Did you know your gut is teeming with trillions of gut bacteria? Over 10,000 species of bacteria call your intestinal tract home. Recently it’s become apparent that these tiny organisms play an important role in health. Many people see bacteria in a negative light because of their role in causing infection. Some bacteria DO cause infection but there are other more benevolent bacteria that help keep the less scrupulous ones in check. These “friendly” probiotic bacteria play an important role in digestive health and, based on preliminary research, help keep your immune system healthy. In fact, more than 70% of your immune system lies in your intestinal tract. Now it appears bacteria in your gut play another important role – they may influence your food selections.
Are Gut Bacteria to Blame for Your Cravings?
Researchers at Arizona State University, University of New Mexico and the University College of St. Francisco are studying the effects bacteria in the gut have on food cravings. According to their findings, bacteria that make their home in your gut, your gut ecosystem, may influence your food preferences more than you might imagine.
Your gut and your brain are closely connected. You probably already knew that. Ever felt your stomach “jump” when you’re nervous or afraid or felt a wave of nausea when you saw something extremely unappetizing? In contrast, picturing a chocolate chip cookie or other tasty food in your mind can perk up your appetite and make your mouth water.
As researchers point out, gut bacteria may influence what we eat by their impact on the vagus nerve, the main nerve by which the brain and central nervous system communicate. They also speculate that gut bacteria may influence food choices in less obvious ways by producing chemicals that reward us when we eat certain foods and make us feel bad when we eat others.
Having a predominance of certain types of bacteria could cause you to crave fatty foods while other bacteria increase your desire to eat sugary ones. The best bacteria of all would be those that increase your desire to eat clean foods like vegetables and lean sources of protein. Are there such bacteria? No one knows for sure. Research in this area, although compelling, is still in its infancy.
One reason these bacteria send out chemical signals that increase cravings for certain foods like fatty foods is that those are the nutrients they’re best adapted to use. Increasing the desire to consume the macronutrient they need most helps them survive and thrive in an environment where they’re competing with other bacteria. Bacteria are looking out for their interests, even when they’re in conflict with yours.
The Role Diet Has on Gut Bacteria
Researchers think you may select for certain strains of bacteria by the type of foods you eat. Eat a diet in sugar and you’ll select for bacteria that thrive on sugar. These bacteria may send out chemical signals that “reward” you when you feed them carby foods. Here’s the good news. Research suggests changing your diet by eliminating sugar may select against “sugar-seeking” bacteria and, hopefully, reduce sugar cravings.
The bacteria in your gut can be changed quickly by simply altering your diet or by enjoying more probiotic-rich foods. Unfortunately, it’s not clear which bacterial species you want more or less of to reduce cravings for particular foods. With more than ten thousand species of gut bacteria, it’ll be a while before they’re characterized.
In support of the idea that gut bacteria influence the desire for certain foods, a small study showed men who ate chocolate daily had different by-products in their urine than men that didn’t eat chocolate. These by-products suggested the chocolate eaters have gut bacteria that differ from non-chocolate eaters. Wouldn’t it make sense that eating a diet rich in chocolate would select for certain types of bacteria that thrive in such a “Candyland” environment? These species of bacteria may produce chemicals that promote chocolate cravings to help keep them well nourished.
Research already suggests that gut bacteria influence mood. Why should it be a stretch that they impact food cravings? Studies in animals and small studies in humans show the effect gut bacteria may have on mood. One study showed participants that received a certain strain of probiotic bacteria for a month felt less stressed and had lower levels of the stress hormone, cortisol. In another study, anxious, timid mice that were transplanted with gut bacteria from bold, fearless mice became less fearful and more social. In addition, probiotic bacteria are even being proposed as a treatment for certain mental health issues like depression. Bacteria are capable of producing brain chemicals that alter mood.
Probiotics and Body Weight
If gut bacteria have an impact on food cravings, you might wonder whether they play a role in obesity? Preliminary studies suggest they do. People who are obese have a different composition of gut bacteria compared to people of normal weight. In a study involving mice, researchers found mice that received a certain strain of genetically-modified bacteria consumed less food and lost body fat relative to a control group. Just as interesting is a study showing mice exposed to antibiotics early in life have different gut bacteria and are predisposed to weight gain and a higher percentage of body fat. Such is the power of gut bacteria.
What Does This Mean?
Gut bacteria may play a pivotal role in controlling body weight by influencing food choices and, possibly, by altering metabolism. It’s already apparent that gut bacteria influence the absorption of nutrients. This can impact body weight too. Unfortunately, it’s unclear what strains of bacteria are most beneficial. Until more is known, your best bet is to eat more probiotic-rich foods like yogurt and fermented foods like tempeh, kefir and miso. Clean up your diet by eliminating sugar so you won’t encourage the growth of gut bacteria that thrive on sugar. These are healthy lifestyle changes you can make to improve your overall health.
The Washington Post. “Scientists Explain Chocolate Cravings”
Medscape.com. “Probiotics a Potential Treatment for Mental Illness”
Benef Microbes. 2014 Mar;5(1):19-28. doi: 10.3920/BM2012.0069.
Medical News Today. “Could a Probiotic Prevent Obesity?”
Medical News Today. “Early antibiotic exposure linked to later-life obesity, metabolic abnormalities”