Are Potatoes Contributing to a Public Health Problem?

Consuming ≥4 servings of baked, boiled, mashed potatoes or French fries, a week, compared to <1 serving of these foods a month, was associated with an increased adjusted risk of developing hypertension. The findings come from a new meta-analysis of 187,453 participants for >20 years follow-up.

Data was collected from the Nurses’ Health Study (NHS; n=121,700 women, aged 30–55 at the time of cohort inception in 1976), the Nurses’ Health Study II (NHS II; n=116,430 women, aged 25–42 at cohort inception in 1989), and the Health Professionals Follow-up Study (HPFS; n=51,529 men, aged 40–75 at cohort inception in 1986). Patients who self-reported hypertension at baseline were excluded from the study.

Participants returned questionnaires regarding health status, which were collected every 2 years, and were asked to self-report a diagnosis of hypertension from their healthcare provider. Potato intake was assessed every 4 years via a food frequency questionnaire. The main outcome measure was incident cases of hypertension.

Compared to eating <1 serving/month of potatoes, the pooled hazard ratio (using random effects models) for incident hypertension with consumption of ≥4 servings per week of mashed, baked or boiled potatoes was 1.11 (0.96–1.28; P=0.05). With regards to French fries, the pooled hazard ratio for eating 4 or more servings per week compared to less than 1 serving per month was 1.17 (1.07–1.27; P=0.001); for potato chips it was 0.97 (0.87 –1.08; P=0.98). Conversely, replacing 1 serving per day of mashed, baked, or boiled potatoes with a non-starchy vegetable was associated with a reduced risk of hypertension development (HR: 0.93, 0.89–0.96). 

These findings that hypertension may be related to potato intake could be critical in light of potatoes being re-inserted into government sponsored health food programs; such as The Healthy, Hunger-Free Act and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Advocates of potatoes in these programs point to the potential cardiovascular benefits of increased potassium that can accompany potato consumption. Higher potassium intake has also been associated with lower blood pressure.

However, it is important to note that the findings of cohort studies such as this one, can offer distorted outcomes. The information collected in the self-reported questionnaires did not include important details, such as cooking methods; which can greatly affect the glycemic index of potatoes. Issues of control also arise when a study focuses on the consumption of just one food. For instance, US National Institutes of Health recommended DASH diet to reduce hypertension which includes potatoes in an overall dietary pattern.

“Potential mechanism that could explain our findings is the high glycemic load associated with potatoes,” write the authors. The postprandial hyperglycemia which is a consequence of a high glycemic meal has been linked with endothelial dysfunction, oxidative stress, and inflammation, all of which are possible mechanisms in hypertension development.

Concluding, the authors questioned the logic of including potatoes in government food programs stating their findings, “do not support a potential benefit from the inclusion of potatoes as vegetables in government food programs but instead support a harmful effect that is consistent with adverse effects of high carbohydrate intakes seen in controlled feeding studies.” Although it is likely that more robust research, with closer scientific monitoring is needed before any changes to government programs take place.

For more information visit BMJ.com.