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Aloe, a popular houseplant, has a long history as a multipurpose folk remedy. Commonly known as Aloe vera, the plant can be separated into two basic products: gel and latex. Aloe vera gel is the leaf pulp or mucilage, a thin clear jelly-like substance obtained from the parenchymal tissue that makes up the inner portion of the leaves . The gel contains carbohydrate polymers, such as glucomannans or pectic acid, plus various other organic and inorganic compounds. Aloe latex, commonly referred to as "aloe juice," is a bitter yellow exudate from the pericyclic tubules just beneath the outer skin of the leaves. For pharmaceutical use as a laxative, the juice is often dried to produce "aloe" granules that are dark brown from exposure to air. The terms "gel" and "juice" are not clearly defined by manufacturers and often are confused by consumers.
The mechanical separation process is not always complete, so aloe latex can be found in some aloe gels. It is desirable to make the gel as pure as possible, because aloe latex contains the anthraquinone glycosides aloin A and B, which are potent laxatives . The processed products are difficult to keep stable, a problem that can cause differences in product potency. Many products advertise special stabilizing procedures, but the best source of aloe gel would be direct from a broken leaf of the plant.
Aloe gel has been used for topical treatment of wounds, minor burns, and skin irritations. American consumers are most familiar with aloe's use in skin-care products, but aloe can also be used as a beverage. Aloe products for internal use have been promoted for constipation, coughs, wounds, ulcers, diabetes, cancer, headaches, arthritis, immune-system deficiencies, and many other conditions. However, the only substantiated internal use is as a laxative [3-6]. The anthroquinones and anthrones in the aloe latex probably produce their laxative effect by increasing colonic peristalsis and increasing the intestinal water content by opening chloride channels of the colonic membrane to cause a net reduction of liquid absorption by the colon . The anthroquinone glycosides reach the colon mostly undigested, although some are metabolized by enzymes produced by intestinal bacteria. The result includes more frequent stools with softer consistency. In most of the studies on the laxative effects of aloe, the aloe was not used alone but in combination with other laxatives, such as celandin or psyllium. Aloe's side effects can include abdominal pain, diarrhea, and electrolyte imbalances, especially at higher doses.
Few studies have tested whether taking aloe gel internally can influence wound-healing. One study has demonstrated improved wound healing in mice, which the authors attributed to increased capillary blood flow to the injured areas . During the 1970s, two FDA advisory panels concluded that there was insufficient evidence that aloe vera gel was useful for treating minor burns, cuts, or abrasions, or for treating minor vaginal irritations .
One study of 5,000 subjects found a positive effect of lowering risk factors in patients with heart disease. The study showed that by adding Isabgol (which increases the bulk of feces) and aloe vera gel to the diet, there was a marked reduction in total lipids, total serum cholesterol, serum triglycerides, fasting and post-meal blood sugar levels in diabetics, and an increase in HDL . Our January 1998 MEDLINE search found no other studies on blood lipids, heart disease risk, and aloe. Some research has shown decreasing fasting blood sugar in diabetic animals given aloe [10-13]. Further studies are needed to explore these issues in humans.
False advertising claims for aloe are common, especially on the Internet. Some Web pages are making bold claims and using testimonials promoting it for treating the AIDS virus, arthritis, or other chronic and debilitating conditions [14,15]. These claims have not been substantiated by scientific studies.
The safety of aloe is another concern. Aloe extract can be taken orally as a dietary supplement, but does not have FDA approval for use as a drug . Currently, aloe is a Category I over-the-counter stimulant laxative, meaning that it is generally recognized as safe and effective if used appropriately for this purpose . The FDA recommends further testing and safety data for aloe. Some deaths have been reported of cancer patients who were treated with aloe vera intravenously by a physician whose license was subsequently revoked [16,18-20]. Injection of aloe vera is illegal in the United States, but desperate people can go to other countries where there is less regulation for unproven treatments.
Ms. Lulinski is a medical nutritionist.
Dr. Kapica is Assistant Professor of Nutrition and Clinical Dietetics, Finch University of Health Sciences/The Chicago Medical School.
Thomas J. Wheeler, Ph.D., and Manfred Kroger, Ph.D., helped edit this article.