Researchers have discovered that a daily dose of vinegar could improve symptoms of depression, pointing to the possibility that future treatments might come with a few spoonfuls of sour.

A team led by Arizona State University not only tested the effects of regular vinegar consumption but also looked at metabolic activity – the chemical processes that convert food into energy and other biological materials – to look for reasons for the benefits seen with vinegar.

A significant 86 percent boost in the levels of nicotinamide (a form of vitamin B₃) was noticed across the study participants who took liquid vinegar each day. The nutrient has previously been linked to anti-inflammatory effects.

"This data provides additional support that daily vinegar ingestion over four weeks can improve self-reported depression symptomology in generally healthy adults and that alterations in [vitamin B₃] metabolism may factor into this improvement," write Arizona State University dietician Haley Barrong and colleagues in their published paper.

The trial was completed by a total of 28 overweight but otherwise healthy adults, who were split into two groups: one group taking two tablespoons of red wine vinegar twice daily, and the other group taking a daily pill with a very small amount of vinegar in it.

Across the course of the four-week experiment, the participants were asked to answer questions across two standard mental health surveys: the Center for Epidemiological Studies Depression (CES-D) questionnaire, and the Patient Health Questionnaire (PHQ-9).

Although there was no significant difference between the groups on the CES-D, on the PH9-Q, there was an average drop of 42 percent in depressive symptoms for the high vinegar level group compared with 18 percent for the control group taking the vinegar pill.

There are some limitations: it was a small sample size, the patients had low-level depression to begin with, and the improvements in PHQ-9 symptoms were not significant in a secondary analysis that adjusted for baseline survey scores. But Barrong and her team say the findings warrant a closer look at the relationship.

"Depressive disorders are the most prevalent mental health conditions in the world," write the researchers.

"The commonly prescribed antidepressant medications can have serious side effects, and their efficacy varies widely. Thus, simple, effective adjunct therapies are needed."

Studies continue to make progress in better understanding what depression is and all the different factors that can potentially play into it – from sleep quality to body temperature.

What's clear is that depression varies a lot between individuals, and that's where having a wider range of potential treatments can be so useful.

"Future research examining the effects of vinegar administration in clinically depressed or at-risk populations, and those on antidepressant medications, is warranted," write the authors.

"A focus on mechanisms and large patient samples will strengthen the science and provide the evidence to more firmly demonstrate vinegar's role in health promotion."

The research has been published in Nutrients.