For constipation: 100-200 mg aloe or 50 mg aloe latex taken in the evening; however, it might not be safe to take aloe latex for this us
REVIEW ARTICLE
Aloe vera: a systematic review of its clinical effectiveness
B K VOGLER
However, total leaf extracts may contain anthraquinones.1
Although most commercially-available products are based on E ERNST
the gel, the British Pharmacopoeia does not contain an entry for aloe vera gel but it does describe aloes.2 The pharmacological SUMMARY
actions of aloe vera, as studied in vitro or in animals (in most
Background. The use of aloe vera is being promoted for a cases the total leaf extract was used), include anti-inflammatory large variety of conditions. Often general practitioners seem and anti-arthritic activity, and antibacterial and hypoglycaemic to know less than their patients about its alleged benefits.
effects.1
Aim. To define the clinical effectiveness of aloe vera, a pop-Aloe vera has been used for medicinal purposes in several cul-ular herbal remedy in the United Kingdom.
tures for millennia: Greece, Egypt, India, Mexico, Japan, and
Method. Four independent literature searches were con-China.2 The therapeutic claims made for aloe vera range over a ducted in MEDLINE, EMBASE, Biosis, and the Cochrane Library. Only controlled clinical trials (on any indication) broad list of conditions, as do the pharmacological activities were included. There were no restrictions on the language associated with it3 (Table 1). Most of these claims are based on of publication. All trials were read by both authors and data historical use rather than hard evidence.
were extracted in a standardized, pre-defined manner.
Aloe vera contains 75 potentially active constituents: vitamins,
Results. Ten studies were located. They suggest that oral enzymes, minerals, sugars, lignin, saponins, salicylic acids, and administration of aloe vera might be a useful adjunct for low-amino acids.4 Box 1 summarizes its most important constituents.5
ering blood glucose in diabetic patients as well as for The clinical use of aloe vera is supported mostly by anecdotal reducing blood lipid levels in patients with hyperlipidaemia.
data.6 While such reports are interesting and relevant for formu-Topical application of aloe vera is not an effective preventa-lating hypotheses, controlled trials are essential for defining its tive for radiation-induced injuries. It might be effective for effectiveness more conclusively.7 The aim of this systematic genital herpes and psoriasis. Whether it promotes wound review was to summarize all controlled clinical trials on aloe healing is unclear. There are major caveats associated with vera preparations with a view to providing evidence for or all of these statements.
against its clinical effectiveness.
Conclusion. Even though there are some promising results, clinical effectiveness of oral or topical aloe vera is not suffi-Method
ciently defined at present.
Computerized literature searches were performed to identify all Keywords: complementary medicine; aloe vera; review.
published articles on the subject. The following databases were used: MEDLINE, EMBASE, Biosis, and the Cochrane Library
— all from their inception to May 1998. In addition, other Introduction
experts working in this area were asked for further papers and THE use of aloe vera is being promoted for a large variety of our own files were searched. Furthermore, major manufacturers conditions. Often general practitioners (GPs) seem to know of aloe vera products were contacted in writing and asked for less than their patients about its alleged benefits. The Department published and unpublished controlled clinical trials. The bibli-of Complementary Medicine at the University of Exeter receives ographies of all investigations thus located were searched for fur-more enquiries from colleagues related to aloe vera than for any ther relevant articles.
other herbal remedy. Considering this high level of interest, it is Only controlled clinical trials of aloe vera (for any indication) relevant to review systematically the evidence for or against its were included. Studies were excluded if not performed on aloe clinical effectiveness.
vera mono-preparations or if they were designed only on a cer-Aloe vera (synonym: Aloe barbadensis Miller) belongs to the tain pharmacological constituent of the plant. There were no Liliaceal family, of which there are about 360 species. Aloe restrictions regarding publication language.
capensis (Cape aloes) belongs to a different species. Aloe vera is All articles (or abstracts if only available as abstracts) were a cactus-like plant that grows readily in hot, dry climates and read in full. Data were extracted in a predefined fashion.
currently, because of demand, is cultivated in large quantities.
Methodological quality was assessed using the Jadad score8
Cosmetic and some medicinal products are made from the (Box 2).
mucilaginous tissue in the centre of the aloe vera leaf and called aloe vera gel. The peripheral bundle sheath cells of aloe vera pro-duce an intensely bitter, yellow latex, commonly termed aloe Results
juice, or sap, or aloes. Aloe vera sap and aloe vera gel are often Ten trials met the above criteria and were included in this confused. Unlike aloes, aloe vera gel contains no anthraquinones, review. Three clinical studies had to be excluded. They were which are responsible for the strong laxative effects of aloes.
either not performed on aloe vera mono-preparation9 or only designed on a pharmacologically active constituent of the plant.10,11 Studies assessing the effects of aloes (including B K Vogler, honorary research assistant; and E Ernst, MD, PhD, FRCP(Edin), anthraquinones) as mono-preparations were not found. No director, Department of Complementary Medicine, School of Postgraduate Medicine and Health Sciences, University of Exeter.
unpublished study was located.
Submitted: 7 August 1998; final acceptance: 16 March 1999.
Two trials investigated the effects of aloe vera gel on wound healing after surgery.12,13 One study tested its efficacy in patients
© British Journal of General Practice, 1999, 49, 823-828.
British Journal of General Practice, October 1999
823
B K Vogler and E Ernst
Review article
Table 1. Aloe vera: therapeutic claims (A) and alleged pharmacological activities (B).
(A) Therapeutic claims
(B) Alleged pharmacological properties
Arthritis
‘Adaptogenic’
Asthma
Non-toxic — no known side-effects
Candida
Provides essential nutrients
Chronic fatigue syndrome
Breaks down and digests dead tissue
Digestive and bowel disorders (e.g. atonic constipation, irritable bowel syndrome, Crohn’s disease, ulcerative colitis) Anti-inflammatory
Lupus erythematodes
Reduces swelling
Skin problems (e.g. eczema, psoriasis, acne, burns, athlete’s foot, cold sores, frostbite) Moisturises
Sports injuries
Penetrates tissue
Ulcers (external and internal)
Antifungal
Relieves itching
Antimicrobial — prevents infections
Anaesthetises — relieves pain
Cleanses and detoxifies
Stimulates cell growth
Modified from Townsend (1998).3
Each ‘yes’ = 1 point; each ‘no’ = 0 points Anthraquinones
Inorganic compounds
A.
Study described as randomized (this includes the use of words such as random, randomly, and randomization)?
Aloin
Calcium
B.
Study described as double-blind?
Barbaloin
Sodium
C.
Description of withdrawals and dropouts?
Isobarbaloin
Chlorine
D.
Method to generate the sequence of randomization described Anthranol
Manganese
and appropriate (table of random numbers, computer gener-Aloetic acid
Zinc
ated, etc.)?
Ester of cinnamic acid
Chromium
E.
Method of double-blinding described and appropriate Aloe-emodin
Potassium sorbate
(identical placebo, active placebo, dummy, etc.)?
Emodin
Copper
Chrysophanic acid
Magnesium
Deduct 1 point if:
Resistannol
Iron
F.
Method to generate the sequence of randomization described and inappropriate (patients were allocated alternately or Saccarides
Enzymes
according to their date of birth, hospital number, etc.) Cellulose
Cyclooxygenase
G.
Method of double-blinding described and inappropriate Glucose
Oxidase
(e.g. comparison of tablet versus injection with no double Mannose
Amylase
dummy).
L-rhamnose
Catalase
Aldopentose
Lipase
Box 2. Jadad scoring system to measure methodological quality.8
Alkaline phosphatase
Carboxypeptidase
suffering from psoriasis.14 The prevention of radiation-induced skin injuries with an aloe vera gel was examined in two trials.15
Vitamins
Essential amino acids
The two most recent studies were performed on men suffering B1
Lysine
from genital herpes.16,17 One further trial examined the effective-B2
Threonine
ness of aloe vera in hyperlipidaemic patients.18 Finally, two stud-B6
Valine
ies assessed the plant’s hypoglycaemic and antidiabetic Choline
Leucine
potential.19,20 Key data from these studies are summarized in Folic acid
Isoleucine
Table 2. All studies included are briefly described in the follow-C
Phenylalanine
ing section.
α-tocopherol
Methionine
β-carotene
Topical use
Nonessential amino acids
Miscellaneous
Fulton12 documented the effects of two different dressings for Histidine
Cholesterol
wound-healing management on full-faced dermabrasion patients.
Arginine
Triglycerides
Eighteen patients suffering from acne vulgaris completed the Hydroxyproline
Steroids
study. Their abraded faces were divided in half. One side was Aspartic acid
β-sitosterol
treated with a standard polyethylene oxide gel wound dressing, Glutamic acid
Lignins
while the other side was treated with a polyethylene oxide dress-Proline
Uric acid
ing saturated with aloe vera. After 48 hours with the aloe vera Glycine
Gibberellin
dressing, intense vasoconstriction and a reduction in oedema was Alanine
Lectin-like substance
Tyrosine
Salicylic acid
noted; less exudate and crusting were eviden
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