There can be no disputing the connection between diet and physical health, and there’s evidence that what we eat can affect our mental health, too. But what might be the implications of the opposite proposition: that our mental and physical health together influence what we choose to eat?

Dr Cliff Roberts from the Institute of Psychiatry, King’s College London, and, before him, Martin Cartwright and colleagues from the Cancer Research UK Health Behaviour Unit at University College London, have investigated the influences of a particular state of mind and body – stress – on the diet of two different groups.

Roberts’s longitudinal study focused on the food choice, mood and body weight of 38 healthy women in their early forties. His investigations also included a food frequency questionnaire to assess the types of foods being consumed.

He found that participants with higher body-mass-index (BMI) scores secreted significantly more of the hormone cortisol in situations of perceived stress. The same combination of factors also tended to mean that those participants gained bodyweight during such episodes; the lower BMI and cortisol group tended to lose weight.

Roberts’s team also found that those with high levels of cortisol ate more energy-dense and sweet foods (and much less meat fish and vegetables) under perceived stress than those with low-level cortisol. There appeared to be a relationship between perceived stress and food choice, but none was found to connect food choice and mood (anxiety and depression).

The King’s College study was limited by the smallness of the sample; less so the earlier work by Martin Cartwright and colleagues which studied the influence of perceived stress on 4,320 children between the ages of 11 and 16. Participants were asked to complete a questionnaire that dealt with perceived stress, frequency of fatty food intake, snacking, breakfast and fruit and vegetable consumption. The height and weight of each participant were also recorded to estimate BMI.

The University College researchers found that higher perceived stress levels were related to a significantly increased likelihood of eating more fatty food, more snacking, lower intake of fruit and vegetables and a smaller likelihood of eating breakfast.

Despite the differences between the two studies, (the Cartwright study included a mix of gender, socio-economic status and ethnicity) both pointed to an association between stress and eating more fatty foods and less fruit and vegetables.

All tends to suggest there may be a reciprocal connection between mental health and diet and highlights the difficulty of knowing where to begin when trying to prevent this interplay from degenerating or attempting to treat it if it becomes problematic.

There begins to be an argument for tackling the degree of stress in children and young people’s lives, similarly for improving the mental health of children who are overweight or for introducing an evidence-based dietary component to mental health services.

But the causal relationship is not yet well enough understood to be able to say that reducing the amount of perceived stress an individual experiences will bring about an increase in the amount of fruits and vegetables they eat – or that somehow lowering stress levels is a remedy for obesity in the broader population.

The case for further research from this relatively new angle is strong, nevertheless.

• See also: There is such a thing as a free lunch – incredible!

References
Roberts, C. (2008) “The effects of stress on food choice, mood and body weight in healthy women.” Nutrition Bulletin 33(1), March 2008, pp33-39
Cartwright, M., Wardle, J., Steggles, N., Simon, A., Croker, H. and Jarvis, M. “Stress and dietary practices in adolescents”. Health Psychology, 22 (4), July 2003, pp362-369

• first published in Prevention Action on April 4th 2008