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Natural nutrition: what can quercetin and beta-alanine do for athletes?
Athletes are always looking for a competitive edge and optimising nutrition is one area where significant gains can be had. In this two-part article, Ron Maughan and Andrew Hamilton look at emerging evidence for the possible benefits of two naturally occurring compounds – quercetin and beta-alanine, both of which are attracting attention from researchers in the field of sports nutrition.
Quercetin – by Ron Maughan
David Nieman is well known around the world, especially for his work on the effects of exercise and stress on the immune system. He has conducted many important studies in this area, including many field studies on marathon and ultra-marathon runners. David Nieman was largely responsible for the first description of the so-called ‘J-shape’ relationship between exercise and the risk of illness and infection. This is important, because it seems that the ability of our immune system to fight off infection is enhanced with moderate levels of exercise, which is good news. With very high levels of exercise stress, however, athletes seem to be more susceptible to minor illness and infection. These usually amount to little more than a few sniffles, but they may be enough to interrupt training. Two or three such interruptions over the course of a season may have serious effects, especially if one of them coincides with a major race.
More recently however, attention has turned to the effects of a range of herbal extracts and botanical compounds on the immune system. There are many such products on the market, and echinacea has for many years been one of the top-selling supplements aided at promoting a healthy immune system, but it is only one of an enormous number of such products. Many of these herbals form an important part of the traditional medicine culture in different parts of the world, but western medicine has largely ignored them in favour of antibiotics and other more powerful pharmaceuticals.
David Nieman has gathered evidence within the last 18 months or so that quercetin, a natural antioxidant that is found in quite high levels in some plants, is able to reduce illness and maintain mental performance in physically stressed test subjects, and it is the public release of this information that led to the press announcement noted above. According to a quote from David Nieman in a press release, ‘These are ground-breaking results, because this is the first clinical, double-blind, randomised, placebo-controlled study that has found a natural plant compound to prevent viral illness’.
Quercetin is a naturally occurring chemical found in many different fruits and vegetables that most of us eat on regular basis, including red grapes (and therefore also red wine) red apples, red onions, green tea, broccoli. Along with a whole range of other compounds, including perhaps most notably vitamin C, it can be shown to have anti-oxidant properties.
This is important for the fruits and vegetables that produce it – it stops them from being attacked by the oxygen in the air. An apple will keep for a ong time, largely because the skin acts as a barrier, protecting it from the oxygen in the air, but also from the bugs that would grow on its flesh. Cut it in half, and the exposed flesh will turn brown rather quickly as the oxygen in the air causes oxidation of various chemical components: this is soon followed by growth of yeasts and other infectious organisms. If you spread some lemon juice on the flesh of the apple as soon as it is cut, the flesh is protected from the chemical attack but the antioxidant action of the vitamin C in the lemon juice.
David Nieman has made the first public presentation of his latest findings at a regional chapter meeting of the American College of Sports Medicine that was held on 9 February in North Carolina. Full details were not presented, but he gave 20 cyclists a daily dose of 1 gram of quercetin for five weeks, while another 20 acted as a placebo group and were given dummy tablets. It is important to note that vitamins C and B1 were also given. Three weeks into the study, the athletes rode a bicycle three hours a day for three days to the point of exhaustion. Monitoring of the subjects showed that nine of the cyclists who took a placebo reported illness following the extreme exercise, while only one in the quercetin group reported any days of sickness. ‘That’s a highly significant difference,’ Nieman said. There was also some evidence that quercetin helped maintain mental alertness and reaction time of the cyclists in a fashion similar to that of caffeine.
Good sources of quercitin
The average adult eating a normal, healthy diet consisting of western foods consumes about 25 to 50 milligrams of quercetin a day, as well as varying amounts of other flavonoids and related compounds. People with a high energy intake (that includes most athletes training hard), and more especially those with a high intake of fruits and vegetables, will get far more than this. The supplement used in David Nieman’s study contained 1 gram (1000 milligrams) – an amount that could not reasonably be obtained from the diet. You could, for example, get this from about 700 grams of onion leaves or 1kg of bird chillies. However, no sensible person would eat these foods in such amounts!
Even though quercetin is relatively stable during cooking, fresh fruits and vegetable are generally better sources of quercetin (as well as the myriad of other biologically active compounds that are present) than cooked or processed products because the compound is mainly concentrated in the skin of many of these rather than in the flesh. Products such as apple juice and apple sauce generally do not contain significant amounts of skin. Red apples tend to have more of the antioxidant than green or yellow ones, although any apple variety is a good source of quercetin.
There are many other good sources for those who don’t like apples. Other foods containing high levels of quercetin include onions, which have some of the highest levels of quercetin among vegetables, as well as berries, particularly blueberries and cranberries. We don’t yet know if the other flavonoids found in these foods will have the same effects as quercetin, but it seems very likely that similar effects might be seen.
It is perhaps too early to know if quercetin supplements really will benefit all athletes, as this study was a rather artificial one – no athlete normally does the sort of exercise that these volunteers were subjected to. What is clear though is that this information adds to the already convincing evidence that everyone should be sure to include lots of fruits and vegetables in their diet. Further research will tell us if supplements are helpful, or even necessary, for athletes training hard.
Beta-alanine by Andrew Hamilton
Although it’s an amino acid found naturally in the body, beta-alanine is something of a curiosity. Unlike nearly all other amino acids, it’s not used in the biosynthesis of any major proteins or enzymes, but is instead formed in the body by the degradation of other compounds. Beta-alanine is structurally unusual too, being the only naturally occurring amino acid in which the amino (-NH2 group) is positioned two carbon atoms away from the carboxyl group (-COOH) instead of one (compare figures 1 and 2 – the structures of alanine and beta-alanine, overleaf).Beta-alanine has been studied in a number of different contexts for some time and indeed when scientists analysed samples from the Martian meteorite known as Nakhla, they were amazed to find that beta-alanine was one of the most abundant amino acids detected(1)! However, until recently there’s been little interest in the role of beta-alanine in sport performance – that is until a flurry of research towards the end of last year (more later).
The first connection between exercise and possible effects of beta-alanine came five years ago, when US scientists conducted studies on the effects of administering the amino acid taurine to rats and also beta-alanine, which competes with taurine for absorption and so lowers taurine levels(2). What they found was that beta-alanine appeared to significantly reduce the amount of lipid peroxidation caused by oxidativedamage in some of the exercising muscles. They also found that beta-alanine helped attenuate the decline in levels of an enzyme called lactate dehydrogenase in the calf muscles during exercise; this enzyme helps break down fatiguing lactate, so a decline during exercise is not desirable.
After this, there was very little interest in beta-alanine until a US study published last year, which looked at the effects on mass and strength gains of administering beta-alanine with creatine in 33 collegiate football players and comparing it with the supplementation of creatine alone(3). All the football players performed a resistance training programme for 10 weeks and took either placebo, creatine or creatine plus beta-alanine.
The results were striking; the beta-alanine/creatine combination produced significantly more lean muscle gain and body fat loss than creatine only or placebo. Moreover, significantly greater gains in actual strength were also seen in the beta-alanine/creatine group.
Just a month later, scientists from Florida Atlantic University decided to compare the beta-alanine/creatine combination with creatine only in a study that looked at aerobic power, ventilatory and lactate thresholds, and time to exhaustion on a cycle ergometer(4). In the four-week study, 55 men were randomly assigned to one of four groups:
*Beta-alanine plus creatine.
Before and after the four-week supplementation period, all the subjects performed a graded exercise test on the bike to determine maximum aerobic capacity (VO2max), the oxygen uptake associated with ventilatory and lactate thresholds and time to exhaustion as well as other parameters. Although no significant group effects were found between the groups as such, a significant effect was observed for the beta-alanine plus creatine combination when the researchers analysed just five of the eight parameters measured (ie the beta-alanine/creatine did seem to enhance endurance when the researchers consider selected physiological markers associated with improved endurance).
The most recent study to be published on beta-alanine appeared in November of last year. In it, US researchers examined the effects of 28 days of beta-alanine supplementation on the physical working capacity at neuromuscular fatigue threshold, ventilatory threshold (VT), VO2max and time to exhaustion (TTE) in 22 women(5). Unlike the studies above however, this compared the effects of pure beta-alanine supplementation against placebo (ie there was no added creatine with the beta-alanine).
Before and after the supplementation period, participants performed a continuous, incremental cycle ergometer test to exhaustion during which the above parameters were measured. The results were as follows:
*Compared to placebo where there was no improvement, the beta-alanine group experienced a 13.9% increase in the workload required to reach ventilatory threshold;
*The beta-alanine subjects were able to increase their power output by 12.6% at neuromuscular fatigue threshold (no improvement with placebo);
*The beta-alanine subjects extended their time to exhaustion by 2.5%.
Although beta-alanine supplementation did not affect maximal aerobic power the results of this study clearly indicated that beta-alanine supplementation alone was able to delay the onset of neuromuscular fatigue and the ventilatory threshold (VT) at submaximal workloads, and it also increased the time to exhaustion during maximal cycling on the ergometer.
Should athletes supplement with beta-alanine? It’s probably too early to give a definitive answer to this question. Only a small number of studies have yet been conducted and while the evidence is certainly persuasive (especially in combination with creatine), more research is needed before firm conclusions can be drawn. Moreover, we’re not yet sure how any ergogenic effects exerted by beta-alanine might arise. The most likely explanation at present is that increased intakes of beta-alanine stimulate the production of another biochemical called carnosine. Carnosine is a powerful buffering agent – ie it can help to neutralise the acidity caused when lactic acid concentrations rise during intense exercise and it’s this acidity that is known to contribute to muscular fatigue.
Athletes who aren’t averse to some experimentation, however, will be pleased to know that beta-alanine is already available as a supplement and is fairly inexpensive; for example, you can expect to pay in the region of $8-$10 for 100 grams in the US and around £5-£7 in the UK. Given the amounts used in studies (typically around a gram per day), you can experiment without breaking the bank. However, as always, the advice is to ensure you have all the proven nutritional strategies well in hand before you even consider experimenting with something new.