vegetables, cereals, nuts and fish.
• A diet rich in plant-based foods increases the production of SCFA from bacteria and thus enhances the energy supply of colonic mucosal cells
• Plant-based proteins encourage the synthesis of vitamins and amino acids, and help degrade sugar alcohols found in the gut. In addition, plant protein is also key to the excretion of ammonia from the body; ammonia is otherwise toxic to living cells.
• Plant-based and animal-based proteins have opposing effects on the gut microflora, with the former showing beneficial effects as described above.

The take-home

Researcher Laura Bolte says, "We looked in depth at the association between dietary patterns or individual foods and gut microbiota. Connecting the diet to the gut microbiome gives us more insight into the relation between diet and intestinal disease. The results indicate that diet is likely to become a significant and serious line of treatment or disease management for diseases of the gut – by modulating the gut microbiome.”

In short, says Bolte, we can maximize gut health by basing our diet on fruits and nuts, with a higher proportion of vegetables and legumes to animal protein. In addition, we should stick to moderate amounts of healthy animal foods, including lean meat and fish, fermented dairy products made from low-fat milk. Red wine in moderate quantities is also recommended. However, red and processed meats, and sweets, need to be taken in small amounts only. This type of diet is linked with benefits to the gut ecosystem according to the present study.