by
Dr. Aparna Pandit B.Sc. Home
Science, M.Sc. Foods & Nutrition, Ph.D. Food Science and
Nutrition Email: vins_aparna@hotmail.com
Mar 2003
SPORTS DRINKS
WHO NEEDS SPORTS DRINKS? Athletes who train hard frequently complain about
"energy drain" and fatigue. Because they are regularly
reminded to consume adequate fluids and fuel to minimize early fatigue
and to maximize performance and recovery. Having more energy can improve
one’s capacity for work, a very desirable characteristic for all and
especially for active individuals (Bonsi, 2002). So athletes will always
be attracted to products that claim to have performance-enhancing
effects.
WHY SPORTS DRINKS ARE REQUIRED? Following training & competition an athlete's glycogen
stores are depleted. In order to replenish them the athlete needs to
consider the speed at which carbohydrate is converted into blood glucose
and transported to the muscles. The rapid replenishment of glycogen
stores is important for the track athlete who has a number of races in a
meeting. Sweating is the way in which the body maintains it's core
temperature at 37 degrees centigrade. This results in the loss of body
fluid and electrolytes (minerals such as chloride, calcium, phosphate,
magnesium, sodium and potassium) and if unchecked will lead to
dehydration and eventually circulatory collapse and heat stroke. Among
the important electrolytes are sodium, chloride, potassium, magnesium
and calcium, which are often included in glucose-containing electrolyte
drinks. Sodium helps maintain proper body fluid volume. A weight loss of
greater than 2% resulting from dehydration can fatigue the athlete,
cause a loss of concentration, increase heart rate and lead to
circulatory collapse. Small amounts of sodium improve water and glucose
absorption in the body. Glucose electrolyte solutions maintain body
fluid balance better than glucose drinks alone. Sodium also plays an
important role in muscle contraction and in the condition of nerve
impulses. A slight deficiency of sodium may impair performance, cause
nausea, vomiting, headache, loss of appetite, muscular weakness and leg
and abdominal cramps.
The electrolyte requirements of most physically active people can be
more than adequately met by consuming a balanced diet. Imbalances may
occur under special circumstances such as during the initial stage of
acclimation to a hot environment, during prolonged repeated exposure to
exercise and heat, and during exercise lasting several hours.
Electrolytes, especially sodium and potassium, in a drink will reduce
urine output, enable the fluid to empty quickly from the stomach,
promote absorption from the intestine and encourage fluid retention. For
PR-seeking runners, sports drinks can be a quick-and-easy way to hydrate
and refuel on the fly. Supplying fluid, carbohydrate (the body's
preferred fuel during exercise) and electrolytes, sports drinks and
energy gels should be an integral part of any runner's nutrition
program.
FLUID ABSORPTION With regard to fluid absorption, there are two main factors
that affect the speed at which fluid from a drink gets into the body.
They are the speed at which it is emptied from the stomach and the rate
at which it is absorbed through the walls of the small intestine. The
higher the carbohydrate levels in a drink the slower the rate of stomach
emptying. Isotonic drinks (These drinks are the choice for most
athletes) with a carbohydrate level of between 6 and 8% are emptied from
the stomach at a rate similar to water. However Hypertonic fluid drinks
with High level of carbohydrate are used to supplement daily
carbohydrate intake normally after exercise to top up muscle glycogen
stores. In ultra distance events high levels of energy are required and
Hypertonic drinks can be taken during exercise to meet the energy
requirements. If used during exercise Hypertonic drinks need to be used
in conjunction with Isotonic drinks to replace fluids.
ARE SPORTS DRINKS BETTER THAN WATER ? Water is the most common beverage consumed. However, Drinking
plain water causes bloating, suppresses thirst and thus further
drinking. It stimulates urine output and therefore is inefficiently
retained. A poor choice where high fluid intake is required. Water
contains no carbohydrates or electrolytes.
WHAT IS THE BEST BEVERAGE ? Majority of the Sports drinks are designed for use during
exercise typically contain more than one type of carbohydrate. Check the
ingredient list and you’ll find a combination of simple carbohydrates
(sucrose, glucose and fructose) and complex carbohydrates, such as
glucose polymers and maltodextrins. The better-formulated (and tasting)
drinks usually contain both, with a higher percentage of complex than
simple carbohydrates.(Labels list ingredients by weight from most to
least). While hydrating with water should be adequate, the rapidly
absorbable carbohydrate supplied by a sports drink can provide the extra
energy needed to mount a strong finishing burst.
During long races, such as half-marathons and marathons, it’s
imperative that competitors drink a sodium-containing beverage to avoid
the potentially life-threatening condition known as hyponatremia (low
blood sodium level). Middle and back-of-the pack runners should
especially rely on a sports drink rather than drinking plain water.
Running at a slower pace often translates into more opportunities to
drink. This can result in a dangerous disturbance of the body’s
fluid-to-sodium ratio if a runner ingests copious amounts of plain water
without also attending to sweat-induced sodium losses. If muscle cramps
have been holding you back, experiment with a sports drink that provides
the recommended amount of sodium at least 110 milligrams per eight-ounce
serving. While the exact cause of muscle or heat cramps is unclear, most
experts believe salt depletion plays a critical role.
Fluid replacement is a must before, during and after activity in order
to safeguard the athletes' health and for optimizing athletes
performance. The ideal fluid replacement beverage is one that tastes
good to the athlete, does not cause gastrointestinal discomfort when
consumed in large quantities, promotes rapid fluid absorption and
maintenance of extracellular fluid volumes and provides energy to
working muscles. Research states that sports drinks containing 6-8
percent carbohydrate solution actually enter the bloodstream as rapidly
as plain water. The 6 percent carbohydrate beverage not only entered the
blood as fast as water but, was associated with improved exercise
endurance. Both drinks had the same favorable influence on
cardiovascular and thermoregulatory function. The key is to experiment
with different brands and flavors in training to find the winning
combination to use on race day.
WHAT ARE THE INGREDIENTS ? Other than water, most of the products marketed as energy and
sports drinks contain carbohydrate and caffeine as their principal
ingredients the carbohydrate to provide nutrient energy and the caffeine
to stimulate the central nervous system, but they may also contain a
wide variety of other ingredients. The other ingredients generally found
in energy and sports drinks are taurine, ribose, ginseng, carnitine,
guarana, inositol, vitamins, Schizandrae, Glutamine, Galactose, protein,
chromium, green tea, Ginkgo biloba, Pyruvate, royal jelly, bee pollen,
damiana, Stabilized oxygen, aloe vera, medium-chain triglycerides,
borage oil, branched-chain amino acids, electrolytes. All these
ingredients are claimed to be the power enhancers, but most of them are
not proven scientifically. Since there is little or no evidence of
athletic performance effect by these ingredients, athelets should be
cautious before consuming energy and sports drinks. Examine sports
drinks carefully and think before buying. Before buying a sports drink,
be sure to check for nutritional/ingredient information, claim given by
the company, dosage etc. Avoid herbal additives if you are taking
prescription medications because there may be adverse interactions among
the herbal chemicals and your medicine. Avoid products containing
ephedra, yohimbe, and mate, all of which are unsafe.
SUMMARY Sports drinks are not adequate substitutes for the time,
training, rest, recovery, and fueling required for sports. Athletes must
take the responsibility for what goes into their bodies, which includes
being informed as well as cautious about dietary supplements. Eating an
optimal amount of calories and being well hydrated are certainly
critical components of athletic success. Sports drinks can supply energy
and fluid, and they may have a role to play in carbohydrate loading
during recovery from exercise. But sports drinks typically are not
optimally formulated to work best to improve strength, speed, stamina,
and other requirements for sport performance when consumed shortly
before or during exercise.
Leslie Bonci, M.P.H., R.D. Director, Sports Medicine Nutrition,
Department of Orthopedic Surgery and the Center for Sports Medicine,
University of Pittsburgh Medical Center, Nutritionist, Pittsburgh
Steelers, Pittsburgh, Pennsylvania, Sports Science Exchange 84, VOLUME
15 (2002) NUMBER 1
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