Aloe vera is a widely recognized plant, popular in cosmetics, food, and as a dietary supplement. Amidst its widespread use, questions have emerged regarding its potential connection to cancer. This concern prompts a closer look at the scientific evidence surrounding various forms of aloe vera and their safety profiles.
Forms of Aloe Vera and Their Differences
The aloe vera plant yields several distinct forms, each with varying compositions due to the part of the plant used and subsequent processing methods. Aloe gel, the clear, viscous substance from the inner leaf, is obtained by removing the outer rind. This gel is commonly used in topical applications and some internal products.
Beneath the plant’s green outer skin lies aloe latex, a yellowish liquid with inherent laxative properties. This latex contains compounds that are largely absent from the inner gel. Whole leaf extract, in contrast, is derived from the entire leaf, including the outer rind and latex, and is often the raw material for commercial products.
Whole leaf extract often undergoes a purification step called decolorization. This process typically involves filtering the extract through activated charcoal to remove undesirable compounds. Non-decolorized whole leaf extract contains significantly higher levels of certain compounds, with aloin content potentially ranging from 10,000 to 20,000 parts per million (ppm). Decolorized products aim to reduce aloin to very low levels, with industry standards often setting a limit of less than 10 ppm for oral consumption.
Scientific Findings on Cancer Risk
Scientific investigations, particularly by the National Toxicology Program (NTP), have focused on the carcinogenicity of non-decolorized whole leaf extract. A comprehensive two-year NTP study involving oral administration to rats and mice found clear evidence of carcinogenic activity in male and female rats, primarily observing large intestine tumors. The NTP indicated that, based on current knowledge, these findings in rats may be relevant to humans.
The International Agency for Research on Cancer (IARC) subsequently classified aloe vera whole leaf extract as a Group 2B substance, “possibly carcinogenic to humans.” This classification was based on sufficient evidence of carcinogenicity observed in experimental animals. It is important to note that these animal studies specifically utilized non-decolorized whole leaf extract, which contains higher concentrations of certain compounds than processed forms.
While these animal findings raise important considerations, human epidemiological data on aloe vera and cancer are limited. There is currently no direct evidence that humans have contracted cancer from consuming aloe vera juice. Research suggests that the clear inner gel of the aloe plant and properly decolorized whole leaf extracts may have different safety profiles than the whole leaf extract containing the outer rind and latex.
Compounds Implicated in Cancer Concerns
The primary compounds within aloe vera that have been linked to cancer concerns are anthraquinones. These naturally occurring organic compounds are found predominantly in the outer leaf, particularly in the yellowish latex just beneath the plant’s skin. Aloin is the most prevalent anthraquinone in aloe vera, recognized for its potent laxative effects.
Anthraquinones, including aloin and aloe-emodin, have shown genotoxic properties in various in vitro and in vivo assays, meaning they can potentially damage DNA. When ingested, these compounds can irritate the digestive tract, leading to effects such as diarrhea and cramping. Long-term exposure to certain anthraquinones has been associated with health risks, including potential links to cancer in animal studies.
The processing method of decolorization is specifically designed to remove these problematic anthraquinones. This purification process, often involving activated charcoal filtration, significantly reduces the concentration of aloin and other undesirable compounds, making the final product safer for consumption.
Guidance for Safe Aloe Vera Use
Regulatory bodies have taken action regarding certain aloe products. In 2002, the U.S. Food and Drug Administration (FDA) required that all over-the-counter oral laxative products containing aloe be removed from the market or reformulated due to a lack of necessary safety data. Similarly, the International Agency for Research on Cancer (IARC) has classified non-decolorized whole leaf aloe vera extract as “possibly carcinogenic to humans,” underscoring safety concerns.
Consumers should carefully examine product labels when considering oral aloe vera supplements or beverages. Labels indicating “decolorized” or “aloin-free” whole leaf extracts suggest that the potentially problematic anthraquinones have been largely removed. The International Aloe Science Council (IASC) recommends that oral aloe vera products contain less than 10 ppm of aloin. Most commercial products that undergo proper processing, particularly those intended for internal consumption, typically do not contain the non-decolorized extract that was linked to cancer in animal studies.
Topical application of aloe vera gel, derived from the inner leaf, is generally considered safe and is not associated with significant side effects. For individuals using whole aloe vera leaves for home remedies, it is advisable to remove the outer green rind and yellow latex to minimize exposure to potentially harmful compounds. Consulting a healthcare professional before incorporating aloe vera products, especially for internal use or specific health concerns, is always a prudent step.