Categorising ultra-processed foods in large-scale cohort studies: evidence from the Nurses’ Health Studies, the Health Professionals Follow-up Study, and the Growing Up Today Study

Abstract

This manuscript details the strategy employed for categorising food items based on their processing levels into the four NOVA groups. Semi-quantitative food frequency questionnaires (FFQs) from the Nurses’ Health Studies (NHS) I and II, the Health Professionals Follow-up Study (HPFS) and the Growing Up Today Studies (GUTS) I and II cohorts were used. The four-stage approach included: (i) the creation of a complete food list from the FFQs; (ii) assignment of food items to a NOVA group by three researchers; (iii) checking for consensus in categorisation and shortlisting discordant food items; (iv) discussions with experts and use of additional resources (research dieticians, cohort-specific documents, online grocery store scans) to guide the final categorisation of the short-listed items. At stage 1, 205 and 315 food items were compiled from the NHS and HPFS, and the GUTS FFQs, respectively. Over 70 % of food items from all cohorts were assigned to a NOVA group after stage 2. The remainder were shortlisted for further discussion (stage 3). After two rounds of reviews at stage 4, 95⋅6 % of food items (NHS + HPFS) and 90⋅7 % items (GUTS) were categorised. The remaining products were assigned to a non-ultra-processed food group (primary categorisation) and flagged for sensitivity analyses at which point they would be categorised as ultra-processed. Of all items in the food lists, 36⋅1 % in the NHS and HPFS cohorts and 43⋅5 % in the GUTS cohorts were identified as ultra-processed. Future work is needed to validate this approach. Documentation and discussions of alternative approaches for categorisation are encouraged.

Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studies

“…For example, nine food items lacked sufficient details in the resource documents to support their classification. 27 We have adopted a more conservative approach assuming a lower level of processing in the primary analyses. Our sensitivity analyses using alternative classification did not materially alter the results.…”

“…Three researchers (NK, SLR, EMS) worked independently to assign each food item to a NOVA group. 27 28 The three researchers reached a consensus on more 70% of all food items at the first attempt of the classification. When discordance existed in classifying a food item, we used discussions with an expert group and additional resources (research dieticians, cohort specific documents, online grocery store scans) to guide the final categorization.…”

Joint association of food nutritional profile by Nutri-Score front-of-pack label and ultra-processed food intake with mortality: Moli-sani prospective cohort study

“… 55 56 57 Moreover, imprecision in the identification of ultra-processed foods may also pertain to 24 hour diet recalls or diet records. 53 Finally, evidence suggests that classification of ultra-processed foods with an FFQ may be valid for the purpose of qualitative comparisons, although less appropriate in absolute intake estimations. 54 However, we expect misclassification to be non-systematic, and this would likely lead to non-differential measurement error possibly resulting in an underestimation of the studied associations.…”

Are dietary patterns becoming more processed? The effects of different dietary patterns on cognition: A review

“…It is well established that the high intake of fresh fruit and vegetable, wholegrains, and fish is positively associated with cognitive function (Loughrey et al, 2017; Opie et al, 2013; McEvoy et al, 2017; Tangney, 2014); however, relatively few studies (Gardener et al, 2015; Parrott et al, 2013) have investigated the combination of whole dietary patterns and UPF in combination. Recently, several studies have started to develop and use food frequency questionnaires and classification methods specifically designed to evaluate UPF (Oviedo-Solis et al, 2022; Martinez-Perez et al, 2022; Khandpur et al, 2021). While these methods are being used within existing large epidemiological studies, new longitudinal studies are needed that aim to understand the associations between UPF and cognitive function.…”