For decades, people have often associated higher intakes of carbohydrate-containing foods with less healthy lifestyles. Yet, evidence suggests this perspective view is overly simplistic, and it is instead the type and quality of carbohydrate foods (CF) that matter most for supporting health. While some measures of carbohydrate quality exist, such methods often use highly variable – and thus unreliable – indicators. In a newly published perspective in Nutrients, a group of nutrition researchers, who collectively make up the Quality Carbohydrate Coalition-Scientific Advisory Council (QCC-SAC), outline the opportunity for a stronger, more evidence-based approach to defining quality CF to support overall health and provide clearer dietary guidance.
To better guide food choices and nutrition literacy, the dialogue around high-quality carbohydrate foods must be advanced to consider the evolving science. As a first step, we conducted a scoping review of the scientific literature to examine the evidence behind existing measures of carbohydrate food quality and ways in which to build upon this work."
Adam Drewnowski, PhD, University of Washington, a QCC-SAC member
The QCC-SAC is a team of six world-renowned experts in carbohydrate research, nutrient profiling, cultural competency and epidemiology. The group was assembled by the Quality Carbohydrate Coalition, which was spearheaded and is funded by Potatoes USA. The Coalition's ambition is to assess and advance evidence to explore the role of CF in health. Collectively, the QCC-SAC members agree that, based on the evidence, carbohydrate guidance must move away from individual and unique biological interactions with foods, and towards recommendations based on intrinsic qualities of a food (i.e., nutrient- and food-based indicators). This includes shifting away from the decades-old focus on glycemic index (GI) when discussing high- versus low-quality CF.
QCC-SAC consensus: GI is a flawed (and misused) approach to defining CF quality
"GI is frequently used as a metric for carbohydrate food quality – but it is an outdated and flawed indicator with too much variability," says Julie Miller Jones, PhD, LN, CNS, St. Catherine University (Emeritus), a member of the QCC-SAC. "In fact, GI was created as a research tool for use in the laboratory and was never intended to be used by the general population. Instead, we require a measure that reflects both a carbohydrate food's contributions to fiber, nutrient and phytochemical intake, as well as its role in a healthy diet. An omnibus measure of carbohydrate food quality indicators that is accurate and applicable to real-life eating patterns is needed."
Specifically, research demonstrates that GI varies considerably based on different contexts, such as eating situations (e.g., mixed meals), and based on individual characteristics (e.g., biological and behavioral factors like age, weight, physical activity and gut microbiome).
"A new review analyzing GI values found the variability with rice can fluctuate so significantly that it can be considered both a low GI and high GI food," shares QCC-SAC member Siddhartha Angadi, PhD, University of Virginia. "Further, even the GI of bread can vary up to five-fold between individuals. These large inter-individual variations make the utilization of GI as a marker of carbohydrate food quality problematic."
Despite its historic use to guide CF choices among consumers with type 2 diabetes, GI is not a consistent predicator of health. A 2019 series of systematic reviews and meta-analyses rated the evidence regarding the long-term effects of GI on health outcomes, such as cardiovascular disease, type 2 diabetes and colorectal and breast cancer, as "low or very low."
"These findings support the need for a new, holistic approach to replace the overreliance on GI as a single evaluator of carbohydrate quality," states Yanni Papanikolaou, MPH, Nutritional Strategies, Inc., a QCC-SAC member.
A new, inclusive approach to defining high-quality CF
The QCC-SAC will develop a series of papers for peer-reviewed publication that will introduce a new, validated approach for measuring CF quality, and will demonstrate how the approach can be integrated into dietary guidance tools to help people of all ages, ethnicities and cultural preferences improve their food choices. The approach will involve developing a composite measure that harmonizes multiple intrinsic CF quality indicators from the scientific literature into an easy-to-use tool.
"Compared to existing metrics, this tool will be unique, evidence-based and practical," notes QCC-SAC member Judith Rodriguez, PhD, RD, University of North Florida. "It will reflect how people actually eat (e.g., mixed meals) and will recognize cultural patterns and traditions – a novel approach that is often underrepresented in similar dietary guidance tools."
The QCC-SAC plans to release more details on their harmonized composite approach to assess CF quality in the coming year.
The Quality Carbohydrate Coalition is a multi-stakeholder engagement of eight organizations across the food industry. Guided by the work of its Scientific Advisory Council, this group aims to support a collaborative, scientific dialogue around the unique and diverse roles that carbohydrate foods play in healthful eating.
The Quality Carbohydrate Coalition-Scientific Advisory Council (QCC-SAC) is a group of six world-renowned experts in carbohydrate research, nutrient profiling, cultural competency and epidemiology. The aim of the QCC-SAC is to determine evidence-based approaches for defining and selecting quality carbohydrate foods. Members of the QCC-SAC include Adam Drewnowski, PhD; Julie Miller Jones, PhD, LN, CNS; Judith Rodriguez, PhD, RD; Joanne Slavin, PhD, RD; Siddhartha Angadi, PhD; and Yanni Papanikolaou, MPH.
Comerford, K.B., et al. (2021) Toward an Evidence-Based Definition and Classification of Carbohydrate Food Quality: An Expert Panel Report. Nutrients. doi.org/10.3390/nu13082667.