Conceptualizing " free -from " food consumption determinants: A systematic integrative literature review focused on gluten and lactose

Background: Glutenand lactose-free products are registering a sudden rise in the market, particularly among tolerant people, and this leads to consumer confusion and nutritional inadequacies. The number of studies around this trend has steadily increased in the last 10 years, as scholars from different disciplines have tried to rationalize consumers' behaviours in these foods' choice. However, the scientific debate appears fragmented and lacks an integrated view. Objectives: We conducted a systematic integrative review of consumers' determinants of gluten-free and lactose free consumption to frame the state of the art and research gaps. Methods: 45 English language articles reporting quantitative empirical studies ranging from 1971 and 2019 were analysed. First we categorized the consumption determinants in six factors applying the model proposed by Koster and Mojet, then we proposed a new integrated conceptualization inspired by Bronfenbrenner's Trans theoretical Model. Moreover, differences and similarities between tolerant and intolerant consumers will be highlighted. Results: Research on intolerant consumers focused more on individuals' determinants, in terms of awareness, trust, morality, and capability to read nutritional facts (as purchase facilitators); while studies targeting tolerant consumers focused more on objective product characteristics (with price and availability in supermarkets as barriers for consumption). In this target the subjective perspective has been studied only referring to the risk for developing psychological issues in the restrictive diet. Conclusion: As information is lacking in the scientific debate, we suggest for future research the integration of consumers' subjective implicit levers to decipher free-from purchase behaviours.