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IQ in childhood and vegetarianism in adulthood: 1970 British cohort study

BMJ 2007; 334 doi: (Published 01 February 2007) Cite this as: BMJ 2007;334:245
  1. Catharine R Gale, senior research fellow1,
  2. Ian J Deary, professor of differential psychology2,
  3. Ingrid Schoon, professor4,
  4. G David Batty, Wellcome fellow3
  1. 1Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton General Hospital, Southampton SO16 6YD
  2. 2Department of Psychology, University of Edinburgh, Edinburgh
  3. 3Department of Psychology, University of Edinburgh, Edinburgh and Medical Research Council Social, and Public Health Sciences Unit, University of Glasgow, Glasgow
  4. 4Department of Psychology, City University, London
  1. Correspondence to: C Gale crg{at}
  • Accepted 28 October 2006


Objective To examine the relation between IQ in childhood and vegetarianism in adulthood.

Design Prospective cohort study in which IQ was assessed by tests of mental ability at age 10 years and vegetarianism by self-report at age 30 years.

Setting Great Britain.

Participants 8170 men and women aged 30 years participating in the 1970 British cohort study, a national birth cohort.

Main outcome measures Self-reported vegetarianism and type of diet followed.

Results 366 (4.5%) participants said they were vegetarian, although 123 (33.6%) admitted eating fish or chicken. Vegetarians were more likely to be female, to be of higher social class (both in childhood and currently), and to have attained higher academic or vocational qualifications, although these socioeconomic advantages were not reflected in their income. Higher IQ at age 10 years was associated with an increased likelihood of being vegetarian at age 30 (odds ratio for one standard deviation increase in childhood IQ score 1.38, 95% confidence interval 1.24 to 1.53). IQ remained a statistically significant predictor of being vegetarian as an adult after adjustment for social class (both in childhood and currently), academic or vocational qualifications, and sex (1.20, 1.06 to 1.36). Exclusion of those who said they were vegetarian but ate fish or chicken had little effect on the strength of this association.

Conclusion Higher scores for IQ in childhood are associated with an increased likelihood of being a vegetarian as an adult.


  • The 10 year follow-up was carried out by the Department of Child Health, Bristol University. The 30 year follow-up was carried out under the auspices of the Joint Centre for Longitudinal Research (comprising the Centre for Longitudinal Studies, Institute of Education, University of London; the International Centre for Health and Society, University College Medical School, London; and the National Centre for Social Research). We thank the UK Data Archive, University of Essex, for providing the data. The original data creators, depositors, or copyright holders, the funding agencies, and the UK Data Archive bear no responsibility for the analyses and interpretation presented here. GDB is a Wellcome fellow. IJD is the recipient of a Royal Society-Wolfson Research merit award.

  • Contributors: CRG and GDB conceived the idea for the present analyses, which were developed by the coauthors. CRG carried out the data analyses and wrote the first draft of the manuscript to which the coauthors made substantial contributions. IJD advised on the psychometric analyses of the mental ability tests. CRG and GDB are guarantors.

  • Competing interests: CRG and GDB are lapsed vegetarians, IS is a committed vegetarian, and IJD is an omnivore. The IQs of three of the authors have never been tested; IJD opts not to disclose.

  • Ethical approval: Not required.

  • Accepted 28 October 2006
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