Performance-enhancing drugs usually bring to mind designer steroids and human growth hormones. Yet some athletes rely on more rudimentary - and legal - means to boost their race times, including using a substance usually tucked away in a kitchen cupboard.

For years, keen runners have sworn that taking a spoonful of bicarbonate of soda (baking soda) helps them to keep going for longer. For years, experts doubted that there was anything other than a placebo effect to these claims until they subjected the substance to rigorous examination. Most exercise scientists investigating the trend for “soda-doping” among athletes and gym-goers have shown that it offers significant benefits for endurance and speed.

At Loughborough University, for instance, physiologists reporting in the June issue of the International Journal of Sports Medicine showed that swimmers who took baking soda about one hour before a 200m event were able to shave a significant time off their usual performances. Dr Jonathan Folland, who led the study, says that it is not uncommon for top swimmers to take sodium bicarbonate (another name for the substance) before a competition to give them an edge. Indeed, he showed that of nine swimmers tested, eight recorded their fastest times after ingesting a supplement of the common baking ingredient.

Another small study by Dr Ronald Deitrick,of the American College of Sports Medicine (ACSM), showed that competitive runners also benefited. Dr Deitrick, who presented his findings at the ACSM annual conference, gave 800m runners either a placebo or a sodium bicarbonate capsule, which they took with water. Although a few of the runners had minor gastrointestinal problems after swallowing the capsules, a greater number benefited significantly.

Helpful for speed-based events

Just last week, an Australian sports scientist said that the use of legal performance-enhancing substances could become a major issue of the Beijing Olympics. “Beijing will probably be remembered for the abuse of legal aids,” said Robin Parisotto on Australian radio.

And Dr Deitrick believes that bicarbonate of soda can significantly improve performance. “If you took out the participants who experienced negative side-effects... you'd see an average improvement in running times of about 2.2 seconds,” Dr Deitrick says. “For a relatively short running distance, that's very significant.”

But how does something so seemingly innocuous have such a dramatic effect? During prolonged or intense exercise muscles produce large amounts of waste products, such as lactic acid, that lead to soreness, stiffness and fatigue. Because sodium bicarbonate naturally reduces acids, it acts as a buffer against these performance-limiting by-products.

Current research suggests that it is particu-larly helpful in speed-based events, including sprints, football and other fast-moving games, and middle-distance (up to 10km) running, swimming and cycling. “Essentially, sodium bicarbonate is an alkali substance that increases the pH of the blood,” Dr Folland says. “This seems to reduce and offset the acidity produced in the muscles during intense, anaerobic exercise that produces lactic acid most quickly, such as fast running or swimming.”

In Dr Folland's study, swimmers who took the sodium bicarbonate knocked 1.5 seconds off their time for 200m, a difference that may seem insignificant to recreational swimmers but which is substantial at elite level.

“At the last Olympics, the top four swimmers in the men's 200m freestyle were separated by just 1.4 seconds,” Dr Folland says. “So, in theory, it could be the difference between winning a medal and not.” Not that he recommends that we all rush down to our nearest supermarket with £2 to buy a packet. While manufacturers may come up with a drink or capsule containing sodium bicarbonate, it is unpleasing to many palates. For optimum effects it should be taken with water, ideally before exercise, on an empty stomach. Most people take about 20g, although it can cause problems.

“It is not dangerous, but it tastes appalling and can make you want to retch,” Dr Folland says. “It can make some people nauseous when it hits their stomach and a few suffer an upset stomach or diarrhoea when they take it.”

Some scientists want it banned from sport

Anyone can try it, he says, but only those who are serious enough to monitor their times and progress in sports such as running, swimming or cycling may notice the few seconds advantage it might provide. “The increments of improvement are relatively small to the average person, although significant to someone who competes,” Dr Folland says. “I certainly wouldn't advocate using it if you do aerobics a few times a week.”

But some experts, including Dr Deitrick, claim that its effects are so powerful that it shouldn't have a place in competitive sport. “It comes down to whether or not the athlete has a competitive advantage by taking an aid,” he says. “And in the case of sodium bicarbonate, I believe the answer is yes. It violates the spirit of fair play by artificially enhancing performance.”

Dr Folland, however, says that baking soda is unlikely to be listed on banned lists. “There are always going to be ethical arguments, but if sports drinks and carbohydrate loading, both of which can enhance performance, are allowed, there should be no issue with sodium bicarbonate,” he says. “If you are serious about exercise and can stomach it, it may help.”

THE PERFORMANCE ENHANCERS IN YOUR LARDER

Caffeine Several studies, including some conducted at the Australian Institute of Sport (AIS), have shown that caffeine can trigger the release of body fats into the bloodstream during activity. This means fat is burned during exercise rather than carbohydrate, the body's primary choice of fuel, and that endurance capacities are improved.

A study at the University of South Carolina found that drinking one or two cups of coffee up to an hour before a gym session can delay or prevent post-exercise tiredness by up to 60 per cent.

It can also help recovery. Last month, Australian researchers reporting in the Journal of Applied Physiology showed that glycogen, the muscles' main source of fuel during exercise, is replenished more quickly when athletes have both carbohydrate and caffeine after a workout.

Chocolate milk A 2006 study published in the International Journal of Sport Nutrition and Exercise Metabolism looked at a group of cyclists who rode until their muscles were depleted of energy, then rested for four hours before cycling again to exhaustion. During rest they were given either chocolate milk, which has an optimal ratio of 4:1 for carbohydrates to protein, an isotonic sports drink or a high protein sports drink.

Researchers say the protein and carbohydrate ratio in the milk complement each other perfectly. Carbohydrates replace the energy lost during exercise, but can't rebuild muscle. On the other hand, protein can help to repair the muscles, but can't refuel them. Chocolate milk is thought to be better for recovery than plain milk because of its extra sugars. In the trial, the cyclists who had chocolate milk rode about 50 per cent longer than those who drank the protein drink and about as long as those who drank the isotonic preparation. Michael Phelps, the multi-gold medallist, is said to drink chocolate milk between swimming events.

Mushrooms A Chinese mushroom, the Cordyceps, has proven performance-enhancing effects. Scientists carrying out clinical trials on CordyMax, an over-the- counter supplement containing Cordyceps extract, reported that of the 131 non-athletes who took it for 12 weeks, most experienced an average reduction of 29 seconds in the time it took them to walk a mile.

Honey Three separate studies at the University of Memphis have shown that honey boosts performance. Nine cyclists were given one of three supplements in gel form - honey, glucose or a flavoured, calorie-free placebo - each week over three weeks. They were put through a weekly 64km time trial and given 15g of one of the gels with 250ml of water before every 16km. The glucose and honey produced a statistically significant reduction in the time to finish, and a significant increase in the athletes' average power.

Cherry juice A 2006 study published in the British Journal of Sports Medicine looked at gym-goers who were given either a placebo or the juice of 50 to 60 cherries, twice a day for eight days. Halfway through the trial they did 40 bicep curls with one arm, using the heaviest weight they could. They then switched drinks and repeated the process with the opposite arm. There was less reduction in strength and less pain with the cherry juice, reported researchers at the University of Vermont.

THE WHITE STUFF

Bicarbonate of soda, or baking soda, forms a slightly alkaline solution when it is mixed with water. It has a range of uses, as granny knows perfectly well.

Baking It acts as a raising agent by releasing carbon dioxide.

Cleaning Sprinkled on a damp cloth it can clean countertops, ovens, hobs and baths.

Teeth Brushing with it once a week may help to keep teeth pearly white.

Cystitis A teaspoon mixed in half a pint of water may ease symptoms.

Nasty smells To banish fridge pongs, leave a couple of teaspoons in an open bowl on one of the shelves.

Peta Bee is the Medical Journalists' Association Freelance Journalist of the Year

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