Research paperVegetarian diets and depressive symptoms among men
Introduction
Vegetarian diets have been associated with decreased risks of cardiovascular death, obesity and diabetes (Fraser, 2009) prompting questions as to whether potential benefits extend to mental health or, in contrast, whether diminished intakes of nutrients that are abundant in excluded foods cause adverse consequences to mental well-being (Beezhold et al., 2010). A large survey of Australian women in their 20's, found a significant increase in elevated depressive symptoms among vegetarians compared to non-vegetarians (22% v. 15%) (Baines et al., 2007). Among 1046 Australian women, lower red meat consumption was associated with nearly a doubling of risk for major depressive and anxiety disorders (Jacka et al., 2012). Among Norwegian students, nearly twice as many men and one third more women with low meat consumption reported having been depressed, after adjustment (Larsson et al., 2002). In a representative sample, depression was more common among completely and predominantly vegetarian German adults, but adoption of vegetarian diets followed the onset of mental illnesses (Michalak et al., 2012). In Minnesota, adolescent vegetarians were more likely to have eating disorders and to have contemplated and attempted suicide (Perry et al., 2001) and Turkish adolescent vegetarians had higher social and physique anxiety scores (Bas et al., 2005). In contrast, a small survey of Seventh Day Adventist adults found no increased risk of depression or anxiety among vegetarians who excluded fish (Beezhold et al., 2010). Not all diets identified as vegetarian are homogeneous, with some including fish, rich in omega-3 highly unsaturated fatty acids (omega-HUFAs) and some meats and others excluding eggs (a source of omega-3 HUFAs and vitamins) and dairy products. Omega-3 HUFA's, specifically docosahexaenoic acid, are selectively concentrated in synaptic membranes and are essential for optimal neural function (Salem and Niebylski, 1995). Meta-analyses of randomized controlled trials indicate that omega-3 HUFAs are effective in treating significant depressive symptoms (Grosso et al., 2014, Hallahan et al., 2016). Red meats are a rich source of vitamin B12 and data suggest that low levels of vitamin B12 and folate may increase the risk of depression (Stanger et al., 2009) and one meta-analysis suggests that vitamin B12 intervention may prevent depressive symptoms in specialized populations (Almeida et al., 2015). Deficits in zinc and iron have also been postulated as risk factors in depression: a systematic review found evidence of benefits but cautioned that well-designed randomized controlled trials are needed to better evaluate effects of improving iron and zinc status on mood and cognition (Lomagno et al., 2014).
Although there has been considerable attention paid to maternal depression and its effect on child development, studies from ALSPAC have reported associations between paternal depression and adverse effects on the developing child (Ramchandani et al., 2005, Ramchandani et al., 2008). Consequently, recognizing and ameliorating paternal depression is important. We sought to determine whether self-identification of a vegetarian diet was associated with increased risk of depressive symptoms among adult men during the pregnancy of their partners.
Section snippets
Methods
The Avon Longitudinal Study of Parents and Children (ALSPAC) (Fraser et al., 2013, Golding et al., 2001) enrolled women resident in the former geographical area of Avon in south-west England who were in the early stages of pregnancy with an expected date of delivery between 1st April 1991 and 31st December 1992. ALSPAC is an ongoing population based cohort study investigating environmental and other influences on the health and development of children; Please note that the study website
Statistical methods
The depression scores for the EPDS were strongly skewed to the left: 17.5% of the whole sample scored zero. Transformation of the data did not produce a closer approximation to a normal distribution due to these zero values. Hence the EPDS data were analyzed untransformed using both parametric (t-test or ANOVA where appropriate) and non-parametric (Mann-Whitney U test or Kolmogorov-Smirnov test where appropriate) tests for univariable analysis, comparing the differences in mean scores. In
Unadjusted associations
EPDS scores were available from 9668 men who also provided information on their vegetarian status. 350 (3.6%) reported that they were vegetarian/vegan (311 vegetarian and 39 vegan). The length of time that these men reported that they had been vegetarian ranged from < 1 to 41 years, with two-thirds having been vegetarian for < 10 years. Vegetarians had a higher mean depression score compared to non-vegetarians (p < 0.0001 for both t-test and Mann-Whitney), similarly a greater proportion of
Discussion
To our knowledge this is the first large epidemiological study to show a relationship between vegetarianism and significant depressive symptoms among adult men. Here we found that self –identification as a vegetarian was associated with an increased risk of depressive symptoms evaluated both as a continuous scale and using a cut-off of greater than 10 on the EPDS. These associations remained after adjustment for vulnerability factors for depression including a family history of depression,
Role of funding sources
The UK Medical Research Council and the Wellcome Trust (Grant ref 102215/2/13/2) and the University of Bristol currently provide core support. This publication is the work of the authors and Joseph R. Hibbeln, Johnathon Evans, Kate Northstone and Jean Golding will serve as guarantors for the contents of this paper. The Intramural Research Program of the National Institute on Alcohol Abuse and Alcoholism, the Waterloo Foundation and a personal gift from John M. Davis, M.D. provided support for
Acknowledgements
We are extremely grateful to all the mothers and fathers who took part in the study, to the midwives for their help in recruiting them and the whole ALSPAC study team which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists and nurses.
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