SOLUTION: Forgotten Source of Nutrients Carbohydrates | My Assignment Tutor

COMMONWEALTH OF AUSTRALIACopyright Regulations 1969WARNINGThis material has been reproduced and communicated to you by or on behalf ofLaureate Education Australia pursuant to Part VB of the Copyright Act 1968 (the Act).The material in this communication may be subject to copyright under the Act.Any further reproduction or communication of this material by you may be thesubject of copyright protection under the Act.Do not remove this noticeSUPPLEMENTWhite Vegetables: A Forgotten Source of NutrientsCarbohydrates, Dietary Fiber, and Resistant Starchin White Vegetables: Links to Health Outcomes1,2Joanne L. Slavin*Department of Food Science and Nutrition, University of Minnesota, St. Paul, MNABSTRACTVegetables are universally promoted as healthy. Dietary Guidelines for Americans 2010 recommend that you make half of your plate fruits andvegetables. 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 diseaseand obesity. In this paper, the important role of white vegetables in the human diet is described, with a focus on the dietary fiber and resistantstarch content of white vegetables. Misguided efforts to reduce consumption of white vegetables will lower intakes of dietary fiber andresistant starch, nutrients already in short supply in our diets. Adv. Nutr. 4: 351S–355S, 2013.IntroductionVegetables have historically had a place in dietary guidancebecause of their concentrations of vitamins, especially Vitamins C and A, minerals, including electrolytes, and morerecently phytochemicals. Additionally, vegetables are recommended as a source of dietary fiber and resistant starch.Most countries have dietary recommendations that includevegetables (Table 1). Separating vegetables into groups isdifficult. Orange vegetables are high in vitamin A, but soare dark green vegetables, including spinach and broccoli.Dividing vegetables into color categories makes for goodmenu planning, but does not predict nutrient content.Vegetables rich in vitamin C, such as green peppers andwhite potatoes, belong in different vegetable categories.Corn, white potatoes, and dried beans are rich in starch.Sweet potatoes are also high in carbohydrates, but mostly sucrose, not starch. Dark green vegetables contain little or nostarch. The vegetable categories in the 2010 Dietary Guidelines for Americans (1) are listed in Table 2.According to the Dietary Guidelines for Americans 2010,the American diet is low in potassium, dietary fiber, calcium,and vitamin D. Energy density and calorie intake are problems with the American diet. Typically, vegetables are low inenergy density and good sources of dietary fiber and potassium, but the nutritional contribution of standard servingsof vegetables varies widely (2).CarbohydratesMost energy in the diet comes from carbohydrates. Carbohydrates are the major source of energy in the diet. The Institute of Medicine recommends that 45–65% of totalcalories come from carbohydrates (3). Dietary Guidelinesfor Americans suggests consumption of carbohydrate-richfoods, including vegetables, fruits, grains, nuts, seeds, anddairy products. Dietary fiber and resistant starch are onlysupplied by carbohydrate-rich foods.The sugar units present and how these units are chemically bonded to each other describe carbohydrates. Carbohydrate categories include sugars, starches, and fibers. Sugarsoccur naturally in fruits and milk products and are addedto foods during processing or preparation. Sugars also preserve food and provide viscosity and texture to foods. Thenutrition facts panel lists total sugars, but does not distinguish between intrinsic and added sugar (4).Starches are many glucose units linked together. Grains,legumes, and vegetables provide starch in the diet. Most1 Published in a supplement to Advances in Nutrition. Presented at the Purdue UniversityRoundtable on “White Vegetables: A Forgotten Source of Nutrients” held June 18–19, 2012in Chicago, IL. The roundtable was sponsored by Purdue University. The roundtable andsupplement publication were supported by an unrestricted grant from the Alliance forPotato Research and Education. All roundtable speakers received travel funding and anhonorarium for participation in the meeting and manuscript preparation. The viewsexpressed are those of the authors. The supplement coordinator was Catherine Nnoka, apaid consultant to the Alliance for Potato Research and Education. Guest editor ConnieWeaver received compensation from the Alliance for Potato Research and Education fortravel expenses, manuscript preparation, and editorial services for the supplementpublication. Guest editor Cheryl Anderson received compensation from the Alliance forPotato Research and Education for editorial services.2 Author disclosure: J. L. Slavin: no conflicts of interest.* To whom correspondence should be addressed. E-mail: jslavin@umn.edu.ã2013 American Society for Nutrition. Adv. Nutr. 4: 351S–355S, 2013; doi:10.3945/an.112.003491. 351SDownloaded from advances.nutrition.org at EBSCOhost on September 10, 2013starches are broken down to sugars by digestive enzymes,but some starches, such as those in legumes and wholegrains, escape digestion. These “resistant starches” functionsimilarly to dietary fiber in the large intestine (5). Carbohydrate fermentation in the gut produces hydrogen gas, whichis absorbed quickly.FiberDietary fiber is the undigested and unabsorbed carbohydratein the diet (6). These resistant carbohydrates may be fermented in the large intestine. Soluble fibers lower serumlipids, whereas insoluble fibers increase stool weight (7).This division of soluble and insoluble fiber is still used in nutrition labeling. Many fiber sources are mostly soluble, butstill increase stool weight, such as oat bran and psyllium.Soluble fibers, including inulin, do not lower blood lipids.Most vegetables are concentrated in insoluble fiber, not soluble fiber (8). Exceptions to this generalization includecooked potatoes. The USDA Nutrient Database includesonly total fiber (9); there are no official databases that include soluble and insoluble fiber. Lists of content of totalfiber, insoluble fiber, and soluble fiber are compilations ofdata from the USDA, the published literature, and estimatedvalues (8). Often the values for soluble and insoluble fiber donot add to total fiber or the values for soluble fiber were estimated by subtracting a literature value for insoluble fiberfrom a USDA value for total fiber.Processing can either increase or decrease the fiber content of a vegetable. Peeling of vegetables will lower thefiber content (8). Cooking generally has negligible effect onfiber content. Cooking, in general, may even increase the fibercontent of a product if water is driven out in the cooking process. Baking or other heat treatments (e.g., extruding) used infood processing also increase fiber content of the product, either by concentrating the fiber by removal of water or production of Maillard products that are captured as fiber ingravimetric methods.Fibers include both dietary fiber, the fiber naturally occurring in foods, and functional fibers, which are isolated fibers that have a positive physiological effect. No analyticalmeasures exist to separate dietary fiber and functional fiber,so the nutrition facts panel lists dietary fiber, which is actually total fiber.Americans consume w15 g of fiber per day, about thehalf recommended levels (6). Most commonly consumedfoods contain from 1 to 3 g of fiber per serving. The majorsources of dietary fiber in the American diets are white flourand potatoes, not because they are concentrated fiber, butthey are widely consumed (6). Fiber is an accepted essentialnutrient and intakes are low, so public health messages to increase fiber consumption are warranted.Resistant starchSome starch escapes digestion in the small intestine and onreaching the large intestine acts similarly to dietary fiber.The starch that is not digested is called resistant starch. Different subtypes of resistant starch have been described (10).Starch that is physically inaccessible to digestive enzymes isTable 1. National guidelines for vegetables: United Kingdom and the United StatesCharacteristic Eatwell Plate (United Kingdom) My Plate (United States)Agency Food Standards Agency/National Health Service USDANumber of foodcategories5 6Key messages Try to eat plenty of fruits and vegetables Increase vegetable and fruit intakeEat a variety of vegetables, especially dark-green andred and orange vegetables and beans and peasUnits Portions1 Servings2Vegetable 3 cups/d Vegetable and fruitVegetable5 portions per day3 heaping tbsp of vegetables (raw, cooked, frozen, tinned); 3 heaping tbsp of beans and pulses (beansand pulses count a maximum of one portion a day);and a dessert bowl of salad1 cup green salad; 1 baked potato; 1/2 cup cookedbroccoli; 1/2 cup serving of other vegetable; 1/2 cuptomato juiceServing examplesPotatoes included? No. Potatoes not included (considered starchy food) YesLegumes included? Beans and pulses count as only 1 portion a day, nomatter how many one eatsYes (protein category as well, but should only be countedin 1 category)Intake estimates Men: 3.5 portions; women: 3.8 portions 4.7 servings (NHANES 1999–2000)1 80 g.2 Cups.Table 2. USDA food patterns: vegetable subgroupsSubgroup and examplesDark green vegetables: all fresh, frozen, and canned dark green leafyvegetables and broccoli, cooked or raw (broccoli, spinach, romaine,collard, turnip and mustard greens)Red and orange vegetables: all fresh, frozen, and canned red and orangevegetables, cooked or raw (tomatoes, red peppers, carrots, sweetpotatoes, winter squash, pumpkin)Bean and peas: all cooked and canned beans and peas (kidney beans,lentils, chickpeas, and pinto beans; does not include green beans orgreen peas)Starchy vegetables: all fresh, frozen, and canned starchy vegetables(white potatoes, corn, green peas)Other vegetables: all fresh, frozen, and canned other vegetables (iceberglettuce, green beans, onions)352S SupplementDownloaded from advances.nutrition.org at EBSCOhost on September 10, 2013called resistant starch type 1, found in whole grains andseeds. Starch that is resistant to digestion due to the natureof the starch granule is referred to as resistant starch type 2.This type of starch is found in raw potatoes, unripe bananas,some legumes, and high amylose starches such as starch obtained from high amylose corn. Resistant starch that formsfrom retrograded amylose and amylopectin during food processing is called resistant starch type 3. This starch is found incooked and cooled foods such as potatoes, bread, and cornflakes. The fourth type of resistant starch, resistant starchtype 4, is produced by chemical modification. Resistant starchintake by Americans is ~3 to 8 g per person per day (10). Intheir database of resistant starch values obtained from published literature, highest resistant starch values (>3 g/100 gcooked serving) were found for toasted Italian bread, pumpernickel bread, corn flakes, muesli, puffed wheat cereal, ricesquare cereal, potato chips, raw bananas, white beans, andlentils. There are no standard databases on the content of resistant starch in common foodstuffs. Processed potato products were found to have the highest resistant starch contentof foods in the Swedish market (11).A nutritional comparison of white vegetables for totalcarbohydrate, fiber, and resistant starch is shown in Table3. Vegetables are often not consumed raw, but are cooked,fried, or combined with other ingredients before consumption. Thus, although a boiled potato is a nutrient-densefood, a fried potato may contribute a significant amountof fat and sodium to the diet. Fiber values of common servings of white vegetables range from 1.0 to 5.6 g per serving.Common serving sizes of fruits and vegetables contain 1–5 gof fiber (6). Most of the fiber in white vegetables is insolublefiber; in fact, white beans are mostly insoluble fiber, although usual dietary guidance suggests that dried beansare a rich source of soluble fiber (Table 3).Resistant starch values are difficult to find in the scientificliterature. Methods to measure resistant starch are not standardized; thus, large variation is seen. For white beans, 1 reference stated that white beans contained an average of 4.2 gof resistant starch in a 100 g serving (10), whereas anotherreference (11) listed the same size serving of white beansas having 11.1 g of resistant starch. Many explanations arepossible for this large discrepancy such as the method ofanalysis, cooking method, and difference in food measured.It is also not clear whether the resistant starch measuresshould be added to the total dietary fiber content of thefood. Thus, values for resistant starch much be considered,at best, estimates.Health benefits of vegetablesA wide range of plants is consumed by humans, includingfruits, seeds, leaves, roots, and tubers (12). The compositional features of certain types of white vegetables are summarized in Table 4 (12). Roots and tubers are importantsources of energy as starch. As foodstuffs, roots and especially tubers can be time-consuming to collect, but can bestored for long periods.Determining exposure to vegetables inepidemiologic studiesGenerally, culinary custom dictates which plants are considered vegetables. Culinary definition misclassifies botanicalfruits, for example, squash, tomatoes, and mature beans,which, despite being culinary “vegetables,” are botanical“fruits.” Mushrooms are technically fungi, but generally considered vegetables in diet planning. Additionally, vegetablescan be raw, cooked, canned, pickled, or leafy green.Table 3. Carbohydrate, total dietary fiber, insoluble dietary fiber, soluble dietary fiber, and resistant starch in white vegetables instandard servings1White vegetable Serving Carbohydrate2 TDF3 IDF3 SDF3 Resistant starch4gPotatoes, boiled 1 med, 138 g 29 2.1 1.7 0.4 1.8French fries 208 g 76 4.4 3.6 0.8 5.6Onions, raw 1/2 cup, 80 g 7.5 1.5 0.9 0.6 —Turnips, peeled, cooked 1 cup, 156 g 7.9 3.1 — — —Mushrooms, white, raw 1 cup, 96 g 3.1 1.0 0.7 0.3 —Cauliflower, cooked 1 cup, 67 g 4.1 2.3 1.9 0.4 —White beans, cooked 1/2 cup, 90 g 23 5.6 5.3 0.3 3.5, 11.1 (12)1 IDF, insoluble dietary fiber; SDF, soluble dietary fiber; TDF, total dietary fiber.2 Data on carbohydrates and total dietary fiber from (9).3 Data on insoluble and soluble dietary fiber content of vegetables from (11). No data found for turnips.4 Data on resistant starch from (12). No data found for onions, turnips, mushrooms, and cauliflower.Table 4. Compositional features of legumes (white beans) androots and tubers (potatoes, turnips) FeatureLegumesRoots and tubersg/100 g edible matterWaterProteinFatSugarStarchDietary fiberEnergy, kcal74.6–80.35.7–6.91.0–151.8–3.25.4–8.14.5–4.7247–34862.3–94.60.1–4.90.1–0.40.5–9.511.8–31.41.1–9.5297–525 Micronutrient B vitamins, vitamin C,potassium, magnesium,phosphorus, ironVitamin E, carotenoids,iron, potassium,calciumToxicconstituentsHemaagglutinins, lectins,trypsin inhibitorsGlycoalkaloidsAdapted from Ref. 15.Carbohydrates, dietary fiber, and resistant starch in white vegetables 353SDownloaded from advances.nutrition.org at EBSCOhost on September 10, 2013Vegetables are often consumed in mixed dishes such assoups, casseroles, and stews, making it difficult to measuretotal vegetable intake in epidemiologic studies. Publishedstudies on 3 methods for counting fruits and vegetables infourth grade students found that different countingmethods yielded significantly different tallies of fruit andvegetable intake (13).Scientific support that vegetable consumption improveshealth outcomes is limited (14). Examination of large prospective cohorts found no significant relationship betweenvegetable consumption and risk of chronic disease (15).No association was found for total vegetable consumptionand breast cancer incidence in a meta-analysis of 8 prospective studies (16). Higher consumption of vegetables, whetherconsumed raw or processed, was protective against coronaryheart disease incidence in a cohort in the Netherlands (17).Fruit and vegetable consumption and prospective weightchange were measured in a European prospective study ofcancer and nutrition. Baseline fruit and vegetable intakeswere not associated with weight change overall in participantsfrom 10 European countries (18).Health benefits of white vegetablesPotatoes are a staple vegetable in many parts of the world.Unlike leafy green vegetables, potatoes are rich in starchand provide protein of high biological value (19). Potatoesare rich in vitamin C and potassium and provide dietary fiber, especially if the skins are consumed. Few prospectivestudies have examined the relationship between potato consumption and health. Some data from the Nurses’ HealthStudy suggest that potatoes and French fries are linked tothe risk of type 2 diabetes in women (20). Epidemiologicstudies generally find an inverse relationship between carbohydrate intake and BMI, even when controlling for potentialconfounders (21). Other white vegetables are consumed inlow amounts in published prospective studies, so no conclusions can be drawn on links to health outcomes. However,white vegetables do provide vitamins, minerals, resistantstarch, dietary fiber, and phytochemicals in the diet.ConclusionsWhite vegetables provide carbohydrate, dietary fiber, andresistant starch to the diet. Epidemiologic studies showthat dietary fiber is linked to less cardiovascular diseaseand has a role in obesity prevention. Resistant starch is similar to dietary fiber, but may have unique protective properties in colon cancer prevention. Carbohydrate intake isgenerally found to be protective against weight gain, so thecarbohydrate, fiber, and resistant starch content of whitevegetables, including potatoes, is linked to positive healthoutcomes.Because vegetable intake is so low in US studies, it is notpossible to isolate the effects of any particular vegetable onhealth outcomes in these studies. Fiber is most concentratedin cooked vegetables because water is removed and fiberconcentrated. Although dietary guidance is supportive of amore vegetarian eating pattern, including increased servingsof vegetables, the scientific support for these recommendations is mixed in an evidence-based review (22). Fiber isan accepted nutrient so public health messages to increasefiber consumption are warranted. Much of the fiber intakein the United States is provided by white potatoes, so effortsto reduce consumption of potatoes will decrease intake ofboth fiber and resistant starch and potentially be detrimentalto public health.AcknowledgmentsThe sole author had responsibility for all parts of themanuscript.Literature Cited1. U.S. Department of Agriculture and U.S. Department of Health andHuman Services. Dietary Guidelines for Americans, 2010. 7th ed.Washington, DC: U.S. Government Printing Office;, 2010.2. Hornick BA, Weiss L. Comparative nutrient analysis of commonly consumed vegetables. Nutr Today. 2011;46:130–7.3. Institute of Medicine. Food and Nutrition Board, dietary reference intakes: energy, carbohydrates, fiber, fat, fatty acids, cholesterol, protein,and amino acids. Washington, DC: National Academies Press; 2002.4. Hess J, Latulippe M, Ayoob K, Slavin J. The confusing world of dietarysugars – definitions, intakes, food sources and international dietary recommendations. Food Function. 2012;3:477–86.5. Muir JG, O’Dea K. Measurement of resistant starch: factors affectingthe amount of starch escaping digestion in vitro. Am J Clin Nutr.1992;56:123–7.6. Slavin JL. Position of the American Dietetic Association: health implications of dietary fiber. J Am Diet Assoc. 2008;108:1716–31.7. Institute of Medicine. Food and nutrition board, dietary reference intakes proposed definition of dietary fiber, a report of the Panel onthe Definition of Dietary Fiber and the Standing Committee on the Scientific Evaluation of DRIs. Washington, DC: National Academies Press;2001.8. Marlett JA, Cheung T. Database and quick methods of assessing typicaldietary fiber intakes using data for 228 commonly consumed foods.J Am Diet Assoc. 1997;97:1139–48, 1151; quiz 1149–50.9. U.S. Department of Agriculture. Agricultural Research Service, Nutrient Database for Standard Reference, Release 24. Washington, DC.Available from: www.ars.usda.gov/ba/bhnrc/ndl. Accessed September12, 2012.10. Murphy MM, Douglass JS, Birkett A. Resistant starch intakes in theUnited States. J Am Diet Assoc. 2008;108:67–78.11. Liljeberg Elmståhl HL. Resistant starch content in a selection of starchyfoods on the Swedish market. Eur J Clin Nutr. 2002;56:500–5.12. Southgate DAT. Nature and variability of human food consumption.Philos Trans R Soc Lond B Biol Sci. 1991;334:281–8.13. Eldridge AL, Smith-Warner SA, Lytle LA, Murray DM. Comparison of3 methods for counting fruits and vegetables for fourth-grade studentsin the Minnesota 5 A Day Power Plus Program. J Am Diet Assoc. 1998;98:777–82.14. Slavin JL, Lloyd B. Health benefits of fruits and vegetables. Adv Nutr.2012;3:506–16.15. Hung HC, Joshipura KJ, Jiang R, Hu FB, Hunter D, Smith-Warner SA,Colditz GA, Rosner B, Spiegelman D, Willett WC. Fruit and vegetableintake and risk of major chronic disease. J Natl Cancer Inst. 2004;96:1577–84.16. Smith-Warner SA, Spiegelman D, Yaun SS, Adami HO, Beeson WL, vanden Brandt PA, Folson AR, Fraser GE, Freudenheim JL, GoldhobohmRA, et al. Intake of fruits and vegetables and risk of breast cancer: apooled analysis of cohort studies. JAMA. 2001;285:769–76.17. Oude Griep LM, Gelejinse JM, Kronhout D, Ocke MC, VerschuernWM. Raw and processed fruit and vegetable consumption and 10-year354S SupplementDownloaded from advances.nutrition.org at EBSCOhost on September 10, 2013coronary heart disease incidence in a population-based cohort study inthe Netherlands. PLoS ONE. 2010;5:e13609.18. Vergnaud AC, Norat T, Romaguera D, Mouw T, May AM, Romieu I,Freisling H, Slimani N, Boutron-Ruault MC, Clavel-Chapelon F, et al.Fruit and vegetable consumption and prospective weight change in participants of the European Prospective Investigation into Cancer and Nutrition–Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out ofHome, and Obesity study. Am J Clin Nutr. 2012;95:184–93.19. Camire ME, Kubow S, Donnelly DJ. Potatoes and human health. CritRev Food Sci Nutr. 2009;49:823–40.20. Halton TL, Willett WC, Liu S, Manson JE, Stampfer MJ, Hu FB. Potatoand French fry consumption and risk of type 2 diabetes in women. AmJ Clin Nutr. 2006;83:284–90.21. Gaesser GA. Carbohydrate quantity and quality in relation to bodymass index. J Am Diet Assoc. 2007;107:1768–80.22. U.S. Department of Agriculture, Agricultural Research Service, DietaryGuidelines Advisory Committee. 2010. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans,2010, to the Secretary of Agriculture and the Secretary of Health andHuman Services, Washington, DC.Carbohydrates, dietary fiber, and resistant starch in white vegetables 355SDownloaded from advances.nutrition.org at EBSCOhost on September 10, 2013Copyright of Advances in Nutrition is the property of American Society for Nutrition and itscontent may not be copied or emailed to multiple sites or posted to a listserv without thecopyright holder’s express written permission. However, users may print, download, or emailarticles for individual use.