Football managers chew it to keep their nerves and emotions under control. Lovers chew it to keep their teeth white and their breath kissing fresh. Kids chew it to look cool and - if they're young enough - practice blowing bubbles. Some people even chew for medicinal purposes - for instance as a substitute for smoking or to get a caffeine 'energy' hit.

Humans have chewed gum for millennia but it's only recently that it has become the hi-tech plastic, minty 'treat' choc full of preservatives that it is today.

The ancient Greeks chewed mastiche - a gum made from the resin of the mastic tree; the Mayans chewed chicle which is the sap from the sapodilla tree; North American Indians chewed the sap from spruce trees and passed the habit along to the settlers.

After World War II, chemists learned to make synthetic rubber, which eventually replaced most natural rubber as a chewing gum base. Today the ubiquitous ingredient 'gum base' is label shorthand for an alphabet soup of potentially toxic ingredients.

Because of the vagaries of chewing gum ingredient labels most of us continue to chew in ignorance - and in vast numbers. Americans consume 40 percent of the world's gum. Across Britain, France, Germany, and Spain for instance almost 50 per cent of adults aged 15 and above use chewing gum. In Britain we spend around £325m a year the on the stuff. Globally just two companies - Wrigley and Cadbury - control 60 per cent of the chewing gum market which is estimated to be worth upwards of £10 billion a year.

Toxic or not?

When a market is this profitable, regulators tend to look the other way and questions about long-term safety can get pushed to the bottom of the agenda.

In 2008, however, Canadian regulators did stick their heads over the parapet by publishing a draft list of 17 substances that they felt were toxic and therefore should not be allowed in products like chewing gum. Vinyl acetate, which is used to manufacture the polyvinyl acetate in gum base, was one of these. Canadian concern was raised because of research from the International Agency for Research on Cancer (IARC), the World Health Organization's cancer research arm, which produced some evidence suggesting that vinyl acetate caused tumors in rats.

The IARC believed that trace amounts of vinyl acetate could make it into the gum base material and the Canadian regulators suggested that a 'precautionary approach' could be justified.

The proposal caused a furore amongst gum manufacturers who argued that even if they did make their gum from vinyl acetate none - or only minute amounts - would remain in the finished product. In 2009 the Canadian regulators backed down.

Sweet talk

Chewing gum does however contain other ingredients that you may wish to think twice about before putting in your mouth. One of these is the preservative butylated hydroxyanisol (BHA.) According to the 11th and most recent report on carcinogens issued by the US National Toxicology Program (a US Government funded programme) based on sufficient evidence of carcinogenicity in experimental animals, BHA is reasonably anticipated to be a human carcinogen.

And then there are those artificial sweeteners such as aspartame and acesulfame K.

Aspartame is an artificial sweetener made from the amino acids aspartic acid and phenylalanine and methyl alcohol (find out more about the health concerns over sweeteners here; for academic references click here).

All regulatory authorities believe aspartame is safe. Nevertheless it has been dogged by health concerns from the outset. During storage and when heated is quickly breaks down into its component parts, each of which is considered toxic. Aspartame’s two major constituents, phenylalanine and aspartic acid, can cause brain damage in very high doses. Even at the low levels permitted in foods, aspartame can be toxic to people with the disease phenylketonuria (PKU), which is why the UK’s Food Standards Agency requires food containing aspartame to be labelled 'contains a source of phenylalanine'.

Aspartame is believed to cause or worsen epileptic seizures, fibromyalgia, multiple sclerosis (MS), lupus, attention deficit disorder (ADD), diabetes, thyroid problems, Alzheimer's disease, chronic fatigue, depression and eye conditions such as macular degeneration, diabetic blindness and glaucoma.

Acesulfame K has been shown to cause cancer in animals, which means it may also be a cancer risk in humans.

These days a few gums also contain sucralose. One of the few sweeteners to be derived from sugar itself, sucralose tastes more like sugar than other artificial sweeteners and contains about one eighth of the calories and carbohydrates of sugar. However it is produced by chlorinating sugar.

Animal studies, conducted by the manufacturers, have found a range of problems at high doses including shrunken thryroid glands and kidney and liver problems. Human studies suggested a dose at half the current approved level over 6 months could raise blood glucose levels. It is widely used in soft drinks, desserts and confectionery and as a table top sweetener, and consumer reports suggest a wide range of adverse effect from regular ingestion of sucralose including gastrointestinal upsets, cramping, and bladder problems.

Laxative effects

Chewing gum stimulates saliva production, which helps to neutralise the effect of acids that follow meals and, in particular, gum containing the sugar alcohol xylitol can help counteract tooth decay. But sugar alcohols such as zylitol, mannitol and sorbitol also have a laxative effect.

The regulatory authorities classify sugar alcohols as GRAS (Generally Recognised As Safe), but they may cause diarrhoea, bloating and stomach pain in high doses over 1 gram. This is because they are more slowly digested and remain longer in the intestinal tract, rather than being absorbed into the blood. The non-absorbed carbohydrates create an osmotic effect that pulls water into the intestines. Also when the non-absorbed carbohydrates reach the colon, normal bacteria metabolise them to gases and short-chain fatty acids.

Some people may be more sensitive than others to this effect and there are case reports of people chewing large amounts of gum (20 sticks a day) becoming ill with gastrointestinal problems, and experiencing a drop in weight.

Environmental impacts

Love it or despise it, gum chewing isn't going to disappear anytime soon - and this may be as bad for the environment as it is for us. Ancient gums broke down with time. The modern chew is non-biodegradeable.

Most local authorities consider chewing gum to be a litter issue, rather than an environmental hazard. It's certainly a nuisance and in Singapore in 1992 it became such a problems that it was a, for more than a decade, banned (although that ban was partially lifted in 2004 as part of a trade deal with the US. Since 2004, chewing gum of therapeutic value, for instance gums which claim to strengthen tooth enamel, is allowed into the country).

The problem lies in that the properties that make the 'best' chewing gum base (stickiness, ability to retain properties like taste and provide a long-lasting chew) also make it very difficult to clean up.

Certainly major manufacturers are looking for viable 'non-stick' gums. In fact it's a potential R&D goldmine. Some are looking to zein, a protein by-product of corn-produced ethanol (though little information exists to say whether this is GM corn or not). But as the Environmental Working Group has noted, most of the current patents for non-stick gum reply on a base of dimethyl, diethyl and dibutyl phthalate - hardly a healthy substitute (though having been banned from the toys children chew on, chemical manufacturers are naturally looking to sell their products into other less discerning markets).

Animal studies show that exposure to very low levels of the phthalates dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP) in the womb causes a number of birth defects, primarily to male offspring, including testicular atrophy, reduced sperm count, and defects in the structure of the penis.

All this does make one wonder, whether better hygiene - simply brushing your teeth properly twice a day with a non-toxic toothpaste - wouldn't be a whole lot easier, and a whole lot safer than chewing on this plastic, potentially toxic mish mash of ingredients.

Response from the Food and Drink Federation

Further reading on aspartame

Olney JW. Excitotoxins in foods. Neurotoxicology 1994;15:535-544.

Olney JW, et al. Brain damage in mice from voluntary ingestion of glutamate and aspartate. Neurobehavioral Toxicolology 1980; 2: 125-129.

Reynolds WA. Et al. Hypothalamic morphology following ingestion of aspartame or MSG in the neonatal rodent and primate: a preliminary report. Environmental Health 1976;2: 471-480.

Brunner RL, et al. Aspartame: assessment of developmental psychotoxicity of a new artificial sweetener Neurobehavioral Toxicology 1979;1: 79-86.

Wurtman RJ. Aspartame: possible effect on seizure susceptibility. Lancet 1985; 2(8463):1060

Maher TJ, et al. Possible neurologic effects of aspartame, a widely used food additive. Environmental Health Perspectives. 1987;75: 53-57.