Currently there is a relentless campaign against the use of even a
single grain of sugar in our diet. The proponents of this “sugar
witch-hunt” are as fanatical as any Medieval Crusader and probably just
as misguided.
Most people are aware of the fact that we require
energy to fuel our muscles, but it may come as a surprise to many that
the brain and the nerves of the central nervous system have what is
called “an absolute requirement for glucose”. The human brain,
therefore, needs glucose to function properly and efficiently, and we
obtain most of our glucose from sugar and other carbohydrates.
Fast brain fuel
Sugar
provides rapid energy to the brain cells because when sucrose has been
absorbed, it is easily split into the two molecules of glucose and
fructose. Obtaining glucose from other carbohydrates, and possibly from
proteins, takes much longer and entails complicated metabolic pathways.
Once the glucose is released into the blood, it is transported rapidly
across the blood-brain barrier to the brain cells to keep them working.
Human
brain cells require twice as much energy in the form of glucose as body
cells. Supporters of the latest high-protein, high-fat diets may try to
persuade you that once ketosis has set in, your brain cells can also
run on fat. However, considering that ketosis is regarded as a serious
medical condition, this type of advice is contrary to the
recommendations regarding balanced, healthy nutrition supported by
dieticians and nutritionists.
To function properly, our brain
cells need a steady supply of energy from the food we eat, which should
contain low- and high-glycaemic index carbohydrates, including some
sugar, proteins and fats and be rich in protective nutrients like
vitamins, minerals, dietary fibre, phytonutrients and essential fatty
acids. In other words, our brains require a balanced diet containing all
the food groups to function efficiently.
Different energy requirements
It
is logical that active people need more energy than those who live a
sedentary life. People who use large amounts of energy to perform their
daily work, sportsmen and sportswomen, as well as children and teenagers
who participate in sport, need more energy from their diets than “couch
potatoes” and office workers.
Vital muscle fuel
For
physically active people, fuel in the form of carbohydrates (sugars and
starches) is essential to maintain energy levels and improve
performance. The human body can only store a limited amount of
carbohydrate fuel in the form of a compound called glycogen in the liver
and the muscles. Top athletes, such as the cyclists who participate in
the Tour de France, must top up their glycogen stores as fast as
possible after a strenuous event and also take in readily available
carbohydrate fuel through energy drinks and high glycaemic
index carbohydrates before, during, and immediately after exercise.
Carbohydrate requirement for top athletes
Most
sports nutrition experts recommend between 5 and 10g of carbohydrate/kg
body weight per day for sportsmen and women. This means that a 70kg
athlete needs to consume up to 700g of carbohydrate a day, which is
difficult to achieve without using some sugar-sweetened foods and
drinks.
Pre-event fuelling
It is
important that sportsmen and women increase their carbohydrate intake on
the days before competitions to fill up their liver and muscle glycogen
stores. This particularly true for endurance events (events that last
longer than 90 minutes like marathons, long tennis matches). However,
all athletes can benefit from eating carbohydrates 3 to 4 hours before
exercising to boost their glycogen stores and enhance their performance
to give them that competitive edge.
Post-event top-up
Post-event
carbohydrate intake is also regarded as important for athletes who take
part in multiple events, and for all athletes to replenish their
exhausted glycogen stores after strenuous exercise. The recommendation
is 1.5g of carbohydrate/kg body weight during the first 30 minutes and
every 2 hours for 4 to 6 hours after the event. Recovery not only of
energy levels to prevent post-exercise fatigue, but also more rapid
recovery from injuries and prevention of respiratory infections after
very strenuous exercise, can be achieved by an intake of a mixture of
low- and high-GI carbohydrates, including sugar, after an event.
Sports drinks
One
method of maintaining carbohydrate intake during physical exertion and
simultaneously ensuring that the athlete is well-hydrated, is to use
sports drinks. The American Dietetic Association, the Dietitians of
Canada and the American College of Sports Medicine state in their
“Position Statement on Nutrition and Athletic Performance” that “sports
beverages containing carbohydrates and electrolytes may be consumed
before, during, and after exercise to help maintain blood glucose
concentration, provide fuel for muscles, and decrease risk of
dehydration and hyponatremia”.
Glucose plays a double role
All
humans require a steady supply of glucose to the brain and nerve cells
to survive. In addition, any person who is physically active,
particularly individuals doing hard physical work and athletes of all
ages, have a high requirement for carbohydrates, including some sugar,
as a fuel for their muscles and to replace used up glycogen in the liver
and muscles. Sugar, therefore, provides valuable energy to all our
brains, and to sportsmen and women, and also to people who work hard.
No fanatics
Matthew
Haines, senior lecturer in health and well-being at the University of
Huddersfield, recently warned that “it is prudent to be cautious of fads
and fashions in research” and that the “toxic truth about
carbohydrates” message should be treated with caution. He also
emphasised that “demonising sugar and carbohydrates is not useful or
accurate. This relates to both performance and health for the Tour de
France cyclist and the general public.”
Let’s, therefore, leave
the crusades to the fanatics and rather concentrate on eating a balanced
diet containing all the food groups, and being as physically active as
possible.
References:
- Burke L, Deakin V. 2002. Clinical Sports Nutrition. 2nd Ed.: The McGraw Hill Company, Pty, Ltd, Australia.
-
Haines M (2015) Let’s hear it for carbs - Tour de France cyclists
couldn’t do it without them. The Conversation. 23 July 2015.
- Schorin MD, Sollid K, Edge MS, Bouchoux A. (2012). The Science of Sugars, Part 4. Nutrition Today, Vol 47(3):1-6.).
- Health24
Why we need sugar
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Oleh
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