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

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.