Context

Potatoes are commonly consumed in the USA and European countries. In the USA, it accounts for ∼21% of all vegetable consumption.1 Potatoes are considered as a healthy vegetable in the National Guideline of Healthy Eating established by the Department of Agriculture2 and as an eligible vegetable by the Special Supplemental Nutrition Programme for women, infants and children by the Institute of Medicine.3 The health effects of potatoes on cardiometabolic health, however, remain inconclusive, because potatoes are high in both high glycaemic carbohydrate and potassium. To address the critical data gap, the present study by Muraki et al aimed to comprehensively and prospectively investigate the association between potato consumption and incident risk of type 2 diabetes (T2DM).

Findings

Higher potato consumption was significantly associated with increased T2DM risk. The pooled HR (95% CI) for every 3 vs <1 serving/week was 1.04 (1.01 to 1.08) for baked, boiled or mashed potatoes and 1.19 (1.13 to 1.25) for French fries. Furthermore, replacing 3 servings/week of total potatoes with the same amount of whole grains was associated with significantly lower T2DM risk; HR (95% CI) was 0.88 (0.84 to 0.91). In addition, compared with stable potato consumption, every 3 servings/week increment of potato consumption in 4 years was associated with a 4% (95% CI 0% to 8%) higher T2DM risk.

Commentary

Previous epidemiological studies on the association of potato consumption with cardiometabolic disorders were sparse and findings were inconsistent. The present study filled the large data gap based on data from three large prospective cohorts with long-term follow-up. Three important findings were generated from the present study: (1) higher potato consumption, both total potato intake and individual potato foods, including baked, boiled or mashed potatoes and French fries, was significantly associated with increased risk of T2DM; (2) replacing whole grains for potato food was associated with reduced risk of T2DM and (3) increased potato consumption over time was associated with elevated subsequent incidence of T2DM. Interestingly, findings from the present study were, in general, consistent with those from a recent study on potato intake and gestational diabetes mellitus (GDM),4 a common pregnancy complication with onset or first recognition of glucose intolerance during pregnancy. More specifically, in the study of GDM, higher intake of total potato or individual potato foods before pregnancy was related to a significantly greater risk of GDM. In addition to T2DM and GDM, more recently, greater potato consumption was also associated with a significantly increased risk of hypertension.5 Taken together, these emerging findings cast doubts on the inclusion of potatoes as healthy vegetables and support a potential harmful effect on cardiometabolic health.

Unique strengths of the present study include its prospective design, large sample size, long-term follow-up with relatively high retention rate, and use of data from multiple cohort studies. Common to other observational studies, residual or unmeasured confounding may still exist although a comprehensive list of potential confounders was adjusted for. Of note, available studies on potato consumption and cardiometabolic health were conducted largely among Caucasian population. Future studies among non-Caucasian populations are warranted to confirm and expand these findings.

Implications for practice

High consumption of potato, including baked, boiled or mashed potato and French fries may have potential harmful rather than beneficial effects on T2DM development. Cautions should be exercised in classifying potato as a healthy vegetable. Replacing potato with whole grains may help reduce the risk of diabetes.