1. INTRODUCTION:

There are several activities in our daily lives that we have a tendency to do merely for pleasure and the chew of gum is one among them. It’s truly a fascinating activity for teenagers and the best part to chew gum is to blow bubbles with it. Besides the bubble-blowing, young girls and boys conjointly relish peeling the gum off their faces. The gum is truly extremely popular among people of all ages. It’s terribly difficult to search out someone who didn't chew gum as a toddler. People around the world chew gum simply for pleasure or generally even to manage their ‘tension’ situations¹. Thus, we frequently observe that our favourite sportspersons chew gum to manage game pressure and to stay nerves and emotions in check. Others might chew gum to keep their teeth white and breath fresh. Examinees are chew gum to beat the stress of associate examination.

Some persons even chew it as a substitute for smoking or to urge a caffeine 'energy' hit^2,3. A recent study prompts that most of the people like it as ‘mouth freshener’.

The art of gum chew is the world’s most well-liked common habit and has been from generation to generation. Recently archaeologists have confirmed that this habit is near of 9000 years old⁴. Surprisingly, evidence suggests that a caveman teenager chewed a piece of tree resin on the Swedish island of Orust. So, chewing gum has indeed a really long history. Interestingly, astronauts also use chew chewing gum! But for them, the problem is how to dispose of it, so they have to swallow it.

Different scientific studies specify that medicated ‘sugar-free’ chewing gum definitely has health benefits, and in the near future, it can even be used as a ‘drug delivery’ material^5,6,7. Gum lovers have always thought that gum chewing is an art and that provides them some sort of ‘mental relaxation’ reduces muscular and nervous tensions.

Interestingly, artists use ‘gum’ as an object of art⁸. Maurizio Savini associate Italian artist, and ben Wilson, an English wood carver and creator have created spectacular sculptures using the items of chew gums as the medium. Besides this fascinating fact, gum chew has conjointly many negative effects. Modern chewing gum is prepared by synthetic polymer materials and contains artificial sweeteners and flavours. Thus, chewing gum means to chew the mixtures of elastomers, polymers, resins and paraffin. So, chew a polymer-based substance over an explicit amount might not be considered a healthy practice. It will create some sort of serious health problem, directly or indirectly.

Most of the cases, a fan of ‘chewing gum’ will throw waste part of it somewhere. Unfortunately, most of the time, after chewing it will not be disposed of properly. Therefore it is the second most common form of litter in publicplace after cigarette butts. When it’s tossed on the sidewalk, there it sits until it’s removed. Removing ‘chewed gum’ from the pavement is a very costly and time-consuming process. As a result, Gum will also create ‘gum pollution’. Account this negative impact of chew gum; the market of chewing gum will increase speedily.

In this review, we've tried to examine, advantages of chewing gum in our health concern and its role in dental hygiene. Here we've highlighted shortly the negative environmental impacts of chewing gum. We tend to hope that this review can make easy people to grasp some fascinating facts regarding chew gum.

2. What is chewing gum?

Chewing gum is a chewable rubber material that contains flavour and artificial sweetener. It’s in fact sugar and flavour coated polymer which are liable for its elastic-plastic, sticky, chewy characteristics⁹. Previously natural rubber was used for gum preparation however modern gum base is radically shifted to synthetic polymeric substances i.e. butadiene-styrene based rubber or isobutylene-isoprene copolymer (butyl rubber). Essential chemicals of gum such as flavourings substance, sweeteners, food colourings and preservatives are mentioned later.

3. Historical background of chewing gum:

The standard of gum has been developed with the evolution of cultural tradition. Thousands of years ago people chewed solely the natural tree sap as a gum¹⁰. The traditional gum was principally based on tree resin lumps however ancient people also used sweet grasses, leaves, grains, and waxes as chewing substances. From the literature survey, some attention-grabbing info is found concerning the historical background of chewing gum.

The historical report says that Ancient Greeks chewed mastic gum made of mastic tree resin. In several languages, the word “mastic” suggests that gum and it's such a lot of medical values like as inhibitor, medicine and antifungal properties¹¹. It also can shield the teeth from decay, periodontal disease, and oral microorganism. It absolutely was wont to fill dental cavities in several ancient countries like India and Persia. The traditional Mayans chewed the coagulated sap of the sapodilla tree and that they additionally used a natural tree gum named chicle gum. The spruce resin was also used to chew by Native ancient Americans.

The first time in history, commercial chewing gum was sold-out by John Bacon Curtis in the year of 1848 and known as the State of Maine Pure Spruce Gum.

On December 28, 1869, William Finley Semple became the first person to patent a chewing gum – (U.S patent #98,304).

In the 1950s, sugarless chewing gum was introduced in the market due to the more health-conscious consumers. Dr. Petrulis, a dentist, first gave the idea of sugar-free chewing gum. Some dentist approves gum contain ammonia to neutralized the acidic effect of bacteria to protect from tooth decay. Finishing off 1960, the presented first-time sugar-free bubble gum called Blammo¹⁰.

4. Manufacturing process of chewing gum:

Commercially chewing gum preparation started in the late nineteenth century in America. Nowadays, the complete method goes through automatic¹². The gum base is prepared by the stepwise manner. Step 1: Natural gum base such as chicle is collected from chicle trees by special technique into a bucket. After a significant amount of chicle has collected, it is strained and boiled to concentrate. Step 2: The natural or synthetic gum base is grinding to form a coarse meal and the mixture is dried for a day or two by passing hot air perpetually through the mixture. Step 3: The mixture may be sterilized and melted in exceedingly steam cookware. Then it passes through high power centrifuge to eliminate unwanted dirt from the gum base. Later on, the gum base ingredients are melted along until the formation of the thick liquid mixture was obtained. After filtered the liquid mixture is heated around 115 °C then it will turn into thick syrup. Step 4: In this stage, in hot condition granulated sugar, syrup or aldohexose, softeners, and flavour additives are added. Step 5: For several hours, machines then pummel, or "knead," the mass of chewing gum until it is properly smooth and rubbery. Step 6: After that, a computerized cutting machine cut it with specific forms as needs which becomes candy-coated later. Then the wrapper machine will wrap and pack the gum¹⁰.

5. Chewing gum ingredients:

Before 1850, traditional chewing gum is made by natural latexes like chile, jelutong, gutta-percha, resin or mastic gum, etc., whereas the modern variety of gum is made by fully artificial synthetic polymers, sweeteners, gum softeners and flavours.

Current chewing gum makers exchange natural latex by artificial substitutes. Synthetic polymers are based on butadiene-styrene rubber, polyethylene, and polyvinyl acetate, etc. Today all multinational companies are using synthetic gum materials which are very much useful to boost flavour, improved texture and reduced stickiness. Due to the hydrophobic nature of synthetic polymers, it cannot be dissolved in water as well as saliva in mouth or stomach acids.

6. Property of chewing gum and the chemistry behind it:

Each type of gum has its own unique recipe. However, there are common types of features found in all types of gums. Here we are going to discuss shortly the characteristics of gum and the role of different chemicals responsible for that.

6.1 Chewiness:

Chewiness is the prime criteria for the gum. Polymer-based materials are used to prepare a ‘gum base’ for that reason. Polymers are long-chain chemicals that are water-insoluble means hydrophobic in nature¹⁰. On the other hand, sugar part of the gum is water-soluble, it can be dissolved by the saliva of mouth and thus gum lost its flavour with time but not gum^’s main part. This mechanism will help to chew long time gum without breaking down like as normal food. Chewing gum has its two different phases as a liquid phase and a crystalline phase which help to balance the plastic and elastic properties. This mechanistic way helps to stick of gum will go from being rigid to squishy after a couple of rounds of mastication.

6.2 Stickiness:

Generally, sticky nature is one of the unique properties of polymer substance and this nature originates from hydrophobic nature. Due to its stickiness, chewing gum is stick easily on the surface and very difficult to remove⁶. When we try to remove a piece of gum from the surface, most of the energy we used to stretch the polymeric linkage rather than break the binding of surface and gum. The presence of strong polymeric linkage is the main reason for elasticity and chewiness property. Polymeric linkage between the repeating units tends to remain intact as they lengthen and contract from an applied external force. During gum chewing, current temperature, saliva, and grinding of human teeth affect both the elasticity and adhesiveness of chewing gum. The explanation of tougher and less elastic nature of chewing gum after a long time because the degree of alignment is a function of the magnitude of applied stresses¹³. After removing the gum from the mouth in a cooler environment can helps to adjust the polymer chain and become a hardened piece.

6.3 Bubble-blowing capability:

Most chewing gum lovers are interested to make bubbles. It can be formed when tension and elasticity of gum polymers force against the constant and equally air pressure blow from the mouth. Such bubbles are the spherical type where normal rules of physics can be applied. The gum polymer can stretch with increasing air blow and bubble expands and becomes thinner. When the excess air pressure cannot tolerate by gum polymer, it pops. The flattened bubble withdrawals due to elastic nature and wad of gum are ready to continue being chewed. Higher molecular weight polymer bases gum will be able to make to more stretchable, larger bubbles and hold their shape for a longer time⁹.

6.4 Flavour release:

Releases of flavour slowly after chew from an extended time attracted the youngsters. In the current market, various flavour contains chewing gum are available. Flavor delivery is extended throughout the mastication process. A thermodynamic clarification will satisfy the flavour delivery method. Entropy plays a crucial role to bring the flavour throughout gum chewing. Some gum components are hydrophilic in natures which are more soluble in saliva than gum base. The flavour parts increase entropy from time to time. The highest solubility is observed of bulking agents like sugar, sorbitol and maltitol with saliva throughout the initial first three to four minutes of chewing. Once dissolving of such components in mouth saliva and fall in the muscle system, it is no longer retained in the gum base. After 4-6 minutes of chewing, intense sweeteners and some acids are dissolved and chewed out. Due to the lower solubility of such components, they are lasting slightly longer than bulking agents. Within 10-15 minutes, the encapsulated flavours will release. In the final stage, syrup and glycerine like softeners are dissolved with saliva and hardening gum at the end of chew¹⁴. Several studies over the gum flavour are perceived better within the presence of sweetener¹⁵. Currently, all chewing gum makers are trying to make some special forms of chemical systems wherever sweetener and flavour unleash along will be manageable. Such kind of procedure will facilitate to get pleasure from chewiness in conjunction with long-lasting flavour¹⁶.

6.5 Cooling sensation:

The application of negative enthalpy of dissolution of bulk sweeteners like sugar alcohol is functioning to urge the cooling sensation. During this mechanism, overall heat will either absorb or discharged throughout the desolvation method. During the dissolving process, bulk sweeteners will absorb the heat with the evaluation of negative enthalpy, leading to the cooling sensation¹⁷.

6.6 Softeners:

Most of chewing gum manufacturing companies used glycerine and vegetable oil as softeners. Such types of components are helping to make gum moisture and try to prevent from hardening.

7. Types of chewing gums:

The various types of chewing gum in attractive wrappers with different flavours, shapes, and sizes are available in the market. Numerous gums are projected in the functions of dental hygiene like to whiten teeth, clean teeth, and mouth freshener. Different types of gum with charming flavour like mint, sour apple, cherry, grape, orange, strawberry, lemon, blueberry, etc., are very popular among teenagers.

8. Is Gum considered as a food?

Now the preliminary question is that gum is considering as food or not. According to the U.S. Food and Drug Administration (FDA), food suggests that a raw or cooked or processed eatable substance, ice, drink, or ingredient used or intended for use or for sale in full or in part for human feeding¹⁸. Chewing gum is outlined as a food of negligible dietary rate. Chewing gum is one among the classes of feeding substance which may solve several issues for the instant.

9. The environmental impacts of gum:

Most of the commercially available chewing gums are based on hydrophobic polymer; therefore it will simply stick to the oily surface and very difficult to eliminate them from any kind of surface by using any type of cleaning solution. It’s general science that hydrophobic substance makes repulsion to a polar molecule and attracts to a non-polar substance like grease and dirt and vice versa for hydrophilic substance¹³. There have some forms of containing hydrophobic and hydrophilic traits called "amphiphilic"¹⁹.

Generally, biodegradable natural latex was used to make ancient gum that was also environment friendly but recently commercially prepare chewing gums are made by synthetic substance. These are created from butadiene-styrene rubber, synthetic resin or vinyl polymer, etc., and all these have been using just to give long-lasting flavour, improved texture and reduced tackiness. So, one of the largest issues that synthetic polymeric materials are not biodegradable, not damaged by bacteria but it can damage the environment. The substance that does not decompose naturally is known as non-biodegradable such as plastic materials, including chewing gum. Non-biodegradable wastes are one of the biggest threats to our ecology. The plastic materials will produce serious types of problems to fish and marine mammals who consume it, like either choke or experience digestive problems. When we will eat fishes or marine living species gum polymer can be reintroduced in the food chain. Thus, it is a great challenge for us to decrease the use of non-biodegradable waste and bigger challenge for the modern researcher to make recyclable chewing gum keeping the fun of gum chewing intact.

10. Chewing gum is a litter issue:

There is no doubt that chewing gum has lots of positive roles but besides its positive site, it will produce harmful hazardous. The effect of such pollution is not only limited to our homes but it can also be found in streets, schools, colleges, offices, etc. It has been found that 92% of Britain’s town paving stones are being stuck by gums. It became a big issue because of every year, London expense $4,000,000 yearly to eliminate gum from pavements, subway trains, and stations²⁰. Several survey analysis indicates that it is the second most common form of litter after cigarette butts. Each and every year gum generates over 250,000 tons of huge waste and this factor is increasing due to growing popularity. Therefore, adhesive chewing gum to be a litter subject comparatively than an environmental hazard. The survey in the year of 2000 on Oxford Street, found million black or white splotches of chewing gum were trapped to its pavement³². The elimination of stuck gum from city streets or even famous landmarks is difficult, cost and time-consuming. A report declares that in Rome 15,000 pieces of chewed gum are discarded on a daily basis and to eliminate that stuck gum they charged one euro per gum. The Local Government Association guesses that £60,000 per year the expanse to clean the chewing gum in the city. In England almost 936 tons and removal cost almost £56 million per year. In 2012 during the London Olympics, they clean 300000 pieces of gum near about 2 miles street and spent 3 months.

Many schools do not give permission to use gum due to the problem of final waste products and discarded gum might transfer diseases or bacteria to other students. Gum is also difficult to eliminate from high-pressure tubes. Not only it is an environmental problem but it also needs the huge amount of water to eliminate. So, this is also nothing but wastage of water.

Singapore's already ban the non-prescribed chewing gum to keep clean the pavement from gum. Due to this disadvantage, the Singapore government outlawed chewing gum in the year of 1992. According to the Singapore Government law, if a drug dealer sells chewing gum without any permission then they can send 2 years jail including $3,000 fine. The government relaxed the ban in 2004 and permitted sugarless gum with a specific reason, although it’s thought due to Singapore –United States free trade agreement.

Gum Busters, New York-based Company, continues their work with sweeping streets, carpets, and floors across the nation with gum removal machines. Gum pollution is now a growing headache, so researcher needs to make attention to it. Several approaches for eliminating gum have been taken such as either blowing steam or chemicals onto the gum, freezing the sticky lump with liquid nitrogen, or scraping it off by hand need to more worker which is cost and time effective. To remove such problem, the researcher of Revolymer Ltd, a UK-based company is working in polymer technology and preceding their work to invent new gum which can be easily removed from all surfaces.

11. Health benefits of gum chewing:

In this section we are going to discuss the positive aspects of gum however this will not be beneficial for everybody. Some surveys specified that a muscular activity of chew gum helps to extend the concentration, stress reduction, releases tension and relaxes the muscles. From the literature survey, we got information that the U.S. military was provided chewing gum to refresh the mind throughout the First World War. Some report informs us the other additional benefit of gum like improving memory; manage weight and oral health although this fact is not fully well-establish. It is clear that more research is needed to complete the establishment of chewing gum effects. Another survey highlighted that usual American chews near about 300 sticks or equal to 1.5 pounds of gum in per annum^21,22. Recently developed gum is applicable to decrease nicotine cravings, protect teeth, and even transport caffeine, vitamins or therapeutic drugs.

11.1 Chewing gum improves oral health:

Several studies concluded that chew gum contains a significant role for oral health and particularly for teeth^23-25. According to the American Dental Association, artificial sweeteners like aspartame, sucralose, and other synthesized sugar have lower calorie than natural sugar and these types of artificial sweeteners have a special role to safeguard teeth decay. It is known to all that artificial sweeteners are a hundred times sweeter than the natural one, thus small amounts are enough to provided desired sweetness that reduces the calories up to 30%²⁶. The artificial sweeteners like sucralose and aspartame are taking to longer metabolism time due to strong bonds however also known as "tooth-friendly" and a harmless substitution for diabetic patients. Sugar-free gum will facilitate to reinforce the secretion of spittle that is vital for oral health as protection from teeth decay and oral cavity. A high excess of saliva makes a harmless surroundings employing a high concentration of buffers, minerals, and antibacterial substances. This helps to wash sugar, foods, and decay- inflicting acids and protect tooth enamel and bacterial effect²⁷. Survey reports say sugar-free gum chewer has fewer cavities than others and also help to quit smoking. This sugar-free gum chewing for 20 minutes following meals will use as decay, mouth cleaner and mouth-freshener²⁸.

11.2 Chewing gum improves memory and concentration:

Some Psychologists recommend chew gum to their patients to progress memory strength and enhance cognitive powers. Chew gum has the capability to release of sugar into our metabolism as like as candies, cookies, cakes, ice creams, puddings, etc., that has some necessary role on our brain function and mental state. Although, such kind of “sugar rush” feeling interesting research topic of food. Chewing gum also covers a huge portion of attention from the public and researcher. According to theory revealed by scientist states that act of “chewing” changes the direction of brain work which has a great positive impact on health^29-31.Chewing gum can increase the psychological feature functions and lots of scientists have studied about that reality³². Such a test was done in over 200 test subjects during starting 15 to 20 minutes after taking chewing gums. The foremost outstanding psychological feature domains that were affected are the sensory activity speed of the process, memory, and long-term memory. It has been found that only the initial period showing enhancements, however, failed to respond later even supposing continuous victimization of chew gum. The relation between brain activity and many types of delicate work up like regular movements of the jaw are the reason for effectiveness in the cognitive domain.

In 2014, Kate Morgan et al. documented their research analysis in British Journal of Psychology tested the memory, concentration, alertness, performance, and mood of subjects chewing gum lover and normal people before the 30-minute test and ensuing it helps to growth concentration, focus, and memory³³.

The research studies “effects of chewing gum on cognitive function, mood, and physiology in stressed and non-stressed volunteers” by Smith in 2010 described the benefit of using of chewing gum but informed about the limited effects of alertness¹. Another important study “Gummed-up memory: chewing gum impairs short-term recall” by Kozlov et al., in 2012 reported that the no role of chewing gum to boosts the cognitive functions of the brain³⁴. They constructed a potential explanation about the reason behind better score obtaining of chewing gum lover than others. The continuous moving of jaws during using chewing gum improves memory (the hippocampus). Blood flow to brain increase during using chewing gum and increasing heart rate allows supplying pure oxygen to the brain which is good for enhancing cognitive powers. Some studies suggested that 25 to 40 percent blood flow increases to the brain during chewing gum. Thus, direct and indirectly lots of activities like supplying more oxygen, glucose, and disposal of more CO₂ help to enhance the memory power during chewing gum^35,36.

11.3 Chewing gum reduces symptoms of stress:

It is the communal practice that students chewed more gum during examination time to increase alertness and concentration or sometimes to minimize the examination pressure. Even though Psychiatrists and Psychologists advice to their patients to use chewing gum because they believe that the process of chewing gum can reduce the mental pressure and helps to release nervous energy. It also helps to get a suitable way to get rid of frustration and irritation. Some scientists trust that it has a rhythmic motion which ultimately gives a stress-free and peaceful mind³⁷.

11.4 Chewing gum helps to manage weight:

Many research studies recommend that chewing gum may help to achieve body fitness indirectly³⁸. The using of regular and sugar-free chewing gum helps to decrease the intention of taking food that means increases the loss of appetite. Some other studies propose that the person who chews gum can get calories less of the snack than normal people. The chewing of gum can decrease the hunger for high-calorie snacks and it can burn up to 11 calories per hour.

11.5 Chewing gum improves digestion:

Research reports say that chewing gum may help to improve intestinal motility and increases the flow of saliva to endorse more frequent swallowing. This helps to prevent the reflux of acid from the stomach back into the throat. It may be also helpful after meals when additional enzymes are needed for digestion. So, several studies and model analyses suggested that chewing gum might have some positive feedback for us in case of digestion, but more research works are needed in this field to establish this fact.

11. 6 Xylitol gum-dental benefits of xylitol:

Aim of gum chewing changes fundamentally from the beginning of the 21^st century. Modern chewing gum is now the aid of dental care and hygiene. According to the literature, the researcher in this field suggested that xylitol contains chewing gum have some potential to reduces the risk of cavities in children. In 2011, the European Food Safety Authority (EFSA) remarked that xylitol induces gum may protect tooth mineralization compare with various sugar-containing foodstuffs³⁹.

Fig. 1: Structure of xylitol

Xylitol (Fig. 1) is a low-calorie carbohydrate, is an essential chemical compound which is currently used by almost every gum manufacturing company. Cavity formation and tooth decay are generally formed due to the presence of oral bacteria. Such kind of harmful bacteria may be protected by taking xylitol up to 5g and consequently minimizes the chance of cavity formation. Since xylitol is a non-fermentable compound, bacteria are unable to break down it, making it an inert environment and create a fence to food contact from their ecosystem. After a long time using of xylitol can fully protect inhibition of harmful micro-organisms growth and reproduction which will allow to natural re-mineralization process easily to the coat teeth and deliver them with a safety wall against decay. The additional positive benefit of xylitol has become a sugarless sweetener which is more useable for the person who is suffering from cardiovascular diseases and diabetes.

12. Chewing gum negative effects and disadvantages:

Chewing gum has always been all time favorite and popular among the people of different ages. Though chewing gum has many positive effects sometimes, unfortunately, it may also endanger to us⁴⁰. In this short review, we have discussed the side effects and disadvantages of gum and also tried to scrutinize the role of chemicals in it.

12.1 Chemical used as food preservative:

The carcinogenic constituent like Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are extensively used as a food additive to manufacture chewing gum. The chemical structure of BHA and BHT are shown in Fig. 2. Butylated hydroxytoluene (BHT) is a chemical antioxidant which is using to preservative the foods. Currently, this substance is found in different foods including chewing gum, baked goods, dehydrated foods, snack foods, processed meats, cosmetics, and animal feeds. Sub chronic feeding and intraperitoneal studies in rats have found to be an application of BHT at lower doses produced liver weight gain and loses activity of several hepatic enzymes. In addition, it can also show toxic effects in lung tissue but till now evidence not found to prove that the harmful nature of BHT in packaged food⁴¹. US National Toxicology programme (a US Government funded programme) identified 11th most recent report on carcinogens issue including BHA which practically expected to be a human carcinogen, particularly high does in the diet. Thus, due to the presence of such type of carcinogenic ingredients, one may wish to think twice about before putting it in the mouth.

Fig. 2: Structure of butylated hydroxyanisol (BHA) and butylated hydroxytoluene (BHT)

12.2 Chemical used as artificial sweeteners:

Generally, aspartame (Fig. 3) and acesulfame potassium or acesulfame K (Fig. 4) are broadly used as artificial sweeteners in chewing gum⁴². The artificial sweeteners like aspartame and sorbitol are the cause of the allergic reaction, irritation or headaches^43,44.

Fig. 3: Structure of aspartame

Aspartame used as a sugar substitute in most of the processed food as well as chewing gum, which is an artificial, non-saccharine sweetener^43,44. This is nothing but a methyl ester compound of aspartic acid prepares from the precursor of aspartic acid, phenylalanine, and methyl alcohol. Aspartame decomposes easily during either storage or on heating to its two main constituents as phenylalanine and aspartic acid which are considered as potentially toxic sub stance⁴⁵. Recent researches inform that the high doses of aspartame can cause brain damage^46,47. Even low level of aspartame presence in food can be effective to the human body as phenylketonuria (PKU) disease. Phenylketonuria (PKU) is an inborn problem of metabolism that generates in decreased metabolism of the essential amino acid phenylalanine⁴⁸. PKU can lead to various physical, behavior problems and mental disorders⁴⁹. UK’s Food Standards Agency strictly handles and gave order to label aspartame-containing food as 'contains a source of phenylalanine'. It is supposed to cause of aspartame are 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. The recommended amount approves by the FDA is a maximum daily intake of 50 milligrams per kilogram of body weight⁵⁰.

Fig. 4: Structure of acesulfame potassium

Acesulfame K can be used as a food additive in the baking product due to stable under heat, even under moderately acidic or basic conditions⁵¹. Although, this compound has a stable shelf life finally it can decompose to acetoacetamide and high doses of this final product is toxic like aspartame⁵². This substance almost always mixed with another sweetener like aspartame or sucralose (Fig. 4) to manufacture soft drinks. According to research, the acceptable daily intake of acesulfame potassium is listed as 15 mg/kg/day⁵³.

Fig. 5: Structure of sucralose (Splenda)

In current markets, Sucralose a sweetener present in a gum in the brand name of Splenda. Among the few sweeteners, it can be produced from sugar itself which is chlorinating sugar. It contains about one-eighth of calories and carbohydrates of sugar and more taste than other artificial sweeteners. Current research suggests that high doses of Splenda (Fig. 5) consummation store the unused chlorine which damages the body cells. According to use of high-level Splenda can cause dried up thyroid glands and start malfunction of kidney and liver. The extensively used of Splenda may also cause of gastrointestinal upsets, cramping and bladder problems.

12.3 Chemical used as gum base:

After the discovery of synthetic rubber, all the chewing gum manufacturers replaced the natural rubber to a synthetic one. Generally, polyvinyl acetate or other synthetic polymeric substances are using to produce chewing gum. Polyvinyl acetate is made by the polymerization of the monomeric vinyl acetate (CH₃COOCH=CH₂) group. It has been found that naturally 100 and 5,000 units of monomers are combined to make polymeric substance and these increases to an average molecular weight between 850 and 40,000. In spite of a carcinogenic substance, people chew it as a gum which is injurious to health. International Agency for research on Cancer (IARC), the World Health Organization's cancer research also supported the fact. Recent research says that vinyl acetate caused tumors in the rat⁵⁴. So according to the IARC statement, the uses of vinyl acetate must be banned to produce gum base material. Hence chew of vinyl acetate contains polymeric substance could be poisonous to health. So, people should avoid chewing gums due to the presence of carcinogenic and neurotoxin ‘artificial sweeteners’.

12.4 Chewing gum uses valuable digestive enzymes:

Recent research was properly unable to inform that the relatively finite value of digestive enzymes that our body can produce in a given lifetime⁵⁵. But, on the contrary, many research results directly say that chewing gum can help to activate the secretion of digestive enzymes in the human stomach. Thus, chewing gum plays the role of fake food that directly wastes the digestive enzyme whenever we chew it. The frequent using of gum between each meal means the reducing of the digestive enzyme which is reserved for the next meal. Thus, lack of digestive enzyme will be unable to digest the food properly. The same habit for everyday life can cause serious health issues like the development of digestive disorders. So, it is fully avoidable if the chewing gum lover is suffering from digestive pain or disorder of any kind.

12.5 Chewing gum contributes to the development of TMJ and other jaw problems:

The use of chewing gum on any occasion is safe but the habitual use of it may cause continuous stress on the jaws, even manufacturers deny all the effective health issues. One of the reasons for the activation of Temporo-Mandibular Joint Disorder (TMD) is chewing gum^56,57. This specific joint attaches the jaw bone with the temporal bone of the skull. Frequently using of chewing gum is the root of differential contraction of the muscles and outcome pain in the joint. Such kind of pain feels more when people chew gum in one side of the jaw and oppose to other side. Lots of outcomes of TMD are chronic pain, tightening and irritation of the jaw muscles, ear pains, tooth pains, as well as migraine-type headaches.

12.6 Chewing gum releases mercury from amalgam dental fillings

Many researchers^58,59 estimated daily doses of mercury from dental amalgams. They also proved that the chewing gum can release the mercury from dental amalgam fillings. A Swedish scientist found from his research that people with dental silver filling, who chew gum for 5 hours or more than it in a whole day, had an excessively higher level of mercury in blood and urine than normal silver filling people⁶⁰. People should know that any amount of mercury is neurotoxin in the human body. So, the use of chewing gum should be known carefully who has even a single silver filling.

12.7 Skip the gum if pregnant with silver fillings:

The women with Silver filling teeth should not chew the gum during pregnancy because the fact is mercury is toxic to women and for their babies– both inside and outside of the womb⁶¹. Some women are habituated to chew the gum and some chew to get relief from heartburn or indigestion and to get relaxation. Although the presence of dental silver filling amalgams, the use of gum can release mercury and it can easily cross the placenta. So, if women are currently pregnant or planning to get pregnant in the near future, it’s really important for those to fully understand what mercury is and how she can avoid the life-threatening issues related with silver fillings.

12.8 Tooth decay:

The regular use of sugared chewing gums can cause the disease like tooth decay, gum-related diseases, and cavities also. Such kinds of diseases happen due to coating the teeth by sugar, resulting slowly root of damaging to the tooth enamel. So, to get rid of from this problem we have to decrease the use of sugar gum as less as possible. Only this way we all can overcome this problem.

12.9 Artificial sweetener allergies:

Nowadays, artificial sweeteners are the most common sugar just because of their long-lasting properties and special kind of sweet taste. These artificial sweeteners have lots of side effects like allergic reactions, especially for aspartame and sorbitol. Other side effects like irritation and headaches can also be seen^62-64.

12.10 Stomach issues and laxative effects:

The production of saliva may be excited by chewing gum which supports to neutralize the effect of acids that follow meals. The sugar alcohol xylitol which is one of the main ingredients of such artificial gum can also help to counteract tooth decay. Different kinds of sugar alcohol like xylitol, mannitol and sorbitol also have a laxative effect. Such sugar alcohol has been classified as GRAS (generally recognized as safe) but recently several studies proved that the use of such sugar alcohol over 1g may cause diarrhea, bloating and stomach pain. Such kind of problems may occur due to slow digestion and remain a long time in the intestinal tract rather than being absorbed into the blood. An osmotic effect can be influenced by non-absorbed carbohydrates which pull water into the intestines. Normal bacteria metabolize the non-absorbed carbohydrates when they reach into the colon and convert into gases and short-chain fatty acids. Lots of cases have reported that who chews large amounts of gum (20 sticks a day) becomes ill with gastrointestinal problems and started losing weight. The stress level of stomach and bowels increases with the continuous chewing of gums. The stomach needs to take a rest after a meal but chewing and continuous swallowing of saliva interferes that rest. Some common stomach problems that can appear in those conditions are irritation, aches, and aggravated gastritis and finally, it transformed into the gastric ulcer.

Air intake into the gastrointestinal (GI) tract increases with using chewing gum and resulting in abdominal cramps and bloating. The condition of that patient becomes worse who suffered from irritable bowel syndrome (IBS). Gastric acid reflux can happen from peppermint flavoured chewing gum. Extremely intake of chewing gum into the mouth causes the brain to send signals to the digestive system to be prepared to expect food intake which directly related to the secretion of saliva and other gastric juices including gastric acid. Although there is no food intake but fake signalling through may compromise the capacity to digest food due to lack of digestive juices when you actually consume food. This can cause indigestion and finally, diarrhea may also happen.

The present sugars are absorbed by our body and indigestible resin is passed along the digestive tract and eliminated with a bowel movement. After that, the undigested form of gum reaches to colon from the digestive tract where it can eliminate as a stool. Such a process generally finished within a day or two days after we eat it. The swallow of chewing gum can really make trouble for the children less than six years ago.

12.11 Social distraction:

Chewing a piece of gum in a social environment like in public areas, schools, workplaces, etc., is considered distracting and irritating in modern culture. Sometimes it is also called bad manners.

12.12 Masseter problems (facial muscle problem):

Masseter problems may occur due to frequent chewing of chewing-gums and as a result of this one can face the problem of constant grinding of teeth at night^65,66.

12.13 Kidney problems:

Mercury is a poisonous metal which leads to making kidney problem in the human body. So, if the cavity of teeth filled with mercury component then chewing of gum may dislodge and release of such poisonous materials to metabolism. Blood, urinary tract, nerves, and brain are the most common targets of mercury and also salivary phosphate-binding chewing gum on serum phosphate in chronic kidney disease⁶⁷.

12.14 Irregular development of facial muscles:

Too much chewing of gum in puberty may lead to the encouragement of jawbone and facial muscles, resulting from an enlargement face^68,69. Thus, to overcome such problems one can either avoid chewing gums or can use limited because it is mainly loaded with chemicals and synthetic ingredients.

In this review, we are trying to highlight the benefits and too alarming people about health hazards due to the chemicals used in chewing gums.

13. The Remedy of gum pollution and “Clean Gum” project:

To make it a successful project, every gum-chewing responsible citizen should use a wrapper to enclose the consumed chewing gum and dispose of it at the nearest public bins. The other possibility to resist gum pollution is to carry a small packet of tissues along with the chewing gum pack because some companies do not provide individual wrappers³⁰. Technically, we can save our planet from gum pollution to prepare bio-degradable chewing gum i.e. ‘clean gum’. Recent research in this field showed positive results with a new formula for a "cleaner" product. The researcher Revolymer has innovated "Clean Gum" in the year of 2007 which can able to remove the gum easily from pavement, shoes, clothes, and hair. Their preliminary results also show its biodegradability i.e. Eco-friendly nature.

Revolymer uses a different technology than other commercial gum manufacturers which minimizes the stickiness of their product. They improved chewing gum formulation based on this unique technology of low-adhesion amphiphilic polymer. Such a unique ingredient has dual nature in polymer structure which allows dissolving in both water and oil due to the presence of a hydrophobic part surrounded by hydrophilic part. This unique nature of moisture-sensitive polymer introduced by Revolymer Clean Gum allows washing easily from any surface of a substance. It has special nature to become soften when exposed to moisture like in mouth secretion saliva and again becomes hard in the air, which can help to remove easily from the surface of any substance.

The aim of the Revolymer engineer is to make it eco-friendly to resist gum pollution besides this they are trying to make some overall improvements such as flavour, texture, and chewability. Professor Cosgrove has described the new eco-friendly product that is "The advantage of our Clean Gum is that it has a great taste, it is easy to remove and has the potential to be environmentally degradable." It is important to note that the principle of low-adhesion technology made by Revolymer can be applied to other products such as medicated gums, personal care products, paints, and coatings. Such kind of research in material science and technology can help to create products that will be easily useable and eco-friendly.

14. CONCLUSION AND FUTURE PROSPECTS:

The non-biodegradable synthetic hydrophobic polymer-based chewing gum has a unique flavour and chewable features that attract the children as well as aged people to overcome mental stress and sometimes to get rid of dental problems. But it has also numerous negative roles apart from its positive roles like its stickiness property. Most of the cases after gum chewing, it can be found being stuck underneath benches, tables, handrails, and escalators which are really hard and expensive to remove once "walked in" and dried. Chewing gum will create bond powerfully with lyophilic materials like asphalt and rubber shoe soles that are made from polymeric hydrocarbons. It also creates a robust bond with concrete in the streets, sidewalks and buildings round the world so created ‘Gum Pollution’. To reduce this problem, researchers should look forward to viable 'non-stick' gums. Recently, numerous manufacturing companies are trying to work with amphiphilic polymers to make "low-adhesion" chewing gum which may be the additional environmental-friendly product. This advanced technology will help to save millions of dollars in clean-up costs and it can also be applied to different fields in attention merchandise, paints, and coatings. Finally, it's considerably required to provide each and every one the fundamental education and civic sense.

Although, several studies suggested that it can increase the sharpness of our brain and make us more concentrated, and also remove dental problems but an excess amount of gum chewing over a long period can produce several serious health problems. It is important to take the partial role of government to make a strict rule to label the wrapper of gum by certain caution so that everybody can aware about the ‘silent killer’ role of chewing gum just like as tobacco substances. But we hope in near future chewing gum can be used as a transport system for different chemical substances like a medium for applying medicinal drugs.

15. CONFLICT OF INTEREST:

The authors declare no conflict of interest.

16. ACKNOWLEDGEMENTS:

I am grateful to School of Sciences, Netaji Subhas Open University for giving me internet and computation facility to collect and write the draft of the manuscript.

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Received on 31.07.2021 Modified on 03.09.2021

Asian J. Research Chem. 2021; 14(6):459-470.

DOI: 10.52711/0974-4150.2021.00081