A study shows that eating more fruit and fewer salty snacks are linked to better mental health

New research in psychology shows that the food we eat has a direct effect on how we feel. The results of the study, which were published in the British Journal of Nutrition, showed that eating more fruit was linked to less depression and better mental health while eating more savoury snacks was linked to more anxiety.

In the past few years, scientists have started to wonder if changing a person's diet might be a way to improve their mental health. This idea comes from research that shows eating nutrient-dense foods (like fruits and vegetables) is linked to fewer mental health problems and eating nutrient-poor foods (like candy and salty snacks) is linked to more stress, anxiety, and depression.

It's not clear why a person's diet might affect their mental health, but study author Nicola-Jayne Tuck and her team think it might have something to do with how nutrients affect the way our brains work. Studies have shown that a diet low in nutrients hurts cognitive function, while a diet high in nutrients helps it. And cognitive problems, like having less control over what you want to do and not being able to do it, have been linked to worse mental health.

Tuck and her colleagues did a study to find out if diet could affect mental health by changing how people think. They also looked at the effects of how often and how much people ate fruits and vegetables.

A group of 428 UK residents who were chosen to be representatives of the whole country filled out an online survey about their eating habits, mental health, and cognitive function. Participants were asked how often they ate fruits, vegetables, sweet snacks (like cakes and cookies), and savoury snacks (like potato chips) per day in the past month, as well as how many portions of fruits and vegetables they ate per day. They also filled out tests for depression, anxiety, stress, and their mental health. To control for possible covariates, the participants filled out some health-related questions, such as how much they smoked, drank, and worked out.

The subjects also filled out a self-report cognitive failures questionnaire that looked at "attentional, memory, perceptual, and action-related mental lapses in everyday tasks" in the past six months (e.g., forgetting appointments, and dropping things). The Stop-Signal Task was then done as a behavioural measure of cognitive control.

After controlling for other factors, the results showed that the frequency of eating fruit (but not the amount) was a good predictor of psychological well-being and a bad predictor of depression. Even though more experiments need to be done, the study's authors think that "how often we eat fruit may be more important than how much we eat."

Eating savoury snacks, but not sweet snacks, made anxiety more likely. This fits with research that says salty and fast foods can make people feel more anxious. The study was cross-sectional, which makes it hard to tell which way this relationship goes. It's possible that people who feel more stress and anxiety eat less healthy foods as a way to deal with their feelings.

The results also showed that cognitive failures were the link between savoury snacks and mental health. In other words, people who ate savoury snacks had more cognitive failures, which led to more depression, anxiety, and stress symptoms and a lower sense of well-being. Studies on animals have shown that saturated fats can make it harder to remember things, so it's possible that savoury snack foods that are high in saturated fat can also make it harder to remember things and hurt your mental health.

After controlling for other factors, it was interesting to see that the frequency of eating vegetables had no effect on mental health. Researchers think this might be because people often eat canned and cooked vegetables, which might make it harder for the body to absorb nutrients. On the other hand, most fruits are eaten raw.

Overall, the results suggest that balancing the amount of processed (low in nutrients) and unprocessed (high in nutrients) foods you eat may help protect your mental health. Tuck and her colleagues say, "Further work is now needed to establish causality and find out if these may be modifiable dietary targets that can directly (and indirectly) affect our mental health."