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Depression

Can Eating More Fruit Reduce Depression?

Some research claims are a bit simplistic.

Key points

  • New research suggests that increasing the frequency of eating fruit can improve wellbeing and reduce depression.
  • Some research findings don't take into sufficient account all factors that may contribute to a particular result.
  • There are simple, proven ways to prevent depression and manage anxiety that can be trusted more than recent claims, such as eating more fruit.

Can we improve our mental well-being simply by upping how often we reach for the fruit bowl? That is what psychologists from the College of Health and Life Sciences at Aston University are suggesting. They surveyed 428 adults from across the UK to establish any relationship between their psychological health and their consumption of fruit, vegetables, and sweet and savoury snacks.

Photo by Andrea Piacquadio / Pexels
Source: Photo by Andrea Piacquadio / Pexels

According to their findings, the more times people ate fruit, the better their mental well-being and the lower their experience of depression, whereas those who tended to grab nutrient-poor savoury snacks, such as crisps, had lower mental well-being and more “everyday mental lapses” (such as forgetting where they had put things), which are linked with anxiety, stress, and depression.

Tellingly, at least to the researchers, there was no direct link between eating vegetables and mental well-being, and no link between mental lapses and either fruit or vegetable intake; or, curiously, intake of sweet (as opposed to savoury) snacks.

Lead author Ph.D. student Nicola-Jayne Tuck reports enthusiastically, “Our findings could suggest that frequently snacking on nutrient-poor savoury foods may increase everyday mental lapses, which in turn reduces psychological health.

“Other studies have found an association between fruit and vegetables and mental health, but few have looked at fruit and vegetables separately—and even fewer evaluate both frequency and quantity of intake.

“Both fruit and vegetables are rich in antioxidants, fibre, and essential micronutrients which promote optimal brain function, but these nutrients can be lost during cooking. As we are more likely to eat fruit raw, this could potentially explain its stronger influence on our psychological health.

“It is possible that changing what we snack on could be a really simple and easy way to improve our mental well-being.”1

A closer look at epidemiological studies

Hmmm. While it is the kind of study that gets pounced on by news media—"eat fruit to avoid depression"—I think there should be alarm bells ringing here. Why should sweet snacks (like custard pies or chocolate biscuits perhaps?) keep us immune from mental lapses, as they are surely as nutrient-poor as the savoury variety? When findings don’t make sense, it usually means that the statistics they are based on are insignificant—in the lay sense of the word.

Tuck also concedes that the team didn’t look at causality directly—a failure that can make epidemiological findings superficial and suspect.

Epidemiological studies, like this one, focus on identifying the incidence of factors relating to health. I remember a powerful review of such studies published 18 years ago, which blamed common misleading or downright inaccurate results on failure to take "confounders" into account.2

For instance, if people who ate organic apricots several times a week were found to be less depressed than people who didn’t, how would we know that it was the organic apricots that did the trick and not the amount or type of exercise those people engaged in, how much they enjoyed their jobs, or whether they had a comfortable lifestyle (enabling them to afford the organic apricots in the first place)? These are confounding factors, which can’t be ignored if meaningful results are to be arrived at.

As the review pointed out, it had been widely reported at the time that taking HRT for menopausal symptoms was also protective against heart disease, upping GP prescriptions as a consequence. But it was a mistaken conclusion, caused by researchers omitting to take into account the socioeconomic status of the women they studied. Higher socioeconomic status was (at the time) associated with more frequent use of HRT and also a lower risk of heart disease. HRT itself had nothing to do with it, as another "unconfounded" study later found.2

So could it not be the case that many people who eat a lot of unhealthy snacks do so because they already feel stressed and anxious and then proceed to feel even worse about themselves?

There are other factors that often get omitted in epidemiological studies. UK experts who built the models predicting frighteningly high numbers of deaths from COVID-19 unless stringent protective measures were taken were asked, in testimony before the House of Commons, why they had not considered collateral damage in their models. (As we know now, that might have included the vast mental health impact of isolation and separation from loved ones, delayed treatments for serious conditions, and so on.) They said that it was not their job to do so.3

So next time you read (and you will) that eating extra fruit, using a certain washing powder, doing star jumps, or altering the temperature in your home will help prevent mental ill health, please stay just a little bit sceptical.

Meanwhile, there are simple, proven ways to prevent depression and manage anxiety. So do check those out instead.4

References

1. Tuck, N-J, Farrow, C V and Thomas, J M (2022). Frequency of fruit consumption and savoury snacking predict psychological health; selective mediation via cognitive failures. British Journal of Nutrition, doi: 10.1017/S0007114522001660

2. Pocock, S J et al (2004). Issues in the reporting of epidemiological studies: a survey of recent practice. British Medical Journal, 329, 883–7.

3. As reported and referenced in Desmet, M (2022). The Psychology of Totalitarianism. Chelsea Green Publishing.

4. Griffin, J and Tyrrell, I (2004). How to Lift Depression Fast; Griffin, J and Tyrrell, I (2007). How to Master Anxiety. HG Publishing, East Sussex.

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