What is aloe as a dietary supplement?
The succulent aloe plant has been valued since prehistoric times for the treatment of burns, wound infections, and other skin problems. Medicinal aloe is pictured in an ancient cave painting in South Africa, and Alexander the Great is said to have captured an island off Somalia for the sole purpose of possessing the luxurious crop of aloe found there.
Most uses of aloe involve the gel inside its cactus-like leaves. However, the skin of the leaves themselves can be condensed to form a sticky substance known as drug aloe or aloes. It is a powerful laxative too, but it is seldom used for this purpose because its effects are unpleasant. The uses described here are intended to refer only to aloe gel, not to drug aloe. However, to make matters trickier, some aloe gel products contain small amounts of drug aloe, and it is possible that this contaminant is the actual source of benefits seen in some studies.
Millions of people might swear by their own experience that applying aloe to the skin can drastically reduce the time it takes for burns (including sunburn) to heal. However, scientific evidence fails to support this belief. Studies suggest that aloe is not effective for treating sunburn and may actually impair the healing of second-degree burns.
Aloe also appears to be ineffective for treating the burn-like skin damage caused by radiation therapy for cancer. In a double-blind, placebo-controlled study of 194 women undergoing radiation therapy for breast cancer, the use of aloe gel failed to protect the skin from radiation-induced damage. Lack of benefit was also seen in an open trial of 225 women. One study evaluated aloe soap in 73 men and women undergoing radiation therapy for various forms of cancer and, overall, failed to find benefit except possibly at the highest doses. Another study failed to find aloe gel helpful for mouth inflammation caused by radiation therapy for head and neck cancer.
Aloe also has been widely recommended for aiding wound healing. However, while the results of test tube and animal studies of aloe for wounds have been positive, one clinical report in people suggests that aloe can actually impair the healing of severe wounds. Does topical aloe provide any benefit? There is some evidence (although quite incomplete) that it might help genital herpes, lichen planus, psoriasis, and seborrhea.
Aloe gel has also been tried as a treatment to be taken internally by mouth. Two studies suggest that aloe gel taken in this way might be helpful for type 2 diabetes. One study found possible benefits for ulcerative colitis. Weak evidence hints that regular intake of aloe might decrease risk of kidney stones.
Oral aloe is also sometimes recommended as an aid in the treatment of asthma and stomach ulcers and for general immune support, but there is no meaningful evidence that it is effective for any of these purposes. One of the constituents of aloe gel, acemannan, has shown some promise in test tube and animal studies for stimulating immunity and inhibiting the growth of viruses. These findings have led to the suggestion that acemannan can help human immunodeficiency virus (HIV) infection. However, the one reported double-blind, placebo-controlled trial failed to show benefits.
Genital herpes. A two-week, double-blind, placebo-controlled trial enrolled sixty men with active genital herpes. Participants applied aloe cream (0.5 percent aloe) or placebo cream three times daily for five days. Use of aloe cream reduced the time necessary for lesions to heal (4.9 days versus 12 days) and also increased the percentage of those persons who were fully healed by the end of two weeks (66.7 percent versus 6.7 percent). A previous double-blind, placebo-controlled study by the same author, enrolling 120 men with genital herpes, found that cream made from aloe was more effective than pure aloe gel or placebo.
Seborrhea. Seborrhea is a fairly common skin condition leading to oily, red, and scaly eruptions in such areas as the eyebrows, eyelids, nose, ear, upper lip, chest, groin, and chin. A double-blind, placebo-controlled study of forty-four persons found that four to six weeks of treatment with aloe ointment could significantly reduce symptoms of seborrhea.
Psoriasis. According to a double-blind study that enrolled sixty men and women with mild to moderate symptoms of psoriasis, aloe cream may be helpful for this chronic skin condition. Participants were treated with either topical aloe extract (0.5 percent) or a placebo cream, applied three times daily for four weeks. Aloe treatment produced significantly better results than placebo, and these results were said to endure for almost one year after treatment was stopped. The study authors also reported a high level of complete “cure,” but what exactly they meant by this was not reported clearly.
However, another study failed to replicate these results. During four weeks of treatment, marked improvement was seen in 72.5 percent of skin patches treated with aloe, but in 82 percent of those treated with placebo. This was a statistically significant difference in favor of placebo. Further studies are needed to sort out these contradictory results.
Lichen planus. Lichen planus is a chronic skin condition characterized by itchy, flat, scaly patches. It can occur in various parts of the body, including the wrists, legs, trunk, mouth, and vagina.
One study evaluated the potential value of aloe vera as a topical treatment for oral lichen planus. In this double-blind, placebo-controlled study of fifty-four people with oral lichen planus, the use of aloe vera gel was significantly more effective than placebo in alleviating symptoms. In another study involving thirty-four women with lichen planus of the vulva (just outside the vagina), aloe vera led to significantly more improvement than placebo.
Diabetes. Evidence from two human trials suggests that aloe gel can improve blood sugar control in persons with type 2 diabetes. A single-blind, placebo-controlled trial evaluated the potential benefits of aloe in either seventy-two or forty persons with diabetes (the study report appears to contradict itself). The results showed significantly greater improvements in blood sugar levels among those given aloe over the two-week treatment period.
Another single-blind, placebo-controlled trial evaluated the benefits of aloe in persons who had failed to respond to the oral diabetes drug glibenclamide. Of the thirty-six persons who completed the study, those taking glibenclamide and aloe showed definite improvements in blood sugar levels over forty-two days compared with those taking glibenclamide and placebo. Although these are promising results, large studies that are double- rather than single-blind are needed to establish aloe as an effective treatment for hypoglycemia.
Ulcerative colitis. In a double-blind, placebo-controlled study of forty-four people with active ulcerative colitis, use of oral aloe gel at a dose of 100 milliliters twice daily for four weeks appeared to improve both subjective symptoms and objective measurements of disease severity. About one-half of the people given aloe showed response to treatment; about 30 percent experienced full remission. Benefits occurred only rarely in the placebo group. However, this was a small study, and its results cannot be taken as conclusive.
Topical aloe vera cream typically contains 0.5 percent aloe and is applied three times daily. For the treatment of diabetes, a dosage of 1 tablespoon of aloe juice twice daily has been used in studies.
Other than occasional allergic reactions, no serious problems have been reported with aloe gel, whether used internally or externally. However, comprehensive safety studies are lacking. Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established.
If aloe is used as a treatment for diabetes, and it proves effective, blood sugar levels could fall too low, necessitating a reduction in medication dosage. Close monitoring of blood sugar levels is, therefore, advised.
In addition, there is one report of an herb-drug interaction between aloe and the anesthesia drug sevoflurane, in which it appeared that aloe may have increased sevoflurane’s blood-thinning effect. Another isolated report appears to connect aloe to liver inflammation in one person. (Because aloe does not appear to possess any liver toxicity in general, this report would seem to suggest an idiosyncratic, in other words, a highly personal, reaction to the herb.)
In persons using medications for diabetes, the oral use of aloe vera might cause blood sugar levels to fall too low. Aloe gel might increase the effectiveness of hydrocortisone cream.
Bottenberg, M. M., et al. “Oral Aloe Vera-Induced Hepatitis.” Annals of Pharmacotherapy 41 (2007): 1740-1743.
Heggie, S., et al. “A Phase III Study on the Efficacy of Topical Aloe Vera Gel on Irradiated Breast Tissue.” Cancer Nursing 25 (2002): 442-451.
Kirdpon, S., et al. “Changes in Urinary Compositions Among Children After Consuming Prepared Oral Doses of Aloe (Aloe vera Linn.).” Journal of the Medical Association of Thailand 89 (2006): 1199-1205.
_______. “Effect of Aloe (Aloe vera Linn.) on Healthy Adult Volunteers: Changes in Urinary Composition.” Journal of the Medical Association of Thailand 89, suppl. 2 (2006): S9-S14.
Langmead, L., et al. “Randomized, Double-Blind, Placebo-Controlled Trial of Oral Aloe Vera Gel for Active Ulcerative Colitis.” Alimentary Pharmacology and Therapeutics 19 (2004): 739-748.