Aloe Vera Gel Research Review

Aloe Vera Gel Research Review – The excerpts below focus primarily on the clinical research and proposed mechanisms of action for aloe vera as an anti-diabetic or hypoglycemic agent. There is much more research on this widely used plant as a topical agent for healing wounds and burns, but there may also be a hypoglycemic effect with oral supplementation as we will see below.

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HeConnection-Vitamins-Minerals-Supplements-Aloe Vera Gel Research ReviewAbstract

Aloe vera, commonly known as Barbados or Curaçao Aloe, is an herbal medicine with a long tradition of use by a variety of cultures. The succulent plant grows in arid and subtropical climates and is best known for 2 distinct preparations: the clear mucilaginous gel that is widely used for the treatment of minor burns, especially sunburns, and the thick sap of the leaves that turns yellow-brown and has strong laxative effects that caution its use. The traditional uses of the clear mucilaginous gel are manifold, ranging from topical applications to reduce perspiration to oral dosing for diabetes and a range of gastrointestinal ailments. The efficacy of aloe vera gel to treat burn wounds, genital herpes, and seborrheic dermatitis have been shown in clinical trials, but other indications such as psoriasis or internal application for the treatment of type 2 diabetes remains inconclusive. The main limitation of the current clinical knowledge about aloe vera gel is small clinical studies that often lack rigorous methodology. Several clinical trials are being conducted to further evaluate the use of aloe vera gel for a variety of disorders, as well as to further confirm traditional uses of the plant extract.

Introduction

Aloe vera (syn. Aloe barbadensis Mill., Fam. Liliaceae), also known as Barbados or Curaçao Aloe, has been used in traditional and folk medicines for thousands of years to treat and cure a variety of diseases. Although the plant is native to northern parts of Africa, it has rapidly spread across the world because its cultivation is easy. An important distinction has to be made between the strongly laxative and purgative latex derived from the bundle-sheath cells and the clear mucilaginous gel. The plant has been used by Egyptians, Assyrians, and Mediterranean civilizations, as well as in Biblical times. A variety of aloe species are still used in folk medicines of Africa and Asia. Hunters in the Congo reportedly rub their bodies in the clear mucilaginous gel to reduce perspiration; some African tribes apply the gel for chronic conjunctivitis; the gel is used in India for the treatment of asthma. (1)

Aloe vera gel is used as an ethnomedicine in Trinidad and Tobago for hypertension. (2) The most common folk use of aloe has been for the treatment of burn wounds and specifically to aid in the healing process, reduce inflammation, and tissue scaring. The gel was described by Dioscorides and used to treat wounds and mouth infections, soothe itching, and cure sores. (3) The use of aloe vera gel as a household remedy in the United States was triggered by reports of its beneficial effect on radiation dermatitis (4) followed by a boom in cultivation in the 1930s; it remains a common plant and for burns and abrasions. (1,5) Important contemporary uses of the gel exist in traditional medicines of India, China, and Mexico, as well as Middle America and the West Indies. Mexico is producing roughly 47% of aloe worldwide with a total sales volume of $123.5 million US dollars as of 2008. (6)

Despite its widespread popularity, scientific evidence on the aloe vera gel remains sparse. Aloe vera gel is regarded as safe if applied topically with only a few allergic reactions being reported. (7) The efficacy of aloe vera gel to treat burn wounds, genital herpes, and seborrheic dermatitis have been shown in clinical trials, but other indications such as psoriasis or internal application for the treatment of type 2 diabetes remain inconclusive. The major application of aloe vera gel remains as a skin moisturizer in cosmetics and as an après treatment for sunburns, for which it has proven its effectiveness. (8,9)

Description

Aloe vera is a succulent plant with thick, fleshy, serrated, lanceolate-shaped leaves of green-greyish color. Aloe vera inner gel is obtained from the lower leaves of the plant by slicing the leaf open. The gel is clear, odorless, and tasteless and should be free of leaf skin or yellow parts. No consistent standardization has been established, but the International Aloe Science Council (IASC), a trade association of internationally based aloe producers and marketers, requires adherence to certain specifications for the product to be certified. (10) Other preparations include a hydrophilic cream containing 0.5% aloe vera gel and an emulsion consisting of 30% aloe vera gel.

Primary Uses

(determined by clinical trials)

  • External
    • Mild to moderate burns (11–13) as well as erythema14
    • Genital herpes (15,16)
    • Seborrheic dermatitis (17)

 

  • Internal
    • Adjunct therapy of spontaneous fibrosarcomas in dogs and cats (18,19)

 

  • Other Potential Uses (determined by clinical trials and/or official monographs and/or empirical use)
    • Psoriasis vulgaris (20)
    • Skin moisturizer (8)
    • Type 2 diabetes (21–23)
    • Malignancies and immunodeficiency viruses in cats (24,25)
    • Oral lichen planus infections (26,27)
    • Angina pectoris (23)
    • Ulcerative colitis (28–31)
    • UV-induced erythema (14)
    • Kidney stones (32,33)
    • Alveolar osteitis (34)

Dosage

External

  • For burns: Clear mucilaginous gel (pure aloe vera inner gel or preparations containing 10%–70% aloe inner gel). Gel must be stabilized by pasteurization at 75–80°C for less than 3 minutes (3) and applied on affected area 3 times daily.
  • For seborrheic dermatitis: 30% aloe vera in a hydrophilic emulsion twice daily to affected area (17)
  • For psoriasis and genital herpes: Hydrophilic cream containing 0.5% aloe gel 3 times daily to affected area (16,20)

Internal

  • Treatment of diabetes and angina pectoris: recommended in humans, 100 mg of fresh inner gel each day or 1 tablespoon twice daily. (23,35)
  • For ulcerative colitis and irritable bowel syndrome: a dose of 25–50 ml of 95% aloe inner gel is recommended 3 times daily. (28)

Duration of Administration

External administration 3–4 times daily to affected area until improvement is seen. (15,17,20) No information for duration after oral application in humans is available, but generally the gel is taken as long as the symptoms persist. (23)

Pharmacological Actions

Note: Information on the precise chemical composition of the aloe vera inner gel used for most of the below listed observed pharmacological activities is lacking. Therefore, results should be interpreted with caution in regard to reproducibility of the stated effect.

Human

Mild (first degree) to moderate (second degree) burn wounds; (11–13,42) genital herpes at first onset; (16,20) seborrheic dermatitis; (17) oral lichen planus infections; (26) post-dermabrasion wound healing; (43) normalization of gastric pH; (44) treatment of diabetes and angina pectoris. (23)

Animal

antidiabetic in type-2 diabetic and insulin-resistant mice; (21,54–57) chemopreventive in skin papillomagenesis in mice; (58,59) anti-inflammatory in mice; (36,60–64) enhancement of immune responsiveness in chicks and mice; (65,66 )

In vitro

Suppresses bactericidal inflammation in human leukocytes; (75,76) inhibits pro-inflammatory cytokines; (81-83) acemannan enhances T cell response through monocyte activation; (84,85) acts as antifungal; (87,88) stimulates cell proliferation in keratinocytes by glycoprotein fraction; (47) accelerates wound healing in diabetic human skin fibroblasts; (89)

Proposed Mechanisms of Action

  • May promote hypoglycemic effect by normalizing membrane-bound enzyme activities of phosphatases and hydrolases and increased glucose metabolism; (55,56) potential active compounds include the phytosterols lophenol, cycloartenol and their alkylated derivatives (21)
  • Anti-inflammatory effect of plant sterols like lupeol, campesterol, and β-sitosterol (92) through bradikinase activation, (61) prostaglandin F2 and E2, as well as thromboxane A2 inhibition (45,81,96) and inhibition of IL-10 secretion (83)
  • Inhibitory effect on release of reactive oxygen species from human neutrophils by reducing intracellular free calcium levels (77)

Pregnancy and Lactation

It is not recommended to use aloe vera gel during pregnancy or while breastfeeding. (7) There is, however, no evidence that suggests a reproductive or genotoxic effect of topical aloe vera inner gel preparations. Internal use in combination with digoxin is contraindicated due to possible acceleration of potassium depletion. (98)

Adverse Effects

Oral application of aloe vera gel may lower blood glucose levels and enhance the activity of antidiabetic treatments. (23) An important factor for adverse effects is the purity of the aloe vera gel used, since anthraquinones like aloin might be related to the development of hypersensitivity reactions. (99,106)

Drug Interactions

When aloe vera gel is administered topical, it is generally regarded as safe. (7) If ingested, it might lead to increased hypoglycemia in conjunction with oral antidiabetics or insulin. (97) Aloe vera inner gel may significantly increase the absorption of vitamins C and E after oral application. (108) Aloe vera gel for systemic application is not recommended in combination with antidiabetic, diuretic, or laxative drugs; sevoflurane; or digoxin. (107) In general, a 2-hour time period is recommended between oral drug application and aloe vera ingestion due to increased intestinal motility and reduced drug absorption. (98) If aloe vera gel is used with any other prescription drug, the patient should inform the physician and/or pharmacist.

Clinical Review

The design of the clinical studies evaluated ranges from placebo-controlled, double-blind, multicenter studies to equivalence investigations. One of the most important factors is the composition of the aloe vera preparation used, which in most cases is a certain purity aloe vera gel without further elucidation of compound quantity. This discrepancy complicates a direct comparison of the studies.

The use of aloe vera gel in the traditional medicine of India has triggered an observational, inter-patient control study using fresh aloe vera inner gel in addition to adding psyllium (Plantago ason, Plantaginaceae) seeds to the daily diet of 5,000 patients diagnosed with angina pectoris. Over the course of 5 years, patients were observed and blood cholesterol, glucose, and triglyceride levels evaluated. A cofounding variable was the influence of aloe vera gel on diabetes mellitus.

Aloe vera gel had a significant influence on normalizing blood parameters and relief of angina pectoris symptoms, as well as diabetic symptoms. (23) In many patients, the continued use of aloe vera gel daily led to the discontinuation of prescription medications.

An important drawback of the study is the absence of a control group and no chemical definition of the aloe vera gel used in the study.

Two studies evaluated beneficial effects of aloe vera gel on irritable bowel syndrome30 and ulcerative colitis, (28) which resulted in no significant effect for either indication, although a patient-evaluated improvement was seen for the treatment of ulcerative colitis after 1 month.

One randomized, double-blind, placebo-controlled study investigated the use of aloe vera inner leaf gel for its anti-hyperglycemic and anti-hypercholesteremic effects in a small study population and found a slight decrease in fasting blood glucose, HbA1C, total cholesterol, and LDL levels, although this may be attributed to a restricted diet that patients in both groups were prescribed. (120)

Two promising clinical trials with fresh aloe vera gel in healthy adult (33) and pediatric32 volunteers showed increased calcium and oxalate urinary secretions, which might confirm the traditional use of aloe vera gel in the treatment of kidney stones. (1) However, confirmation through clinical studies for this indication in patients suffering from kidney stones is lacking to date.

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