Competitive cyclists who have achieved maximal results from their training programs often turn to extrinsic aids (termed ergogenic aids) to enhance their performance.  These include mechanical aids (equipment), psychological aids (hypnosis, psychotherapy), pharmacological aids (erythropoietin) and nutritional aids (creatine phosphate, vitamins, minerals).

The use of performance enhancing dietary supplements can be traced back to the Romans who reportedly drank lion's blood to improve their strength and courage. Today, unfortunately, nutritional supplements are frequently promoted with unsubstantiated claims.

Based on various reviews, those supplements that are clearly helpful and beneficial for improving cycling performance are shown with (++). The text will be clear for those that have nothing other than anecdotal information to recommend them.

The following are in alphabetical order.

ALCOHOL

Occasional articles will appear touting the benefits of alcohol as an energy source for sports activities. Although alcohol does contain more energy per gram (7 Cal/gram) than carbohydrates, and is rapidly absorbed from the intestinal tract, the available evidence suggests these Calories are not utilized to any significant extent during exercise. Thus its negative effects outweigh any theoretical positive ones. These include:

it is a diuretic and contributes to dehydration
it slows down glucose production and release from the liver
it disturbs motor skills including balance and coordination

In a recent study 10 women were given a mixed drink equal to a moderate drink. They then rode stationary bikes for 30 minutes at 70% of their maximum heart rate. Compared to their own baseline performance off alcohol, cycling after alcohol required more energy, produced a higher heart rate, and stimulated a higher cardiovascular demand. Even moderate drinking while exercising placed increased demands on the cardiovascular system. The bottom line is therefore a definite negative influence on performance, as if you didn’t know.. 

ASTRAGALUS
A root herb from the Mongolian wilderness. Reported to increase the body's capacity to handle stress, and help reduce fatigue and enhance endurance. There are no studies with specifics. aAll information is purely anecdotal. 

BORON
Boron has been reported to increase serum testosterone levels and subsequently the lean body mass and strength of male athletes. However, a carefully controlled study of 19 male body builders, half of whom received 2.5 mg of boron per day for 7 weeks, demonstrated no significant difference in total testosterone, lean body mass, or strength. A normal diet will provide 10 mg/day of boron; 50 mg per day appears to be a toxic level.

CAFFEINE (++)
Caffeine is a member of a group of compounds called methylxanthines found naturally in coffee beans, tea leaves, chocolate, cocoa beans, guarana, and cola (kola) nuts.

During prolonged exercise, the onset of fatigue correlates closely with the depletion of muscle glycogen stores.  The metabolism of free fatty acids (FFA) as an alternative energy source can lead to decreased use of muscle glycogen. Caffeine can increase blood FFAs, and it is felt that this is its major method of action. In one study, caffeine produced a 50% increase in FFA at 3 to 4 hours. This effect was seen after 300 mg of caffeine (An average 6 ounce cup of brewed coffee contains 100 - 150 mg of caffeine).

There is speculation that some of its benefits may also be related to its central nervous system effect as a stimulant, and a recent study has demonstrated a direct positive effect on the muscle fibre itself with a reported 7% increase in power output over a 6 second cycle exercise task.

In one controlled study, subjects were able to perform for 90 minutes to fatigue as compared to 75 minutes in controls (a 20% increase) after the drinking the equivalent of 3 cups of coffee or 6 caffeinated colas 1 hour before, even though values for heart rate and oxygen uptake were similar in both groups. Another study, looking at performance with acute altitude change (4300 meters), demonstrated a 50% increase in performance with caffeine supplements.
 
A suggested dose of caffeine for the recreational rider is 5 mg per kg of body weight if you are taking a tablet or 1.2 cups of coffee per 100 pounds of body weight taken 1 hour before the ride although some riders prefer smaller doses taken periodically throughout the ride itself.

But there are potential side effects. Caffeine can cause headaches, insomnia, and nervous irritability. In addition it is a potent diuretic and can lead to dehydration. However the biggest negative is that in high concentrations it is considered a drug and is therefore banned.

The bottom line is that most endurance athletes consider caffeine useful if used correctly. This includes a period of abstinence for several weeks before the event as habitual use induces tolerance.

CALCIUM
Calcium metabolism in the athlete is still not completely understood. The question of an increased calcium requirement is linked to concerns about osteoporosis in women athletes who, because of the intensity of their training, have become amenorrheic. The hormonal changes that occur with amenorrhea (associated with intense training programs) affect bone formation and are thought to be one of the causes of osteoporosis. Recent evidence has suggested that the positive effects of exercise on bone formation may counteract and cancel out bone loss. At this time, there is no consensus on the need for calcium supplements.

CHOLINE
An amine widely distributed in food, as well as synthesized in the body, choline has been postulated to increase the production of the neurotransmitter acetylcholine and thus prevent fatigue in endurance events. Even with increased blood levels (ingestion of choline bitartrate, 2.34 grams), two separate studies failed to demonstrate any significant improvement in cycling times to exhaustion at 70% VO2max.

CHROMIUM PICOLINATE
A chemical compound reported to potentiate the effect of insulin, and help build muscle and dissolve fat. However, 8 different studies, using up to 200 micrograms of chromium picolinate daily, have failed to demonstrate any changes in body composition or strength compared to control groups administered a placebo. Current information indicates that daily intakes of up to 400 micrograms are not toxic.

CITRATE (Sodium Citrate) (++)
Sodium citrate was evaluated in a 30 km high intensity time trial event at a dose of 0.5 grams per kg body weight. Total power output, but not peak power output, was greater in this treated group. At 30 km, the riders using sodium citrate had an average 100 second lead. The cyclists using the sodium citrate had a higher venous blood pH throughout the ride, and it is presumed that this buffering effect led to the improved performance (by optimising the pH within the muscle cell and enhancing contractility).

Sodium citrate has also been shown to increase peak power over a placebo control group during short, high intensity cycle ergometry of 120 and 240 seconds duration. Again, this is thought to be related to optimising the pH within the active muscle cell.

CIWUJIA (Endurox tm)
Ciwujia is an herb derived from a root grown in the northeast section of China and used in traditional Chinese medicine for over 1700 years to treat fatigue and bolster the immune system. It is commercially prepared and marketed under the trade name Endurox, and is claimed to shift energy metabolism in the exercising muscle from carbohydrate to fat, thus sparing carbohydrate and slowing lactic acid build-up. There is also a decrease in heart rate during moderate exercise.

CoQ10 (coenzyme Q10; ubiquinone)
A lipid found in mitochondria, as well as an anti-oxidant. In a recent review of research on this compound, supplementation of 100-150 mg/day for 4 - 8 weeks elicited no enhancement on metabolic responses to sub maximal or maximal exercise, VO2max or cycle time to exhaustion.

COLA NUT (see also caffeine)
A natural source of caffeine.

CREATINE
An organic compound which, when combined with phosphate, yields creatine phosphate, an intermediary in the energy transfer pathway in the muscle cell which resynthesises ATP. Creatine is available through nutritional supply stores in the form of creatine monohydrate, and will increase body weight (whether this is water retention of true muscle mass is still unproven). It is claimed to improve performance during maximal strength or power tests (weight lifting) and in repetitive high intensity bouts with short recovery intervals (short sprints of 5 to 15 second duration).  However, the literature is split evenly on the question of benefits for the competitive cyclist, and there are some questions as to whether long term use of high doses might affect the kidneys. No short-term toxicity has been reported at doses of 20 to 30 grams per day.

This compound may be effective in limited situations. It is doubtful that it is of any benefit for sprints lasting more than 30 to 45 seconds. The study most like a real life cycling situation, an 18-mile time trial that included 6-15 second sprints, demonstrated no difference between riders receiving creatine or a placebo. So if competitors using this supplement are beating you, it is probably for other reasons.

CYTOCHROME C
Cytochromes are iron containing cellular enzymes that facilitate energy transfer. The only controlled study of this compound examined the effects of a supplement containing 500 mg cytochrome C on eleven trained triathletes. The performance test included a treadmill for 90 minutes at 70% VO2 max. followed by cycling to exhaustion again at 70% VO2 max. There was no significant improvement.

DHEA (dehydroepiandrosterone)
DHEA is a steroid, related to cortisone, produced by the adrenal gland. Maximum production occurs during the third decade of life and then gradually declines with aging. Studies to date on it's "anti-aging" effects are only preliminary and have given conflicting results. Doses of 25 to 100 mg per day have been given for 6 months to subjects over 60 years of age with variable results on muscle strength and lean body mass. It appeared that men had more of a response than women. At this time there is absolutely no evidence that physical performance is modified in young, healthy individuals.

DHAP (dihydroxyacetone pyruvate)
A metabolic by-product of glycolysis that includes di-hydroxyacetone and pyruvate in a 3:1 ratio. Several studies have suggested that 100 grams per day of DHAP for 7 days increased arm ergometer endurance at 60% VO2max and cycle ergometer endurance time at 70%VO2max. These studies are yet to be confirmed in well-trained athletes.

EPHEDRA
A short acting stimulant found in the traditional Chinese herb tea Ma Huang, ephedra mimics adrenaline. The synthetic version, ephedrine, is found in asthma and nasal decongestant (pseudoephedrine) products. It has been used in tandem with other natural caffeine sources such as kola nut and guarana. In higher doses it can cause tremors, rapid breathing, nervousness and insomnia - common side effects of caffeine as well.

Although it appears to be safe in small amounts (up to 50 mg of ephedrine or 2 cups of Ma Huang tea per day), a tolerance will develop (i.e. it becomes less effective as time passes), and the International Olympic Committee bans its use in any amount. In fact the USOC advises athletes to eliminate all herb based teas and diet supplements for one week prior to a race (and urine testing) if they are unsure whether they might contain ephedra. Likewise check on any decongestant and asthma medications to see if they contain ephedrine.

ERYTHROPOIETIN (EPO)
EPO is a hormone, produced by the kidney, which stimulates the bone marrow to produce red blood cells. It is available in injectable form and can be self administered to "hyper"stimulate the bone marrow. The result is an abnormally high red blood count that effectively creates the same physiologic conditions as blood doping. Unfortunately, when administered in an unmonitored manner, the haematocrit can increase above 60%, increasing blood viscosity and predisposing to the formation of blood clots (also aggravated by the dehydration which occurs in competitive cycling). This clotting tendency is speculated to be the explanation for the cases of "sudden death , which have been reported after hard training or racing - most likely from a heart attack or a pulmonary embolism.

EPO is banned in sanctioned events. But as it is almost impossible to monitor for an excess of a hormone that is naturally produced, it is the haematocrit that is monitored, not the hormone itself. Any cyclist with a haematocrit greater than 50% is not allowed to compete, regardless of the mechanism of the increased haematocrit. Unfortunately this is not as fair as a test for EPO, but health concerns were felt to override those of fairness.

FERULIC ACID
Ferulic acid is derived from the natural plant sterol, frac, and has been claimed to assist the body in maintaining greater workloads. However these performance claims are not supported by published research studies.

FRUCTOSE
A 6 carbon carbohydrate derived from fruit often touted as superior to glucose as an energy source for the endurance athlete. However, there is little evidence that fructose alone has any advantages over glucose and may in fact have less of a glycogen sparing effect. There is some evidence that its benefits lie in a combination fructose/glucose sports drink.

GLUCOSAMINE SULFATE
An over the counter agent derived from shark cartilage, glucosamine sulfate is helpful in decreasing the joint pain from degenerative or wear and tear arthritis (osteoarthritis). There is no evidence that it decreases the muscular pain associated with over training.

GLYCEROL (++)
A chemical compound that together with fatty acids forms triglycerides (the most plentiful lipid in the body and the major form of lipid stored in fat cells), glycerol is a clear, syrupy, and extremely sweet substance which also has water retaining effects when taken orally. In 1987, it was shown that resting subjects drinking a glycerol solution retained 50% more fluid than when drinking a similar volume of water alone. This led to investigation of its ability to help prevent dehydration under extreme conditions of exercise, heat, and high humidity.

GUARANA
A South American herb used as a natural source of caffeine. The caffeine effect of one teaspoon (100 mg) of guarana is equivalent to one cup of coffee.

HERB TEA (see also Ma Huang)
The biggest shortcoming of herb teas is the inability to identify the active ingredients, increasing the possibility of taking a substance banned by the IOC.  Strength of these teas is directly related to the brewing time, making calculation of a "safe" dose difficult and increasing the chances of a toxic side effect.

HMB (beta-hydroxy-beta-methylbutyrate)
This metabolite of the amino acid leucine was studied in a group of serious weight lifters (1.5 hours a day, 3 days a week) on their "normal" diet of 117 grams of protein per day (twice the Recommended Daily Requirement) and a high protein diet of 175 grams per day.

HMB (1.5 and 3.0 grams per day) decreased the products of muscle breakdown (muscle damage) found in the urine during the training period, and increased the amount of weight lifted in each week of the study when compared to a control group not using the supplement. There was a dose related effect, that is the 1.5 gram per day dose of HMB was beneficial but greater improvement was noted on 3.0 grams perday. There was no benefit of a high protein diet compared to a normal protein diet (117 grams per day) either in the control (no HMB) or HMB groups. Lower body strength improved more than upper. The average increase in overall (averaged) strength compared to the control (no HMB) group at week 3 was 13% for the 1.5 gram per day HMB supplement and 18% for the 3.0 gram per day HMB supplemented group. No adverse effects were noted during the study period.

HMB is of use in a program of regular resistance training and appears to work by minimizing the muscle damage that normally occurs. It's role in aerobic conditioning or cycling where strength is less of a factor has not been studied.

HUMIC ACID
Humic substances (including humic acid) are ubiquitous in the environment and may constitute as much as 95% of the total dissolved organic matter in aquatic systems Although they have been touted as a health supplement, their use at this time should be considered risky.

INOSINE
Inosine is a nucleoside theorized to enhance oxygen delivery during exercise. However, the only available study in 9 highly trained runners after 6 grams per day for 2 days reported no significant benefit either during submaximal running or peak oxygen uptake and performance in a treadmill run to exhaustion.

IRON
Iron is important as a component of haemoglobin in red blood cells that transports oxygen from the lungs to the muscle cells, and iron deficiency can cause fatigue and weakness. Although some riders use iron supplements to alleviate the beat feeling they experience after a long ride, a balanced diet easily meets the RDA for iron (10 mg for men and 15 mg for women). Four ounces of red meat contains 8 - 10 mg. As excess iron can be toxic, any questions of a deficiency state are best resolved with a screening blood test before resorting to supplements - any self-prescribing has definite risks.

Athletes involved in contact sports (including runners) are more likely to be iron deficient than cyclists, but even regular cyclists have an additional need of around 18 mg of iron per month.  As you might expect, iron deficiency is more of a problem in women athletes because of monthly menstrual blood loss. If you ride regularly, taking a multivitamin with iron will help to prevent anaemia. An alternative is to eat extra portions of iron containing foods (dark green vegetables, prune juice, figs, and raisins).

KOLA NUT (see caffeine)
The caffeine effect of one teaspoon (100 mg) of kola nut is equivalent to one cup of coffee.

L-CARNITINE
A nitrogenous compound found mainly in meats (a non-vegetarian diet contains 100-300 mg per day), but also synthesized in the kidney and liver from lysine and methionine. Theorised to enhance aerobic endurance by increasing the oxidation of glucose, decreasing the accumulation of lactic acid, and enhancing fatty acid metabolism by the cellular mitochondria.

NIACIN (NICOTINIC ACID, VITAMIN B3)

The concentration (and thus availability) of fatty acids in the blood is believed to directly influence their uptake and oxidation by skeletal muscle. The use of niacin as a vitamin supplement results in a lowering of blood free fatty acids levels at rest and a blunting of the rise in free fatty acid levels normally associated with prolonged exercise. Theoretically this should reduce the use of free fatty acids as an energy source for skeletal muscle during exercise, and require a compensatory increase in the amount of carbohydrate metabolised from muscle glycogen stores or blood glucose supplies. And one might even expect a potential decrease in TOTAL muscle energy output because of a decrease in the total energy Calories available to the muscle cell (fatty acids and glucose).

However, as measured in actual controlled studies, the effects on performance have been inconsistent. One investigator reported impaired "run to exhaustion" times with nicotinic acid supplements while another reported no impairment in performance in a 10 mile run. As to cycling performance, one study failed to demonstrate a difference in "cycling time to exhaustion" while another reported a decrease in physical work capacity to exhaustion in a one legged cycling model.

These conflicting results suggest that any decrease in overall performance is probably small, affecting at most only a minority of elite cyclists. However, as with all medications, there is the occasional individual with a particular sensitivity and exaggerated response in which case this medication could have an adverse effect on their personal performance.

ORYZANOL
A plant extract claimed to have anabolic effects, this is a ferulic acid compound derived from rice bran oil. Recent studies have indicated it may actually decrease testosterone production. Any effect on performance is purely speculative.

PANGAMIC ACID (VITAMIN B15, D15)
Touted by many athletes as a performance enhancer (increased aerobic capacity, increased endurance, decreased blood lactate levels), there is no evidence from controlled studies as to any benefits in athletic performance. Concern has been expressed as to possible harmful effects to humans, and the FDA in America has made it illegal to sell this as a diet supplement or drug.

PHOSPHATE
A blood phosphate compound (2,3 diphosphoglycerate, DPG) binds with haemoglobin to facilitate the release of oxygen at the level of the muscle capillary. Thus oral phosphate, a building block of DPG, has been investigated as a performance enhancer. However results have been conflicting and although there is some suggestive evidence, this compound should be considered as unproven as an ergogenic aid at this time.

Usual doses are 3 to 4 grams of calcium or sodium phosphate for 3-6 days. Phosphate supplements may cause gastrointestinal distress unless consumed with ample fluids or food, and chronic consumption may interfere with calcium balance.

PYCNOGENOL
A procyanidin extracted from the tree bark of the pine, Pinus maritima. It is a free radical scavenger and antioxidant when studied in the test tube. However there have been limited animal studies and no human studies of this compound. There is no proof as to benefits of this compound compared to the antioxidant effects of Vitamins C or E.

QUININE
This medication is used by cyclists as a cure for leg cramps. However it can cause a drop in blood count and has been linked to 16 deaths, so the FDA in America has banned it. Cramping cyclists should fight leg cramps with proper hydration, training, and electrolyte replacement instead.

SELENIUM
Thought to have a possible role as an antioxidant, there is little evidence this mineral plays a significant role in minimizing the harmful effects of free radicals. It almost certainly plays a less significant role than Vit C or Vit E, and the occurrence of specific selenium deficiency in humans is quite rare. It is found naturally in seafood, meats, and grains, and specific supplementation is not recommended.

SIBERIAN GINSENG
A chinese herb, questionably related to ginseng - as in many of these herbal products it is difficult to determine the exact chemical makeup - claimed to have benefit as a brain stimulant. A group of volunteers is reported to have shown an increase in mental alertness and work output, while another study suggested an increase in athletic performance under stressful conditions such as heat and noise. As with other herbal products, these claims are anecdotal and there is no scientific proof of increased athletic performance.

SMILAX (smilax officinalis)
Smilax Officinalis, native to the tropics of Brazil, began as a pharmaceutical base for the production of certain anabolic steroids. However, without the chemical modifications, smilax officinalis is thought to be non-toxic and its use has no known negative side effects. It is alleged to raise the blood content of testosterone - the male growth hormone - and to be equivalent to anabolic steroids in gains of lean muscle mass and defined tissue. However these performance claims are not supported by published research studies.

SODIUM BICARBONATE (baking soda) (++)
A chemical compound available as baking soda or Alka Seltzer, sodium bicarbonate buffers lactic acid allowing longer bouts of near maximal cycling for short, high intensity sprint events lasting 1 to 7 minutes (400m. or 800m. sprints, time trials), but of minimal additional effect compared to the body's natural buffering capacity for lactic acid during very short intense exercise lasting less than 30 seconds or sustained endurance events. Generally, studies that used doses of 300 mg/kg body wt. found an ergogenic effect, while those using less than 200 mg/kg showed no effect. Sodium bicarbonate should be considered of probable benefit in very specific circumstances but has certain drawbacks that may outweigh these advantages.

SODIUM CHLORIDE
Over a 24-hour period, the athlete's standard training diet will replace two to three times the normal salt losses. Only under extreme environmental conditions of high temperature or high humidity is a salt supplement needed. An exception might be the cyclist who has not trained for an event and can lose excessive amounts of salt in his/her perspiration. Although exercise cramps were once thought to be the result of salt deficiency, it now appears that they are related to dehydration and a decreased blood flow to the muscles.

VITAMIN B12
No studies have documented enhanced lean muscle mass or strength. It is non-toxic even at high doses.

YOHIMBINE
An alkaloid extracted from the bark of the yohimbe tree and claimed to have an anabolic effect through stimulating the release of testosterone or human growth hormone. Performance claims are not supported by published research studies.