Why we need sugar
06 September 2015, 16:29
Nairobi - 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.
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 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.
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.
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.
- 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.).
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