Depression is a complicated condition that nearly 48 million Americans grapple with. While talk therapy and antidepressants are the mainstays of treatment, a growing body of research has found that making certain lifestyle tweaks such as exercising more and doing your best to eat a healthy diet can also help to support your mental health. Now, new research suggests focusing on fiber could do your mental health a solid, too.
It’s worth noting this now: The study didn’t find that ramping up your fiber intake alone will magically cure your depression. Instead, the researchers found a link between higher fiber intake and fewer depression symptoms.
If you have depression and want to do everything you can to try to feel better, leaning into this macro a little more might help you to feel a little better—and even help your gut health along the way. Here’s why doctors say this is worth considering.
Meet the experts: Zohra Lassi, PhD, study co-author and associate professor in the School of Public Health at Adelaide University; Davide Cappon, PhD, director of neuropsychology at Tufts Medical Center; and Hillary Ammon, PsyD, a clinical psychologist at the Center for Anxiety and Women’s Emotional Wellness.
What did the study find?
The study, which was published in the journal Clinical Nutrition ESPEN, analyzed data from 12,000 people who participated in the National Health and Nutrition Examination Survey (NHANES) before and during the COVID-19 pandemic. The participants were also asked about their mental health, with researchers analyzing their symptoms based on the Patient Health Questionnaire-9 (PHQ-9), a common tool used by doctors to screen for depression and depression severity.
The researchers found some interesting links between fiber intake and mental health. Overall, the participants’ dietary fiber intake dropped from 16.52 grams a day before the pandemic to 15.95 grams a day during the pandemic. The researchers also found that eight percent of participants reported depressive symptoms before the pandemic, while 10 percent reported them during the pandemic.
But after combining the data, the researchers discovered that there was a 14 percent lower risk of having symptoms of depression for every extra five grams of fiber intake before the pandemic. This association got a little weaker for the study participants as a whole during the actual pandemic (but, to be fair, there was a lot happening during the pandemic that could’ve affected someone’s mental health). Worth noting: The protective link between eating fiber and mental health stayed true for women during the pandemic, but not for men.
What’s behind this?
The study found a link between eating more fiber and fewer symptoms of depression, making it tough to say that one led to the other. Still, doctors say there’s likely something here.
One possibility is the gut-brain axis. “Fiber is fermented by bacteria in the gut, producing compounds called short-chain fatty acids,” explains Zohra Lassi, PhD, a study co-author and associate professor in the School of Public Health at Adelaide University. “These compounds are involved in processes including inflammation, immune function, and communication between the gut and the brain.”
Hillary Ammon, PsyD, a clinical psychologist at the Center for Anxiety and Women’s Emotional Wellness, agrees that this is likely at the heart of the link. “Fiber can act as prebiotics that fuel microbes in the digestive tract,” she says. Ammon points out that recent research suggests that people with depression may have lower levels of short-chain fatty acids in their guts.
“What this research may be suggesting is that people [who] consume more fermentable fiber may have healthier gut microbes, which in turn, produces more short-chain fatty acids, which ultimately can reduce inflammation, impact brain functioning, and improve mood,” she says.
But it’s also possible that the reverse is true. “People experiencing fewer depressive symptoms may also eat healthier,” says Davide Cappon, PhD, director of neuropsychology at Tufts Medical Center. “Future studies should follow people over time and include biomarkers of inflammation and gut health to better understand whether fiber itself is driving the association and through what mechanisms.”
Does the type of fiber matter?
There are two main types of fiber: soluble and insoluble. Soluble fiber dissolves in water to create a gel-like substance in your gut, while insoluble fiber passes through your gut mostly unchanged.
It’s not clear if the type of fiber matters, Lassi says. “We measured total dietary fiber intake and did not have information that allowed us to distinguish between different types of fiber,” she says. “Different types and sources of fiber can have different physiological effects, so this is an important question for future research.”
How much fiber do people need to get the perks?
Overall, the study participants didn’t have as much fiber intake as dietary guidelines recommend. (It’s generally recommended that adults consume 25 to 38 grams of fiber a day, or about 14 grams of fiber for every 1,000 calories you take in.) But the researchers found that ramping up that intake a little and at least nearing the recommended amounts each day was linked to better mental health.
“The main message is that diet may be one part of the mental health picture, and fiber appears to be part of that conversation,” Lassi says. But she cautions against loading up on fiber supplements in an effort to prevent or manage depression.
“A practical approach is to include more naturally fiber-rich foods such as vegetables, fruit, whole grains, beans, lentils, and nuts as part of a healthy diet,” she says. Overall, Lassi emphasizes that depression is complicated. “Depression is influenced by many biological, psychological, and social factors, and diet is only one part of that much bigger picture,” she says. But if you want to add more fiber to your plate, go ahead. It may do your mind—and your gut—a solid.