Carbohydrates have traditionally been the largest source of energy intake for much of the world's population1. However, without a standard definition for carbohydrate quality, some foods that contain carbohydrates are often stigmatized based on isolated and reductionist assessment methods that fail to consider their contributions to nutrient intakes and balanced, healthy diets. A new perspective piece, published in Advances in Nutrition, brings to light the pressing need to define carbohydrate quality, to better assess the value of nutrient-dense carbohydrate-containing foods in healthy lifestyles. Ultimately, the authors call for a more holistic approach to carbohydrate guidance to address the complex needs of both people and the planet.
"To date, terms like 'good carbs' and 'bad carbs' have been inconsistently assigned to a plethora of foods based on overly simplistic and narrowly focused measures, like glycemic index (GI) or fiber content," states Rebekah Schulz of University of Minnesota and perspective piece coauthor. "While these aspects can be individual pieces of the puzzle, they don't reflect the full picture of carbohydrate quality. For example, while GI may be a useful index in isolation, it is not representative of real-life dietary intake when carbohydrates are consumed with other foods, nor does it account for a food's overall nutrient content or planetary impact."
This paper addresses the strengths and weaknesses of current methods used to assess carbohydrate quality, proposes additional indices to include in a standardized quality carbohydrate definition, and defines research questions for further exploration. Within the perspective piece, authors analyzed various existing frameworks for carbohydrate quality and weighed the pros and cons of indexing based solely on measures such as GI, whole grain foods, fiber and added sugar.
The authors concluded that, "for truly relevant and applicable dietary guidance, the framework should focus on nutrient contributions and take into account various ways to measure and analyze nutrients, as well as be nimble to adjust for new research findings and data."
Carbohydrate Quality: Spotlight on Fruits & Vegetables
The authors also note that current approaches to assessing carbohydrate quality may lead to even greater consumer confusion of nutritional recommendations for specific foods, including fruits and vegetables. Given that one in 10 Americans fall short of meeting their fruit and vegetable requirements2, it's important that a holistic and standardized approach to dietary carbohydrate guidance is established to promote both human and planetary health as effectively as possible.
"Potatoes are one example of a food that tends to be misclassified or misunderstood based significantly on their GI value - even though preparation techniques and common consumption methods are not reflected accurately within a GI value," points out Joanne Slavin, PhD, RD of University of Minnesota and perspective piece coauthor. "Potatoes are a nutrient-dense vegetable that provide several important nutrients - like fiber, potassium, Vitamin C and resistant starch - to Americans' diets and have been consumed for centuries as a main staple in various cultures. Additionally, potatoes serve an important role in food security in developing countries."
A Forward-Looking Solution: Establishing a Standardized Carbohydrate Quality Metric
Overall, there is a general shift away from one-directional and overly simplified dietary guidance, as any food or nutrient can have a place as part of a healthy lifestyle. Thus, to best define high quality carbohydrates, the authors call for a standardized carbohydrate quality metric, such as an algorithm that encompasses a broader spectrum of factors.
"There is a need to provide easy tools grounded in strong science," added Schulz. "When consumers need to make a quick choice about carbohydrate-containing foods, they should feel comfortable knowing that there is a comprehensive, science-backed formula or algorithm behind-the-scenes helping guide this decision."
The authors propose several potential quality indices to be considered when assessing carbohydrate quality:
- Whole-grain, fiber, and added-sugar content
- Ratios of total carbohydrate to fiber and added sugar to fiber in a food
- Protein quality
- Degree of processing
- Environmental impact of a food
"As dietary guidance rightly moves away from isolated nutrient recommendations toward broader and more flexible dietary patterns, it's clear we need to better define the quality underpinnings of these patterns, including carbohydrates," notes Slavin. "By establishing an algorithm to assess carbohydrate quality, the result would positively impact both health and environmental outcomes and create consistent ways to measure intake across populations."
The perspective piece, "Perspective: Defining Carbohydrate Quality for Human Health and Environmental Sustainability," is published in Advances in Nutrition (https://doi.org/10.1093/advances/nmab050). Authors include Rebekah Schulz and Joanne Slavin, PhD, RD, University of Minnesota. The authors reported no funding received for this work. Joanne Slavin has received prior funding from Potatoes USA.
1 FAO. FAOSTAT. Available from: http://www.fao.org/faostat/en/#data/QC
2 Lee-Kwan SH, Moore LV, Blanck HM, Harris DM, Galuska D. Disparities in State-Specific Adult Fruit and Vegetable Consumption -- United States, 2015. MMWR Morb Mortal Wkly Rep 2017;66:1241-1247. DOI: http://dx.doi.org/10.15585/mmwr.mm6645a1 external icon
Advances in Nutrition