QUESTION: There are two schools of thought among fluid replacement company principals as to how many nutrients need to be included in a beverage meant to be used during exercise. One end of the spectrum holds that carbohydrate and a couple of electrolytes are sufficient, while the other that a drink with upwards of 100 nutrients is optimal, since that's what the body will use during exercise. What is your company's approach; if you want you may include any scientific reasoning to support your company's position.

GPUSH: The human body requires a continual supply of energy and a variety of nutrients to successfully manage everyday activity. Natural mechanisms exist in the body to ensure sustained activity, even when the gaps between dietary intakes are large. Therefore, it is not necessary to constantly ingest supplements throughout everyday activities. Additional supplementation of specific nutrients is necessary only when there is either a deficiency in dietary intake, or during sustained exercise when demands are high. Considerable research exists to show that significant nutrients such as carbohydrate, water and certain minerals need to be supplemented during exercise.

QUESTION: What type of sugar do you use, and why?

GPUSH: All G-Push products contain galactose. G-Push owns the patent for its use in sports drinks. The benefits of galactose were discovered through research at the University of Leeds in the UK in the mid 1990’s, and are just now being introduced to the market. Galactose is a "super-sugar" with no existing specific usage in any food products, but with enormous benefits over other sugars in the sports area. We supplement galactose with other sugars, maltodextrin and a little fructose, depending on the formula (G1/2/3/4) to achieve specific product objectives. A major concern of our researchers was how to get carbohydrate into the body without a) compromising the hydration need and b) without inducing an insulin-driven hypoglycemic response. Galactose uniquely gets over these problems.*

Galactose has the following advantages:

• Non insulogenic (does not initiate a primary insulin response) (Macdonald 1990, Gande et al. 1979) and hence reduces the likelihood of an unwanted hypoglycaemia
• Naturally occurring monosaccharide, needs no digestion (Williams & McDonald, 1982)
• Rapidly absorbed by sodium co-transport (the fastest sugar transfer mechanism) (Shie et al, 1995, Shi & Gisolfi, 1998)
• Integrates well into energy metabolism (liver pathway) (Williams & McDonald 1982, Williams 1986)
• Low glycemic index – 0.20 versus glucose - 1

Fructose Characteristics

• Monosaccharide
• Slow absorption (does not use sodium co-transporter)
• Primarily metabolized by the liver (Hargreaves et al, 1985)
• Non insulogenic (does not initiate a primary insulin response)
• Limits to the amount the body can absorb

Maltodextrin Characteristics

• Oligosaccharide sugar, broken down in the gut to monosaccarides followed by absorption
• Glucose polymer (ie maltodextrin) feedings during exercise are able to maintain blood glucose and delay fatigue by providing energy to exercising muscles when glycogen levels are low (Thomas et al, 1991).

G-Push G2 Momentum Formula contains galactose, maltodextrin and fructose in a carbohydrate concentration of 7.5%. Galactose supplies all of the benefits listed above, but the inclusion of maltodextrin supplies a separate source of energy once this carbohydrate has been digested to glucose. This and the phased delivery of galactose and glucose (linked sodium co-transport) (Solberg & Diamond 1987, Wright et al, 1997) occurs together with rapid rehydration, due to its marginally hypotonic solution (Shi & Summers, 1995) This formula is able to provide extensive delivery of energy and rapid rehydration in exercise situations where both are important. The provision of a carbohydrate yielding glucose normally potentiates insulin responses but the insulin production is reduced somewhat during exercise, allowing us to use some maltodextrin. Since galactose and fructose do not have primary insulin responses, the overall insulin produced by intake of the drink is reduced. The combination of maltodextrin, fructose and galactose provides a mixture of fuels, which act significantly to support carbohydrate metabolism to supply energy demands during exercise.

It is believed but not yet understood that there are additional energy oxidation benefits from the combination of different carbohydrates – which becomes important when you are trying to get the most energy out from a set input. Jeukendrup et al, 2000 (see our website for the precise reference) have demonstrated the combined enhanced oxidation effect of glucose plus fructose. The internal test data that G-Push has on the combination of galactose and fructose and maltodextrin suggests that this set of carbohydrates can oxidize even more energy.

*The recent article "Pre-Exercise Ingestion of Carbohydrate and Transient Hypoglycaemia During Exercise" (1999) [Kuipers H, Fransen EJ, Keizer HA. Int J Sports Med 20:227-231], shows how insulin sensitivity can be particularly acute for over 30% of people, whose performance can suffer significantly from insulin induced hypoglycemia. Glucose or maltodextrin, let alone sucrose or other sugars fed pre-event will have a significant insulin response.

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QUESTION: Most companies describe the ratio of solute-to-solvent in terms of their beverage's percent solution. Do you feel that this is sufficient for the discussion, or whether the discussion of osmotic pressure is germane? Please add any detail on this subject you feel is needed.

GPUSH: The composition of fluid formulations used by athletes is significant to their intended use. Certainly, solute concentration is important - fluids having a carbohydrate content less than 8% w/v have been shown to have preferred characteristics for fast gastric emptying and rapid absorption, which ensures rapid rehydration and significant delivery of energy (Vist & Maughan, 1995).

However, It is too simplistic to base usage on simple % concentration of constituents alone. Knowledge of the full osmotic potential of all the ingredients is also necessary. Osmotic pressure is a colligative property of solution and depends on the number of particles in solution. The % concentration does not define the number of particles and so is no guide to osmotic potential. The product range introduced by G-Push Sport is defined in terms of both osmolality and % concentration.

The osmotic potential of our body’s own fluids is approx 290mosm/kg water and is regulated by the intrinsic mechanisms within our own system. Fluids supplied with osmolality above this, i.e. hypertonic solutions, cause not only delays in gastric emptying but more importantly will cause fluid shifts from the body to the gut before absorption occurs. Such delays in rehydration introduce the real potential to delay and reduce performance. (Alonso, 1998, Hargreaves, 1991, Sowka et al, 2000). Solutions which are isotonic, having the same osmotic potential as our own body fluids, are without this effect but those which are marginally hypotonic, that is are below the osmotic potential of the body, are known to be emptied quickly from the stomach and have the potential to be absorbed the most rapidly. (Leiper, 1998).

We have carefully used this information to design our products for optimum combinations of fluid and energy absorption. Our G1 Hydration formula is uniquely designed with an osmolality of 240 molm/kg. Our G2 Momentum formula is formulated to achieve a marginally hypotonic (almost isotonic) solution of 280 mosm/kg. These two formulas are designed to achieve rapid gastric emptying and fast fluid absorption. Both G3 Endurance and G4 Recovery are hypertonic solutions designed to provide energy when glycogen stores are low.

• G1 Hydration – Hypotonic
• G2 Momentum – marginally Hypotonic (almost isotonic)
• G3 Endurance – Hypertonic
• G4 Recovery – Hypertonic

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QUESTION: There has been a lot of talk recently about supplementing salt to one's during-race intake, especially in long, hot races where salt loss is extreme. Can you offer your company's position on this, and perhaps your view on the pros and cons of this?

GPUSH: The important thing is to understand the role of sodium and to ensure that enough is getting in to carry out this role. Sodium tablets are like Gu gels, in the sense that they isolate one nutritional aspect for supplementation, but at the same time they require other nutrients (like water) to be effective. Both Gu and salt tablets exist in isolation because up until now it has been difficult to get products that contain sufficient sodium and carbohydrate (for the gel) in an acceptable sports drink format.

G-Push believes that it is preferable to take the sodium (and the carbohydrate) in the right combined nutritional amounts, as this guarantees that your body gets what it needs. You really do not need athletes playing hit and miss by trying to get the right mix of nutrients in their body during an event.

We include high levels of sodium in all our products. As a result we took more than 18 months of flavour work development – in order to ensure that we could offer this high level and still offer a highly palatable drink.

The inclusion of common salt (NaCl, sodium chloride) in all our formulations is essential and based on five principal reasons.

1. Sodium ions are used in sodium co-transport of galactose (and glucose) and so are necessary for rapid movement of carbohydrate (i.e. energy) from the gut to the bloodstream (Solberg & Diamond, 1987).

2. Sodium ions are used in sodium co-transport of galactose (and glucose) and as such are necessary for rapid rehydration of the body. The quickest and most effective mechanism of water gain by the body is that associated with this process (Wright et al., 1997).

3. Sodium ions are lost in sweat and inclusion of sodium ions in the formulation act to replace those lost and restores normal sodium balance and homeostasis (Hubbard et al., 1990).

4. Sodium ions are included to aid retention of absorbed fluid. It is well established that supplementation with sodium ions decreases fluid losses by unwanted diuresis (e.g. as with plain water) and increases the net gain of absorbed water, especially after exercise (Maughan et al., 1998). drinking plain water with no added sodium will simply dilute the already depleted sodium in blood plasma. If the concentration of minerals becomes further diluted, more water would be excreted and lost. Therefore, both sodium concentration and fluid volume interact to affect the rehydration process.

5. In addition, if sodium stores are not replenished, hyponatremia – a condition that may be far more dangerous than dehydration, may result. Hyponatremia, if left untreated can lead to muscle cramps, cold pale skin and severe alterations in cerebral function

Therefore, we suggest the use of sodium ions in all formulations designed to aid performance during exercise. However, it is important to ensure that the addition of sodium ions does not compromise osmolality (the desired solution osmolality is different for the cases of pre/during and post event supplementation – see above) yet is adequate to address all four situations detailed above. This is done by inclusion of sodium ions at a concentration of approximately 35 mmol/L.

In our formulations rapid rehydration and optimum delivery of carbohydrate is ensured.

Scientists believe that optimum sodium levels are above about 170-180 mg sodium per 8 fl oz. G-Push products provide 170 mg sodium per 8 fl oz serving, compared to the leading national brand which provides only 110 mg sodium per 8 fl oz serving. In fact, we know of no other sports drinks on the market to contain the optimum amounts of sodium, due to the difficulties of disguising its taste.

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QUESTION: It is customary for a race organizer to offer a variety of food and drink. In particular, one might find bananas on the course, gels such as GU, and defizzed Coke. What is your company's position on these other food and drink sources, and is it in the athlete's best interest to take any of them? If so, which, and when, and under what circumstances?

GPUSH: Our view is as follows: What matters is the total exogenous nutritional support an athlete is able to get during an event. The prime need is hydration and the (slightly) secondary need is energy. Both are continuous and developing needs. There are two problems with their replenishment: a) there are real limits to the amount of carbohydrate that can be oxidised (and therefore that it is worth taking in at a time); b) the carbohydrate intake can fight with the fluid intake if the osmolality etc is ignored.

That said, it does not really matter how an individual optimizes for him/herself within what is available, as long as they are attending to the overall hydration and energy needs as best they can and they minimise side-effects (like hypoglycemia): salt tablets, bananas and water can provide the right ingredients; so could the right gel and water.

Obviously in the longer events other things will come into play – type of exercise, weather, breaks/stops, intensity etc, but the same basic principles apply.

For the shorter events (up to about 3 hours) our position is that even though it is possible that an athlete could get to the right mix using gels/water or whatever, all they are really doing is effectively creating a drink inside anyway, so why not get it right from the start and take the proper drink. The web-sites of the bar and gel people are very clear: take them with water/electrolytes. That is the clue for the answer you are trying to get at!

Our research tests have not gone beyond 3 hours, so we need to be a little careful about what we claim for those longer events. We should also condition this answer by saying again, that different bodies are different, and the most important thing is to figure out what works for a particular individual: know that it could be a variety of solutions, but that we believe it is more logical to replenish in the form of a drink.

Please also be clear – we do not recommend taking Gu with our products (G2 or G3 – though it would be an interesting experiment to take Gu with G1).

QUESTION: We may not have asked a question you feel is important. Please feel free to expand and expound on anything we've missed on the topic in general, or with regard to your brand in particular.

GPUSH: (EDITOR'S NOTE: We asked these people for a more complete explanation of their unique carbohydrate choices, and their tiered approach to matching fluid replacement drink to duration of exercise. Here is that they wrote).

Rationale for the Carbohydrate Type and Quantity in G-Push Formulations

Introduction

Our diet consists of various types of carbohydrate found in unitary or polymeric form either exclusively or in combination (McCance & Widdowson). We are presented with a diverse spectrum ranging from glucose as monomer, through disaccharides such as sucrose consisting of glucose and fructose, lactose consisting of glucose and galactose to complex polysaccharides consisting typically of repeat units of glucose such as found in starch.

The enzymes necessary for digestion of these carbohydrates and mechanisms for their absorption exist in the GI tract for all the common forms found (Marieb). There are significant differences in the way in which carbohydrates from more than one source are digested and absorbed in terms of both the mechanisms of uptake and the final monomeric sugar units formed. These features determine the selection of specific carbohydrates as to type and quantity within each of the G-Push formulations.

The over-riding influence for formulation of a sports drink would be to incorporate into its design features which permit the desired metabolic objectives when that drink is consumed (Lamb 1994, Gisolfi 1994, Maughan & Leiper 1995). Such is the nature of individual sports and susceptibility of the athlete to different physiological constraints at different times during exercise, that a single sports drink would be a compromise. For these reasons the specific design of G-Push formulations use carbohydrate types and quantity appropriate to recognised phases of activity and demand (Coombes & Hamilton 2000).

Exercise depletes the body of energy reserves, especially glycogen; it also produces heat, which is dissipated by the evaporation of sweat. Thus the two key features which limit performance are hydration and energy. The extent and duration of any bout of exercise determine the balance and rates of loss of these components and is influenced dramatically by the type of exercise, the status of the athlete and pertaining environmental conditions (Alonso 1998, Hargreaves 1991).

A typical athlete will progressively dehydrate during exercise and during the initial phase the primary requirement is replacement of lost fluid. G1 (Hydration) is suitable both before and during exercise to limit this problem. Most athletes will enter exercise with full energy reserves so during this initial phase hydration is much more of an issue than energy. G1 (Hydration) is a rehydration/energy drink. As exercise continues a phase is entered where energy reserves become more of an issue and the additional requirement changes and becomes biased towards energy replacement. G2 (Momentum) is suitable during longer lasting exercise because it is an energy/rehydration drink. However, continuing progressive serious exercise results in a phase that necessitates a mandatory requirement for both more energy and fluid, if performance is to be maintained. G3 (Endurance) is a higher energy density rehydration drink. Finally a recovery phase is necessary to restore the body to its optimum state. During this phase both fluid and energy deficits should be addressed and corrected. G4 (Recovery) is a drink of high energy density designed to replete fuel stores and aid rehydration after exercise in as short a time as possible.

The types and quantities of carbohydrate within a sports drink have important implications for its ultimate digestion, absorption and assimilation. These range from osmotic constraints determined by actual osmolality (Hunt & Pathak 1960), which effects both gastric emptying and initial fluid exchange within the gut (Elias et al 1968); carbohydrate content (% carbohydrate) which affects gastric emptying (Foster 1994, McHugh &Moran 1979, Murray 1987); digestive constraints determined by the nature of the bonds needed to be broken by gut enzymes, absorption constraints determined by the nature of the transporter needed to move carbohydrates from gut to bloodstream (Wright et al 1997, Solberg & Diamond 1987; to metabolic constraints which facilitate opportune involvement of the carbohydrate into metabolism (McDonald 1990).

The design of each G-Push formulation is based on the best use of specific carbohydrate(s) for the provision of the most appropriate balance between fluid and energy during the different phases of exercise.

In detail these formulations are:

G-Push 1 Hydration

The carbohydrate in this formulation is D (+) galactose. Galactose at 2.5% w/v does not produce a hyperosmolar solution. Together with NaCl at 35mM, the conditions exist for sodium co-transport of this sugar from the lumen of the gut into the bloodstream. Movement of galactose and sodium ions is the primary stimulus for the uptake of water. Carbohydrate, in this case in the form of galactose, is essential for this process. This facilitates fast fluid absorption. Thus this formulation will be suitable for rapid rehydration. Further galactose does not induce a primary insulin response so eliminating the danger of a reactive hypoglycaemia (McDonald 1990, Ganda et al 1979). G1 is a rehydration/energy drink; though primarily supplying rapid fluid uptake it does provide some energy.

Features

1. Enjoy rapid gastric emptying (its hypotonic)
2. Not pull fluid into the gut (its not hypertonic)
3. Will be absorbed rapidly (sodium co-transportable sugar)
4. Very fast fluid absorption (galactose & sodium co-transporter)
5. Does not induce a primary insulin response (no danger of unstable blood glucose level i.e. highs & lows)
6. Galactose can be used to make liver glycogen or produce glucose in the liver as conditions demand.
7. Promotes fluid retention (inclusion of sodium)

G-Push 2 Momentum

The carbohydrates in the formulation include galactose, maltodextrin and fructose. At 7.5% w/v these constituents permit the drink to be marginally hypotonic (almost isotonic) and thus do not cause hypersmotic problems. The galactose content 2.5% w/v provides the same benefits as G-1.

The maltodextrin content contributes to the sustained production of glucose, which does, after absorption, introduce an insulin response, but since both galactose & fructose do not have primary insulin responses the overall insulin produced by intake of the drink is reduced. Further glucose will also use the sodium co transport system to facilitate rapid fluid absorption. Both galactose and fructose do not need enzymic hydrolysis and are more immediate sources of carbohydrate than maltodextrin. It is likely that combination of glucose, fructose and galactose is a very effective source of energy for athletic performance (Jeugendrup & Jentjens 2000). In addition it is known that combinations of these substrates can enhance overall water absorption (Shi et al 1995, Shi & Gisolfi 1998). Therefore the higher and combined carbohydrates content of this formulation is suited ideally to optimise delivery of energy with effective rehydration. Thus the carbohydrate content of this drink provides both energy and rehydration over a period but balances more on energy than rehydration.

Features

1. Enjoy rapid gastric empting. (its hypotonic and carbohydrate is not greater than 8%)
2. Not pull fluid into the gut (its not hypertonic)

Phased energy delivery

1. Rapid absorption of galactose part (sodium co-transportable sugar)
2. Sustained absorption of glucose from digestion of maltodextrim (sodium co-transportable sugar)
3. Slower absorption of fructose (does not use sodium co-transporter)
4. Facilitate fluid absorption (linked to galactose and glucose sodium co-transporter)
5. Galactose & fructose can be used to make liver glycogen or liver glucose.
6. Glucose can be used to make liver glycogen or be used in working muscle
7. Reduced insulin response (includes galactose and fructose)

G-Push 3 Endurance

The carbohydrates in this formulation include Galactose, Maltodextrin & Fructose. At 10% w/v this is a hypertonic solution designed to provide energy in situations when energy is the prime consideration. Although this solution will provide rehydration this is not as rapid as in either G1 or G2 because the drink is hyperosmotic and energy dense. Nethertheless the design is one to provide energy before rehydration and it does this in much the same way as G2 in terms of phased energy delivery. Due to the inclusion of galactose there will be reduced insulin release (as in G2, since both galactose & fructose do not have primary insulin responses the overall insulin produced by intake of the drink is reduced.).

Although it is known the solutions greater than 8% w/v carbohydrate delay gastric emptying the higher concentration of carbohydrate means that a sustained energy delivery to the gut is possible from the stomach. In situations where energy is the crucial key factor G3 not only provides more energy, and supplies it in an efficient combination of carbohydrate types, but also will supply it in an easily assimilated form together with essential fluid for rehydration.

Features

Phased high-energy delivery

1. Absorption of galactose part (sodium co-transportable sugar)
2. Sustained absorption of glucose from digestion of maltodextrin (sodium co-transportable sugar)
3. Slower absorption of fructose (does not use sodium co-transporter)
4. Facilitate fluid absorption (linked to galactose and glucose sodium co-transporter)
5. Galactose & fructose can be used to make liver glycogen or liver glucose.
6. Glucose from maltodextrin can be used to make liver glycogen or be used in working muscle

G-Push 4 Recovery

It is known that the best time to replace lost reserves of glycogen in muscle and liver after an event is immediately and no later than the 1.5 hours following, by ingestion of carbohydrate-rich sources (Hargreaves 1991, Ivy et al 1988). The carbohydrates in this formulation at 12 % w/v are designed to provide rapid and efficient repletion of these reserves. The fact that the drink is hypertonic is of minor importance since gastric emptying, though delayed, is not halted and intestinal aborption is slightly prolonged ensuing that a high concentration of sugar is absorbed over the required period to sustain full repletion of glycogen reserves in liver and muscles. It is very important for an athlete to replete energy reserves and restore euhydration efficiently and quickly when major events and heats are spaced closely in time.

Features:

1. High density of carbohydrate energy.
2. Combination of carbohydrates promotes rapid restoration of energy reserves.
3. Specific carbohydrates restore both liver and muscle glycogen.
4. Sustained energy release in the critical period after exercise.
5. Galactose and fructose restore liver glycogen
6. Glucose from maltodextrin restores both liver and muscle glycogen.