Which of the following individuals will benefit the most from consuming a sports beverage?

Sports Drinks Market

Sports drinks are a fast growing segment of the worldwide beverage market. In the United States, sports drinks sales increased more than 25% in 2005, followed by the bottled water sector with a 16.5% increase (Sloan, 2006), during which time, both carbonated beverage and bottled juice sales declined. Since entering the market in 1969, Gatorade® has controlled the predominant share in the global market, with over 80% of sales in the United States. However, Powerade® (Coca-Cola Company), introduced in 1998, is growing fast taking a 13% and 12% share of the American and European markets, respectively. Gatorade® and Powerade® are the most popular sports drinks in the United States; but the market is also shared with other smaller competitors, notably Capri Sun Sport® (Kraft Foods) and Allsport® of PepsiCo, Inc. (Holay, 2005). Just 30 years after the introduction of sports drinks into the American market, sales have reached over $2.2 billion per year, with per capita consumption exceeding 8 liters. This is small in comparison to carbonated drinks, which are still averaging $14 billion per year (Murray and Stofan, 2001), but nonetheless, sports drink sales and consumption are on the rise.

Asian countries are also experiencing a boom in the sports drink market. Japan has the largest and most established sports drink market in the world, with per capita consumption higher than 11 liters and total volume sales of over 2.4 billion liters per year (Hilliam, 2002). The United States and Japan together share 83% of the total market volume, leaving 17% for Australia and the major European markets (Figure 8.1).

In Europe, Germany remains the leading market for sports drinks with a 26% volume share, followed by Italy (19%) and the United Kingdom (15%). Spain has around 11%, while the Netherlands have 9% of the market, but the highest consumption per person—2.8 liters, over twice the European average. Greece, with 0.4 liters per capita, lags well behind the overall average of 1.2 liters, beating only France and Portugal, where per capita consumption is only 0.2 liters (Zenith, 2003).

The dominant form of sports drinks is ready to drink liquids (88%). However, there are powders and liquid concentrates (11% and 1%, respectively) on the market, which require mixing by the individual who plans to consume them (Figure 8.2) (Ford, 2002). These are popular among sports teams, where mixing can be performed in bulk. These alternatives can also be appealing to the average consumer, because they eliminate the need to transport heavy or bulky bottles of liquid.

The fact remains, that even if scientifically formulated to enhance performance, sports drinks are still a relatively small part of the mainstream market. This means taste, packaging, and convenience play as much a role in formulation as physiological consideration. There is a balance to be maintained between a nutritionally superior product, and a product that will be appealing to the senses of the general population.

Background on Sports Beverages

A sports drink is any drink consumed in association with sports or exercise, in preparation for exercise, during exercise itself, or as a recovery drink after exercise. The main role of a sports beverage is to stimulate rapid fluid absorption, to supply carbohydrate as substrate for use during exercise, to speed rehydration, and to promote overall recovery after exercise [2].

Basic sports drinks refer to those drinks formulated for quick replacement of fluids and electrolytes lost during exercise and that provide carbohydrate fuel to the muscles. Sports beverages usually contain a source of carbohydrates, various salts to provide electrolytes, and water. Secondary components of sports beverages include vitamins, minerals, choline, and carbonation.

The hydration effect of sports beverages is not immediate because the fluid must be absorbed in the proximal small intestines, and 50%–60% of any given fluid ingested orally is absorbed here [1].

Sports drinks are hypertonic, isotonic, or hypotonic. Most sports beverages tend to be moderately isotonic, meaning their concentration of salts and carbohydrates is similar to that found in the human body. Most sports drink have a carbohydrate content of 6%–9% weight/volume and contain small amounts of electrolytes in the form of salts, most commonly sodium [2].

1.2.3 Do special regulations exist for sports drinks? What is an isotonic drink?

There are currently no specific regulations for sports drinks. In 2004 the EU Commission published a ‘Draft Directive on foodstuffs intended to meet the expenditure of intense muscular effort, especially for sportsmen’, generally known as the Sports Foods Directive. However, the document was never progressed and enacted. At the time of writing the position of sports drinks is under discussion. The Commission could either introduce specific sports drinks regulations under the PARNUTS Framework Directive (89/398/EC) or make provision under the nutrition and health claims regulations (1924/2006). At the time of writing it appears that it will be the former. This will enable claims to be made referring to the action of the sports drink.

Sports drinks can be formulated in three ways in order to perform three specific functions relating to energy and hydration. The two major requirements for athletes expending energy are carbohydrates (sugars) and water. The three categories of sports drinks are as listed in the following table:

A hypotonic drink is intended for rehydration and contains only low levels of carbohydrate (sugars) and electrolytes (minerals, predominantly sodium). The presence of carbohydrate and sodium at low levels speeds the adsorption of water by the body, maximising rehydration.

An isotonic drink contains glucose and sodium at similar levels to those found in the body. This maximises the rate at which glucose (energy) is taken up by the body.

Hypertonic drinks contain high levels of carbohydrate and minerals to replace those used during prolonged strenuous exercise.

Sports Drinks

Sports drinks have reached mainstream consumption, but their calories and nutrients are formulated for the sports market—not daily consumption, unless there is regular fluid and electrolyte loss. Sports drinks are designed to help delay the onset of fatigue during exercise and help rehydrate athletes after training or competition by replenishing carbohydrates, electrolytes, protein, and other nutrients. Most sports drinks provide a readily absorbable form of carbohydrates, important to exercising muscles, since carbohydrates are the primary fuel for exercise and are critical to performance.

Overconsumption of plain water can cause water intoxication or hyponatremia, an electrolyte disturbance in which the sodium concentration in blood plasma is too low. Severe or rapidly progressing hyponatremia can result in swelling of the brain and death. Fluids that supply 60 to 100 calories per 8 ounces help prevent this condition and provide needed carbohydrates, calories, electrolytes, and fluids for continuous performance, especially in extreme conditions over three hours.

The three primary categories of sports drinks are isotonic, hypertonic, and hypotonic. Isotonic sports drinks are said to be in balance with the body’s fluids and nutrients; hypertonic sports drinks have more nutrients and other substances than in the blood; and hypotonic sports drinks have fewer nutrients and other substances than in the blood.

Isotonic sports drinks contain water and other nutrients that are similar in proportion to the fluids and nutrients in the blood. They quickly replace fluids that are lost by sweating and supply absorbable carbohydrates in the form of glucose, the body’s preferred energy source. The concentration of glucose in isotonic sports drinks is 6 to 8 percent (13 to 19 grams per 8 ounces). Higher quantities of sugar can delay stomach emptying and increase the risk of cramps.

Gatorade is a flavored noncarbonated, isotonic sports drink produced by PepsiCo. It is designed for consumption during physically active conditions to rehydrate and replenish carbohydrates, electrolytes and fluids. Per 21.4 ounces, Gatorade supplies 158 calories, 39 grams of carbohydrates, 32 grams of sugar, and 238 milligrams of sodium. POWERade is another isotonic sports drink produced by the Coca-Cola Company.

Hypertonic sports drinks contain a high level of carbohydrates. They are used to supplement daily carbohydrate intake and are normally consumed after exercise to “top” muscle glycogen stores. Hypertonic drinks may be too high in sugar to be absorbed during exercise. They are sometimes used in ultra-distance events in conjunction with isotonic drinks to replace fluids.

Hypotonic sports drinks contain a low level of carbohydrates. They can quickly replace fluids that are lost by sweating and provide some energy in the form of sugar calories. They are suitable for athletes who need fluids without a significant boost of carbohydrates.

Taurine, found in energy drinks, often in combination with performance enhancing substances such as creatine and anabolic steroids, is designed to alleviate muscle fatigue in strenuous workouts and raise exercise capacity. Its safety has been questioned. More information about electrolyte-replacement fluids and exercise can be found in Chapter 10.

17.5.7 Benefits of sports drink consumption during and after physical activity

As discussed above, sports drink consumption during vigorous physical activity is associated with improved performance as a result of maintaining hydration and related cardiovascular functions (e.g., plasma volume, cardiac output, blood flow to muscles and skin) and by supplying a metabolizable source of exogenous carbohydrate to muscles and brain. It is well established that carbohydrate ingested during exercise in the form of monosaccharides (e.g., glucose, fructose), disaccharides (e.g., sucrose, maltose), oligosaccharides (e.g., maltodextrins), and even polysaccharides (e.g., some starches) increase the overall rate of carbohydrate oxidation,78,103,109–111 a response frequently linked to improved performance,77,112,113 and enhanced by the ingestion of mixtures of simple sugars.102,104,113–116

Sports drink ingestion during exercise has also been linked to reductions in the subjective rating of perceived exertion (RPE), a response that has been reported in many but not all studies on the topic.93,94,97,117–126 In 2011, the EFSA disallowed claims associating the consumption of carbohydrate-electrolyte solutions with a reduction in RPE because no scientific references were provided in the claim application,14 even though there appears to be ample evidence in the literature to support such a claim.

Although the functional ingredients in sports drinks are water, carbohydrate and electrolytes, the sensory properties of sports drinks also confer hydration-related advantages because physically active people voluntarily consume more sports drink than plain water.48 This increase in voluntary fluid intake is likely due to the flavor and sweetness characteristics of sports drinks, as well as to sodium content.48,127–129 The presence of sodium helps sustain the osmotic drive to drink, resulting in greater fluid intake during exercise.130,131

Following exercise, ingestion of sports drinks is an effective means of rapid rehydration when compared with ingesting plain water.132 The presence of sodium (20–50 mmol/L) in a rehydration fluid not only increases voluntary fluid intake but also provides an osmotic impetus that helps restore plasma volume, reduces urine production and thereby increases fluid retention.133–137 Rapid rehydration is important for athletes, workers, soldiers and others whenever there is limited time between bouts of physical activity and sports drinks are effective at accomplishing that goal.29,31,138

14.8 Commercially available formulations

Most of the mainstream commercial sports drinks have a rather similar formulation, suggesting some consensus among the manufacturers as to the key components of an effective sports drink (Table 14.2). In general, these drinks are approximately isotonic, with an osmolality that is typically between about 280 and 340 mosmol/kg. The carbohydrate content is usually about 6–7% and usually includes some combination of glucose, fructose, sucrose and maltodextrin. The sodium concentration in typically about 20–30 mmol/l and the potassium concentration about 5 mmol/l.

Table 14.2. Composition of selected mainstream commercial sports drinks. For comparison, the composition of typical fruit juices and a standard carbonated cola beverage are also shown. The composition of fruit juices can be highly variable, so these examples are for illustrative purposes only

C Sugar-Sweetened Beverages

Sugar-sweetened beverages (SSBs) include all sodas, fruit drinks, sport drinks, low-calorie drinks, and other beverages that contain added caloric sweeteners, such as sweetened tea. Consumption of SSBs has received increasing attention in recent years as playing a role in the obesity epidemic for several reasons. First, examination of national dietary intake data trends suggests that adults and children are consuming significantly greater amounts of SSBs than in previous years. Nielsen and Popkin [193] examined nationally representative data from the 1977–1978 Nationwide Food Consumption Survey, the 1989–1991 and 1994–1996 (also for children aged 2–9 years in 1998) CSFII, and the 1999–2001 NHANES and found that across all age groups, sweet consumption increased with energy intake from sweetened beverages by 135%. The majority of findings derived from large cross-sectional studies and prospective cohort studies with long periods of follow-up indicate that there is a positive association between SSB intake and unhealthy weight gain and obesity in both children and adults [194,195]. Moreover, there is emerging evidence that reducing consumption of SSBs may result in reductions in body mass index in youths and adults [196,197].

26.1 Introduction

Vitamin-fortified foods range from products such as breakfast cereals and milk powder to sports drinks and confectionary products. In developing countries staple foods such as flour and oil may be fortified in order to reduce the incidence of vitamin deficiencies caused by the lack of more expensive components of the diet (fish and meat, for example). Consequently there are a large number of factors which must be considered when discussing shelf life of vitamin-fortified products, depending on matrix, packaging and the nature of individual vitamins. Foods may be fortified in order to obtain a product about which a claim may be made, or in some cases vitamins are added back to products to compensate for losses of naturally present vitamins during processing. Table 26.1 shows the recommended daily allowances (RDAs) for vitamins. In all cases, where the level of a vitamin is stated on the packaging, that vitamin must be present at that level at the end of its shelf life. All vitamins degrade to a greater or lesser extent during processing and storage, so it may be necessary to add excess vitamin during product manufacture to ensure that the correct level of vitamin is maintained. This procedure needs careful control, in that the addition of excess vitamin incurs added cost, and may also lead to excess consumption since the vitamin content at the beginning of the storage period will be in excess of that stated on the label. For some vitamins, where there are upper maximum recommended limits this may be of concern to particular consumers. For both of these reasons, knowledge of the degradation patterns of vitamins and ways to minimise losses on storage are important for both the food industry and the consumer.

Table 26.1. Recommended daily allowances (RDAs) for vitamins

As specified in Council Directive 90/496/EEC of 24 September 1990 on nutrition labelling for foodstuffs.

A search of the scientific literature reveals little data that could be used to predict the pattern of vitamin degradation in food products. Much of the work on vitamin loss in foods is likely to have been carried out within the food industry, since the information is highly product-dependent. The many factors affecting vitamin degradation mean that each combination of ingredients, processing method, packaging and storage conditions is likely to lead to a different rate of vitamin loss. A study carried out at Leatherhead Food Research on levels of folic acid, vitamin B12, vitamin B5 and biotin demonstrated the different stabilities of different vitamins in different matrices, with their associated differences in packaging and storage conditions. Folic acid in fortified margarine was relatively stable over a six-month storage period, whereas it degraded by as much as 50% in a fortified liquid dietary supplement stored at room temperature. Vitamin B12 was also far more stable in the refrigerated margarine than in the liquid dietary supplement or a confectionary product also stored at room temperature (Wilson, 2006). Experimental studies to determine the kinetics of vitamin loss must therefore be carried out to determine the length of time a product can be stored before its vitamin content drops below the required level.

Quinoline Yellow

It is a greenish yellow food dye, produced by chemical synthesis that can be found in sport and energy drinks, ices, and confectionary, among other products.

It has a limited absorption in mammal animal models, and the bulk of the dose is excreted unchanged via the feces. Nonetheless, this color additive is to some extent bioavailable, concerning some systemic effects found in long-term toxicity studies. Adverse sensitivity reactions (urticaria and rhinitis) after intake of Quinoline Yellow have been reported although no conclusive results on the induction of sensitivity by this food color have been achieved. It may also have an adverse effect on activity and attention in children, similarly to some azo dyes.

Fish oil and inflammation, immune, and oxidative stress

In a series of recent publications relating to applied sports science (Table 10.2), an enriched-DHA sports drink consumed over 8 weeks of training was reported to increase red blood cell DHA in soccer players (Capo et al., 2015). In this same group of soccer players, the authors also reported that DHA lowered acute inflammation (Capo et al., 2014) whilst paradoxically increasing plasma PGE2 (Martorell et al., 2014) and decreasing reactive oxygen stress markers (Capo et al., 2015; Martorell et al., 2015). The limitations of field-based research are certainly apparent in the series of publications steaming from the study, namely: the small sample size (n = 9 fish oil; n = 6 control), variability in exercise intensity during training-induced exercise stimulation and the large number of measured blood markers which raises the risk of type 1 statistical error. Nonetheless, marathon runners provided with 3 g/day of DHA-rich fish oil for 10 weeks were also reported to improve lymphocyte function (Santos et al., 2013) although this time a control placebo was not used in the study and limits relevance of interpretation (Table 10.2). Nevertheless, given the acknowledged interaction of essential fatty acids with human immunology and inflammation, there has emerged a line of research, with varying level of first principles study design, that warrant interpretative discussion against the background of applied sports science.