Editing Dietary supplement (section)

===Proteins and amino acids===
{{main|Protein (nutrient)|Amino acid}}

Protein-containing supplements, either ready-to-drink or as powders to be mixed into water, are marketed as aids to people recovering from illness or injury, those hoping to thwart the [[sarcopenia]] of old age,<ref>{{cite journal | vauthors = Liao CD, Tsauo JY, Wu YT, Cheng CP, Chen HC, Huang YC, Chen HC, Liou TH | display-authors = 6 | title = Effects of protein supplementation combined with resistance exercise on body composition and physical function in older adults: a systematic review and meta-analysis | journal = The American Journal of Clinical Nutrition | volume = 106 | issue = 4 | pages = 1078–91 | date=October 2017 | pmid = 28814401 | doi = 10.3945/ajcn.116.143594 | doi-access = free }}</ref><ref name=Colonetti2017 /> to athletes who believe that strenuous physical activity increases protein requirements,<ref name=IOC/> to people hoping to lose weight while minimizing muscle loss, i.e., conducting a [[protein-sparing modified fast]],<ref>{{cite journal | vauthors = Stonehouse W, Wycherley T, Luscombe-Marsh N, Taylor P, Brinkworth G, Riley M | title = Dairy Intake Enhances Body Weight and Composition Changes during Energy Restriction in 18–50-Year-Old Adults-A Meta-Analysis of Randomized Controlled Trials | journal = Nutrients | volume = 8 | issue = 7 | page = 394 | date = July 2016 | pmid = 27376321 | pmc = 4963870 | doi = 10.3390/nu8070394 | doi-access = free }}</ref> and to people who want to increase muscle size for performance and appearance. [[Whey protein]] is a popular ingredient,<ref name=Colonetti2017>{{cite journal | vauthors = Colonetti T, Grande AJ, Milton K, Foster C, Alexandre MC, Uggioni ML, Rosa MI | title = Effects of whey protein supplement in the elderly submitted to resistance training: systematic review and meta-analysis | journal = International Journal of Food Sciences and Nutrition | volume = 68 | issue = 3 | pages = 257–64 | date = May 2017 | pmid = 27653283 | doi = 10.1080/09637486.2016.1232702 | s2cid = 205659209 | url = https://ueaeprints.uea.ac.uk/id/eprint/66111/1/Accepted_manuscript.pdf }}</ref><ref>{{cite journal | vauthors = Naclerio F, Larumbe-Zabala E | title = Effects of Whey Protein Alone or as Part of a Multi-ingredient Formulation on Strength, Fat-Free Mass, or Lean Body Mass in Resistance-Trained Individuals: A Meta-analysis | journal = Sports Medicine | volume = 46 | issue = 1 | pages = 125–37 | date = January 2016 | pmid = 26403469 | doi = 10.1007/s40279-015-0403-y | s2cid = 31140351 | url = http://gala.gre.ac.uk/id/eprint/15355/2/15355_Naclerio_Effects%20of%20whey%20protein%20%28AAM%29%202016.pdf }}</ref><ref name=Miller2014>{{cite journal | vauthors = Miller PE, Alexander DD, Perez V | title = Effects of whey protein and resistance exercise on body composition: a meta-analysis of randomized controlled trials | journal = Journal of the American College of Nutrition | volume = 33 | issue = 2 | pages = 163–75 | year = 2014 | pmid = 24724774 | doi = 10.1080/07315724.2013.875365 | s2cid = 19434136 }}</ref> but products may also incorporate [[casein]], [[Soy protein|soy]], [[Pea protein|pea]], [[Hemp protein|hemp]] or [[rice protein]]. A meta-analysis found a moderate degree of evidence in favor of whey protein supplements use as a safe and effective adjunct to an athlete's training and recovery, including benefits for [[endurance]], average power, [[muscle mass]], and reduced perceived [[exercise intensity]].<ref name="Lam_2019">{{cite journal | vauthors = Lam FC, Bukhsh A, Rehman H, Waqas MK, Shahid N, Khaliel AM, Elhanish A, Karoud M, Telb A, Khan TM | display-authors = 6 | title = Efficacy and Safety of Whey Protein Supplements on Vital Sign and Physical Performance Among Athletes: A Network Meta-Analysis | journal = Frontiers in Pharmacology | volume = 10 | page = 317 | date = April 2019 | pmid = 31068804 | pmc = 6491698 | doi = 10.3389/fphar.2019.00317 | doi-access = free }}</ref>

According to US and Canadian [[Dietary Reference Intake]] guidelines, the protein [[Recommended Dietary Allowance]] (RDA) for adults is based on 0.8 grams protein per kilogram body weight. The recommendation is for sedentary and lightly active people.<ref name="DRIProteinChpt">{{cite book | title = Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids| publisher = Institute of Medicine. National Academy Press| year = 2005| url = https://archive.org/details/isbn_9780309085250| doi = 10.17226/10490| isbn = 978-0-309-08525-0| url-access = registration}}</ref><ref name="IJSNEM">{{cite journal | vauthors = Bilsborough S, Mann N | title = A review of issues of dietary protein intake in humans | journal = International Journal of Sport Nutrition and Exercise Metabolism | volume = 16 | issue = 2 | pages = 129–52 | date = April 2006 | pmid = 16779921 | doi = 10.1123/ijsnem.16.2.129 | s2cid = 10339366 | doi-access = free }}</ref><ref name=tarnopolsky>{{cite journal | vauthors = Tarnopolsky MA, Atkinson SA, MacDougall JD, Chesley A, Phillips S, Schwarcz HP | title = Evaluation of protein requirements for trained strength athletes | journal = Journal of Applied Physiology | volume = 73 | issue = 5 | pages = 1986–95 | date = November 1992 | pmid = 1474076 | doi = 10.1152/jappl.1992.73.5.1986 | s2cid = 46188182 }}</ref> Scientific reviews can conclude that a high protein diet, when combined with exercise, will increase muscle mass and strength,<ref name=lemon>{{cite journal |last1=Lemon|first1=PW | title=Do athletes need more dietary protein and amino acids? | journal = International Journal of Sport Nutrition | volume = 5 | issue = Suppl | pages = S39–61 | date = June 1995 | pmid = 7550257 | doi = 10.1123/ijsn.5.s1.s39 | s2cid = 27679614 }}</ref><ref name=Morton2017>{{cite journal | vauthors = Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, Aragon AA, Devries MC, Banfield L, Krieger JW, Phillips SM | display-authors = 6 | title = A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults | journal = British Journal of Sports Medicine | volume = 52 | issue = 6 | pages = 376–84 | date = March 2018 | pmid = 28698222 | pmc = 5867436 | doi = 10.1136/bjsports-2017-097608 }}</ref><!-- defined by transclusion from Bodybuilding supplement --><ref>{{cite journal | vauthors = Cermak NM, Res PT, de Groot LC, Saris WH, van Loon LJ | title = Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis | journal = The American Journal of Clinical Nutrition | volume = 96 | issue = 6 | pages = 1454–64 | date = December 2012 | pmid = 23134885 | doi = 10.3945/ajcn.112.037556 | doi-access = free }}</ref> or conclude the opposite.<ref>{{cite journal | vauthors = Finger D, Goltz FR, Umpierre D, Meyer E, Rosa LH, Schneider CD | title = Effects of protein supplementation in older adults undergoing resistance training: a systematic review and meta-analysis | journal = Sports Medicine | volume = 45 | issue = 2 | pages = 245–55 | date = February 2015 | pmid = 25355074 | doi = 10.1007/s40279-014-0269-4 | s2cid = 31362761 }}</ref> The International Olympic Committee recommends protein intake targets for both strength and endurance athletes at about 1.2–1.8 g/kg body mass per day.<ref name=IOC>{{cite web | url = https://hub.olympic.org/athlete365/wp-content/uploads/2016/01/1378_IOC_NutritionAthleteHandbook_1e.pdf | title = Nutrition for Athletes | work = International Olympic Committee | archive-url = https://web.archive.org/web/20180122235001/https://hub.olympic.org/athlete365/wp-content/uploads/2016/01/1378_IOC_NutritionAthleteHandbook_1e.pdf | archive-date = 2018-01-22 | author = Nutrition Working Group of the Medical and Scientific Commission of the International Olympic Committee | date = June 2016}}</ref> One review proposed a maximum daily protein intake of approximately 25% of energy requirements, i.e., approximately 2.0 to 2.5 g/kg.<ref name="IJSNEM"/>

The same protein ingredients marketed as dietary supplements can be incorporated into [[meal replacement]] and [[medical food]] products, but those are regulated and labeled differently from supplements. In the United States, "meal replacement" products are foods and are labeled as such. These typically contain protein, carbohydrates, fats, vitamins and minerals. There may be content claims such as "good source of protein", "low fat" or "lactose free".<ref>{{cite web|url=http://www.foodprocessing.com/articles/2004/53.html|title=Regulatory Issues: Meal Replacements – Convenience or Compromise?|publisher=Food Processing|access-date=2018-01-22|archive-date=2013-08-15|archive-url=https://web.archive.org/web/20130815230155/http://www.foodprocessing.com/articles/2004/53.html|url-status=dead}}</ref> Medical foods, also nutritionally complete, are designed to be used while a person is under the care of a physician or other licensed healthcare professional.<ref>{{cite web | url = https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/MedicalFoods/default.htm | title = Medical Foods Guidance Documents & Regulatory Information | date = 6 December 2017 | publisher = U.S. Food and Drug Administration. }}</ref><ref name = "FDA_FAQ_2016" /> Liquid medical food products – for example, [[Ensure]] – are available in regular and high protein versions.

Proteins are chains of [[amino acid]]s. Nine of these proteinogenic amino acids are considered essential for humans because they cannot be produced from other compounds by the human body and so must be taken in as food. Recommended intakes, expressed as milligrams per kilogram of body weight per day, have been established.<ref name="DRIProteinChpt"/> Other amino acids may be conditionally essential for certain ages or medical conditions. Amino acids, individually and in combinations, are sold as dietary supplements. The claim for supplementing with the [[branched-chain amino acid]]s leucine, valine and isoleucine is for stimulating muscle protein synthesis. A review of the literature concluded this claim was unwarranted.<ref>{{cite journal | vauthors = Charles EJ, Johnston LE, Herbert MA, Mehaffey JH, Yount KW, Likosky DS, Theurer PF, Fonner CE, Rich JB, Speir AM, Ailawadi G, Prager RL, Kron IL | display-authors = 6 | title = Impact of Medicaid Expansion on Cardiac Surgery Volume and Outcomes | journal = The Annals of Thoracic Surgery | volume = 104 | issue = 4 | pages = 1251–58 | date = October 2017 | pmid = 28552372 | pmc = 5610068 | doi = 10.1016/j.athoracsur.2017.03.079 }}</ref> In elderly people, supplementation with just [[leucine]] resulted in a modest (0.99&nbsp;kg) increase in lean body mass.<ref>{{cite journal | vauthors = Komar B, Schwingshackl L, Hoffmann G | title = Effects of leucine-rich protein supplements on anthropometric parameter and muscle strength in the elderly: a systematic review and meta-analysis | journal = The Journal of Nutrition, Health & Aging | volume = 19 | issue = 4 | pages = 437–46 | date = April 2015 | pmid = 25809808 | doi = 10.1007/s12603-014-0559-4 | s2cid = 24759289 | doi-access = free }}</ref> The non-essential amino acid [[arginine]], consumed in sufficient amounts, is thought to act as a donor for the synthesis of nitric oxide, a vasodilator. A review confirmed blood pressure lowering.<ref>{{cite journal | vauthors = Dong JY, Qin LQ, Zhang Z, Zhao Y, Wang J, Arigoni F, Zhang W | title = Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials | journal = American Heart Journal | volume = 162 | issue = 6 | pages = 959–65 | date = December 2011 | pmid = 22137067 | doi = 10.1016/j.ahj.2011.09.012 }}</ref> [[Taurine]], a popular dietary supplement ingredient with claims made for sports performance, is technically not an amino acid. It is synthesized in the body from the amino acid [[cysteine]].<ref>{{cite web|url=http://www.dictionary.com/browse/amino-acid|title=the definition of amino acid|website=Dictionary.com|access-date=2017-02-22}}</ref>