There has been a lot about mental health in the news lately, so I was interested to see this new study suggesting there might be a link between higher sugar intake and depression, at least in men.
UK adults consume approximately double the recommended level of added sugar, with sweet foods and drinks contributing ~3/4 of the intake (in the USA, adults consume around three times the recommended amount). A number of studies have found that higher sugar consumption (particularly added sugars, soft drinks, juices and pastries) is linked with higher rates of depression. However, many of these studies have not been able to account for the possibility that having a mood disorder may actually lead to a higher sugar intake, so that the diet-mental health association is the result of poor mental health rather than of the high sugar intake.
In this paper, published in the journal Scientific Reports, researchers working at University College, London used data from the ‘Whitehall II study’ which recruited >10,000 non-industrial civil servants aged 35-55 in London during 1985–1988. This longitudinal study had repeated measures of food intake and mental health over a number of years, allowing the researchers to investigate the effect of sugar dense diets on mental health.
They found that men with the highest sugar intake from sweet food and drinks had an increased risk of common mental health disorders and this was independent of health behaviours, sociodemographic and diet-related factors, fatness and other diseases. There were no definite associations in women, but this may have been due to that fact that there were fewer women than men in the study. Importantly, having a mental health disorder did not result in an increased intake of sugar. The authors of the study suggest that their research confirms an adverse effect of sugar intake from sweet food and/or drinks on psychological health. This is important, since mental health disorders are predicted to become a leading cause of disability in high-income countries in the near future.
As with many of these sorts of studies, there are a number of potential problems: the use of questionnaires to measure food intake can be problematic since the rates of misreporting and under-reporting of intake can be affected by mood and body mass index. There may also be factors which influence both food intake and mental health which the study did not account for. Finally, a number of people did not complete the entire study, meaning that there are missing data which could affect the results. Repeating this sort of analysis in other large population studies is necessary to show how robust these findings are.
Although studies such as this one do not tell us anything about how increased sugar intake might lead to mental health disorders, they do provide important evidence that reducing sugar intake could have benefits for our mental as well as physical health.
Pictures by Jeremy Perkins, Harman Abiwardani and Kosal Ley on Unsplash