Researchers squeeze a new benefit out of oranges

BY HPN Staff

Eating citrus fruits may reduce depressive risks, according to a recent study from a Harvard research team.

“We found that eating one medium orange a day may lower the risk of developing depression by about 20 percent,” researcher Raaj Mehta told The Harvard Gazette.

The reason may be that citrus stimulates the growth of a particular gut bacteria, F. prausnitzii, which impacts serotonin and dopamine — neurotransmitters that regulate the digestive tract but also improve people’s mood.

“The effect seems to be specific to citrus,” Mehta told The Gazette. “When we look at people’s total fruit or vegetable consumption, or at other individual fruits such as apples or bananas, we don’t see any relationship between intake and risk of depression.”

Why it matters

Nearly 20% of Americans have been diagnosed with depression, according to a 2020 Centers for Disease Control study.

Estimates vary, but Americans spend billions each year on antidepressants, and analysts expect that market to grow significantly.

Mehta said it’s hard to compare citrus's impact to prescription antidepressants because the fruit seems to prevent depression as opposed to treat it.

“In the future, eating citrus could perhaps be part of a strategy for managing depression that also involves these more traditional pharmaceuticals. But more research is needed before we can conclude that,” he told The Gazette.

There’s a growing food-is-medicine movement in the United States, but it often focuses on the link between diet and obesity. Medicaid, a government-run health insurance program, launched a North Carolina pilot project in 2022 that, among other things, uses federal funding once restricted to medical care to pay for healthy food deliveries.

That program may shutter this year, though, due to budget cuts.

The bigger picture

The Harvard team was inspired by a 2016 paper that suggested a connection between mood and citrus, particularly in older women, but concluded further study was needed.

For the newer study, researchers pulled data from the Nurses’ Health Study II, which began in 1989 and involved more than 100,000 women who reported information about their lifestyles, diets, medications and health. Researchers also analyzed data from the Men’s Lifestyle Validation Study, a smaller data collection project.

In both data sets, researchers saw that higher levels of F. prausnitzii, a gut bacteria already linked to good health in other ways, correlated with better depression risk scores.

The nursing study involved stool samples, and researchers used DNA sequencing to look for particular species of bacteria.

“F. prausnitzii was more abundant in people who were not depressed than people who were, and consuming a lot of citrus was also associated with high levels of F. prausnitzii,” Mehta said.

Additional details

Mehta told The Gazette he’d like to see a clinical trial testing citrus’s impact in real time.

“There’s such a huge unmet need for depression treatments and eating citrus doesn’t really have any major side effects, so it would be great to see how much this simple treatment can help,” he said. “More broadly, I hope our results inspire other researchers to look into the link between diet and mental health.”