Why potatoes and grains can’t replace each other in a healthy diet

By Priyanjana Pramanik, MSc.Reviewed by Lauren HardakerDec 1 2025

Researchers have shown that white potatoes provide crucial nutrients that Americans lack, yet swapping them for grains triggers significant losses in iron, folate, and other essential nutrients, reshaping our understanding of “healthy carbs.”

Study: Assessment of the unique nutrient contribution of white potatoes in the diet and the nutrient implications of replacing Refined and Whole Grains with Starchy Vegetables. Image credit: Lerner Vadim/Shutterstock.com

In a recent study published in Frontiers in Nutrition, researchers investigated the contribution of starchy vegetables such as white potatoes to nutrient intake in the United States, particularly when compared to whole and refined grains.

White potatoes provide substantial potassium, fiber, and several vitamins, and starchy vegetables supply far more potassium and vitamin C than grains. However, replacing grains with starchy vegetables lowers intakes of iron, folate, calcium, and several B vitamins.

Why potatoes matter in Americans’ nutrient intake

Potatoes are naturally nutrient-rich, supplying complex carbohydrates, potassium, fiber, protein, and key vitamins such as B6 and C. A medium potato contributes meaningful amounts of fiber and potassium, two nutrients many Americans underconsume.

Despite their nutrient density and popularity, both total vegetable and starchy vegetable consumption remain below recommended levels, even though potatoes have been associated with better overall diet quality and show no harm in relation to chronic disease risk in observational and clinical research.

Recently, the Dietary Guidelines Advisory Committee (DGAC) reevaluated the roles of vegetables and “staple carbohydrate foods,” including whether grains and starchy vegetables could be considered interchangeable.

The proposed pattern ultimately reduced starchy vegetable recommendations to expand servings of legumes. However, lowering intake of a widely consumed, nutrient-dense, and already underconsumed subgroup may negatively affect nutrient adequacy.

Modeling diets to compare grains and potatoes

This study modeled the nutritional comparison of white potatoes and other starchy vegetables with refined and whole grains, and examined how dietary patterns would shift if these foods were substituted.

Researchers focused on women aged 19 to 30 and men aged 51 and above to reflect the 2,000-calorie Healthy U.S.-Style (HUSS) Dietary Pattern, using DGAC modeling methods and United States Department of Agriculture (USDA) datasets.

Their objectives were to determine how grains and starchy vegetables contribute to nutrient intake relative to HUSS recommendations. They also compared the nutrient profiles of whole grains, refined grains, white potatoes, and other starchy vegetables. Finally, they assessed how nutrient intake changes when grain intake is reduced and starchy vegetable intake is increased, including scenarios where both grain subgroups are reduced simultaneously.

Nutrient values for the representative were weighted by the proportion each food contributes to its subgroup, and cup or ounce equivalents were converted to grams. For white potatoes and other starchy vegetables, subgroup percentages were recalculated to reflect their internal composition.

Nutrient contributions to both recommended and current dietary patterns were estimated by combining subgroup nutrient content with consumption-weighted nutrition profiles. Replacement scenarios simulated stepwise reductions in grains and increases in starchy vegetables to assess the impact of these shifts on the percentage of nutrient recommendations achieved.

Potatoes raise key nutrients but reduce others

Recommended daily servings of white potatoes supplied notable proportions of key nutrients: 11 % of daily potassium, around 10 % of vitamin B6 and copper, and at least 5 % of fiber, magnesium, vitamin C, thiamin, and niacin, all while contributing only 5 % of daily calories.

Potassium content in white potatoes was substantially higher than in whole grains and more than triple that of refined grains. However, whole grains provided far more fiber than starchy vegetables.

Current intake patterns showed overconsumption of refined grains and underconsumption of whole grains and white potatoes, while intake of other starchy vegetables nearly met recommendations.

Comparing nutrient profiles revealed that a one-cup equivalent of starchy vegetables or potatoes delivered vastly more potassium and vitamin C than a two-ounce equivalent of grains but provided lower amounts of minerals such as calcium, iron, zinc, and several B vitamins.

Replacement modeling revealed that substituting refined grains with starchy vegetables increased potassium, fiber, vitamins B6 and C, and choline, but decreased iron, folate, selenium, riboflavin, and vitamin D.

Replacing whole grains produced larger declines in fiber, calcium, iron, magnesium, zinc, and key vitamins. When both grain subgroups were replaced simultaneously, choline increased. Still, most micronutrient levels declined further, highlighting that grains and starchy vegetables provide distinct nutrient packages and are therefore not nutritionally interchangeable.

Potatoes help fill gaps but can’t replace grains

This analysis shows that white potatoes meaningfully contribute nutrients many Americans lack, including several vitamins, fiber, and potassium. Modeling results consistently indicate that starchy vegetables and grains offer different nutrient profiles and cannot be substituted for one another without trade-offs.

Replacing grains with starchy vegetables increases potassium, vitamin C, and choline, but reduces iron, folate, riboflavin, and other micronutrients typically found in enriched or fortified grains.

The findings also highlight the potential implications of reducing starchy vegetable recommendations, particularly given the widespread potassium shortages and evidence that potatoes are a leading, affordable source of this nutrient. While the study does not directly evaluate DGAC decision-making, its results suggest that decreases in starchy vegetable targets could affect nutrient adequacy.

Strengths include alignment with DGAC modeling methods and clear estimation of both recommended and actual potato intake. Limitations come from the theoretical nature of modeling and the likelihood that some substitution scenarios are unrealistic for consumers.

Overall, the study concludes that reducing recommendations for starchy vegetables may compromise nutrient adequacy, particularly potassium, and that both grains and starchy vegetables remain essential yet non-interchangeable components of a healthy diet.

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