can probiotics help reduce sugar cravings?

If you are like most people, you have a sweet tooth. And when you get a craving for something sweet, it can be tough to manage. Eating too much sugar can lead to weight gain, tooth decay, and other health problems.

But why do sugar cravings occur?

There are usually many factors involved in the appearance of cravings in general, including genetics, food palatability, past food experiences, emotional state, and the environment. 

To investigate why we crave sugary foods and what can we do to better control it, we tend to look at animals first. 

Do mice like very palatable foods?

To study sugar cravings, scientists have used mice models which hopefully resemble how humans act. Perhaps not surprisingly, mice that were given high-sugar or high-fat foods showed a binge-like consumption behavior, meaning they overconsumed calories when food felt very tasty to them.¹ Sounds familiar?

Gut bacteria regulate diet cravings 

Interestingly, a major environmental contributor is the gut microbiota. Gut bacteria impact our body's physiology and metabolism, and several articles point toward the idea that gut bacteria can change our feeding behaviors.^{2, 3, 4, 5, 6}

Therefore, it is interesting to study how gut bacteria affect mice's cravings for certain foods. Scientists can measure how much of a certain palatable food a mouse wants to eat by tracking the effort that they put into obtaining a food reward.

To eliminate gut microbiota, scientists treat mice with several antibiotics. These mice show changes in blood sugar levels and circulating hormones related to hunger.^{3, 7} Gut microbiota seems to influence diet selection in mice. This happens because the mice's brain sense bacterial compounds that regulate the appetite of the mice.^{4, 8} Quite incredible if you ask me! 

Antibiotic treatment increases sugar cravings 

In another study, mice lacking gut microbiota had increased motivation to pursue high-sugar foods and ended up overconsuming several palatable foods, including high-sucralose and high-fat foods.⁹ Surprisingly, these mice did not overconsume when they were fed normal food. Scientists also measured the levels of stress which could correlate with higher motivation for sugar foods, but there was no difference in stress levels.

The increased motivation to seek high-sugar foods was linked to increased neurotransmitters in the brain, including dopamine, brain-derived neurotrophic factor, and endocannabinoids. This means that treating mice with antibiotics changes neuronal activity in the brain.

The overall conclusion from this research is that gut microbiota depletion increases feeding behaviors for palatable foods!

Fecal microbiota transplant (FMT) reduces sugar cravings

An alternative method to link gut microbiota effects in their host is by introducing the gut bacteria to germ-free mice (mice that are born without a microbiome) or to antibiotic-treated mice. This is called fecal microbiota transplant (FMT). 

The same scientists showed that introducing bacteria to antibiotic-treated mice was sufficient to rescue overconsumption of high-sucrose food.⁹ This reminds me of those older studies in which microbiota from diet-induced obese mice was transplanted into skinny mice, and they became obese!⁶

Scientists identify the bacteria that reduce sugar cravings

Finally, by treating the mice with several combinations of antibiotics that kill different bacteria, they found the bacteria that reduced sugar cravings in these mice.⁹

Lactobacillus johnsonii and Lactobacillus gasseri and bacteria from the family S24-7 (uncultured bacteria within the order of Bacteroidales) correlated with suppression of high-sugar foods consumption. When introducing these bacteria to antibiotic-treated mice, scientists noticed a reduction in binge eating behaviors. 

Another paper also found that a bacterium from the family S24-7 (Bacteroides uniformis) could suppress binge eating in mice.⁵ Moreover, several Lactobacillus species also affect metabolism and feeding behaviors in rodents. ^{10, 11}

In conclusion: should you take probiotics to help reduce sugar cravings?

We already knew that different bacteria prefer certain foods: some bacteria like fiber, but other prefer proteins and fats. Previous research has shown us that bacteria communicate with our brain cells to direct us to consume the kind of food that the bacteria want.

It is very interesting to see that the previous speculation on how gut bacteria could modulate our eating behaviors is now more certain than ever. This body of research suggests that certain bacteria induce changes in our body and brain so that we crave high- or lower-calorie foods. 

If you are interested in buying these probiotics, some companies are already selling Lactobacillus johnsonii and Lactobacillus gasseri probiotics. Lactobacillus gasseri can establish itself in an already stable gut microbiome,13 and has a positive impact on the immune system.14

The bacterium Bacteroides uniformis has also relevant research behind it and has been proposed to be used as a probiotic, but so far companies are not selling it.^{5, 12}