In your gut right now, trillions of bacteria and other microbes are bustling with activity. They are helping digest your food, communicating with the immune system and providing healthful compounds. And this bunch of microbes — known as the microbiome — may also be playing a role in obesity and cancer prevention.
Outnumbered 10 to 1
It’s only in the past couple decades that scientists began to delve into our microbiome. Then in 2008, the National Institutes of Health launched the Human Microbiome Project with the goal to identify all the human-dwelling microbes and how they link to health.
Two years ago, scientists published the first map of a healthy human’s microbiome, revealing the complexity of our microbiome community.
Scientists identified about 10,000 species of microbes, many recognized for the first time. These microorganisms living in our body outnumber human cells by 10 to 1. Put them all on a scale and they weigh as much or a few pounds more than our brain, which tips the scales at about three pounds.
These microbes also contribute more genes than we do. The human genome carries approximately 22,000 genes; researchers estimate that the human microbiome has about 8 million.
Each person’s microbiome is unique. Your microbiome becomes formed by the time you’re an adult. But it appears it can shift.
Researchers know that the gut microbiome of a healthy person looks different than someone with a disease such as inflammatory bowel disease, a risk factor for colon cancer. They have also found that foods and exercise can cause a microbiome change.
Diet: It’s known that gut microbes help digest compounds in food. Research suggests that foods can lead to shifts in our microbial community, leading to changes in its activity. Eating soy protein versus meat protein, for example, has shown changes to the microbiome. Healthy diets may lead to certain microbes living in the gut that protect people from weight gain.
Exercise: For the first time, a study published last month has linked vigorous exercise with increased diversity of the microbiome. The exercisers were also eating a high-protein diet, suggesting it could be both exercise and diet. The study also found that the athletes had more of a certain bacteria that previous studies have linked to lower rates of obesity and metabolic disorders.
Obesity and Our Microbiome
A growing body of evidence suggests there is a link between a person’s microbiome and the tendency toward obesity, a known risk factor for eight types of cancer. In both humans and animals, obesity links with fewer microbes and a less diverse mix of bacteria species.
Studies with mice suggest that it’s the bacteria having a role in the excess weight, as opposed to the body fat causing a change in bacteria. For example, transferring microbes from an obese into a lean mouse has led to the thinner mice gaining weight.
How the microbes may influence obesity risk is not well understood. Lab studies suggest a few possibilities, including that bacteria may affect how our body senses nutrients and feelings of fullness.
The Take Away
So how do all these microbes affect you? At this point, there’s not enough research for any guidelines or recommendations to support a healthy microbiome.
What we do know is that eating a healthful, plant-based diet, getting at least 30 minutes of daily moderate physical activity, limiting how much time we sit and getting to and staying a health weight are all important actions for lowering risk of many cancers, as well as other chronic diseases.