In the second in a series of endurance nutrition articles, IsoWhey Sports Dietitian Belinda Reynolds advises how to supplement in the lead up to race day.

Nutrition and training go in hand in hand, so whilst following a strict diet is extremely important when preparing for a big endurance race, your increased nutritional requirements may call for additional supplementation. IsoWhey Sports dietitian, nutritionist and Education Manager, Belinda Reynolds, gives her insight and recommendations for incorporating supplementation to overcome nutritional deficits whilst training.


BCAAs make up close to one third of the amino acids in muscle tissue and can also be burned there as an energy source. This is why intense and frequent exercise increases the need for BCAAs, as energy production and muscle recovery processes are required to be performed in a capacity that exceeds the diet’s ability to support it. For this reason BCAA supplements are popular amongst athletes and individuals looking to increase their strength and/or muscle mass.

But is there solid evidence behind BCAA use? A review of the research suggests there is BCAAs have been shown to enhance muscle recovery and growth, whilst providing an energy source to the muscle cells. Their consumption before and after training (and on a daily basis) is shown to reduce markers of muscle damage, reduce delayed onset muscle soreness, improve performance, enhance recovery and increase exercise capacity (the maximum amount of physical exertion that you can sustain). These benefits are particularly useful when you need to back up for multiple hard sessions per week, or more than one session in a day.

Although BCAAs naturally occur in a range of protein-containing foods including red meat, chicken, fish, eggs, certain nuts (e.g. peanuts and almonds), whey protein, lentils and specific beans (e.g. soy beans), when training frequently and for long and intense periods, you may require additional BCAA supplementation.


Athletes often think of glutamine as a supplement for muscle protein synthesis, repair and growth, and for good reason. Glutamine, along with the BCAAs make up a large component of muscle protein mass. Training at high intensities has been found to deplete available glutamine levels in the body, and low concentrations have been noted in athletes experiencing significant discomfort from over-training.1, 2

Glutamine not only assist the formation of other amino acids (e.g. L-arginine), it plays fundamental roles in energy production, the clearance of “fatigue factors” from the blood during training (e.g. ammonia, phosphorous) and regulating acid-base balance to enhance performance.,3 It also supports immune function4 reduces exercise-induced inflammation,1,5 and maintains intestinal health in athletes.5

Although more research is required, glutamine appears to be a useful addition to the training protocol of athletes, not just in the recovery stages but also when taken prior to training. Glutamine is readily available in many plant and animal foods, such as raw spinach and cabbage; beef, chicken, pork and fish. As an athlete, however, you may require additional glutamine in a supplement form to aid in muscle recovery from extreme exercise.


There are many complications that can stem from a magnesium deficiency, and they are not limited to compromised performance and recovery. Due to the role magnesium plays in regulating excitability of nerves and relaxation of muscle cells, one of the first signs of a deficiency may be muscular cramps and/or spasms. This can occur in both smooth muscle (e.g. contributing to headaches) and in skeletal muscle (contributing to leg cramps). Magnesium is also involved in normal contractility of the heart muscle, and assists in the maintenance of healthy blood pressure.

Magnesium also acts as an antioxidant and plays a role in metabolism, meaning the higher energy needs and greater oxidation that occurs in athletes will see increased utilisation of this mineral compared to sedentary individuals. This places athletes at a heightened risk of magnesium deficiency. Like other electrolytes (e.g. sodium), magnesium is lost through sweat and also through the urine. To replace this higher demand for magnesium, an intake of magnesium-rich foods is recommended, such as raw nuts and seeds, unprocessed whole grains (e.g. brown rice), quinoa, spinach, legumes and bananas. A dietary magnesium supplement can also be useful in achieving rapid magnesium resuscitation to minimise any present symptoms of deficiency, and potentially enhance performance and recovery.


It takes guts to race and train through intense heat – healthy guts, to be exact. Firstly, it’s important to understand that when the body experiences high temperatures, like those associated with intense training, hot ambient temperatures and humidity, this contributes to the release of inflammatory chemicals. This process causes damage to the tightly packed cells of the intestinal tract. A consequence is local inflammation that may (in the short term) go unnoticed in some athletes. There are, however, a number of individuals who may experience this as an upset gut (e.g. intestinal cramps and/or nausea) and diarrhoea.

The good news is that emerging research has established that beneficial microbes, known as probiotics, have the ability to protect the intestinal lining from this heat-induced damage, restoring integrity to the gastrointestinal tract (GIT) and calming the detrimental inflammatory processes. Trials have also shown probiotic ingestion to improve performance in the heat.6Natural sources of probiotics include yoghurt, kefir and miso soup, however if these are not your preferred food choices, a probiotic supplement is a safe, convenient and effective alternative.

Speak to your healthcare practitioner for more information about choosing the right supplements for you. When taking supplements, make sure to always read the label and use only as directed. If symptoms persist, see your healthcare practitioner.


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