Scientific evidence for the cosmetic and therapeutic effectiveness of aloe vera is limited and when present is frequently contradictory.[5][6] Despite this, the cosmetic and alternative medicine industries regularly make claims regarding the soothing, moisturizing, and healing properties of aloe vera, especially via Internet advertising.[7][3][4][2][39] Aloe vera gel is used as an ingredient in commercially available lotions, yogurt, beverages, and some desserts,[40][41][42] although at certain doses, it has toxic properties when used either for ingested or topical applications.[43]
[edit] Folk medicine
Aloe vera has a long association with herbal medicine, although it is not known when its medical applications were first suspected. Early records of Aloe vera use appear in the Ebers Papyrus from 16th century BC,[17] in both Dioscorides’ De Materia Medica and Pliny the Elder’s Natural History written in the mid-first century CE[17] along with the Juliana Anicia Codex produced in 512 AD.[40] The species is used widely in the traditional herbal medicine of China, Japan, Russia, South Africa, the United States, Jamaica, Latin America and India.[7]
[edit] Dietary supplement
Aloin, a compound found in the exudate of some Aloe species, was the common ingredient in over-the-counter (OTC) laxative products in the United States prior to 2003, when the Food and Drug Administration ruled that aloin was a class III ingredient, thereby banning its use.[44] Aloe vera has potential toxicity, with side-effects occurring at some dose levels both when ingested or applied topically.[43] Although toxicity may be less when aloin is removed by processing, aloe vera that contains aloin in excess amounts may induce side-effects.[7][8][45] A 2-year National Toxicology Program (NTP) study on oral consumption of non-decolorized whole leaf extract of aloe vera found evidence of carcinogenic activity in male and female rats. The NTP says more information is needed to determine the potential risks to humans.[46]
Aloe vera juice is marketed to support the health of the digestive system, but there is neither scientific evidence nor regulatory approval to support this claim.[47] The extracts and quantities typically used for such purposes appear to be dose-dependent for toxic effects.[43]
[edit] Phytochemicals
Aloe vera leaves contain phytochemicals under study for possible bioactivity, such as acetylated mannans, polymannans, anthraquinone C-glycosides, anthrones and anthraquinones, and various lectins.[7][48][49]
[edit] Commodities
Aloe vera is now widely used on facial tissues, where it is promoted as a moisturiser and/or anti-irritant to reduce chafing of the nose of users suffering hay-fever or cold.[50] It is common practice for cosmetic companies to add sap or other derivatives from Aloe vera to products such as makeup, tissues, moisturizers, soaps, sunscreens, incense, shaving cream, and shampoos.[40] Other uses for extracts of aloe vera include the dilution of semen for the artificial fertilization of sheep,[51] use as fresh food preservative,[52] and use in water conservation in small farms.[53] It has also been suggested that biofuels could be obtained from Aloe vera seeds.[54] Aloe is also used as a food substance. Some molecular gastronomists have begun to take advantage of its gelling properties. Perhaps the most notable among these is Chef Quique Dacosta’s “Oysters Guggenheim,” created at El Poblet in Spain.[55]
[edit] Research for possible medical uses
Aloe vera may be effective in treatment of wounds.[8] Evidence on the effects of its sap on wound healing, however, is limited and contradictory.[8] Some studies, for example, show that aloe vera promotes the rates of healing,[56][57] while, in contrast, other studies show that wounds to which aloe vera gel was applied were significantly slower to heal than those treated with conventional medical preparations.[58][59] A 2007 review concluded that the cumulative evidence supports the use of aloe vera for the healing of first to second degree burns.[60] Topical application of aloe vera may also be effective for genital herpes and psoriasis.[61] However, it is not effective for the prevention of radiation-induced injuries. Although anecdotally useful, it has not been proven to offer protection from sunburn or suntan.[62]
In a double-blind clinical trial, both the group using an aloe vera containing dentifrice and the group using a fluoridated dentifrice had a reduction of gingivitis and plaque, but no statistically significant difference was found between the two.[63]
There is preliminary evidence that A. vera extracts may be useful in the treatment of diabetes and elevated blood lipids in humans.[7] These positive effects are thought to be due to the presence of compounds such as mannans, anthraquinones and lectins.[7][48][49]Internal intake of aloe vera has been linked in preliminary research with improved blood glucose levels in diabetics,[64][65] although it has been suggested by the NTP that aloe may lower blood glucose levels.[46] It has also been linked with lower blood lipids in hyperlipidaemic patients,[66] but also with acute hepatitis (liver disease).[45] In other diseases, preliminary studies have suggested oral aloe vera gel may reduce symptoms and inflammation in patients with ulcerative colitis.[67] Abdominal cramps and diarrhea have been reported with oral use of aloe vera. Diarrhea, caused by the laxative effect of oral aloe vera, can decrease the absorption of many drugs.[46] Compounds extracted from aloe vera have been used as an immunostimulant that aids in fighting cancers in cats and dogs;[48] however, this treatment has not been scientifically tested in humans.
Gels from Aloe vera have been compared to those derived from other aloe species and with other plants belonging to the family Asphodelaceae. Bulbine frutescens, for example, is used widely for burns and a host of skin afflictions.[68] Aloe vera extracts might have antibacterial and antifungal activities, which possibly could help treat minor skin infections, such as boils and benign skin cysts and may inhibit growth of fungi causing tinea.[69] For bacteria, inner-leaf gel from aloe vera was shown in one study to inhibit growth of Streptococcus and Shigella species in vitro.[70] In contrast, aloe vera extracts failed to show antibiotic properties against Xanthomonas species.[71] [edit] See also
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Aloe
Asphodelaceae
Herbal medicine
Succulent plants
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[edit] References
1.^ a b c Akinyele BO, Odiyi AC (2007) Comparative study of the vegetative morphology and the existing taxonomic status of Aloe vera L. Journal of Plant Sciences 2(5):558-563.
2.^ a b “Forever Living Website”. http://www.foreverliving.com. Retrieved 2008-06-23.
3.^ a b “Miracle of Aloe”. http://www.miracleofaloe.com. Retrieved 2008-06-23.
4.^ a b “Aloe Vera Australia”. http://www.aloevera.com.au/. Retrieved 2008-06-23.
5.^ a b Ernst E. (2000) Adverse effects of herbal drugs in dermatology. Br J Dermatol 143:923–929
6.^ a b Marshall JM (2000) Aloe vera gel: what is the evidence? Pharm J 244:360–362.
7.^ a b c d e f g Boudreau MD and Beland FA (2006) An Evaluation of the Biological and Toxicological Properties of Aloe Barbadensis (Miller), Aloe Vera. Journal of Environmental Science and Health Part C 24:103–154.
