Vegetables are universally promoted as healthy. Dietary Guidelines for Americans 2010 recommend that you make half of your plate fruits and vegetables. Vegetables are diverse plants that vary greatly in energy content and nutrients. Vegetables supply carbohydrates, dietary fiber, and resistant starch in the diet, all of which have been linked to positive health outcomes. Fiber lowers the incidence of cardiovascular disease and obesity. In this paper, the important role of white vegetables in the human diet is described, with a focus on the dietary fiber and resistant starch content of white vegetables. Misguided efforts to reduce consumption of white vegetables will lower intakes of dietary fiber and resistant starch, nutrients already in short supply in our diets.
Research Category: Starch/Resistant Starch/Carbohydrate
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.
Effects of Potatoes and Other Carbohydrate-Containing Foods on Cognitive Performance, Glycemic Response, and Satiety in Children
Dietary carbohydrates have been shown to influence cognitive performance and satiety in children. However, it remains unclear whether the carbohydrate source is a primary determinant of cognitive performance and satiety. The objective was to compare the effects of white potatoes and other carbohydrate-containing foods on cognitive performance, glycemic response, and satiety in children. On six separate mornings, in random order, children (n=22) consumed 50 g of available carbohydrates from microwaved mashed potatoes (prepared from fresh potatoes then frozen), deep-fried potato strips (French fries), hash browns, white rice, white beans, or skipped a meal. Cognitive performance, glycemic response and satiety were measured over 180 min. Cognitive performance was measured using a battery of tests assessing verbal declarative memory, spatial memory, short-term memory, working memory, and information processing speed. Although cognitive performance after the treatment meals did not differ from meal skipping, children recalled more words after French fries (9.1±0.4 words) compared with mashed potatoes (8.2±0.3 words; p<0.001) and white rice (8.4±0.3 words; p=0.04) on the verbal declarative memory test. Blood glucose concentrations were higher after white rice compared with white beans, mashed potatoes, and hash browns (p<0.05). Change from baseline subjective average appetite (mm/kcal) was lowest after mashed potatoes compared with all other treatment meals (p<0.05). In conclusion, verbal declarative memory was higher after French fries and subjective average appetite was lowest after mashed potatoes. Future longitudinal studies are needed to confirm these short-term findings and to elucidate the mechanism of action.
Potato as a Source of Nutrition for Physical Performance
Health professionals universally agree on the importance of a balanced diet, and the fallacy of relying on any one or two food groups, as the means of achieving peak physical performance and health. A review of the existing sports nutrition literature indicates that different types of athletes and physically active people may have slightly different nutritional requirements, but the main tenets of sports nutrition have not changed much over the last 25 years. The specific combinations may vary, but carbohydrates, protein, and fluids are vital components of an active individual’s diet. Further, most available research supports the notion that optimal physical performance requires carbohydrate – and, specifically, high-quality, nutrient-dense carbohydrate from whole food sources, like potatoes. High- quality carbohydrate sources – foods that offer an array of macro- and micronutrients as well as energy, can help to build a strong nutritional foundation for the level of training, recovery, and adaptation that most physically active people seek to achieve. Low carbohydrate diets will not generally allow athletes to train at the intensity required to attain peak physical performance.
Fundamentals of Glycogen Metabolism for Coaches and Athletes
The ability of athletes to train day after day depends in large part on adequate restoration of muscle glycogen stores, a process that requires the consumption of sufficient dietary carbohydrates and ample time. Providing effective guidance to athletes and others wishing to enhance training adaptations and improve performance requires an understanding of the normal variations in muscle glycogen content in response to training and diet; the time required for adequate restoration of glycogen stores; the influence of the amount, type, and timing of carbohydrate intake on glycogen resynthesis; and the impact of other nutrients on glycogenesis. This review highlights the practical implications of the latest research related to glycogen metabolism in physically active individuals to help sports dietitians, coaches, personal trainers, and other sports health professionals gain a fundamental understanding of glycogen metabolism, as well as related practical applications for enhancing training adaptations and preparing for competition.
High-Quality Carbohydrates and Physical Performance: Expert Panel Report
While all experts agreed that protein needs for performance are likely greater than believed in past generations, particularly for strength training athletes, and that dietary fat could sustain an active person through lower-intensity training bouts, current research still points to carbohydrate as an indispensable energy source for high-intensity performance.