The popular succulent plant, Aloe Vera, has been used for centuries in traditional medicine, particularly for its topical soothing properties for skin irritations and burns. Its clear gel is a common ingredient in cosmetics and health products, leading to widespread consumer use. However, a controversy surrounds its safety, specifically concerning a potential link between consuming certain forms of the plant and an increased cancer risk. This concern is not directed at the topical application of the gel but at the oral ingestion of some extracts derived from the whole leaf. To understand the risk, it is necessary to examine the specific chemical components of the plant and how different processing methods affect their presence in commercial products.
The Chemical Basis of the Concern
The cancer-related alarm centers on a group of compounds known as anthraquinones, which are naturally present in the Aloe leaf. These phenolic compounds are highly concentrated in the yellow, bitter latex layer situated just beneath the leaf’s outer skin. The main anthraquinone of concern is aloin, which is a potent laxative and has demonstrated genotoxic potential in laboratory settings. The initial scientific evidence raising the alarm came from a two-year study conducted by the National Toxicology Program (NTP) in the United States, which involved administering non-decolorized whole-leaf Aloe Vera extract in drinking water to rats. The results showed clear evidence of carcinogenic activity, specifically an increased incidence of tumors, including adenomas and carcinomas, in the large intestine of the exposed rats.
Understanding Different Aloe Products
The safety of an Aloe product depends on how the leaf is processed. The whole leaf is composed of a tough outer rind, a layer of bitter yellow latex, and the clear, inner fillet or gel; the latex contains anthraquinones like aloin and is physically separate from the clear gel. Products labeled as “Whole Leaf Extract” that are not purified retain the latex layer and, consequently, the high levels of aloin. Conversely, “Inner Leaf Fillet” products are made only from the clear gel found inside the leaf, which naturally contains negligible amounts of anthraquinones. “Decolorized Whole Leaf Extract” starts with the entire leaf but undergoes a rigorous filtration process, typically using activated carbon, to actively remove the anthraquinones and aloin, reducing the concentration by a factor of up to 100 times compared to unfiltered extracts.
Regulatory Findings and Official Classification
Major health organizations have addressed the safety of Aloe Vera, drawing a clear distinction between the raw extract and processed products. The International Agency for Research on Cancer (IARC), a branch of the World Health Organization, classified non-decolorized whole-leaf Aloe Vera extract as “possibly carcinogenic to humans” (Group 2B). This classification is based on the sufficient evidence of carcinogenicity observed in the experimental animal studies. Regulatory bodies focus on the presence of anthraquinones as the determining factor for risk, meaning the IARC classification applies only to the non-decolorized whole-leaf extract, not to purified inner leaf gel or decolorized juice. A purified, decolorized whole leaf extract that has been filtered to remove the aloin is not included in the same risk category as the unfiltered extract, as the risk is concentrated in the bitter latex component.
Guidance for Safe Consumption
Consumers can reduce potential risk by choosing purified products that meet industry standards for aloin content. The International Aloe Science Council (IASC) sets a standard for orally consumed products, recommending the maximum allowable aloin content be less than 10 parts per million (ppm). Products adhering to this limit are considered safe for consumption because the components linked to the cancer concern have been effectively removed. When purchasing oral Aloe Vera products, such as juices or dietary supplements, consumers should look for specific terms on the label, such as “purified,” “decolorized,” “aloin-free,” or “inner leaf fillet.” Topical use of Aloe Vera gel, the most common application, does not pose the same oral consumption risk, as aloin absorption through the skin is not a significant concern.