Cycist refuellingThe last few years have seen a big increase in the amount information available on the use of nutrition to support endurance sports performance, with easily accessible sources including blogs, podcasts and online forums as well as books and research papers. Social media like Twitter and Facebook is a great way of finding out what’s new and hearing a range of opinions on the subject. But it also creates confusion: there’s a lot of conflicting information out there. Research studies can produce very different results, depending on the type of people studied and methods used, which doesn’t help, and there’s also plenty of advice out there based on people’s personal experiences or as part of the marketing plan for a particular sports nutrition product or supplement. This doesn’t make the information wrong, but it isn’t necessarily robust and can be confusing.

One of the best sources of information on the use of nutrition to support sporting performance are the Position Stands published periodically by well-respected organisations such as the American College of Sports Medicine (ACSM), the International Olympic Committee (IOC) and the International Society of Sports Nutrition (ISSN). These are put together by a range of experts in the field after reviewing the research evidence that has been accumulated over the past few years and selecting the most reliable to produce a summary of recommendations. A new Position Stand entitled “Nutrition and Athletic Performance” 1 was published in March 2016 concurrently in three journals by experts from the ACSM, the Academy of Nutrition & Dietetics (AND) and Dieticians of Canada (DC). This gives a very good summary of the latest evidence based nutrition practices recommended for optimal sports performance. It contains much information that is relevant for the endurance athlete, which I summarise in this blog post.

Sharing these guidelines does not mean that they are necessarily right for all endurance athletes. Everyone is different and some will respond better or worse to particular products or types of food for fuelling and recovery than others. So it is important to experiment to find what works for you, and a good way of doing this can be to work with a sports nutritionist. But, being based on high quality research, these guidelines make a great place to start, to see if you are missing anything shown to work effectively and to help stop you wasting money or time on nutrition products or dietary approaches which are unproven to help performance. Research is also ongoing and it could be that when the Position Stand is updated in a few years’ time, there could be some different conclusions. But this is what we have for now in terms of best practice recommendations.

Here are the main points from the Position Stand that you may find useful as an endurance athlete. I’ve also included links to blog posts that I’ve previously written which explore some of these topics in more details. If you want to read the Position Stand itself, it’s freely available, here.

  1. Nutrition Periodisation: your energy intake from food should vary according to the demands of your training sessions on a day by day and week by week basis. Base your meal planning on the changing volume and intensity of your training cycles. See my blog post on nutrition periodisation here.
  1. Energy availability: sufficient calories are required to support both performance and health. Being in a regular state of low energy availability through under-eating may have consequences both directly on your ability to train and compete and indirectly on musculoskeletal function, immune function, hormone balance, gastrointestinal health, cardiovascular function and metabolism, which may compromise your performance over time.
  1. Body composition: a low body mass and/or body fat level may benefit distance cyclists and runners, although this should not be achieved at the cost of continual low energy availability. Instead, periodize your weight and body composition in line with your training cycle, accepting fluctuations throughout the year. Avoid both excessive weight gain in the off season and the use of rapid weight loss strategies in the competition season, which may be dangerous for your health or trigger disordered eating patterns. The best time to lose weight or body fat is in the base training period, using a slight (250-500 kcal) daily energy deficit to achieve gradual weight loss and increasing the amount of protein in your diet (to c 2-2.5g/kg of body weight), which helps you feel full and maintain lean body mass. Carbohydrate and fat intake should be reduced to enable the required calorie deficit.
  1. Use of carbohydrate in training: there is evidence to suggest that deliberately training with low glycogen stores for specific, low to moderate intensity sessions enhances the adaptation of the muscle to training by altering signalling and upregulating the metabolic response to exercise. Strategies include occasional fasted training, not replenishing carbohydrate stores after the first of two training sessions of the day and training for at least 90 minutes before taking on any carbs. However, it is also important to undertake high intensity training sessions with high carbohydrate stores and to check gastrointestinal tolerance in sessions prior to races. Between 30-60g per hour from sports drinks, gels, bars or foods high in carbohydrate is the recommendation for sessions lasting between 1 and 2.5 hours, with up to 90g per hour for longer sessions (although this is very individual). See my blog post on low glycogen training here.
  1. Daily dietary intake:
    1. Carbohydrate: 5-7g/kg on moderate intensity or c 1 hour training days, 6-10g/kg on high intensity or c 1-3 hour training days. The latter should incorporate carbohydrate consumed during training.
    2. Protein:2-2.0g/kg, with a greater amount on days with more intense or strength/power specific training sessions to optimise muscle adaption to training. Protein intake should be spread regularly across the day in 15-25g amounts, including within 2 hours of completing each training session. Dairy protein seems superior to other sources of protein, largely due to its leucine content, an amino acid required for muscle protein synthesis.
    3. Fat: 20-35% of total calorie intake, with no more than 10% from saturated fats. Less than 20% is likely to result in inadequate intake of the essential fatty acids such as omega 3 and the fat soluble vitamins A,D,E &K. Research currently shows that while enhanced fat oxidation as a result of a high fat diet (c 65-80% of calorie intake) may match the exercise capacity/performance achieved by high carbohydrate availability at moderate intensities, performance at high intensities is impaired on a high fat diet as a result of the down regulation of carbohydrate metabolism, even when glycogen is available. More research is required in this area.
  1. Vitamins and Minerals: the intake of vitamin and mineral supplements does not improve performance unless reversing a pre-existing deficiency. The research supporting supplementation is often weak and its findings. Four micronutrients are commented on specifically.
    1. Iron: iron deficiency, with or without anaemia (low haemoglobin), can impair muscle function and limit exercise capacity. Vegetarian and female athletes are particularly at risk. Iron deficiency should be monitored by a doctor who is likely to prescribe iron supplements. These should not be self-prescribed. Athletes with low ferritin (iron stores) but normal haemoglobin should first improve their intake of iron rich food plus vitamin C. See my blog post on iron and the endurance athlete here.
    2. Vitamin D: research suggests a role for vitamin D in muscle function as well as bone health and immunity. Little vitamin D is consumed from the diet. Most is made by the action of sunlight on your skin. If you live in northern latitudes (above 35°) and/or train primarily indoors, you are at increased risk of vitamin D insufficiency(50-75 nmol/L) or deficiency (<50 nmol/L), particularly in the winter months. Supplementation may be warranted following a blood test for 25(OH)D levels. Other reasons for taking a vitamin D test include a history of stress fracture, bone or joint injury, muscle pain or suspected over-training. See more about vitamin D and endurance sport in my blog post here.
    3. Calcium: low calcium intake as a consequence of low energy availability, disordered eating or avoidance of dairy products increases risk of stress fractures and low bone mineral density. A calcium supplement may be warranted in these cases. See my blog post for more about calcium and the endurance athlete here.
    4. Anti-oxidants: there is little evidence that anti-oxidant supplementation (eg vitamins C & E) enhance athletic performance and some evidence that it may negatively influence training adaptations. The best strategy is to consume a diet rich in fruit and vegetables, which are rich in anti-oxidant nutrients such a vitamin C and polyphenols but to avoid supplementation with anti-oxidants. See my blog post for more on this topic.
  1. Hydration: fluid and electrolyte balance:
    1. Pre-exercise: Start exercising in a hydrated state by consuming 5-10ml/kg of bodyweight in the 2-4 hours prior to exercise. Urine should be pale yellow. Sodium in pre-exercise drinks and foods may help to retain fluid.
    2. Sweat rates during exercise vary between 0.3-2.4 L/hr. Differences depend on factors such as intensity, fitness and heat acclimatisation, but also on individual sweat rate. Routinely weight yourself before and after exercise, accounting for fluid consumed and urine lost, to estimate your sweat loss during exercise. A loss of 1kg bodyweight equates to 1L of sweat lost. Avoid over-drinking, which may lead to hyponatraemia (dilution of sodium in the blood), a potentially fatal condition.
    3. Sodium should be consumed where athletes have a high sweat loss (more than 1.2L/hr), are ‘salty’ sweaters or when exercise duration exceeds 2 hours. Athletes who sweat profusely and have a high concentration of sodium in their sweat may be at greater risk of muscle cramp.
    4. Post-exercise: consume 25-50% more fluid than that lost in sweat. Do not restrict salt in food as it helps to retain fluid. There is no need to restrict caffeine; this is no longer as regarded as a diuretic when habitually consumed in moderate amount (less than 180mg.)
  1. Race Day Nutrition:
    1. Before your race: adequate glycogen stores are required for optimal performance, both to delay muscular fatigue and to support the nervous system. Performance in events longer than 90 minutes may benefit from a carbohydrate-loading strategy undertaken in the 48 hours beforehand (10-12g of carbohydrate per kg of body weight per 24 hours). During the 1-4 hours prior to a race, consume 1-4g of carbohydrate per kg of bodyweight. Food choices should be high in carbohydrate and moderate in protein, while low in fat and fibre to reduce risk of gastrointestinal problems. Choose a pre-race meal strategy that suits your situation and based on your past experience.
    2. During your race:
      1. In races lasting less than 75 minutes, carbohydrate is not required to replenish glycogen stores but rinsing the mouth with a sports drink has been shown to enhance perception of wellbeing and reduce perception of fatigue through the impact on your brain and nervous system.
      2. In races lasting 1-2.5 hours, consume 30-60g per hour of carbohydrate through sports drinks or gels to replenish muscle glycogen. Practise in training to establish what fuelling and hydration strategies work best for you.
      3. In races lasting more than 2.5 hours, increase carbohydrate intake to up to 90g per hour. This may include solid foods, eg bars. Use products containing glucose/maltodextrin: fructose mixes to achieve faster carbohydrate absorption. Consider consuming small amounts 2–30g of protein or 10g of essential amino acids during ultra-endurance events (>6 hrs) to enhance recovery.

C. After your race: restore glycogen by consuming 1-1.2g of carbohydrate per kg of body weight in the first 4-6 hours after finishing. Consume around 50g of protein during the same period (in 15-25g servings) to provide the amino acids needed for muscle recovery. Rehydrate with 25-50% more fluid than that lost in sweat.

  1. Ergogenic Aids: manufacturing and marketing for sports supplements is currently unregulated, which may result in false advertising, unsubstantiated claims and the risk of contamination with banned or toxic substances. Relatively few supplements that claim ergogenic benefits (increased performance) are supported by robust evidence. The quality of research is often compromised by small sample sizes, use of untrained subjects, irrelevant performance tests or poor control of confounding variables. For endurance athletes, only caffeine (see my blog post on this here) and nitrate (as found in beetroot juice – see my blog post here) are considered to have a strong enough evidence base to be recommended as ergogenic aids, along with sports drinks, gels, bars, electrolyte supplements and protein powders. For those competing in events where there is an element of anaerobic work (ie sprinting), sodium bicarbonate, creatine and beta alanine are supplements which have been found to be beneficial. For more on which supplements are worth using, see the guide produced by the Australian Institute of Sport, which can be found here: http://www.ausport.gov.au/ais/nutrition/supplements/groupa

The end….I appreciate that this is a long blog post, but it does provide a summary of the current nutrition recommendations for endurance athletes in one place, based on good quality research. I hope you will find it useful as a framework to develop your personal nutritional strategy to support your endurance sports performance. Good luck!

Jo Scott-Dalgleish BSc (Hons) is a BANT Registered Nutritionist, writing and giving talks about nutrition for endurance sportBased in London, she also works as a Registered Nutritional Therapist, conducting onetoone consultations with triathletes, distance runners and cyclists to help them eat well, be healthy and perform better through the creation of an individual nutritional plan. To learn more about these consultations, please visit www.nutritionforendurancesports.co.uk

 

References

1 Position of the Academy of the Nutrition & Dietetics, Dieticians of Canada and the American College of Sports Medicine. Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise: March 2016, 48(3): 543-568 http://www.ncbi.nlm.nih.gov/pubmed/26891166