As it’s revealed that health ingredient aloe vera is as carcinogenic as lead, exhaust fumes and aspartame… Can it really raise the risk of cancer?

Earlier this month, aspartame — the sugar substitute in Diet Coke — was added to the World Health Organization’s list of more than 300 substances that “possibly” cause cancer.

The WHO pointed out that the sweetener, which is also found in a wide variety of foods, is still safe to use and that the average adult would need to consume between nine and 14 cans of Diet Coke per day to exceed recommended limits. Even then, any risks were based on “limited scientific evidence,” including decades of animal research.

Scientists were quick to state that the results of these studies, in which large amounts of aspartame were force-fed to lab rats, were widely disputed.

Others tried to reassure the public that there was no need to panic: After all, the same list of “possible” carcinogens included aloe vera — the ubiquitous plant extract added to everyday skincare products, supplements, and even mouthwashes and toothpastes.

No doubt it was meant to show how much of a non-issue this all was. But in some cases, the allegation only added to the fear.

“Aloe vera is carcinogenic?” wrote one concerned Twitter user.

“Amazed that aloe vera is on the same list as lead, welding fumes and engine exhaust,” another commented. “Does that mean I can’t use it for sunburn?” asked a third.

So what are the ‘risks’ of aloe vera – and should we be concerned about it being on a list of ‘possible’ carcinogens? The short answer is no, according to toxicology experts.

The cactus-like aloe vera plant has been used in traditional medicine for centuries, with the ancient Greeks and Romans applying its translucent inner pulp to wounds.

Today, aloe vera extract has found its way into just about every kind of skincare product – from sunburn-relieving gels and moisturizers to shampoos, soaps, and even deodorants.

The global aloe vera extract market is worth around £1.2 billion – and demand is rising every year.

However, there may be grounds for caution if you intend to consume it, rather than simply rubbing it on the skin. There is some evidence that a specific component of aloe – the yellow liquid sap contained within the leaves, between the outer ‘shell’ and inner pulp, known as aloe vera latex – can cause problems if eaten.

In 2013, researchers studying the toxic effects of aloe vera gave rats water with varying concentrations of “whole leaf aloe vera extract,” which contains aloe vera latex, for two years. After two years, some rats given the higher concentrations developed a rare intestinal tumor. The animals that received lower concentrations of aloe vera liquid did not develop these tumors.

Scientists believe that compounds in aloe vera latex known as anthraquinones — which have a laxative effect and irritate the digestive tract — are responsible. In addition to skin products, aloe vera extracts are also found in health food supplements—claimed to do everything from “detoxify” to improve digestion—and drinks.

In light of the 2013 findings, the European Food Safety Authority has issued a warning advising against ‘prolonged use and consumption [of anthraquinone-containing supplements] at high doses because of potential safety concerns’.

And in 2019, it proposed a ban on certain aloe vera extracts known to contain the most harmful anthraquinones. Around the same time, it was added to the WHO list of ‘possible’ cancer causes.

Alan Boobis, professor emeritus of toxicology at Imperial College London, says: ‘It’s a rare type of tumor that they found in that 2013 study [investigating the effect of aloe vera on rats]meaning they were pretty sure it was directly related to the substance the rats were consuming.

“There is also evidence from other studies that anthraquinones cause damage to DNA in cells that can lead to cancer.”

Interestingly, the same study found that mice fed the same water did not develop the tumors. Prof Boobis says: ‘There is no evidence of an adverse effect in humans – but the studies we have mean the risk cannot be ruled out and that’s why it’s on the ‘possible’ list.’

The WHO’s list of carcinogens, prepared by its International Agency for Research on Cancer, is divided into categories.

Groups 1 and 2A are substances known to be carcinogenic to humans or ‘probably’ carcinogenic, such as smoking, processed meats, asbestos, red meat and acrylamide – a substance produced when food is ‘brown’ at a high temperature.

Group 2B are ‘possible’ risks, as there is some evidence of cancer risk, but it’s not strong. An example of this is when evidence is drawn only from animal studies, such as with aloe vera latex.

Aloe vera supplements and drinks available in shops in the UK are approved by the government’s Food Standards Agency, so should have safe levels of anthraquinones, adds Prof. Boobis.

But those who grow their own aloe vera—and extract the insides of the leaves to add to smoothies—may want to consider that there could be dangers.

In higher concentrations, aloe vera taken orally can cause diarrhea and cramps.

There have also been individual reports of heavy bleeding during surgery and of kidney and liver problems in patients using aloe vera preparations. There are also suggestions that supplements may interfere with certain medications, such as blood thinners.

“It’s a myth that ‘natural’ is always safer or better for you,” says Professor Boobis. “Some of the most toxic substances come from natural sources. That said, my main concern with health food products is not safety, but for many there is little convincing evidence of the claimed positive effects.’

…And should we all avoid kimchi?

It’s billed as a gut-friendly boost before any meal.

But also trendy Asian pickles, such as the Korean kimchi, are on the WHO list of things that ‘possibly’ cause cancer.

These foods are made by adding large amounts of salt to vegetables, as well as sugar, spices, and fish sauce. The mixture is then left to ferment for several days, releasing lactic acid.

This acid is said to feed the healthy bacteria in our gut, leading to numerous benefits.

But studies show that countries where pickled vegetables are a staple food, such as Korea and Japan, have higher rates of stomach and esophageal cancer than countries that eat relatively little. A 2012 review of 60 studies said regularly eating pickled vegetables was associated with a 50 percent increased risk of stomach cancer, compared to those who rarely or didn’t eat them at all.

This is believed to be due to the amount of salt that converts substances called nitrates in the vegetables into nitrites – which have been linked to cancer – during fermentation. But pickling with vinegar and less salt is thought to interfere with the nitrates and is not associated with the same cancer risk.

Researchers also say the connection isn’t clear, as most evidence is based on observations rather than direct cause and effect. Since the evidence is weak, it is only a ‘possible’ cause and nothing definitive anymore.