Fermented foods such as vinegar have been part of the human diet for thousands of years. Long valued for their flavour and preservative qualities, they have also played a role in traditional medicine across many cultures; records suggest that Hippocrates used vinegar to support wound care as early as 400 BC. Today, scientists are beginning to uncover the complex ways fermented foods interact with our gut microbiome and influence our overall health. Could an ancient fermented food also help manage one of the most frustrating side effects of mental health medications? Our latest research1 suggests it might.
Mood and anxiety disorders affect about one in every five Canadians and are a leading cause of disability worldwide. Psychiatric medications such as antidepressants, mood stabilizers, and antipsychotics have transformed the lives of millions of people, providing effective treatment for many mental health conditions and often playing an essential role in recovery. Unfortunately, many of these medications can also cause unwanted metabolic side effects, including weight gain and changes in cholesterol and blood sugar. For some people, especially young adults, these side effects can become so problematic that they hesitate to start taking the medication, or stop treatment prematurely. Finding safe ways to reduce these side effects is an important challenge in mental health care.
The gut microbiome connection:
Over the past decade, scientists have discovered that our gut microbes do much more than help us digest food. Through what is now known as the gut-brain-axis, the microbes living in our intestines communicate with our immune system, metabolism, and brain. They play a part in regulating our mood, appetite, energy level, and so much more.
Research has shown that people living with anxiety and depression often have different gut microbial communities than those without those conditions. Psychiatric medications can also alter the gut microbiome, while the gut microbiome itself may influence how people respond to these treatments. In addition, the gut microbiome plays a key role in regulating metabolic health, including body weight and cholesterol metabolism.
This led us to ask an interesting question: could supporting the gut microbiome help reduce some of the metabolic consequences of psychiatric medications?
Why apple cider vinegar?
Apple cider vinegar(ACV) is one of the world’s oldest fermented foods. Beyond its familiar place in salad dressings and our home kitchens, previous studies have linked ACV consumption with improvements in cholesterol, blood sugar, and weight management.
One of the key compounds in ACV is acetate, a short-chain fatty acid. Acetate is also naturally produced by our gut microbes when they ferment dietary fibre, and it plays an important role in the gut microbial ecosystem.
Our previous research2 suggested that when acetate reaches the large intestine, it can help reshape the gut microbiome in beneficial ways. But there’s a catch: when you consume liquid ACV, much of the acetate is quickly absorbed before it ever reaches the colon where most of our microbes live.
So instead of using liquid ACV, we took a different approach. In a study supported by the London Community Foundation and recently published in Translational Psychiatry1, we used an over-the-counter powdered ACV product and a specially designed delayed-release capsule to develop a novel delayed-release ACV supplement. This formulation was designed to protect the acetate as the capsule passes through the stomach, allowing more of it to reach lower in the intestine where it could interact with the gut microbiome.
Putting the idea to the test:
We recruited young adults from the First Episode Mood and Anxiety Program (FEMAP) at London Health Sciences Centre who had experienced weight gain after starting their psychiatric medications (NCT05022524).
Eleven participants completed the study, taking the delayed-release ACV supplement twice daily for three months. Throughout the study, we monitored their gut microbiome, weight, cholesterol, blood pressure, mood, anxiety, and overall health.
As this was a first-of-its-kind intervention, we first had to assess whether it was practical and safe to use. We found that the capsules were very well tolerated, that participants were highly committed to the study, and that no product-related adverse events were reported.
We also observed some encouraging biological changes. Patients’ gut microbiomes changed over the course of the intervention, including increases in several bacteria that have previously been associated with metabolic and gut health. Many participants also experienced improvements in metabolic markers. Specifically, one participant achieved clinically meaningful weight loss, while several others showed improvements in cholesterol levels. Some participants also reported improvements in mood and anxiety symptoms, although our study was not designed to determine whether the capsules directly caused these changes.
Perhaps one of the most intriguing findings was that not everyone responded in the same way. Some participants appeared to be “responders,” showing greater metabolic improvements and distinct gut microbiome characteristics compared with others. Understanding why some people benefit more than others could become an important area of future research.
What do these findings mean?
While this was a small pilot study, we found that this novel delayed-release ACV supplement was safe and showed promise as a practical way to influence the gut microbiome and improve metabolic health in people taking psychiatric medications. What makes this approach particularly exciting is that it builds on a safe, well-tolerated, and inexpensive intervention derived from one of the world’s oldest fermented foods. If future studies confirm our findings, delayed-release ACV could become an accessible tool to help protect metabolic health and improve quality of life for people receiving mental health treatment. That’s an encouraging prospect, not only for people living with mental illnesses, but also for the broader population affected by metabolic disorders, and for the growing field of fermented food and gut microbiome research.
At a time when obesity and metabolic dysfunction are increasingly common, safe and affordable approaches that support metabolic health are urgently needed. Larger, placebo-controlled clinical trials will be required before we know how effective the delayed-release ACV approach really is, and who is most likely to benefit from it. In the next phase of this study, generously funded by the Weston Family Foundation and currently in development, we hope to do exactly that.
So, while there is still much to learn, we look forward to further exploring whether a familiar pantry staple like apple cider vinegar may have uncorked potential to support the gut microbiome and help address today’s health challenges.
References:
- Al, K.F., Wammes, M., Warren, M. et al.A case-series of oral acetate supplementation for gut microbiota alteration and metabolic improvement in patients with affective disorders on psychotropics. Transl Psychiatry 16, 298 (2026). https://doi.org/10.1038/s41398-026-04046-x
- Daisley, B.A., Chanyi, R.M., Abdur-Rashid, K. et al.Abiraterone acetate preferentially enriches for the gut commensal Akkermansia muciniphila in castrate-resistant prostate cancer patients. Nat Commun 11, 4822 (2020). https://doi.org/10.1038/s41467-020-18649-5