Carbohydrates are a diverse group of compounds, ranging from simple monosaccharides – such as glucose and fructose – to various types of polysaccharides, like starch and dietary fiber. And, the foods that contain them are even more diverse – from highly nutrient-dense and health-promoting, to energy-dense and potentially detrimental to human health. Despite this diversity, the role that carbohydrates play in human health and nutrition is often overly reduced to a source of calories, frequently assumed to have the same function in the body and the same impact on health – and without consideration of other important determinants of health like food access, cost and cultural acceptance.
The Alliance for Potato Research and Education interviewed a select group of carbohydrate experts to better understand how the carbohydrate debate got to where it is today, and what the research community and health professionals can do to provide clarity and enhance understanding of the nutritional role carbohydrates play in our diet.
Nuanced carbohydrate guidance is needed
According to Jamie Baum, PhD, a nutrition scientist from the University of Arkansas, “There is a wide knowledge gap between what nutritional scientists understand about carbohydrates, and what consumers believe about carbohydrates. There is a need to educate consumers about nutrient-dense carbohydrate foods that contain high amounts of fiber, vitamins and minerals, and food sources that contain a lot of added sugar and refined carbohydrates with little-to-no additional nutrients.”
Part of this knowledge gap stems from a lack of nuance in current carbohydrate guidance. While the Dietary Guidelines for Americans recommends people consume nearly two-thirds of calories from carbohydrates, with some advice around fiber and added sugar specifically, in general, the advice is simplistic. The research and public health communities have more nuanced recommendations for the other macronutrients (protein, fat), usually including specific guidance on the subtype of macronutrient (i.e., unsaturated vs. saturated fat, complete vs. incomplete protein) and the food sources of these macronutrients (i.e., plants, animals). Such detailed advice does not yet exist for carbohydrate-containing foods.
Dr. Baum suggests we think of carbohydrate quality in a similar way to how we think about protein – in terms of the nutritional value. Indeed, nutrition is a foundational pillar for any definition that identifies quality sources of carbohydrates, but other non-nutritive social determinants of food decisions and health should also be considered as well.
Current carbohydrate indicators need to be reexamined
Several different sources of data and contextualizing factors are required to understand carbohydrate’s role in the diet and provide dietary guidance. The current scientific dialogue focuses on just a few and, some would argue, flawed sources and indicators of carbohydrate quality. In fact, a recently published article outlines at least 20 factors that should be taken into consideration when defining carbohydrate quality, including the nutritional value of the food in question, the biological and metabolic changes it promotes, and the cost and accessibility of the food. Brooke Devlin, PhD, the clinical research officer at the Australian Catholic University in Australia, emphasized that she doesn’t “[think] there is necessarily one metric that is most meaningful in defining carbohydrate quality. We need to take into consideration several factors.”
However, carbohydrate dietary guidance often relies on a single metric, the measurement of a food’s Glycemic Index – which does not consider the multitude of ways a carbohydrate-containing food can impact health. Nick Bellissimo, PhD, a nutrition scientist at Ryerson University, questions the over-reliance on GI, a measurement of how one food consumed in isolation impacts glycemic changes in the hours following consumption of that food, to develop food-based guidance. “The field must move beyond a GI-based approach for judging carbohydrate quality,” suggests Dr. Bellissimo. Instead, he proposes we take a different approach. “Food and function studies (e.g., satiety, cognition, performance) are needed that investigate carbohydrates first in isolation, secondly within mixed meals, and then followed by studies investigating a dietary pattern
s approach on functional markers of interest.” See more detail on the limitations of GI here.
The current dialogue has created confusion about carbohydrate sources, like the potato
As one example, Dr. Devlin notes that potatoes are often the victim of reductionist carbohydrate guidance. “Despite being a vegetable, potatoes are sometimes associated negatively with carbohydrates.” Dr. Baum agrees, suggesting that the nutritional value of white potatoes is misunderstood, as is the myriad of ways that potatoes can be prepared and consumed. The white potato is a nutrient-rich vegetable, an excellent source of vitamin C and a good source of potassium. It is also a high-quality source of carbohydrates, like resistant starch, as well as a source of high-quality protein, on par with many animal proteins. While white potatoes have a reputation for negatively impacting glycemic response, Dr. Bellissimo explains that “recent experimental trials show benefits of consuming potatoes on many functional outcomes that are uncoupled from their glycemic response; and glycemic response to various forms of potatoes has been shown to be low-to-moderate in both young and elderly adults.”
Where do we go from here?
So how do we ensure that consumers know which carbohydrate-containing foods are the most nutritious and the highest quality? Adding more nuance to carbohydrate guidance while needed, is a big undertaking, requiring multi-stakeholder input and support. More importantly, it must be led by a multicultural diverse group of researchers who are experts in nutrition, carbohydrates and diverse populations so that realistic and relevant guidance is developed.