Potatoes are often equated with refined grains due to their carbohydrate content. Yet, potatoes contain fiber, resistant starch, and key micronutrients that Americans need more of in their diet. A randomized crossover study that included 50 generally healthy adults directly compared the nutrient quality and impact on cardiometabolic risk factors of non-fried potatoes to refined grains. The study was conducted by researchers at Penn State and was recently published in the British Journal of Nutrition. Its findings demonstrate that potatoes can support a healthy diet; daily intake of one serving of non-fried potato did not affect markers of glycemia and was associated with better diet quality compared to refined grains.
Clinical studies are important to contextualize observational findings. Some epidemiologic studies have suggested an association between potato intake and increased risk of cardiometabolic diseases. However, the context around how potatoes are eaten, such as their preparation method or other foods eaten alongside them, may be important factors in explaining why our clinical trial findings differ from those of observational studies."
Penn State researchers
Participants were randomly assigned to eat either a refined grain side dish (e.g., pasta, rice, white bread) or a steamed/baked potato side dish of equal calories each day with a main meal for four weeks. After a two-week break, the same individuals ate the opposite side dish with a main meal for another four weeks. Aside from being required to consume either a potato or refined grain side dish, no other dietary restrictions were placed on participants. Several markers of cardiometabolic risk were measured including plasma glucose, serum insulin, cholesterol and other blood lipids, blood pressure, and participants' reported diet quality.
While neither refined grains nor potatoes impacted cardiometabolic risk factors, participants' potassium and fiber intake, total vegetable and starchy vegetable intake and Healthy Index Score - a sign of how well people are following the Dietary Guidelines for Americans were higher when they ate potatoes, compared to refined grains.
"Americans eat too many refined carbohydrates and not enough whole grains or starchy vegetables, according to the 2015-2020 Dietary Guidelines for Americans. Our study findings suggest that eating 1 serving of non-fried potatoes in place of refined grains can help individuals meet more dietary recommendations."
The study had several strengths, such as the randomized crossover design and isocaloric dietary substitution. All dishes were prepared in a healthy way with limited added fat or sodium. However, the researchers noted a few limitations: the need for larger sample sizes, a longer intervention time and controlled dietary intake rather than self-reported diets. "It is important to replicate our findings in other groups, such as those at higher risk of cardiometabolic disease. These findings apply to the generally healthy population."
Johnston, E.A., et al. (2020) Daily intake of non-fried potato does not affect markers of glycemia and is associated with better diet quality compared to refined grains: A randomized, crossover study in healthy adults. British Journal of Nutrition. doi.org/10.1017/S0007114520000252.