Government scientists have found evidence that relatively high doses of aloe vera — traditionally known as a natural skin treatment but now also widely used in alternative medicines — can cause intestinal tumors in rats. Aloe vera was examined for possible “tumor-producing activities” by researchers with the National Toxicology Program, who gave doses of it to rats over two years. In rats that consumed water spiked with aloe vera extract, the study says, “there was clear evidence of carcinogenic activity.” Thirty-nine per cent of female rats and 74 per cent of the males had malignant or benign tumors in their large intestines, the researchers found, while no tumors were seen in the control group of rats given pure drinking water. What these results mean for human consumers of aloe vera products is unclear. About half of all chemicals, whether natural or synthetic, tested in rodents at high doses cause cancer.
“At this stage, we’re looking at designing the next round of experiments,” Daniel Fabricant of the Food and Drug Administration, which contributed to the report, told New Scientist. “We want to relate the results to the commercial products that are out there.”
The prime suspect for causing the tumors in rodents is a substance called aloin A, which, together with other aloe extracts, was removed from laxatives sold over the counter in 2002 because manufacturers had failed to provide the FDA with sufficient information on safety. Aloe vera gel and “decolorized” extracts that have been filtered through activated charcoal contain much less aloin A than the whole leaf extracts given to the rats. Herbal supplements such as aloe vera do not require FDA approval, but the agency can take action against an unsafe product after it goes on sale. A previous study found that aloe vera did not have “any clear toxic effects” on the central nervous system of rats. It is taken orally as an alternative medicine to treat such conditions as diabetes, asthma, epilepsy and ulcers.