What makes a plant-based diet? a review of current concepts and proposal for a standardized plant-based dietary intervention checklist

Abstract

Within the last decades, plant-based diets have received increasing interest for their potential benefits to human and environmental health. The concept of plant-based diet, however, varies widely in its definition. Current definitions range from the exclusion of all animal products to diets that include meat, fish, and dairy in varying quantities. Therefore, the main objectives of this review were twofold: (a) to investigate how researchers use the term plant-based diet in nutrition intervention studies and (b) what types of food a plant-based diet may include. Searching two databases, we found that the term "plant-based diet" evokes varying ideas to researchers and clinicians. Fifty percent of the retrieved studies that included a plant-based dietary intervention completely proscribed animal products and used the term plant-based diet interchangeably with a vegan diet. In contrast, an ~33% of trials included dairy products and 20% of dietary interventions emphasized a semi-vegetarian dietary pattern. Based on specific examples, we point out how the usage of the umbrella term "plant-based diet" may cause significant ambiguity. We often encountered incomplete descriptions of plant-based dietary interventions, which makes comparison and reproducibility of studies difficult. As a consequence, we urge others to use the term "plant-based diet" only in conjunction with a detailed dietary description. To facilitate this process, we provide a template of a standardized plant-based intervention reporting checklist. Finally, the present review also highlights the urgent need for a consensus definition of the term plant-based diet and its content.

Fig. 1. The spectrum of diets including none or only certain types of animal-based products.

From right to left: vegan diet (excluding all flesh foods and animal products), lacto-ovo-vegetarian diet (excluding meat, fish, or poultry but including eggs and dairy), pesco-vegetarian diet (excluding meat or poultry but including fish) and omnivorous diet (containing all food groups) [56]. Modified from Medawar et al. [4].

Fig. 2. PRISMA 2009 Flow Diagram.

The PRISMA flow diagram for the present review detailing the number of identified records, the number of records screened and the full texts retrieved.

Fig. 3. Assignment of the intervention diets to one of five pre-defined dietary groups (including a vegan diet, a lacto-ovo-vegetarian diet, a pesco-vegetarian diet or a semi-vegetarian diet).

Based on missing or inconclusive data, assignment was not possible in few cases.

Fig. 4

Template: the plant-based dietary intervention reporting checklist.