When you hear “bacteria” you probably think of illness, spoiled food, and a whole host of other icky things. These diminutive microbes definitely are not all bad, and as scientists are learning some of them are essential to our health and wellbeing. Some may even play a role in both type 1 and type 2 diabetes, as well as obesity, and other metabolic disorders.
The microbiome, which is essentially a collective name for all the bacteria in our bodies and their genes, has been a hot topic recently both in the lab and in the media. Other names for it include “gut microbiota” and “microflora,” (suggesting a complex garden of species, which is pretty accurate).
Our microbiome is determined by a number of factors: the bacteria given to us from our mother during birth, the bacteria we pick up in our environment, and whether we’re exposed to anti-bacterial products like hand sanitizer or antibiotics. But the number-one driving factor is our diet. What we eat determines what grows in our gut; much the way putting out specialized birdseed attracts specific songbirds.
How do you cultivate good bacteria?
“One sure thing that I can recommend is a high fiber diet,” says Suzanne Devkota, Ph.D., a research fellow at Joslin Diabetes Center, and an expert in the quickly evolving field of microbiome research. “By eating fiber you are providing nutrients for the good bacteria.”
However, as Dr. Devkota points out, on average Americans don’t get anywhere near the recommended amount of fiber in their diets. Instead, we eat foods that have been linked with promoting undesirable bacteria: diets high in long-chain saturated fats, low or no fiber diets, as well as diets high in artificial sweeteners.
The connection to Obesity and Type 2 diabetes?
An area where Dr. Devkota thinks microbiome research will make a huge impact is human metabolism. There are some links that have shown that the composition of bacteria in our gut can actually determine how much energy we derive from foods, which translates to how much weight we gain or lose.
For example, previous literature has shown that an abundance of a group of bacteria called Firmicutes in the gut can cause our bodies to absorb a greater amount of calories.
Researchers don’t yet know the mechanism behind this increase in Firmicutes in the gut, but they do know their impact. Picture two people eating two identical 700 calorie hamburgers. The person with low levels of Firmicutes may only absorb 550 calories from the hamburger, while the person with abundant Firmicutes may extract 650 calories or more. “That’s a link to obesity that has been explored quite a bit in a few different studies,” says Dr. Devkota.
Studies involving bariatric surgery offer clues
To learn more about what causes obesity, researchers have also been looking at the changes in gut bacteria before and after gastric bypass surgery. “We all have the same species of bacteria, but the proportion of them is different from person to person,” explains Dr. Devkota.
In patients post-surgery, there seems to be an increase in beneficial bacteria and a decrease of less desirable ones like firmicutes. “There’s no new bacteria introduced. You’re not really changing who is there but the proportion of who is there,” she says. A team from Joslin, led by Allison Goldfine, M.D., Head of the Section of Clinical Research at Joslin Diabetes Center, is also focused on bacteria in obesity.
There seems to be bacteria that can translocate through out of the gut through the blood and into other tissues like fat cells and the liver (a process dubbed “gut leakage”).
The bacterial displacement may cause low grade inflammation over time, and since chronic inflammation of these tissues has been linked with developing type 2 diabetes, this could be the “missing link” explaining why obesity leads to metabolic disorders.
This is all very new, however, and Dr. Devkota points out that although the team has interesting findings, the research hasn’t yet been extensive enough to point to a definitive cause and effect.
Other Joslin studies
There are many other projects at Joslin looking at our microbiomes, asking everything from how intermittent fasting and re-feeding can alter gut bacterial populations , to whether Latino diabetics have a unique microbiome that affects their response to the disease, to the effect of consuming brown vs. white rice in Asian cultures and whether that changes their microbomes and therefore insulin resistance.
While she is quick to say that decoding the microbiome isn’t going unlock all the secrets of diabetes, Dr. Devkota does think it’s an important piece of the puzzle. Furthering our understanding the microbiome opens up a new way to think about human physiology of the disease.
“It’s like a whole other organ we’ve been ignoring for years.”