Monday, November 12, 2012
Does fruit and vegetable consumption influence mental health?
A study recently published in Social Indicators Research (Blanchflower, Oswald and Stewart-Brown 2012) investigated the relationship between fruit and vegetable consumption and mental health. The study drew upon three robust, representative, cross-sectional studies of random samples of adults in three UK countries; England, Scotland, and Wales. Each of these surveys gathered self-reported intake data, measured in portions of fruit and vegetables of up to eight or more a day. Most surveys stop at the recommended five or more. The study also gathered data on seven different measures of mental health, from mental wellbeing (WEMWBS) through mental illness (GHQ-12), life satisfaction, happiness, nervousness and downheartedness.
Together these surveys captured information from more than 80,000 people, taking account of a wide range of other potential explanatory factors such as age, sex, ethnic group, socioeconomic and educational circumstances; and other lifestyle factors, such as smoking. They show a remarkably monotonic dose-response relationship between mental health and the number of portions of fruit and vegetables consumed. That is, the more fruit and vegetables consumed, the greater the mental wellbeing. In models based on indicators of positive mental health (WEMWBS, Life Satisfaction and Happiness) the corresponding coefficients continued to increase by up to seven or more portions of fruit and vegetables. In models based on mental health problems (GHQ-12, nervousness, feeling downhearted) they increased by up to five or more.
A strong and consistent dose-response relationship, as shown in these studies, acts as evidence that fruit and vegetable consumption is influencing mental health. Yet, the possibility remains that we could just be documenting a simple correlation; people with better mental health tend to look after themselves – by eating more fruit and vegetables – than those with worse mental health.