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A recent study published in the journal Nutritional Psychiatry suggests that consuming higher amounts of specific dietary nutrients, like fiber and folate, is associated with a lower likelihood of experiencing depressive symptoms. The findings provide evidence that everyday dietary choices might play an underlying role in supporting mental health and managing mood. This research adds to a growing scientific interest in how the foods we eat might help reduce the risk of mental health conditions.
Depression is a highly prevalent mental health condition that affects hundreds of millions of people globally. The economic and personal impacts of depression are massive, leading to lost productivity and steep healthcare costs. Current pharmacological and psychological treatments do not work adequately for everyone experiencing depression. Because standard therapies leave a gap in care, scientists are actively searching for complementary strategies to prevent and manage the condition.
In recent years, the scientific community has shown increased interest in nutritional psychiatry. This is an area of study that examines how dietary habits and specific vitamins or minerals affect brain health. Even though the human brain accounts for a very small fraction of total body weight, it consumes a large portion of our daily energy. The brain requires specific nutrients to produce chemicals that regulate mood and to manage inflammation.
“Nutritional psychiatry has grown rapidly over the past decade, but most existing evidence has focused on single nutrients or on specific dietary patterns such as the Mediterranean diet,” said study author Takayuki Fujii, an assistant professor in the Department of Nursing at Yasuda Women’s University in Japan and a clinical psychologist. “We wanted to take a broader look at multiple nutrients simultaneously in a large U.S. adult sample, using a standardized depression screening tool (the PHQ-9),” Fujii explained.
To do this, the authors analyzed data from the National Health and Nutrition Examination Survey. This is an ongoing public health project that tracks the health and nutritional status of adults and children in the United States. “NHANES gave us a useful platform for examining these associations across a wide range of adults,” Fujii added. The researchers looked specifically at the 2017 to 2018 survey cycle, and their final analysis included 5,068 adults who were at least 18 years old.
To measure mental health, the researchers used the Patient Health Questionnaire-9. This is a standard nine-item survey that asks individuals to rate how often they have experienced symptoms of depression over the past two weeks. Participants answer on a scale ranging from “not at all” to “nearly every day.” A total score of ten or higher on this survey generally indicates clinically significant depression.
To measure dietary intake, trained interviewers asked the participants to detail everything they had consumed over a 24-hour period. This interview process was conducted twice for each participant. The scientists then calculated a two-day average of these food diaries to get a more accurate representation of each person’s typical diet. They focused on several specific nutrients, including dietary fiber, folate, magnesium, selenium, zinc, and vitamins B6, B12, and D.
When running their mathematical models, the authors accounted for several personal characteristics that might influence the results. They adjusted their calculations for age, sex, body mass index, smoking status, and total daily calorie intake. Body mass index is a common measurement of body fat based on a person’s height and weight. By including these factors, the researchers attempted to isolate the specific relationship between the nutrients and the participants’ mood.
Based on the survey scores, the researchers found that 9.1 percent of the participants were experiencing clinically significant depression. When analyzing the dietary data, the scientists noticed distinct differences between those with and without depression. Participants with depression consumed significantly lower amounts of dietary fiber, folate, magnesium, and selenium.
“Among U.S. adults in our analytic sample, those with higher intakes of dietary fiber, folate, magnesium, and selenium had lower odds of clinically relevant depressive symptoms (PHQ-9 ≥ 10) in our fully adjusted primary model,” Fujii told PsyPost. “These nutrients are abundant in foods such as whole grains, legumes, leafy greens, nuts, seeds, and seafood, essentially the staples of a Mediterranean-style diet.”
Folate, a nutrient naturally found in foods like leafy green vegetables and beans, showed the strongest inverse association. For every standard unit increase in folate intake, the odds of having depression dropped by 28 percent. A standard unit increase is a statistical tool used to show how much a value differs from the average of the group. Similar protective associations were seen with the other nutrients.
The researchers also observed a dose-response relationship for these four nutrients. A dose-response relationship occurs when increasing amounts of a substance are linked to increasingly stronger outcomes. Participants who consumed the highest amounts of folate had a 45 percent lower risk of depression compared to those who consumed the lowest amounts.
“The consistency across four nutrients with distinct biological roles was striking in our primary models,” Fujii noted. “The picture became more nuanced in our extended sensitivity analyses, however: fiber and folate were the most consistent signals. They remained significantly associated with lower depression odds across our extended unweighted models, and their point estimates stayed in the protective direction even in the most heavily adjusted survey-weighted analyses.” Point estimates are the specific numbers calculated by the researchers’ statistical models to represent the most likely effect.
When the authors ran secondary tests that included extra lifestyle variables, the results for some nutrients changed. “By contrast, magnesium and selenium were less robust,” Fujii explained. “Magnesium lost statistical significance once we added further covariates (poverty-income ratio, physical activity, and alcohol use), and selenium attenuated under both that adjustment and when NHANES survey weights were applied. That was a useful reminder that observational nutrition findings can be quite sensitive to analytic choices.”
Biologically, there are several ways these nutrients might support mental health. Dietary fiber is broken down by bacteria in the digestive system to produce short-chain fatty acids. This process is part of the gut-brain axis, a communication network between the digestive system and the brain. These fatty acids can travel to the brain and help reduce inflammation.
Folate is required by the body to produce important brain chemicals like serotonin and dopamine, which heavily influence mood. Magnesium acts on specific pathways in the nervous system and helps block certain receptors in the brain that are linked to depression. However, the researchers emphasize that these biological processes do not mean people should immediately buy nutrient pills.
“The practical takeaway is not to chase supplements but to consider that diverse, whole-food eating patterns may be one of several modifiable factors relevant to mental wellbeing,” Fujii said. “It’s also worth noting that the average fiber intake in our sample was about 16.6 g/day, well below the 25-38 g/day generally recommended, so there is real room for improvement in U.S. diets.”
But the study, like all research, has some limitations. The study captured a single snapshot in time, which makes it impossible to prove that low nutrient intake directly causes depression. “The most important is the cross-sectional design: we cannot determine whether lower nutrient intake contributes to depressive symptoms, whether depressive symptoms reduce intake of nutrient-dense foods, or both,” Fujii explained.
“We deliberately use associative, not causal, language throughout the paper, and I would ask readers to do the same,” Fujii said. “The effect sizes were also modest (Cohen’s d roughly 0.16-0.25 in unadjusted comparisons; odds ratios of 0.72-0.81 per 1-SD increase in the fully adjusted primary model), so these are not large effects.” Cohen’s d and odds ratios are mathematical measurements used to describe the strength of a relationship between two variables.
“Dietary intake was captured by 24-hour recalls, which are subject to measurement error and do not necessarily reflect long-term habits,” Fujii said. “The analysis also used a single NHANES cycle (2017-2018), and replication in pooled multi-cycle data is warranted. Finally, our findings should not be read as a recommendation to take specific supplements, the evidence here is about nutrients consumed as part of a varied diet.”
Moving forward, the scientists hope to track participants over several years. Following individuals over a long period would provide better evidence regarding whether dietary habits actively manage depression.
“We would like to extend this work using longitudinal data to better address temporality, examine overall dietary patterns rather than only individual nutrients, and explore whether the associations differ across population subgroups, depression subtypes (e.g., melancholic vs. atypical), or among individuals with treatment-resistant depression, a group of particular interest given that roughly one-third of patients with major depression do not respond adequately to conventional treatments,” Fujii said.
Overall, the authors recommend interpreting the findings cautiously and not viewing dietary changes as a replacement for standard medical care. People should also consider the broader socioeconomic factors that influence dietary choices.
“Diet is one of many modifiable factors associated with mental health, and our findings should be seen as one piece of a much larger picture,” Fujii concluded. “Anyone experiencing depressive symptoms should consult a qualified clinician rather than making major changes based on any single study. Access matters too: nutrient-dense foods are not equally affordable or available to everyone, and any conversation about diet and mental health needs to take socioeconomic disparities and food access into account.”
The study, “Association between depressive symptoms and multiple nutrient intakes in US adults: A cross-sectional study using NHANES 2017-2018,” was authored by Takayuki Fujii, Taiga Seo, and Yuji Nogami.
