Plant-based diet diversity: Experts stress need for uniform assessment tools

Researchers are calling for stronger definitions and standardized assessment tools for plant-based food diversity to better guide public health. Experts recommend the tools build upon a growing body of research that supports better health outcomes from diets cutting down on animal protein. However, inconsistent definitions, lack of validated tools, and methodological differences hinder progress.

In the “first review of its kind,” the researchers analyzed 43 observational studies that found associations between plant-based food diversity and specific health outcomes, which needed further investigation in future randomized controlled trials.

The studies focused on high-income countries and used varied measurement methods to define categories of fruit and vegetables. 

Measuring diversity and food groups

According to the research, sales of plant-based foods increased 60% from 2017 to 2020. These included fruits, vegetables, grains, legumes, nuts, seeds, and plant-based fats.

Previous research has also linked these foods to lower mortality, reduced cancer and cardiovascular disease risk, and a dose-response health benefit. 

However, the review authors found limited evidence available on plant-based food diversity, positing that the associated health effects may be attributed to several factors. Their study aimed to identify and characterize methods used to measure these correlations.

Researchers flag that most studies included a limited selection of plant-based food groups when defining plant-based food diversity, mainly fruits and vegetables, with some grains.“First, there is a lack of a standardized definition of plant-based foods, as well as of diversity of plant-based food consumption, and characterization of the specific foods and food groups included/excluded in this definition,” reads the paper. 

“Second, there is a lack of a standardized and validated methodology of measuring plant-based food intake and diversity, primarily in the assessment tools and analyses used.”

How studies shape public health messaging 

Based on the review published in Nutrition Reviews, most studies included a limited selection of plant-based food groups when defining plant-based food diversity. The analysis focused mainly on fruits and vegetables, with some grains.

“This is likely a result of the emphasis of public health messaging on the importance of consuming a sufficient quantity of fruits and vegetables for health in recent decades,” explains the paper. 

For the best evaluation, the researchers advise specifying plant-based food items and subgroups, as this guarantees thorough documentation of all plant-based foods consumed and makes comparing diets easier.“Plant-based food groups frequently omitted from definitions included legumes, herbs and spices, nuts and seeds, plant-based fats and oils (e.g., olive oil), and plant-based beverages (e.g., tea and coffee), all of which have well-documented benefits for human health that are often unique to a particular plant-based group.”

The authors point out that a meta-analysis revealed that fiber from whole grains is linked to lower colon cancer, but fiber from fruit and vegetables does not offer the same level of protection.

“In contrast, another study showed that fiber from cereals and fruits provided greater protection from the development of diverticular disease than fiber from vegetables, suggesting that the health benefit associated with a food may depend on the specific form of a nutrient within that food, in this case the specific type of fiber,” the paper continues.

“This reinforces the importance of exploring the biological benefits of a diverse intake of all plant-based foods to maximize health outcomes.”

For the best evaluation, the researchers advise specifying plant-based food items and subgroups, as this guarantees thorough documentation of all plant-based foods consumed and makes comparing diets easier.

Nutrition Insight recently spoke to the FAO and UNICEF about the UN’s newly adopted indicator to measure minimum dietary diversity. This indicator is part of the UN’s framework to reach Sustainable Development Goal 2 — end hunger, achieve food security, and improve nutrition and sustainable agriculture.