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1、from the associationPosition of the American Dietetic Association:Vegetarian DietsABSTRACTIt is the position of the American Di-etetic Association that appropriatelyplanned vegetarian diets, includingtotal vegetarian or vegan diets, arehealthful, nutritionally adequate, andmay provide health benefit
2、s in theprevention and treatment of certaindiseases. Well-planned vegetarian di-ets are appropriate for individualsduring all stages of the life cycle, in-cluding pregnancy, lactation, infancy,childhood, and adolescence, and forathletes. A vegetarian diet is definedas one that does not include meat
3、(in-cluding fowl) or seafood, or productscontaining those foods. This articlereviews the current data related tokey nutrients for vegetarians includ-ing protein, n-3 fatty acids, iron, zinc,iodine, calcium, and vitamins D andB-12. A vegetarian diet can meet cur-rent recommendations for all of thesen
4、utrients. In some cases, supplementsor fortified foods can provide usefulamountsofimportantnutrients.An ev-idence-based review showed that veg-etarian diets can be nutritionally ad-equate in pregnancy and result inpositive maternal and infant healthoutcomes. The results of an evidence-based review s
5、howed that a vegetar-ian diet is associated with a lower riskof death from ischemic heart disease.Vegetarians also appear to have lowerlow-density lipoprotein cholesterol lev-els, lower blood pressure, and lowerrates of hypertension and type 2 diabe-tes than nonvegetarians. Furthermore,vegetarians t
6、end to have a lower bodymass index and lower overall cancerrates. Features of a vegetarian dietthat may reduce risk of chronic diseaseinclude lower intakes of saturated fatand cholesterol and higher intakes offruits, vegetables, whole grains, nuts,soy products, fiber, and phytochemi-cals.Thevariabil
7、ityofdietarypracticesamong vegetarians makes individualassessment of dietary adequacy essen-tial.Inadditiontoassessingdietaryad-equacy, food and nutrition profession-als can also play key roles in educatingvegetarians about sources of specificnutrients, food purchase and prepara-tion, and dietary mo
8、difications to meettheir needs.J Am Diet Assoc. 2009;109:1266-1282.POSITION STATEMENTIt is the position of the American Di-etetic Association that appropriatelyplanned vegetarian diets, includingtotal vegetarian or vegan diets, arehealthful, nutritionally adequate, andmay provide health benefits in
9、the pre-vention and treatment of certain dis-eases. Well-planned vegetarian dietsare appropriate for individuals duringall stages of the lifecycle, includingpregnancy, lactation, infancy, child-hood, and adolescence, and for athletes.VEGETARIAN DIETS IN PERSPECTIVEA vegetarian is a person who does n
10、oteat meat (including fowl) or seafood,or products containing these foods.The eating patterns of vegetariansmay vary considerably. The lacto-ovo-vegetarian eating pattern is based ongrains, vegetables, fruits, legumes,seeds, nuts, dairy products, and eggs.The lacto-vegetarian excludes eggsas well as
11、 meat, fish, and fowl. Thevegan, or total vegetarian, eating pat-tern excludes eggs, dairy, and otheranimal products. Even within thesepatterns, considerable variation mayexist in the extent to which animalproducts are excluded.Evidence-based analysis was usedto evaluate existing research on typesof
12、 vegetarian diets (1). One questionfor evidence-analysis was identified:What types of vegetarian diets areexamined in the research? The com-plete results of this evidence-basedanalysis can be found on the Ameri-can Dietetic Associations EvidenceAnalysis Library (EAL) Web site() andare summarized bel
13、ow.EAL Conclusion Statement: The twomost common ways of defining vege-tarian diets in the research are vegandiets: Diets devoid of all flesh foods;This American Dietetic Association (ADA) position paper includes theauthors independent review of the literature in addition to systematicreview conducte
14、d using the ADAs Evidence Analysis Process and informa-tion from the Evidence Analysis Library. Topics from the Evidence AnalysisLibrary are clearly delineated. The use of an evidence-based approachprovides important added benefits to earlier review methods. The majoradvantage of the approach is the
15、 more rigorous standardization of reviewcriteria, which minimizes the likelihood of reviewer bias and increases theease with which disparate articles may be compared. For a detailed descrip-tion of the methods used in the evidence analysis process, access ADAsEvidence Analysis Process at http:/ Stat
16、ements are assigned a grade by an expert work groupbased on the systematic analysis and evaluation of the supporting researchevidence. Grade I?Good; Grade II?Fair; Grade III?Limited; GradeIV?Expert Opinion Only; and Grade V?Not Assignable (because there isno evidence to support or refute the conclus
17、ion).Evidence-based information for this and other topics can be found athttps:/ and subscriptions for nonmembers areavailable for purchase at https:/ 10.1016/j.jada.2009.05.0271266Journal of the AMERICAN DIETETIC ASSOCIATION 2009 by the American Dietetic Associationand vegetarian diets: Diets devoi
18、d ofall flesh foods, but also include egg(ovo) and/or dairy (lacto) products.However, these very broad cat-egories mask important variationswithin vegetarian diets and dietarypractices. These variations withinvegetarian diets make absolute cat-egorizationofvegetariandietarypractices difficult and ma
19、y be one ofthe sources of unclear relationshipsbetween vegetarian diets and otherfactors. Grade II?Fair.In this article, the term vegetarianwill be used to refer to people choosinga lacto-ovo-, lacto-, or vegan vegetariandiet unless otherwise specified.Whereaslacto-ovo-,lacto-,andvegan-vegetariandie
20、tsarethosemost commonly studied, practitionersmay encounter other types of vegetar-ian or near-vegetarian diets. For ex-ample, people choosing macrobioticdiets typically describe their diet asvegetarian. The macrobiotic diet isbased largely on grains, legumes, andvegetables. Fruits, nuts, and seedsa
21、re used to a lesser extent. Some peo-ple following a macrobiotic diet arenot truly vegetarian because they eatlimited amounts of fish. The tradi-tional Asian-Indian diet is predomi-nantly plant based and is frequentlylacto-vegetarian although changes of-ten occur with acculturation, includ-ing great
22、er consumption of cheeseand a movement away from a vege-tarian diet. A raw foods diet may be avegan diet, consisting mainly or ex-clusively of uncooked and unproc-essed foods. Foods used include fruits,vegetables, nuts, seeds, and sproutedgrains and beans; in rare instancesunpasteurizeddairyproducts
23、andeven raw meat and fish may be used.Fruitariandietsarevegandietsbased on fruits, nuts, and seeds. Veg-etables that are classified botanicallyas fruits like avocado and tomatoesare commonly included in fruitariandiets; other vegetables, grains, beans,and animal products are excluded.Some people wil
24、l describe them-selves as vegetarian but will eat fish,chicken, or even meat. These self-de-scribed vegetarians may be identifiedin research studies as semivegetarians.Individual assessment is required toaccuratelyevaluatethenutritionalquality of the diet of a vegetarian or aself-described vegetaria
25、n.Common reasons for choosing avegetarian diet include health consid-erations, concern for the environ-ment, and animal welfare factors.Vegetarians also cite economic rea-sons, ethical considerations, worldhunger issues, and religious beliefs astheir reasons for following their cho-sen eating patter
26、n.Consumer TrendsIn 2006, based on a nationwide poll,approximately 2.3% of the US adultpopulation (4.9 million people) consis-tentlyfollowedavegetariandiet,stating that they never ate meat, fish,or poultry (2). About 1.4% of the USadult population was vegan (2). In2005, according to a nationwide pol
27、l,3% of 8- to 18-year-old children andadolescents were vegetarian; close to1% were vegan (3).Many consumers report an interestin vegetarian diets (4) and 22% reportregular consumption of meatless sub-stitutes for meat products (5). Addi-tional evidence for the increasing in-terest in vegetarian diet
28、s includes theemergence of college courses on vege-tarian nutrition and on animal rights;the proliferation of Web sites, period-icals, and cookbooks with a vegetar-ian theme; and the publics attitudetoward ordering a vegetarian mealwhen eating away from home.Restaurants have responded to thisinteres
29、t in vegetarian diets. A surveyof chefs found that vegetarian disheswere considered “hot” or “a perennialfavorite” by 71%; vegan dishes by 63%(6). Fast-food restaurants are begin-ning to offer salads, veggie burgers,and other meatless options. Most uni-versity foodservices offer vegetarianoptions.Ne
30、w Product AvailabilityThe US market for processed vegetar-ian foods (foods like meat analogs,nondairy milks, and vegetarian en-trees that directly replace meat orother animal products) was estimatedto be $1.17 billion in 2006 (7). Thismarket is forecast to grow to $1.6 bil-lion by 2011 (7).The avail
31、ability of new products, in-cluding fortified foods and conveniencefoods, would be expected to have animpact on the nutrient intake of vege-tarians who choose to eat these foods.Fortified foods such as soy milks, meatanalogs, juices, and breakfast cerealsare continually being added to the mar-ketpla
32、ce with new levels of fortifica-tion. These products and dietary sup-plements,whicharewidelyavailableinsupermarkets and natural foods stores,can add substantially to vegetariansintakes of key nutrients such as cal-cium, iron, zinc, vitamin B-12, vitaminD, riboflavin, and long-chain n-3 fattyacids. W
33、ith so many fortified productsavailable today, the nutritional statusof the typical vegetarian today wouldbe expected to be greatly improvedfrom that of a vegetarian 1 to 2 decadesago.Thisimprovementwouldbeenhanced by the greater awarenessamong the vegetarian population ofwhat constitutes a balanced
34、 vegetariandiet. Consequently older research datamay not represent the nutritional sta-tus of present-day vegetarians.Health Implications of Vegetarian DietsVegetarian diets are often associatedwith a number of health advantages,includinglowerbloodcholesterollevels,lower risk of heart disease, lower
35、 bloodpressure levels, and lower risk of hy-pertension and type 2 diabetes. Vege-tarians tend to have a lower body massindex (BMI) and lower overall cancerrates. Vegetarian diets tend to be lowerin saturated fat and cholesterol, andhavehigherlevelsofdietaryfiber,mag-nesium and potassium, vitamins C
36、andE, folate, carotenoids, flavonoids, andotherphytochemicals.Thesenutri-tional differences may explain some ofthe health advantages of those follow-ing a varied, balanced vegetarian diet.However, vegans and some other vege-tarians may have lower intakes of vita-minB-12,calcium,vitaminD,zinc,andlong
37、-chain n-3 fatty acids.Recently, outbreaks of food-borne ill-ness associated with the consumptionof domestically grown and importedfresh fruits, sprouts, and vegetablesthat have been contaminated by Sal-monella, Escherichia coli, and othermicro-organismshavebeenseen.Health advocacy groups are callin
38、g forstricter inspection and reporting proce-dures and better food-handling prac-tices.NUTRITION CONSIDERATIONS FORVEGETARIANSProteinPlant protein can meet protein re-quirements when a variety of plantfoods is consumed and energy needsJuly 2009 Journal of the AMERICAN DIETETIC ASSOCIATION1267are met
39、. Research indicates that anassortment of plant foods eaten overthe course of a day can provide allessential amino acids and ensure ad-equate nitrogen retention and use inhealthy adults; thus, complementaryproteins do not need to be consumedat the same meal (8).A meta-analysis of nitrogen bal-ance s
40、tudies found no significant dif-ference in protein needs due to thesource of dietary protein (9). Based ontheproteindigestibility-correctedamino acid score, which is the stan-dard method for determining proteinquality, other studies have found thatalthough isolated soy protein canmeet protein needs
41、as effectively asanimal protein, wheat protein eatenalone, for example, may result in areduced efficiency of nitrogen utiliza-tion (10). Thus, estimates of proteinrequirements of vegans may vary, de-pending to some degree on dietarychoices. Food and nutrition profes-sionals should be aware that prot
42、einneeds might be somewhat higherthan the Recommended Dietary Al-lowance in those vegetarians whosedietary protein sources are mainlythose that are less well digested, suchas some cereals and legumes (11).Cereals tend to be low in lysine, anessential amino acid (8). This may berelevant when evaluati
43、ng diets of in-dividuals who do not consume animalprotein sources and when diets arerelatively low in protein. Dietary ad-justments such as the use of morebeans and soy products in place ofother protein sources that are lowerin lysine or an increase in dietary pro-tein from all sources can ensure an
44、adequate intake of lysine.Although some vegan women haveprotein intakes that are marginal,typical protein intakes of lacto-ovo-vegetarians and of vegans appear tomeet and exceed requirements (12).Athletes can also meet their proteinneeds on plant-based diets (13).n-3 Fatty AcidsWhereas vegetarian di
45、ets are gener-ally rich in n-6 fatty acids, they maybe marginal in n-3 fatty acids. Dietsthat do not include fish, eggs, or gen-erous amounts of algae generally arelow in eicosapentaenoic acid (EPA)anddocosahexaenoicacid(DHA),fatty acids important for cardiovascu-lar health as well as eye and braind
46、evelopment. The bioconversion of?-linolenic acid (ALA), a plant-basedn-3 fatty acid, to EPA is generally lessthan 10% in humans; conversion ofALA to DHA is substantially less (14).Vegetarians, and particularly vegans,tend to have lower blood levels of EPAand DHA than nonvegetarians (15).DHA suppleme
47、nts derived from mi-croalgae are well absorbed and posi-tively influence blood levels of DHA,and also EPA through retroconver-sion (16). Soy milk and breakfastbars, fortified with DHA, are nowavailable in the marketplace.The Dietary Reference Intakes rec-ommend intakes of 1.6 and 1.1 g ALAper day, f
48、or men and women, respec-tively (17). These recommendationsmay not be optimal for vegetarianswho consume little if any DHA andEPA (17) and thus may need addi-tional ALA for conversion to DHA andEPA. Conversion rates for ALA tendto improve when dietary n-6 levelsare not high or excessive (14). Vege-t
49、arians should include good sources ofALA in their diet, such as flaxseed,walnuts, canola oil, and soy. Thosewith increased requirements of n-3fatty acids, such as pregnant and lac-tatingwomen,maybenefitfromDHA-rich microalgae (18).IronThe iron in plant foods is nonhemeiron, which is sensitive to bot
50、h inhibi-tors and enhancers of iron absorption.Inhibitors of iron absorption includephytates, calcium, and the polypheno-lics in tea, coffee, herb teas, and cocoa.Fiber only slightly inhibits iron absorp-tion (19). Some food preparation tech-niques such as soaking and sproutingbeans, grains, and see