Dr. Ron’s Research Review – December 11, 2019

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This week’s research review focuses on potatoes.

Potatoes contain an enzyme that reduces appetite. (Zhu et al., 2017)

Type 2 Diabetes

A study investigated the associations between total, boiled and fried potato intake and the risk for incident diabetes in Tehranian adults. This cohort study was conducted in 1,981 adults, aged 19 to 70 years, who participated in the Tehran Lipid and Glucose Study and were followed up for 6 years. Usual dietary potato intakes were assessed using a valid and reliable food-frequency questionnaire. The risk for incident diabetes in participants was 6.7% after 6 years of follow up. After adjusting for age, sex, body mass index, physical activity, smoking, family history of diabetes, hypertension, serum triglyceride levels, high-density lipoprotein cholesterol levels, energy intakes and consumption of saturated fat, fruit, whole grains, vegetables, nuts and legumes, the risk for incident diabetes was lower in subjects with higher intakes of total potato (OR=0.46; 95% CI 0.25 to 0.84) and boiled potato (OR=0.47; 95% CI 0.26 to 0.85) in comparison with those who had the lowest intakes (p for trend <0.05). However, there was no significant association between fried potato intake and risk for diabetes (OR=0.50; 95% CI 0.25 to 1.07; p for trend >0.05). These findings indicate that, in Tehranian adults, a moderate intake of dietary total and boiled, but not fried, potatoes may be associated with a lower risk for incident diabetes. (Farhadnejad et al., 2018)
A study examined whether potato consumption is associated with a higher risk of type 2 diabetes (T2D). The study analyzed data in three cohorts consisting of U.S. male and female health professionals without diabetes, cardiovascular disease, and cancer at baseline: 70,773 women from the Nurses' Health Study (1984-2010), 87,739 women from Nurses' Health Study II (1991-2011), and 40,669 men from the Health Professionals Follow-up Study (1986-2010). Potato consumption was assessed quadrennially using validated food frequency questionnaires (FFQs), and we calculated 4-year change in potato consumption from consecutive FFQs. Self-reported T2D diagnosis was confirmed using a validated supplementary questionnaire. During 3,988,007 person-years of follow-up, 15,362 new cases of T2D were identified. Higher consumption of total potatoes (including baked, boiled, or mashed potatoes and french fries) was significantly associated with an elevated risk for T2D: the pooled hazard ratio (HR) of T2D compared with <1 serving/week was 1.07 (95% CI 0.97-1.18) for 2-4 servings/week and 1.33 (95% CI 1.17-1.52) for ≥7 servings/week after adjustment for demographic, lifestyle, and dietary factors. In addition, the pooled HRs of T2D for every 3 servings/week were 1.04 (95% CI 1.01-1.08) for baked, boiled, or mashed potatoes, and 1.19 (95% CI 1.13-1.25) for french fries. The study further estimated that the HR of T2D was 0.88 (95% CI 0.84-0.91) for replacing 3 servings/week of total potatoes with the same amount of whole grains. Last, in comparison with stable potato consumption, every 3-servings/week increment of potato consumption in 4 years was associated with a 4% (95% CI 0-8%) higher T2D risk. Greater consumption of potatoes, especially french fries, was associated with a higher T2D risk, independent of BMI and other risk factors. Replacement of potatoes with whole grains was associated with a lower T2D risk. (Muraki et al., 2016)

Potato Protease Inhibitor II

The effect of potato protease inhibitor II (PI2) on postprandial appetite was examined in a randomized double-blind placebo-controlled cross-over trial involving 44 healthy women. In separate test sessions, participants consumed a capsule containing placebo or potato extract standardized to 15 or 30 mg PI2 after overnight fasting. One hour later, a standard 390 kcal breakfast was served. At regular time points during the three-hour period after breakfast, appetite was measured by visual analog scales, and blood samples were collected for assay of cholecystokinin, insulin, and glucose. Compared with the placebo, consumption of 15 mg or 30 mg PI2 one hour prior to a standard breakfast meal resulted in significantly lower postprandial hunger, desire to eat, and prospective consumption, as well as significantly higher postprandial fullness. Consumption of 15 mg PI2 also resulted in significantly higher postprandial plasma levels of cholecystokinin compared with the placebo. No significant main effect of treatment was found on insulin and glucose. No adverse events were reported. Results from the study revealed that consumption of potato PI2 at the examined doses was well tolerated, suppressed subjective appetite in a dose-dependent manner, and increased plasma concentrations of cholecystokinin. (Zhu et al., 2017)

 

Dr. Ron

 


Articles

 

The Association of Potato Intake With Risk for Incident Type 2 Diabetes in Adults.
(Farhadnejad et al., 2018) Download
OBJECTIVES:  Previous studies indicate that the risk for diabetes associated with high consumption of potato differs in various populations. We aimed to investigate the associations between total, boiled and fried potato intake and the risk for incident diabetes in Tehranian adults. METHODS:  This cohort study was conducted in 1,981 adults, aged 19 to 70 years, who participated in the Tehran Lipid and Glucose Study and were followed up for 6 years. Usual dietary potato intakes were assessed using a valid and reliable food-frequency questionnaire. Anthropometric, biochemical and blood pressure data were determined, and diabetes was defined according to the criteria of the American Diabetes Association. RESULTS:  The mean (± SD) age and potato intake of participants was 38.9±13.4 years and 30.2±30.7 g/day, respectively. The risk for incident diabetes in participants was 6.7% after 6 years of follow up. After adjusting for age, sex, body mass index, physical activity, smoking, family history of diabetes, hypertension, serum triglyceride levels, high-density lipoprotein cholesterol levels, energy intakes and consumption of saturated fat, fruit, whole grains, vegetables, nuts and legumes, the risk for incident diabetes was lower in subjects with higher intakes of total potato (OR=0.46; 95% CI 0.25 to 0.84) and boiled potato (OR=0.47; 95% CI 0.26 to 0.85) in comparison with those who had the lowest intakes (p for trend <0.05). However, there was no significant association between fried potato intake and risk for diabetes (OR=0.50; 95% CI 0.25 to 1.07; p for trend >0.05). CONCLUSIONS:  Our findings indicate that, in Tehranian adults, a moderate intake of dietary total and boiled, but not fried, potatoes may be associated with a lower risk for incident diabetes.

Potato Consumption and Risk of Type 2 Diabetes: Results From Three Prospective Cohort Studies.
            (Muraki et al., 2016) Download
OBJECTIVE:  We aimed to elucidate whether potato consumption is associated with a higher risk of type 2 diabetes (T2D). RESEARCH DESIGN AND METHODS:  We analyzed data in three cohorts consisting of U.S. male and female health professionals without diabetes, cardiovascular disease, and cancer at baseline: 70,773 women from the Nurses' Health Study (1984-2010), 87,739 women from Nurses' Health Study II (1991-2011), and 40,669 men from the Health Professionals Follow-up Study (1986-2010). Potato consumption was assessed quadrennially using validated food frequency questionnaires (FFQs), and we calculated 4-year change in potato consumption from consecutive FFQs. Self-reported T2D diagnosis was confirmed using a validated supplementary questionnaire. RESULTS:  During 3,988,007 person-years of follow-up, 15,362 new cases of T2D were identified. Higher consumption of total potatoes (including baked, boiled, or mashed potatoes and french fries) was significantly associated with an elevated risk for T2D: the pooled hazard ratio (HR) of T2D compared with <1 serving/week was 1.07 (95% CI 0.97-1.18) for 2-4 servings/week and 1.33 (95% CI 1.17-1.52) for ≥7 servings/week after adjustment for demographic, lifestyle, and dietary factors. In addition, the pooled HRs of T2D for every 3 servings/week were 1.04 (95% CI 1.01-1.08) for baked, boiled, or mashed potatoes, and 1.19 (95% CI 1.13-1.25) for french fries. We further estimated that the HR of T2D was 0.88 (95% CI 0.84-0.91) for replacing 3 servings/week of total potatoes with the same amount of whole grains. Last, in comparison with stable potato consumption, every 3-servings/week increment of potato consumption in 4 years was associated with a 4% (95% CI 0-8%) higher T2D risk. CONCLUSIONS:  Greater consumption of potatoes, especially french fries, was associated with a higher T2D risk, independent of BMI and other risk factors. Replacement of potatoes with whole grains was associated with a lower T2D risk.

Potato protease inhibitor II suppresses postprandial appetite in healthy women: a randomized double-blind placebo-controlled trial.
            (Zhu et al., 2017) Download
The effect of potato protease inhibitor II (PI2) on postprandial appetite was examined in a randomized double-blind placebo-controlled cross-over trial involving 44 healthy women. In separate test sessions, participants consumed a capsule containing placebo or potato extract standardized to 15 or 30 mg PI2 after overnight fasting. One hour later, a standard 390 kcal breakfast was served. At regular time points during the three-hour period after breakfast, appetite was measured by visual analog scales, and blood samples were collected for assay of cholecystokinin, insulin, and glucose. Compared with the placebo, consumption of 15 mg or 30 mg PI2 one hour prior to a standard breakfast meal resulted in significantly lower postprandial hunger, desire to eat, and prospective consumption, as well as significantly higher postprandial fullness. Consumption of 15 mg PI2 also resulted in significantly higher postprandial plasma levels of cholecystokinin compared with the placebo. No significant main effect of treatment was found on insulin and glucose. No adverse events were reported. Results from the study revealed that consumption of potato PI2 at the examined doses was well tolerated, suppressed subjective appetite in a dose-dependent manner, and increased plasma concentrations of cholecystokinin. Future studies are needed to evaluate the long-term effect of PI2 on body weight.

 


References

Farhadnejad, H, et al. (2018), ‘The Association of Potato Intake With Risk for Incident Type 2 Diabetes in Adults.’, Can J Diabetes, 42 (6), 613-18. PubMed: 29909965
Muraki, I, et al. (2016), ‘Potato Consumption and Risk of Type 2 Diabetes: Results From Three Prospective Cohort Studies.’, Diabetes Care, 39 (3), 376-84. PubMed: 26681722
Zhu, Y, JA Lasrado, and J Hu (2017), ‘Potato protease inhibitor II suppresses postprandial appetite in healthy women: a randomized double-blind placebo-controlled trial.’, Food Funct, 8 (5), 1988-93. PubMed: 28485429