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Healthy Potatoes?

September 9, 2011 Written by JP       [Font too small?]

A presentation given at last week’s national meeting of the American Chemical Society made headlines that you may have heard or read about. The claim made was that eating two daily servings of potatoes can lower blood pressure so that the “undeserved bad reputation” of potatoes ought to be reassessed. To that I say, not so fast. There are several key details that are important to note when considering this research and topic: 1) The variety of potatoes used in the current trial (purple potatoes) contain antioxidant pigments, similar to those found in blueberries and red wine, which may reduce blood pressure in and of themselves.  2) Some research suggests that purple potatoes contain higher potassium content than more popular varieties such as white Idaho potatoes. 3) Diets rich in foods containing potassium are capable of lowering hypertension whether they contain potatoes or not. 4) There are many other ways of managing high blood pressure naturally, such as switching from common table salt to any number of salt alternatives which feature essential minerals including magnesium and potassium.

Finally, it’s vital to understand that many wholesome foods contain significant quantities of potassium. While bananas and potatoes are most frequently singled out, you should know that a 5 oz fillet of halibut contains approximately 817 mg of potassium, a cup of spinach offers up 838 mg, and an 8 ounce serving of unsweetened yogurt will provide upwards of 600 mg of this often deficient mineral.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

To learn more about the studies referenced in today’s column, please click on the following links:

Study 1 - Potatoes Reduce Blood Pressure in People With Obesity and … (link)

Study 2 - Pigmented Potato Consumption Alters Oxidative Stress and … (link)

Study 3 - Aronia Melanocarpa Extract Reduces Blood Pressure, Serum (link)

Study 4 - Changes in Potassium Content of Different Potato Varieties (link)

Study 5 - DASH Lowers Blood Pressure in Obese Hypertensives Beyond … (link)

Study 6 - Feasibility and Antihypertensive Effect of Replacing Regular Salt (link)

Study 7 - Appendix B. Food Sources of Selected Nutrients (link)

Antioxidant Pigments (Polyphenols) May Promote Cardiovascular Health

Source: Cardiovasc Res. 2004 Sep 1;63(4):593-602. (link)

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15 Comments & Updates to “Healthy Potatoes?”

  1. Sai Says:

    Dear JP

    Yes i heard about this on the radio.I personally think that Hibiscus tea offers good results for people with hypertension with no calories or carbs added. I think this study mentioned about microwaving potatoes and adding no oil etc. Thanks JP for sharing this information.

    Best regards

    Sai

  2. JP Says:

    Good day, Sai.

    I agree with you about hibiscus tea. A few family members are using it for this purpose to good effect.

    The study in question employed microwave cooking in order to preserve the antioxidants and nutrients naturally present in purple potatoes. For instance, boiling the potatoes would have likely resulted in much lower quantities of anthocyanins and potassium.

    Be well!

    JP

  3. Mark Says:

    Garden note for next year….purple potatoes

  4. JP Says:

    Mark,

    Also consider purple asparagus, purple broccoli and purple cauliflower! My favorite purple veggies. :)

    Be well!

    JP

  5. Steve Says:

    I rarely see these in the store. Are they difficult to grow or store? I don’t see why they would???

  6. Eric Says:

    Yes, heard a lot about hibiscus tea. It is very good from the health point of view.

  7. JP Says:

    Hi, Steve.

    Not that I’m aware of.

    Be well!

    JP

  8. JP Says:

    Preliminary evidence showing that purple (and red) potatoes may affect blood sugar to a lesser extent than white and yellow potatoes:

    http://pubs.rsc.org/en/content/articlelanding/2014/fo/c3fo60395d#!divAbstract

    The glycemic index of pigmented potatoes is related to their polyphenol content

    D Dan Ramdath, Emily Padhi, Aileen Hawke, Theva Sivaramalingam and Rong Tsao

    Food Funct., 2014, Accepted Manuscript

    Polyphenol extracts from coloured fruits and vegetables inhibit α-glucosidase in vitro, however it is not known whether this translates into an attenuation of blood glucose response in vivo. We examined this relationship in a GI study by feeding coloured potatoes to 9 healthy volunteers. We also examined the in vitro inhibitory activity of potato anthocyanin extracts on rat intestinal α-glucosidase. Potatoes (Purple Majesty; Red-Y38; Yukon Gold and Snowden) were fed with skin after cooking in a convection oven, using a random block design and 50 g available carbohydrate. Glucose was used as the standard and venous blood collected at 0, 15, 30, 45, 60, 90, 120 min. Areas under the curve (AUC) for glucose and insulin were calculated, and GI and Insulin Index derived. Neither AUC for blood glucose response nor insulin was significantly different among the various potatoes studied. Although the mean GI (±SE) values for the potato types varied (Purple = 77.0±9.0; Red = 78.0±14.0; Yellow = 81.0±16.0; and White = 93.0 ±17.0), these differences were not significantly different. The mean (±SE) polyphenol content (mg GAE/100g DW) was 234±28; 190 ±15; 108 ±39; 82±1 for purple, red, yellow and white potatoes, respectively. There was a significant inverse correlation between polyphenol content and GI of the potatoes (r = -0.825; p<0.05; n=4). In vitro, polyphenol extracts of red and purple potatoes inhibited α-glucosidase by 37.4±2.2% and 28.7±3.2%, respectively. The GI of coloured potatoes is significantly related to their polyphenol content, possibly mediated through an inhibitory effect of anthocyanins on intestinal α-glucosidase.

    Be well!

    JP

  9. JP Says:

    Update 06/01/15:

    http://archpedi.jamanetwork.com/article.aspx?articleid=2272973

    JAMA Pediatr. 2015 Apr 27.

    Longitudinal Effects of Dietary Sodium and Potassium on Blood Pressure in Adolescent Girls.

    Importance: Identification of risk factors early in life for the development of high blood pressure is critical to the prevention of cardiovascular disease.

    Objective: To study prospectively the effect of dietary sodium, potassium, and the potassium to sodium ratio on adolescent blood pressure.

    Design, Setting, and Participants: The National Heart, Lung, and Blood Institute’s Growth and Health Study is a prospective cohort study with sites in Richmond, California; Cincinnati, Ohio; and Washington, DC. Participants included 2185 black and white girls initially aged 9 to 10 years with complete data for early-adolescent to midadolescent diet and blood pressure who were followed up for 10 years. The first examination visits were from March 1987 through February 1988 and follow-up continued until February 1999. Longitudinal mixed models and analysis of covariance models were used to assess the effect of dietary sodium, potassium, and the potassium to sodium ratio on systolic and diastolic blood pressures throughout adolescence and after 10 years of follow-up, adjusting for race, height, activity, television/video time, energy intake, and other dietary factors.

    Exposures: Mean dietary sodium and potassium intakes and the mean potassium to sodium ratio in individuals aged 9 to 17 years. To eliminate potential confounding by energy intake, energy-adjusted sodium and potassium residuals were estimated.

    Main Outcomes and Measures: Mean systolic and diastolic blood pressures throughout adolescence and at the end of follow-up (individuals aged 17-21 years).

    Results: Sodium intakes were classified as less than 2500 mg/d (19.4% of participants), 2500 mg/d to less than 3000 mg/d (29.5%), 3000 mg/d to less than 4000 mg/d (41.4%), and 4000 mg/d or more (9.7%). Potassium intakes ranged from less than 1800 mg/d (36.0% of participants) to 1800 mg/d to less than 2100 mg/d (26.2%), 2100 mg/d to less than 2400 mg/d (18.8%), and 2400 mg/d or more (19.0%). There was no evidence that higher sodium intakes (3000 to <4000 mg/d and ≥4000 mg/d vs <2500 mg/d) had an adverse effect on adolescent blood pressure and longitudinal mixed models showed that those consuming 3500 mg/d or more had generally lower diastolic blood pressures compared with individuals consuming less than 2500 mg/d (P = .18). However, higher potassium intakes were inversely associated with blood pressure change throughout adolescence (P < .001 for systolic and diastolic) and at the end of follow-up (P = .02 and P = .05 for systolic and diastolic, respectively). While the potassium to sodium ratio was also inversely associated with systolic blood pressure (P = .04), these effects were generally weaker compared with effects for potassium alone.

    Conclusions and Relevance: In this study of adolescent girls, consumption of 3500 mg/d of sodium or more had no adverse effect on blood pressure. The beneficial effects of dietary potassium on both systolic and diastolic blood pressures suggest that consuming more potassium-rich foods during childhood may help suppress the adolescent increase in blood pressure.

    Be well!

    JP

  10. JP Says:

    Updated 12/23/15:

    http://care.diabetesjournals.org/content/early/2015/12/09/dc15-0547.abstract

    Diabetes Care. 2015 Dec 17.

    Potato Consumption and Risk of Type 2 Diabetes: Results from Three Prospective Cohort Studies.

    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.

    Be well!

    JP

  11. JP Says:

    Updated 12/29/15:

    http://www.sciencedirect.com/science/article/pii/S0308814615301941

    Food Chem. 2016 Apr 15;197 Pt B:1264-70.

    Domestic cooking methods affect the phytochemical composition and antioxidant activity of purple-fleshed potatoes.

    The effects of domestic cooking methods (boiling, baking, steaming, microwaving, frying, and stir-frying) and a new cooking method (air-frying) on the composition of phytochemicals (phenolics, anthocyanins, and carotenoids) and the antioxidant activity in purple-fleshed potatoes were investigated. Compared with raw potatoes, reductions of 23.59-90.42%, 7.09-72.44%, 7.45-83.15%, and 20.15-76.16% in the vitamin C, total phenolic, anthocyanin and carotenoid contents, respectively, was observed after cooking. Decreases of 7.88%, 21.55%, 22.48, 6.31%, and 61.38% in DPPH radical-scavenging activity was also observed after boiling, steaming, baking, microwaving and stir-frying, respectively, whereas an increase of 30.52% was noted after air-frying. A correlation analysis revealed that the antioxidant activity was in accordance with the total phenolic content and that this activity showed the lowest correlation with the vitamin C content. Among all of the cooking methods investigated in this study, stir-frying retained only slight levels of the phytochemicals and antioxidant activity observed in raw potatoes, whereas steaming and microwaving were able to retain most of the health-promoting compounds found in raw potatoes and may thus be suitable methods for cooking potatoes.

    Be well!

    JP

  12. JP Says:

    Updated 05/11/16:

    http://www.ncbi.nlm.nih.gov/pubmed/27163964

    Int J Food Sci Nutr. 2016 May 10:1-11.

    Comparison of the postprandial effects of purple-fleshed and yellow-fleshed potatoes in healthy males with chemical characterization of the potato meals.

    The aim of the current study was to characterize the anthocyanin content and composition of a purple potato landrace cultivar (Solanum tuberosum ‘Synkeä Sakari’) and to compare the postprandial effects of purple-fleshed potatoes, yellow-fleshed potatoes and bilberries in potato starch on postprandial glycemia and insulinemia in healthy males. The purple potato meal caused smaller insulinemia than the yellow potato meal (iAUC 120 min 1347 and 2226, respectively, p = 0.012 and iAUC 240 min 1448 and 2403, p = 0.007) or the bilberry meal (iAUC 120 min 1920, p = 0.027). The purple potato meal caused a smaller plasma glucose at 40 min postprandially compared with the yellow potato meal (p = 0.044). The results of this study suggest that anthocyanin-containing purple-fleshed potatoes influence the postprandial insulinemia positively. Since potatoes are the world’s largest non-grain commodity, replacing yellow-fleshed potatoes with purple-fleshed potatoes as staple food could have large potential in maintaining public health.

    Be well!

    JP

  13. JP Says:

    Updated 08/12/16:

    http://www.ncbi.nlm.nih.gov/pubmed/27508114

    Biosci Microbiota Food Health. 2016;35(3):129-36.

    Effect of consuming a purple-fleshed sweet potato beverage on health-related biomarkers and safety parameters in Caucasian subjects with elevated levels of blood pressure and liver function biomarkers: a 4-week, open-label, non-comparative trial.

    An open-label study with one treatment arm was conducted to investigate changes in health-related biomarkers (blood pressure and liver enzyme activity) and the safety of 4 weeks of consuming a purple-fleshed sweet potato beverage in Caucasian subjects. Twenty healthy adults, 18-70 years of age, with a body mass index >25 kg/m(2), elevated blood pressure and elevated levels of liver function biomarkers consumed two cartons of purple-fleshed sweet potato beverage (125 ml, including 117 mg anthocyanin per carton) daily for 4 weeks. Hematology, serum clinical profile, dipstick urinalysis and blood pressure were determined before consumption, at 2 and 4 weeks of consumption and after a 2-week washout period. A trend was found toward lowering systolic blood pressure during the treatment period (p=0.0590). No significant changes were found in diastolic blood pressure throughout the study period. Systolic blood pressure was significantly lower after 4 weeks of consumption compared with before consumption (p=0.0125) and was significantly higher after the 2-week washout period compared with after consumption (p=0.0496). The serum alanine aminotransferase level significantly increased over time, but aspartate aminotransferase and γ-glutamyltransferase levels stayed within the normal range of reference values. Safety parameters of the blood and urine showed no clinically relevant changes. The consumption of a purple-fleshed sweet potato beverage for 4 weeks resulted in no clinically relevant changes in safety parameters of the blood and urine and showed a trend toward lowering systolic blood pressure.

    Be well!

    JP

  14. JP Says:

    Updated 09/27/16:

    http://link.springer.com/article/10.1007/s00394-016-1309-7

    Eur J Nutr. 2016 Sep 21.

    Glyceamic and insulinaemic response to mashed potato alone, or with broccoli, broccoli fibre or cellulose in healthy adults.

    PURPOSE: To examine the role of realistic serving sizes of broccoli, broccoli fibre and cellulose co-consumed with mash potato, or mashed potato eaten alone, on glycaemic and insulinaemic responses (GR and IR) in healthy adults.

    METHOD: A non-blind randomized crossover trial was conducted with thirteen healthy subjects consuming four different meals. Capillary blood samples between 0 and 180 min were analysed for glucose and insulin. The incremental area under the fasting blood glucose and insulin curves (iAUC) was calculated for different time increments. Differences in GR and IR between meals were assessed by repeated measures analysis of variance.

    RESULTS: The immediate GR and IR to one serving of mashed potato eaten with two servings of broccoli were significantly lower than mashed potato eaten alone. The peak, incremental peak and iAUC0-30min for GR and iAUC0-30min for IR were all significantly lower for the broccoli-potato meal. This meal also takes longer to return to fasting baseline with a time-delayed lag in IR and GR compared to the potato only meal. The iAUC60-120min for IR was significantly greater for the broccoli-potato meal compared to the other meals. Yet there was no corresponding significant difference between the broccoli-potato meal and the other meals for peak, incremental peak IR or any other iAUCs for GR and IR. For the potato meals containing added broccoli fibre or cellulose, no significant differences in GR or IR were observed when compared with the potato eaten alone.

    CONCLUSION: Co-consumption of cooked broccoli with mashed potato has a significant effect on glycaemic and insulinaemic responses compared to potato eaten alone. Our study suggests broccoli eaten with potato improves glucose homeostasis and therefore indicates a general beneficial nutritional role for broccoli when eaten with a carbohydrate staple.

    Be well!

    JP

  15. JP Says:

    Updated 08/27/18:

    https://www.ncbi.nlm.nih.gov/pubmed/30144898

    Clin Nutr ESPEN. 2018 Oct;27:86-91.

    Potato consumption and risk of type 2 diabetes: A dose-response meta-analysis of cohort studies.

    BACKGROUND & AIMS: High potato intake has been suggested as a risk factor for the development of type 2 diabetes. We aimed to investigate the association between potato consumption and risk of type 2 diabetes.

    METHODS: A systematic review was conducted on PubMed and Embase from the database commencement until September 2017 (updated by June 2018) following the MOOSE guidelines. The random effect model dose-response meta-analysis method of Greenland and Longneck was used to estimate the maximally adjusted log hazard ratio (HR) for a unit (serving per day) increment of potato consumption. A restricted cubic spline model with three knots was used to evaluate the potential non-linear relationship.

    RESULTS: A total of 3544 citations were retrieved from the databases, of which six prospective cohort studies including 4545230 person-year of follow-up and 17,758 diabetes cases met the inclusion criteria. The pooled dose-response HR per an increment of 1 serving/day of total potato consumption was 1.20 (95% CI 1.13 to 1.127, P < 0.001, I2 = 27.1%, P for heterogeneity = 0.23) both in men and women. The larger risk were observed for 2 serving/day (HR 1.44, 95% CI 1.28 to 1.63) and 3 serving/day (HR 1.74, 95% CI 1.45 to 2.09). We found significant evidence of a non-linear association between total potato consumption and risk of type 2 diabetes (X2 = 17.5, P for linearity < 0.001).

    CONCLUSION: Long-term high consumption of potato (each serving a day increase) may be strongly associated with increased risk of diabetes. These findings suggest that diet-health policy may be of importance in the prevention of diabetes.

    Be well!

    JP

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