A total of 8,179 men and women participated in the study, who were involved in the 1970 British Cohort Study (born between 5 and 11 April 1970).
The odds ratio for one standard deviation increase in childhood IQ score 1.38, 95 per cent.
Their IQs were tested at the age of 10, and the researchers from Southhampton University in the UK found that those with a higher IQ - of as many as five points - had a greater chance of being vegetarian by the age of 30.
In total, 366 (4.5 per cent) of the participants self-reported being vegetarian at the age of 30 - but 122 of these admitted that they eat fish or chicken.
According to the UK's Vegetarian Society, fish and/or chicken-eating precludes a person from being considered a vegetarian.
Although vegetarians were more likely to be female, and to have higher academic or vocational qualifications, these advantages were not reflected in their income. Moreover, IQ remained a statistically significant predictor of vegetarianism as an adult even after adjustment for social class.
Interestingly, the association between IQ and vegetarianism remained just as strong when the fish- and/or chicken-eaters were excluded.
Since the vegetarian diet has been linked to a lower incidence of heart disease, lead researchers Catharine Gale speculated that this could help explain the link between higher IQ in childhood or adolescence and a reduced risk of coronary heart disease as an adult. Source: BMJ Early online edition Doi: doi 10.1136/bmj.39030.675069.55 " IQ in childhood and vegetarianism in adulthood: 1970 British cohort study" Authors: Catharine R Gale, Ian J Deary, Ingrid Schoon, G David Batty