It’s not just technology on the pitch that’s helping athletes change their game. After a fantastic couple of years for sport in Britain, we’ve heard a lot about the nutritional requirements of high performance athletes. From Michael Phelps\' 10,000 calories a day diet to criticisms that Chris Froome might not have been eating enough in the year preceding his Tour de France victory. But what effect does what we eat have on our physical performance? Could changing our diet really make us run faster or jump higher? Kate Lamble spoke to Dr. Phil Watson from the University of Loughborough. Kate - So Phil, what do athletes need to watch in their diet? Phil W. - It’s a difficult question to answer because athletes are so diverse. The nutritional requirements of a 50 kilo gymnast for instance would be considerably different to the nutritional requirements of a 100 kilo heavyweight rower or Mo Farah running the 10,000 meters. So, there\'s certainly no one-size fits all. There\'s certainly evidence that high level athlete’s performance will be impacted by what they eat. But you\'re not going to make a mediocre athlete an Olympic champion by eating correctly, but certainly, you could lose that Olympic gold medal by eating poorly. Kate - Is there anything in particular that will help most athletes perform on the day? What should you be eating just before your race? Phil W. - Well, researchers over the past 100 years has supported the idea that carbohydrate is important to performance certainly in a more prolonged event. So, something like the Tour de France or a marathon or the 10,000 meters that I mentioned previously. Carbohydrate, we obtain that from a variety of foods, things like pasta or rice, potato and sugary type foods. Carbohydrate is important because it’s the primary fuel for exercise. So certainly, the evidence suggests that carbohydrate is important. The other dietary component that’s kind of persisted over the years obviously, dietry fads come and go, and you see these fad diets, but the other staple of sports nutrition is fluid. We lose fluid as we exercise particularly when we exercise in the heat. We sweat, we perspire, we lose fluid from our body and it’s important that we replace that. Kate - As well as a dietary plan, professional athletes also often take supplements. Why do they do that? Phil W. - Well, there\'s a number of reasons for that. The most apparent reason is to improve their performance. There\'s a little bit of evidence that some supplements do that. A substance called creatine for instance has consistently shown to improve strength and power in those sorts of athletes. Caffeine is another supplement that has consistently been shown to improve performance. There are a few ‘new kids on the block’ substances like beta alanine, beetroot juice which there\'s a bit of growing evidence now to support their use. Kate - Talking about beetroot juice, one of our team members is a very keen rower and she’s been bringing in these beetroot juice supplement drinks that they’ve been giving out. Why particularly do we think that that might be helpful to athletes? Phil W. - Beetroot is rich in dietary nitrate. Nitric oxide is very important for the body for a number of reasons. It regulates blood flow and it’s important in muscle metabolism as well. Research over the past 4 or 5 years coming out of the University of Exeter has really shown that by ingesting beetroot in these beetroot juice shots that have become popular, you increase dietary nitrites which is a product used to generate nitric oxide within the body and it does certainly seem to improve performance. Kate - Some of these supplements you mentioned earlier as well like caffeine are obviously also drugs. Where is the difference between the supplements that we take to help our performance and the supplements which we now consider in certain sports to be prohibited aids that go beyond what we normally eat? Phil W. - There is actually a very fine line. Caffeine for instance was on the World Anti-doping Agency prohibited list up until 2004 and you were allowed a certain urinary level of caffeine. Above that, you would be banned for using too much. My PhD supervisor, Professor Ron Maughan used the adage that, if it works, it’s probably banned and obviously, there are some exceptions. So, caffeine and creatine are two that have hung around and have persisted in terms of nutrition. Kate - We hear a lot about athletes who were banned for doing illegal substances or substances that are prohibited in their sport and some of them say, “I didn’t know it was in the supplement that I was taking. I didn’t know it was within my diet.” Why is that the case? Why are they so confused about what they\'re consuming? Phil W. - It’s an interesting one. So, the World Anti-doping Agency rules are very explicit and strict liability applies. So, if you test positive, you can\'t point a finger and say I don’t know. That doesn’t stand up in court. But there has been a number of cases over the last I\'d say, 10 to 15 years of athletes testing positive and going through that exact same scenario. They say, “I didn’t take anything. I\'m innocent.” And then a study conducted in Germany a few years ago now, almost 10 years ago analysed dietary supplements brought from all over the world and found that some of those supplements were actually contaminated with steroid prohormones – precursors of anabolic steroids. And these substances weren’t included on the label. So, the authors of that particular study concluded that there\'s cross contamination occurring and this contamination could lead to positive doping tests in athletes. Certainly, some of our research has demonstrated that very trace amounts of these pro-hormones substances added to a dietary supplement can cause an athlete to test positive. So perhaps there is some link there. Kate - When you talk about precursors to steroids, is that something that is actually a steroid or is that something that later gets turned into it somehow? Phil W. - Yeah, it’s a substance that later gets metabolised into a steroid. So, some of the substances are made available as dietary supplements, particularly to the body building industry, to the guys who are trying to get massive and look good on the beach. There\'s actually very little evidence that they do enhance muscle growth, but the body builders like the idea that, “I\'m going to take a steroid precursor and that will make me grow muscle faster.” So, these supplements are on the market and yeah, there\'s some evidence that the company that are making these types of supplements, there\'s some degree of cross contamination occurring and that’s probably what\'s led to some of these positive doping cases. Kate - By this point, sports nutrition has become a very exact science and we all hear about how a sports nutritionist is embedded into almost every professional sports team. Where can we go next? What\'s the next stage in us, helping develop nutrition that can help our athletes? Phil W. - I don’t know if sports nutrition and sport science has been slightly slow to adopt other areas of science, but in the last 10 years, molecular biology has become a big explosion area within exercise, physiology and sports nutrition. So, we’re really starting to understand some of the molecular processes going on within the muscle. The signalling that tells the muscle to grow in a certain way and that’s being used by sports nutritionists now to look at the interaction between diet and training to try and maximise the training games from the given bout of training. So, something that has become popular in the last couple of years and some of your listeners may have heard of it is the idea of train low, compete high and that means you train with low carbohydrate availability and then you compete with high carbohydrate availability. That seems to be beneficial because training with low carbohydrate stimulates a greater adaptive process. So, your body is under more stress during the training session. Your body responds to that stress and you seem to get greater training gains. Now, you can\'t undertake all your training sessions in this low carbohydrate situation because eventually, you\'ll breakdown and it’s difficult to maintain the intensity. So they\'ll perhaps do two sessions in one day, one session with high carbohydrate availability which allows them to really push hard and then one session with low carbohydrate availability which puts this additional stress in the body and seems to enhance the adaptive process to trainings. Source: Dr Phil Watson, University of Loughborough