Energy drinks refer to beverages that contain large doses of caffeine and other legal stimulants such as taurine, carbohydrates, glucuronolactone, inositol, niacin, panthenol, and β-complex vitamins which are considered as source of energy (Attila and Çakir, 2009). The consumption of readily available energy drinks has increased significantly with young adults forming the largest part of the consumers. History of energy drink dates back to 1987 when Red Bull was introduced in Austria. It became more popular in the 1990s following its introduction to the United States. Since then the sale of this drink has increased exponentially. In 2006, the energy drink market grew by 80% (Foran et al., 2011). This is because manufactures claim the drinks can boost energy levels as well as physical endurance, improve concentration and reaction speed (Van den Eynde et al., 2008).
In recent years, a number of different energy drinks have been introduced in the Nigerian market to provide an energy boost or as dietary supplements. These drinks are marketed specifically to children and young adults. These products have been used for various reasons. A survey conducted among college students shows that 67% of students admitted using energy drinks to cope with insufficient sleep, 65% mentioned increasing energy and 54% use it for fun at parties; 50% for studying or completing a major course project, 45% used it while driving a car for a long period of time and 17% for treating hangover (Malinauskas et al., 2007). These products have also been used to reduce the depressor effect of alcohol or even to gain social status (Ferreira et al., 2004; Kaminer, 2010).
Many energy drinks are promoted as being nutraceutical foods, boosting health, energy, or otherwise having sought-after benefits. There is some concern among health professionals that these beverages, and the drinking behaviours of the targeted consumers, may in fact have adverse health consequences. The most commonly reported adverse effects include insomnia, nervousness, headache, and tachycardia (Clauson et al., 2008). In a recent study, heavy consumption of energy drinks was attributed to new onset seizures in four patients (Iyadurai and Chung, 2007) and hospitalization of individuals with pre-existing mental illness (Chelben et al., 2008).
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Energy drinks first appeared in Europe and Asia in the 1960s in response to consumer demand for a dietary supplement that would result in increased energy (Reissig et al., 2008). In 1962, a Japanese company, Taisho Pharmaceuticals, launched Lipovitan D, one of the very first energy drinks, which is still dominating the Japanese market. Since the 1960s, the energy drink market has grown into a multibillion dollar business which has been reported as being the fastest growing segment in the beverage industry. Energy drinks have established a viable position in the beverage market as evidenced by their commonplace consumption in the morning, afternoon, and night, not only by the general consumer, but those of age 18 to 34 in particular (Lal, 2007).
The popularity of energy drinks and the growth in their consumption among adolescents and young adults have brought worries regarding general health and well being of these consumers. Adolescents and young adults are often uninformed about the content of energy drink (Rath, 2012).
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There are hundreds of energy drinks available in the market, many share very similar ingredient profiles. Most of these energy drinks consist mainly of caffeine, Taurine, Guarana, Ginseng, B vitamins, Ginko Biloba, L-carntine, sugars, Antioxidants, Glucuronolactone, Yerba Mate, Creatine, Acai Berry, Milk Thistle, L-theanine, Inositol and artificial sweetners (Babu et al., 2008).
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1.2.1     Caffeine
Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is one of the main ingredients of stimulant drinks and it is also present in tea, coffee and other beverages and foods. Caffeine is extracted from the raw fruit of over sixty species of coffee plants (coffea Arabica), all part of the methylxanthine family. The dimethylxanthine derivatives, theophylline and theobromine, are also found in a variety of plants. It is also extracted from tea, kola nuts, and cocoa. The average total intake of caffeine in the Republic of Ireland and the UK is estimated to be 214 and 278 mg per person per day, respectively (FSPB, 2010). Data from the consumption survey, based on weekly intake, indicates that among stimulant drink consumers, the average daily caffeine intake from stimulant drinks alone would be approximately 35 mg, rising to about 90 mg among the highest consumers (FSPB, 2010). This does not appear excessive. However, when the consumption of stimulant drinks in a single session was investigated, the average caffeine consumed was approximately 240 mg (3 cans), rising to about 640 mg (8 cans) among the highest consumers (FSPB, 2010). Such large intake levels among the highest consumers are a cause of concern, particularly in relation to the known potential acute health effects of caffeine such as tachycardia, increases in blood pressure and dehydration, as well as behavioural and cognitive effects. The health effects of chronic or habitual caffeine consumption remain uncertain.
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1.2.2     Taurine
Taurine (2-aminoethyl sulfonic acid) is a sulfur containing amino acid that is the most abundant amino acid found naturally in our bodies, primarily in the retina and skeletal and cardiac muscle tissue (Timbrell et al., 1995; Imagawa et al., 2009). Taurine is derived from the metabolism of methionine and cysteine (Huxtable, 1992; Stipanuk, 2004). It is also present in common food items such as meat and fish. The data on stimulant drink intake among stimulant drink consumers indicate that average daily taurine intake from stimulant drinks was approximately 0.4 g, increasing to about 1 g among the highest consumers (FSPB, 2010). The most taurine consumed from stimulant drinks in a single session was averaged at approximately 3 g, rising to about 8 g by the highest consumers (FSPB, 2010). Stimulant drink intake at the maximum level of intake provides taurine far in excess of that from other foods or beverages in the diet. Data available indicate no evidence of adverse effects of taurine at such intakes and in a recent report the EU Scientific Committee for Food (SCF) was unable to conclude that the ‗safety-in-use‘ of taurine in the concentration range reported for stimulant drinks has been adequately established (EU SCF, 1983).
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1.2.3     Guarana
Guarana (Paullinia cupana) is a native South American plant containing guaranine, a substance chemically similar to caffeine with comparable stimulant effects. Guarana is often added to stimulant drinks, either in combination with caffeine or on its own. The stimulant effect of guarana is related to its caffeine content; one gram of guarana contains as much caffeine (40 mg) as a medium strength cup of coffee. The precise source and nature of the stimulant activity of guarana is not well understood. However, it has been reported that guarana exerts a more prolonged effect than an equivalent amount of caffeine. The Food and Drinks Administration (FDA) in the USA currently prohibits the use of guarana in food and drinks while awaiting further clarification on its safety (USFDA, 2011).
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1.2.4     Glucuronolactone
This is a naturally occurring substance produced in small amounts within the body. Supplementation with d-glucarates, including glucuronolactone, may favor the body‘s natural defense mechanism for eliminating carcinogens and tumor promoters and their effects (Zołtaszek et al., 2008). The data from the consumption survey indicate that average daily glucuronolactone intake from stimulant drinks was approximately 0.25 g, rising to about 0.7 g among the highest consumers (FSPB, 2010). The most glucuronolactone consumed from stimulant drinks in a single session was averaged at approximately 1.8 g, rising to about 4.8 g among the highest consumers (FSPB, 2010). These maximum levels of intake provide more glucuronolactone than would otherwise be achieved through other foods or beverages in the diet. There is very little information available for risk assessment of glucuronolactone at such intakes. There is no indication from the available data that there is any risk to health from consumption of high amounts of glucuronolactone, although these data are limited.
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1.2.5     Ginseng
Ginseng is a herb that has been used for over 2000 years by people in East Asian countries including China, Japan, and Korea as a remedy for various diseases and for promoting longevity (Lee et al., 2005; Nam et al., 2005). Panax ginseng is the primary commercial species and is often referred to as Korean or Asian ginseng. Siberian ginseng (Eleutherococcus senticosus) is not truly a ginseng since it contains eleutherosides as its active constituent and no ginsenosides. P. ginseng is a small, shade loving perennial shrub that reaches about 60cm in height and belongs to the plant family Araliacae. The entire ginseng plant has been used for medicinal purposes; however, the root is the most prominent and dominates the commercial sales. Ginseng has been incorporated into a variety of energy drinks although little medical literature supports these uses. Adverse effects associated with ginseng use tend to be mild. However more serious complications have been reported, including diarrhoea, vaginal bleeding, severe headache, and Stevens-Johnson syndrome (Enerst, 2002; Dega et al., 1996). Many of these effects may be attributed to contaminants. Agranulocytosis in 4 patients taking ginseng had been linked to unreported phenylbutazone and aminopyrine contained in the preparation (Ries et al., 1975). A ginseng abuse syndrome, characterized by morning diarrhoea, hypertension, rashes, insomnia, and irritability had been reported (Siegel, 1979). Little is known regarding the effects of ginseng in children and adolescents (Braganza and Larkin, 2007).
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1.2.6     Vitamins
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B vitamins are a group of 8 individual water-soluble vitamins, usually referred to as the B complex when grouped together, and all play essential roles in cellular processes. B vitamins are incorporated into many of the mainstream energy drinks. A typical can of 250ml may contain 360% of the recommended daily allowance (RDA) of B6, 120% of B12, and 120% of B3 (niacin). The container size varies among brands and it may hold multiple servings. The addition of excess amounts of B vitamins is also observed in the more extreme energy drinks like 5-Hour Energy which contains 8333% of the RDA for vitamin B12 and 2000% of the RDA for B6. It is claimed that the consumption of these large amounts of B vitamins increases mental alertness and focus, as well as improves mood. The average person, however, consumes the RDA of B vitamins from a typical diet since B vitamins are found in a variety of foods including bananas, lentils, potatoes, tuna, and turkey. Vitamins B2 (riboflavin), B3 (niacin), B6 (pyridoxine, pyridoxal, pyridoxamine), and B12 are the most common of the B vitamins that are incorporated into energy drink formulations (Wardlaw and Smith, 2009).
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Vitamin B2 is a coenzyme in the metabolism of carbohydrates. Vitamin B3 plays a major role as a coenzyme in energy metabolism, fat synthesis, and fat breakdown (Wardlaw and Smith, 2009). Vitamin B6 is a group of 3 structurally similar compounds that all can be converted into the vitamin B6 coenzyme which aids in the utilization of carbohydrates, fats, and proteins (Wardlaw and Smith, 2009). Vitamin B12 assists in folate metabolism and in nerve function (Wardlaw and Smith, 2009). Since all of the B vitamins are water soluble, once the RDA has been met, the excess vitamins are excreted from the body via urine. Although the consumption of a large amount of B vitamins does not possess any adverse health effects, the logic behind the extreme amounts of B vitamins in these beverages is not well rationalized (Wardlaw and Smith, 2009).
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1.2.7     Sugar
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Sugar is one of the most common as well as most dangerous additives on the market today.
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It‘s sweet taste and short-term positive effects lead health experts to consider the possibility of sugar addiction. Natural sugars, such as those found in fruits and dairy products, provide an easily digestible form of good-for-you energy. The synthetic copycats like refined sugar, sucrose, fructose and glucose do far more harm than good (Nash, 1992).
More than 32 g of extra sugar a day can cause a myriad of health problems (Bauer, 2011) such as raised cholesterol levels, suppressed immune system, hyperactivity, anxiety, difficulty concentrating, crankiness, decreased emotional stability, a raised level of neurotransmitters, hypoglycemia, increased blood pressure, interference with protein absorption, and impaired DNA structure (Appleton, 2011). Just one serving of Red Bull contains 27 g of sugar (Red Bull Energy drink USA), and the average cup of coffee contains 32 g (Starbecks coffee company) (Nash, 1992).
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Energy drinks have established an enviable position in the beverage market as evidenced by their commonplace consumption. There are a number of scientific reports on the adverse consequences of excessive consumption of these drinks. Many of these products do not provide the complete chemical composition, and the caffeine content and other ingredients present are unknown to the consumer. Hence there is need to quantify the major content of these energy drinks and compare with those of accepted standards. Also, energy drinks occur mostly in liquid and powdered forms. There has been little or no research on the powdered products as more attention has been given to those in liquids.
These powdered products are usually dissolved in water by consumers before intake. It is therefore imperative to determine the caffeine, aspartame and other energizers of the powdered products and compared them with those of the liquid products. It will also be necessary to determine some other physicochemical properties of the energy drinks.
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The aim of this work is to carry out comparative study on the physicochemical properties and some chemical constituents of selected energy drinks. This will be achieved through:
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