Findings from the American Gut Project

June 18th, 2018 | Posted in Info

Researchers working with the American Gut Project have recently published the largest study to date into the human microbiome (1). The aim of the project is to further the understanding of which bacteria live in which populations and how diet, lifestyle, and disease affect the balance of bacteria in the gut. There is also a UK gut project doing similar work.  All information gathered is anonymous and open access in order to allow researchers from around the world to use the data to find out which factors affect microbial health and diversity.

Here are few observations from the American Gut Project so far:


A greater diversity of microbes live in human guts than had previously been observed. The likelihood is that the range of organisms in our guts is even more diverse than has been observed to date.


The number of plant foods that a person eats appears to increase the diversity of their microbiome. Eating more than 30 different plant foods each week appears to increase the range of bacteria in the gut compared to eating 10 or fewer types of plant foods each week. See blog posts on How to Eat 30+ Plant Foods a Week and 3 Meals, 30 Foods for ideas on how to increase the number of plant foods you are eating.

Antibiotic resistance

Taking antibiotics appears to decrease microbial diversity. Eating more than 30 plant foods each week appears to reduce the number of antibiotic resistant genes in the gut microbiome. This may be because people who eat fewer plant foods eat more meat and animal products or processed foods containing preservatives which may favour the survival of antibiotic resistant bacteria.

Mental Health

The project examined the microbiomes of people with mental health problems such as depression, schizophrenia, post traumatic stress disorder or bipolar disorder. The research found that people with mental health problems have gut microbiomes that are more similar to other people with mental health problems than with people of the same gender, age, BMI and nationality. In other words there may be specific bacteria that are associated with mental health disorders (1).

So what can we take from the findings?

The human microbiome is incredibly diverse and dynamic. Dietary and lifestyle factors may affect different people in different ways. For example, dietary fibre is generally good for health but may be detrimental if you have an inflammatory bowel disease. Additionally, there are many types of fibre and they may all have different effects on different people.

Exciting research into the microbiome is continuing apace all around the world and is informing many aspects of health care. Whilst what we know has increased massively in the past decade or two, our current level of understanding may be just the tip of the iceburg. Watch the space for more information!



  1. 1. Daniel Mcdonald et al. American Gut: an Open Platform for Citizen Science Microbiome Research. Msystems, 2018; 3 (3): e00031-18