New research suggests that french fries may be linked to depression

  (CNN) — French fries — they’re greasy, starchy and a comfort food for many.

But reaching for fried foods may have a negative impact on mental health.

A research team in Hangzhou, China, found that frequent consumption of fried foods, especially fried potatoes, was linked with a 12% higher risk of anxiety and 7% higher risk of depression than in people who didn’t eat fried foods.

The link was more pronounced among young men and younger consumers.

Fried foods are known risk factors for obesity, high blood pressure and other health effects. These results “open an avenue in the significance of reducing fried food consumption for mental health,” according to the paper published Monday in the journal PNAS.

However, experts who study nutrition said the results are preliminary, and it’s not necessarily clear whether the fried foods were driving mental health issues, or people experiencing symptoms of depression or anxiety turned to fried foods.

The study evaluated 140,728 people over 11.3 years. After excluding participants diagnosed with depression within the first two years, a total of 8,294 cases of anxiety and 12,735 cases of depression were found in those that consumed fried food, while specifically fried potatoes were found to have a 2% increase in risk of depression over fried white meat.

The study had also found that the participants consuming more than one serving of fried food regularly were more likely to be younger men.

“The human component of this study may indicate just what it purports: that higher intake of fried food increases the risk of anxiety/depression,” said Dr. David Katz, a lifestyle medicine specialist who was not involved in the study, via email.

“However, the causal pathway could just as readily go the other way: people with anxiety/depression turn to ‘comfort food’ with increasing frequency for some semblance of relief,” added Katz, founder of the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.

Those with underlying symptoms of anxiety and depression could turn to comfort foods as a way of self-medicating, he said.

Unhealthy food and poor nutrition can lower one’s mood and progress a mental health condition, as found in a prior study cited within this new one.

The same goes for zebrafish

In the new study, the researchers suggest that acrylamide, a chemical formed during the frying process, especially in fried potatoes, is to blame for the higher risk of anxiety and depression.

In a separate paper referenced in the new study, the researchers exposed zebrafish to the chemical, finding that long-term exposure had caused the fish to dwell in dark zones within the tank, a common sign of a higher anxiety level in the fish.

The zebrafish had also displayed a reduced ability to explore their tanks and socialize, as they did not swim closely with other zebrafish, even though zebrafish are known to form schools with their species.

“Zebrafish were presumably chosen … because they were already known to be vulnerable to acrylamide toxicity, and because their behavioral responses to anxiety are established and consistent — offering a source of both biological and behavioral data,” Katz said.

Dr. Walter Willett said the results “should be regarded as very preliminary, especially the connection with fried food and acrylamide.”

“The health effects of fried food will depend greatly on what food is fried and what type of fat is used for frying,” said Willett, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health, via email. “Potatoes are a concern for possible effects of mood because they can cause large surges in blood sugar and then hormonal responses to these surges. However, these surges are partly blunted by fat, which would be provided by the fat from frying.”

Willett also noted that acrylamide isn’t only produced by frying. It’s in coffee, because of the roasting of the beans, and in toast, because “heating carbohydrates together with protein can do this.”

He also said that the zebrafish “data are hard to interpret in relation to human health because we are obviously quite different, and the authors recognized this.”

Anxiety and depression on the rise

Zhejiang University researcher Yu Zhang, an author of the study, told CNN in an email that “there is no need to panic about the adverse effects of fried food.” But maintaining a healthy lifestyle and reducing consumption of fried foods may be helpful for mental health in addition to overall health.

The researchers had pointed to a recent rise in depression and anxiety worldwide, with 2020 seeing an increase of 27.6% and 25.6%, respectively. The World Health Organization also estimates that more than 5% of adults suffer from depression, globally, as noted in the paper.

By looking at the effects of fried food consumption in humans and acrylamide exposure in zebrafish, the researchers had compared the two to suggest that frequent consumption of the chemical commonly found in fried food could have a negative effect on mental health.

A lack of variety in food has also been shown to decrease well-being, according to Katz.

“If a take-away is needed it is simply that overall diet quality, and the selection of wholesome foods, matters profoundly to every aspect of health — mental and physical alike,” Katz said.

Willett said there’s also the possibility of reverse causation — that people may change their diets because they have depression or anxiety. “These mood changes are, in general, more difficult to study because they may come and go, unlike the diagnosis of major cancer or heart attack, the study in this analysis was not designed to address these challenges,” he said.