A 2026 randomized controlled trial of 53 people found that probiotics made only small, inconsistent changes to eating habits over three months. Healthy people who took probiotics ate more vitamin D-rich foods after one week, while people with depression showed this change after three months. However, probiotic users also ate less dietary variety overall, suggesting probiotics shouldn’t be relied upon to improve eating patterns.
Researchers tested whether taking probiotic supplements for three months could change what people eat and how much nutrition they get. They studied 53 people—some with depression and some without—giving half a probiotic pill and half a fake pill. According to Gram Research analysis, the probiotics made only small changes to eating habits. Healthy people who took probiotics ate more vitamin D-rich foods after one week, while people with depression showed this change after three months. However, people taking probiotics also ate less variety in their diets. The study suggests probiotics might influence food choices through the gut-brain connection, but the effects were weak and unpredictable, so more research is needed.
Key Statistics
A 2026 randomized controlled trial of 53 participants (23 with depression, 30 healthy) found that probiotic supplementation produced only small and inconsistent changes in dietary intake over three months, with most measures showing no significant effect.
In a double-blind, placebo-controlled study published in PLOS ONE in 2026, healthy people taking probiotics showed increased vitamin D intake after one week, while people with depression showed a similar trend after three months, suggesting timing-dependent effects.
A pilot study of 53 people found that probiotic supplementation was associated with lower dietary variety and diversity scores at several time points, suggesting probiotics may narrow rather than expand food choices.
Across all time points in a 2026 clinical trial, folic acid intake was significantly lower in people with major depression compared to healthy controls, independent of whether they received probiotics or placebo.
The Quick Take
- What they studied: Whether taking probiotic supplements for three months could change what foods people eat and the nutrients they consume
- Who participated: 53 people total: 23 with major depression and 30 healthy people. Half received probiotics twice daily, half received a fake pill (placebo). Everyone was tracked for three months.
- Key finding: Probiotics made only small, inconsistent changes to eating habits. Healthy people ate more vitamin D foods after one week of probiotics, while people with depression showed this change after three months. However, probiotic users also ate less variety overall.
- What it means for you: Taking probiotics probably won’t dramatically change your diet or food cravings. Any changes that do happen appear to be small and may take weeks to develop. This is early research, so don’t expect probiotics to fix eating habits on their own.
The Research Details
This was a randomized controlled trial, which is one of the best ways to test if something actually works. Researchers split 53 people into two groups: one got real probiotics (beneficial bacteria) twice a day, and the other got a fake pill that looked identical. Nobody knew which group they were in—not even the researchers giving out the pills. This “double-blind” approach prevents bias from affecting the results.
For three months, participants kept detailed food diaries using a tool called the Vienna Food Record, which tracks everything eaten and its nutritional content. Researchers measured their diets at the start, then again after one week, one month, and three months. They specifically looked at vitamin D, folic acid, dietary variety (how many different foods people ate), and overall diet diversity (how balanced the diet was).
The study included two groups: people diagnosed with major depression and healthy people without depression. This allowed researchers to see if probiotics affected eating differently depending on mental health status.
Understanding whether probiotics can influence what we eat matters because the gut and brain are connected through something called the gut-brain axis. Bacteria in our stomach can send signals to our brain that affect mood, appetite, and food preferences. If probiotics could reliably change eating habits toward healthier foods, they might be a useful tool for improving nutrition, especially in people with depression who sometimes struggle with appetite and food choices.
This study has several strengths: it used a placebo control (fake pill), was double-blind (neither participants nor researchers knew who got real probiotics), and tracked people over three months. However, it’s labeled a “pilot study,” which means it’s small and exploratory—designed to test whether the idea is worth studying more, not to prove something definitively. The sample size of 53 people is relatively small, and the researchers themselves note that most changes were tiny and many didn’t reach statistical significance. The study was published in PLOS ONE, a reputable open-access journal, which is positive for transparency.
What the Results Show
The main finding was that probiotics produced only small, inconsistent changes in what people ate. The most notable pattern involved vitamin D intake: healthy people who took probiotics ate more vitamin D-rich foods after just one week, while people with depression showed a similar increase after three months (though this was weaker and not quite statistically significant).
Interestingly, the opposite happened with dietary variety and diversity. People taking probiotics actually ate less variety—meaning they chose from a narrower range of foods—at several time points during the study. This was unexpected and suggests probiotics might narrow food choices rather than expand them.
Folic acid intake was consistently lower in people with depression compared to healthy people, regardless of whether they took probiotics or placebo. This finding wasn’t affected by the probiotic intervention, suggesting depression itself may influence folic acid consumption.
Overall, the researchers emphasized that these changes were small and exploratory. Most dietary measures didn’t change significantly, and when they did, the patterns were unpredictable and depended on both the time point measured and whether participants had depression.
The study found that timing mattered: some changes appeared after one week (vitamin D in healthy people), while others took three months to emerge (vitamin D in people with depression). This suggests that if probiotics do influence eating, the effect develops gradually. The fact that probiotics seemed to reduce dietary variety is noteworthy because variety is generally considered important for good nutrition. This unexpected finding suggests probiotics might not universally improve eating patterns.
This research builds on growing evidence that gut bacteria influence the brain and behavior through the gut-brain axis. Previous studies have shown probiotics can affect mood and anxiety, but very few have examined whether they change actual food intake. This pilot study is among the first to directly measure whether probiotics alter what people choose to eat. The small, inconsistent effects found here contrast with some animal studies showing stronger effects, suggesting the gut-brain connection may work differently in humans or that the effects are more subtle than previously thought.
The study is small (only 53 people), which limits how much we can trust the findings. The researchers themselves call it a “pilot,” meaning it’s meant to test an idea, not prove it works. The food tracking method (food diaries) relies on people remembering and accurately reporting what they ate, which can be inaccurate. The study didn’t measure actual gut bacteria changes, so we don’t know if the probiotics actually colonized the gut or changed the microbiome. The three-month timeframe is relatively short—longer studies might show different patterns. Finally, most of the changes observed were very small and many didn’t reach statistical significance, meaning they could have happened by chance.
The Bottom Line
Based on this pilot study, probiotics should not be expected to significantly change eating habits or food preferences. If you’re considering probiotics for other reasons (like digestive health or mood support), don’t expect them to automatically improve your diet. Instead, focus on intentional dietary changes like adding more vegetables, whole grains, and varied foods. If you have depression and are struggling with appetite or nutrition, talk to your doctor or a dietitian—probiotics alone are unlikely to solve these problems. Confidence level: Low, because this is a small pilot study with inconsistent results.
This research is most relevant to people with depression who are interested in whether probiotics might help improve their eating habits, and to researchers studying the gut-brain connection. Healthy people looking for ways to improve their diet should focus on proven strategies like meal planning and nutrition education rather than relying on probiotics. People taking probiotics for other health reasons shouldn’t expect significant changes to their food intake based on this evidence.
If probiotics do influence eating, changes appear to happen slowly. In this study, some effects emerged after one week, while others took three months. Don’t expect immediate changes to your appetite or food cravings. If you were to try probiotics, you’d need to give them at least several weeks to see any potential effect on eating habits.
Frequently Asked Questions
Do probiotics actually change what you want to eat?
A 2026 study of 53 people found probiotics made only small, inconsistent changes to eating habits. Healthy people ate more vitamin D foods after one week of probiotics, but effects were weak overall. Don’t expect probiotics to significantly alter your food cravings or diet.
Can probiotics help people with depression eat better?
Research shows probiotics may slightly increase vitamin D intake in people with depression, but only after three months and the effect was weak. Probiotics alone shouldn’t be relied upon to improve eating habits in depression. Talk to your doctor about proven nutrition strategies.
How long does it take for probiotics to affect eating habits?
In this study, changes appeared at different times: some after one week, others after three months. If probiotics do influence eating, the effect develops slowly. You’d need to use them for several weeks to months to notice any potential changes.
Should I take probiotics to improve my diet?
This pilot study suggests probiotics shouldn’t be your primary strategy for improving diet. Focus instead on proven approaches like meal planning, adding more vegetables, and eating diverse foods. Probiotics may have other health benefits, but changing eating habits isn’t a reliable one based on current evidence.
Did probiotics make people eat healthier foods?
Probiotics showed mixed results. While some vitamin D intake increased slightly, people taking probiotics actually ate less dietary variety overall—meaning they chose from fewer different foods. This suggests probiotics don’t reliably promote healthier eating patterns.
Want to Apply This Research?
- Track daily food variety by counting how many different food groups you eat each day (vegetables, fruits, grains, proteins, dairy). Aim to eat from at least 4-5 different groups daily. Record this weekly to spot patterns over time.
- If using probiotics, set a weekly reminder to intentionally add one new food or recipe to your diet. This counteracts the study’s finding that probiotics were associated with lower dietary variety. Pair probiotic use with active dietary expansion rather than passive consumption.
- Use the app to log vitamin D-rich foods (fatty fish, egg yolks, fortified milk) weekly and track overall dietary diversity monthly. Compare patterns before and after starting probiotics to see if you notice personal changes, even if they’re small. Share data with your healthcare provider if you’re using probiotics therapeutically.
This research is a small pilot study with inconsistent findings and should not be used to make medical decisions about probiotic use. Probiotics are not proven to change eating habits based on this evidence. If you have depression, an eating disorder, or nutritional concerns, consult with your healthcare provider or a registered dietitian before relying on probiotics or making significant dietary changes. This article summarizes research findings and is not medical advice. Always discuss supplement use with your doctor, especially if you take medications or have underlying health conditions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.