Social networks' role in vegetarian diet adoption and maintenance: A prospective study from the northern Netherlands

Wider adoption and maintenance of vegetarian diets would be mutually beneficial for human and environmental health. Social networks have been identified as a factor that would support this transition. While social networks' role in vegetarian diet adoption has been studied, their role in vegetarian diet maintenance over time has received much less attention. To address this gap, we investigated the extent to which having vegetarian close ties (family members and/or partners) was related to participants' likelihood of eating vegetarian. Data were derived from Lifelines, a large cohort study from the northern Netherlands (n = 60,639). Two assessments an average of 3.9 years apart were used. We studied the interaction of close ties' diet trajectories (either vegetarian or omnivore) at baseline and follow-up, and their relationship to participants' own diet trajectories at baseline and follow-up. Mixed multinomial logistic regression was used to account for clustering among families. Participants closely mirrored their close ties' diet trajectories. Having close ties who were vegetarians at baseline and follow-up was associated with the highest probability of the participants themselves also eating vegetarian at both assessments (Pr = 0.08, 95 % CI: 0.07-0.08). In contrast, participants with no vegetarian close ties at baseline and follow-up were the least likely to be vegetarians themselves at both assessments (Pr = 0.02, 95 % CI: 0.02-0.02). Partners particularly had a strong influence on participants' diet trajectories compared to other family members. It appears that the closer the tie was, the more closely diet trajectories paralleled each another. More broadly, leveraging social networks could be effective in encouraging more widespread adoption and maintenance of vegetarian diets.