Research Category: Cardiometabolic Health

Effects of potato resistant starch intake on insulin sensitivity, related metabolic markers and appetite ratings in men and women at risk for type 2 diabetes: a pilot cross‐over randomised controlled trial

The intake of certain types of resistant starch (RS) has been associated in some studies with increased whole‐body insulin sensitivity. This randomised, cross‐over pilot trial evaluated the effect of consuming cooked, then chilled potatoes, a source of RS, compared to isoenergetic, carbohydrate (CHO)‐containing control foods, on insulin sensitivity and related markers. Nineteen adults with body mass index 27.0‐39.9 kg m−2 consumed 300 g day−1 RS‐enriched potatoes (approximately two potatoes; ~18 g RS) or CHO‐based control foods, as part of lunch, evening and snack meals, over a 24‐h period. After an overnight fast, insulin sensitivity, CHO metabolism markers, free fatty acids, breath hydrogen levels and appetite were assessed for up to 5 h after the intake of a standard breakfast. The primary endpoint was insulin sensitivity, assessed with the Matsuda index. P < 0.05 (one‐sided) was considered statistically significant. Insulin sensitivity was not significantly different between the potato and control conditions. The potato intervention resulted in higher postprandial breath hydrogen (P = 0.037), lower postprandial free fatty acid concentrations (P = 0.039) and lower fasting plasma glucose (P = 0.043) compared to the control condition. Fullness ratings were significantly lower after potato versus control (P = 0.002). No other significant effects were observed; however, there was a trend toward lower fasting insulin (P = 0.077) in the potato versus the control condition. The results of this pilot study suggest RS‐enriched potatoes may have a favourable impact on carbohydrate metabolism and support the view that additional research in a larger study sample is warranted.

Daily Intake of Non-Fried Potato Does Not Affect Markers of Glycemia and is Associated with Better Diet Quality Compared to Refined Grains: A Randomized, Crossover Study in Healthy Adults

Epidemiologic studies suggest that consumption of potatoes is associated with increased risk of cardiometabolic diseases. However, few clinical trials have empirically tested these observational findings. The aim of this single-blind, randomized, crossover study was to evaluate the effect of daily potato consumption, compared to refined grains, on risk factors for cardiometabolic diseases. It was hypothesized that no difference in cardiometabolic endpoints would be detected between conditions, but diet quality would improve with potato consumption. Healthy participants on self-selected diets received one potato-based side dish or one refined grain-based side dish daily, for four weeks, separated by a minimum two-week break. Dishes were isocaloric, carbohydrate-matched, and prepared without excess saturated fat or sodium. Participants were instructed to consume the side-dish with a meal in place of carbohydrates habitually consumed. Lipids/lipoproteins, markers of glycemic control, blood pressure (BP), weight and pulse wave velocity (PWV) were measured at baseline and condition endpoints. Diet quality was calculated, based on 24-hour recalls, using the Healthy Eating Index (HEI)-2015. Fifty adults (female n=34; age: 40±13; BMI: 24.5±3.6 kg/m2) completed this study. No between-condition differences were detected for fasting plasma glucose (-0.97; mg/dL, 95% CI: -2.3, 0.35; p=0.15), the primary outcome, or any other outcomes. Compared with refined grains, the HEI-2015 score (3.5, 95%CI: 0.6, 6.4 p=0.01), potassium (547 mg, 95%CI: 331, 764, p<0.001) and fiber (2.4 g, 95% CI: 0.6, 4.2, p=0.01) were higher following the potato condition. Consuming non-fried potatoes resulted in higher diet quality, potassium and fiber intake, without adversely affecting cardiometabolic risk.

Intake of Boiled Potato in Relation to Cardiovascular Disease Risk Factors in a Large Norwegian Cohort: The HUNT Study

Overall potato consumption is positively associated with cardiovascular disease (CVD) risk factors, such as measures of adiposity. However, few studies have explicitly stated the preparation method of potatoes, which may impact these associations. We examined cross-sectional associations between self-reported dietary intake of boiled potatoes and levels of body mass index, waist circumference, blood pressure, and blood lipids among 43,683 participants in the HUNT Study, Norway in 2006–2008. All estimated associations were adjusted for possible imbalance in age, sex, physical activity, smoking, intake of other foods and alcohol between categories of boiled potato consumption. Overall, there were no large differences in mean levels of CVD risk factors between categories of boiled potato consumption. Compared to the reference group of individuals who consumed boiled potatoes less than once/week, those who reported eating boiled potatoes every day had slightly higher prevalence of high waist circumference (odds ratio [OR] 1.16, 95% confidence interval [CI] 1.05–1.29), high triglycerides levels (OR 1.20, 95% CI 1.07–1.34), and metabolic syndrome (OR 1.17, 95% CI 1.03–1.33). In summary, consumption of boiled potatoes showed weak and small associations with the CVD risk factors under study, but the cross-sectional design prevents us from drawing any firm conclusions.

Potato-Resistant Starch Supplementation Improves Microbiota Dysbiosis, Inflammation, and Gut–Brain Signaling in High Fat-Fed Rats

(1) High-fat (HF) diet leads to gut microbiota dysbiosis which is associated with systemic inflammation. Bacterial-driven inflammation is sufficient to alter vagally mediated satiety and induce hyperphagia. Promoting bacterial fermentation improves gastrointestinal (GI) epithelial barrier function and reduces inflammation. Resistant starch escape digestion and can be fermented by bacteria in the distal gut. Therefore, we hypothesized that potato RS supplementation in HF-fed rats would lead to compositional changes in microbiota composition associated with improved inflammatory status and vagal signaling. (2) Male Wistar rats (n = 8/group) were fed a low-fat chow (LF, 13% fat), HF (45% fat), or an isocaloric HF supplemented with 12% potato RS (HFRS) diet. (3) The HFRS-fed rats consumed significantly less energy than HF animals throughout the experiment. Systemic inflammation and glucose homeostasis were improved in the HFRS compared to HF rats. Cholecystokinin-induced satiety was abolished in HF-fed rats and restored in HFRS rats. HF feeding led to a significant decrease in positive c fiber staining in the brainstem which was averted by RS supplementation. (4) The RS supplementation prevented dysbiosis and systemic inflammation. Additionally, microbiota manipulation via dietary potato RS prevented HF-diet-induced reorganization of vagal afferent fibers, loss in CCK-induced satiety, and hyperphagia.

Magnesium in Disease Prevention and Overall Health

Magnesium is the fourth most abundant mineral and the second most abundant intracellular divalent cation and has been recognized as a cofactor for >300 metabolic reactions in the body. Some of the processes in which magnesium is a cofactor include, but are not limited to, protein synthesis, cellular energy production and storage, reproduction, DNA and RNA synthesis, and stabilizing mitochondrial membranes. Magnesium also plays a critical role in nerve transmission, cardiac excitability, neuromuscular conduction, muscular contraction, vasomotor tone, blood pressure, and glucose and insulin metabolism. Because of magnesium’s many functions within the body, it plays a major role in disease prevention and overall health. Low levels of magnesium have been associated with a number of chronic diseases including migraine headaches, Alzheimer’s disease, cerebrovascular accident (stroke), hypertension, cardiovascular disease, and type 2 diabetes mellitus. Good food sources of magnesium include unrefined (whole) grains, spinach, nuts, legumes, and white potatoes (tubers). This review presents recent research in the areas of magnesium and chronic disease, with the goal of emphasizing magnesium’s role in disease prevention and overall health.

Potassium and Health

Potassium was identified as a shortfall nutrient by the Dietary Guidelines for Americans 2010 Advisory Committee. The committee concluded that there was a moderate body of evidence of the association between potassium intake and blood pressure reduction in adults, which in turn influences the risk of stroke and coronary heart disease. Evidence is also accumulating of the protective effect of adequate dietary potassium on age-related bone loss and reduction of kidney stones. These benefits depend on organic anions associated with potassium as occurs in foods such as fruits and vegetables, in contrast to similar blood pressure-lowering benefits of potassium chloride. Benefits to blood pressure and bone health may occur at levels below current recommendations for potassium intake, especially from diet, but dose-response trials are needed to confirm this. Nevertheless, intakes considerably above current levels are needed for optimal health, and studies evaluating small increases in fruit and vegetable intake on bone and heart outcomes for short periods have had disappointing results. In modern societies, Western diets have led to a decrease in potassium intake with reduced consumption of fruits and vegetables with a concomitant increase in sodium consumption through increased consumption of processed foods. Consumption of white vegetables is associated with decreased risk of stroke, possibly related to their high potassium content. Potatoes are the highest source of dietary potassium, but the addition of salt should be limited. Low potassium-to-sodium intake ratios are more strongly related to cardiovascular disease risk than either nutrient alone. This relationship deserves further attention for multiple target tissue endpoints.

Potato Product Form Impacts In Vitro Starch Digestibility and Glucose Transport but Only Modestly Impacts 24h Blood Glucose Response in Humans

Potatoes are rich in phenolic compounds which have been reported to impact starch digestion and intestinal glucose transport in model systems through phenolic-starch interactions. While these effects are well documented for pigmented potatoes and in model systems, the relevance of phenolics to the glycemic properties of processed colorless potato-based foods under naturalistic conditions remains unclear. This study assessed impacts of processing on phenolic concentrations, resistant starch content and glycemic properties of Russet Burbank and Shepody potatoes. Product forms included French fries, shredded (hash browns) and diced (home fries) produced through commercial processing as well as parallel in-home techniques. Commercial products had significantly higher concentrations of resistant starch (p < 0.05, 1.48-6.57 vs. 1.23-2.22 g/100 fresh weight, FW) and resistant starch/total starch ratio (5.42-18.3 % vs. 3.58-7.62 %) compared to freshly prepared counterparts, while statistically lower total caffeoylquinic acid content (2.94-10.9 vs. 11.5-25.2 mg/100 FW). Glucose release and intestinal transport assessed using an in vitro digestion/Caco-2 cell monolayers model demonstrated a reduction in d7-glucose intestinal transport from commercially processed products relative to fresh prepared counterparts (p < 0.05, 31.3-61.2 % vs. 79.3-110 % at 60 min). Commercial Russet Burbank potato products including French fries, home fries and hash browns were then selected for clinical assessment of glycemic response and appetite rating by 23 participants (11 male and 12 female). The three products presented a subtle but discernable ascending trend (French fry ≥ home fry ≥ hash browns) for incremental area under the curve (IAUC, 95.2 ± 12 vs. 105 ± 10 vs. 107 ± 14 mM•min, p < 0.05) at 2 h post breakfast and for appetite rating (45.2 ± 6.3 vs. 52.4 ± 4.1 vs. 57.7 ± 7.2 for hunger) at 4 h post breakfast with no significant difference from the control (whole wheat pancake). These results suggest that potato phenolics have only a modest influence on acute glycemic responses.