Sports nutrition in practice: what are the scientific insights?

Summary of satellite symposium on sports nutrition at EFAD Conference

Nutrition and sports performance: what are the latest scientific insights and nutrition strategies which can make a difference to dietetic practice? On 29 and 30 September 2017 the annual conference of the European Federation of the Association of Dietitians took place in Rotterdam (The Netherlands). During the EFAD sports nutrition satellite symposium professor Emma Stevenson and professor Luc van Loon gave an overview of scientifically proven nutrition strategies for optimal performance and recovery.

Sports nutrition in practice: what are the scientific insights? 3On 29 and 30 September 2017 the annual EFAD Conference took place in Rotterdam (The Netherlands). With more than 400 dietitians from across Europe it was the perfect occasion to network, learn and discuss various nutrition topics, ranging from nutrition economics, social media, microbiotics, elderly nutrition to sports nutrition.

The FrieslandCampina Institute attended the EFAD conference and supported the satellite symposium on sports nutrition. Professor Emma Stevenson (Newcastle University) and Luc van Loon (Maastricht University) are both experts in the field of sports nutrition and presented convincing evidence that a well-balance diet, adapted to the specific individual athletes needs and exercise level can improve performance. However, as mentioned by van Loon, an optimal diet does not guarantee a winning performance, but without proper nutrition optimal performance will not be achieved! There is a place for supplements, but a food first food approach is preferred. (Sports)dietitians and nutritionists can encourage athletes to incorporate good nutrition practices into their training plans. For an optimal nutrition strategy type, frequency, duration and intensity of the exercise need to be taken into account and dietary advice individualised to the athlete’s personal requirements.

Fuelling performance

During metabolism of carbohydrates in the muscle cells more energy is released per time unit than from metabolism of fats. Carbohydrates are referred to as a ‘fast’ fuel and fats a ‘slow’ fuel. During low intensity exercise, energy is supplied by both carbohydrates and fats, whereas during more intense exercise a higher proportion of energy is supplied by carbohydrates. Only 3% of the body’s energy is stored as a carbohydrate. The body stores of carbohydrate could be a limiting factor for performance. Optimizing glycogen stores before exercise is therefore necessary for exercise lasting longer than 1 hour. Increasing carbohydrate intake towards 75% of the total energy intake (en%) is recommended. Carbohydrate intake during exercise can help spare muscle glycogen and allow exercise to continue for a longer time and/or at a higher intensity. The necessary amount of carbohydrate depends on duration of the exercise, intensity and the climate. A recent report of The American College of Sports Nutrition includes all the current recommendations on the optimal intake of carbohydrate.

Recovery

Generally, post-exercise nutrition includes fluid replenishment, carbohydrates to restore muscle glycogen and protein to support muscle protein synthesis. Professor Stevenson and van Loon gave an overview of post-exercise nutrition strategies for endurance and resistance exercise.

Endurance exercise

The consumption of carbohydrates to restore muscle glycogen and the intake of fluid for rehydration are important nutrition strategies for endurance athletes to optimize recovery and subsequent performance. An athletes’ carbohydrate requirements range between 3-12 gram per kilogram body weight per day. When recovery time is less than 8 hours – for example in tournaments – it is recommended to consume a snack or meal high in carbohydrates (~ 1 g carbohydrate/kg body weight) within 30 minutes after exercise. Next to the fluid and carbohydrate needs the athlete should consume 10-20 grams protein within 2 hours after exercise to enhance muscle protein synthesis.

Resistance exercise

Both protein intake and exercise stimulate muscle protein synthesis. The intake of 20 grams protein within 2 hours after exercise is therefore the most important nutrition goal in resistance athletes. The amino acid leucine is the key metabolic regulator of muscle protein synthesis. Stevenson emphasized that ‘fast proteins’ like whey and soy give a transient rise in amino acids, whereas ‘slow proteins’ like casein give a longer lasting rise in amino acid (see also Burke et al., 2012). Different protein sources will have different effects on recovery. To promote an anabolic environment including a combination of fast and slow proteins such as whey and casein in the diet is recommended.

Nutrition strategies for exercise-induced muscle damage

Exercise-induced muscle damage (EIMD) can occur when the athlete performed unaccustomed and very hard exercise. Delayed onset of muscle soreness (DOMS), lower performance and an increase in intramuscular enzymes are indications of EIMD. Stevenson presented nutrition strategies for EIMD recovery including the consumption of milk(products) and phytonutrient rich foods like beet juice, blueberries and cherry juice. Research (Cockburn et al., 2008 and Cockburn et al., 2012) shows that the consumption of 500 ml milk benefits muscle force production after exercise. This effect maintains for 48 hours after consumption.

Beverage Hydration Index

Fluid intake after exercise is needed to replenish the fluid lost during exercise. The Beverage Hydration Index (Maughan et al., 2016) provides an overview of the hydration capacities of beverages such as water, coke, sports drink, juice, and milk. This research indicates that the consumption of (skimmed) milk after exercise supports restoration of fluid balance in the body.

Sports nutrition in practice: what are the scientific insights?

Role of Vitamin D

Stevenson also mentioned the importance of monitoring vitamin D status as studies have reported low circulating 25-hydroxyvitamin D (25-OHD) levels in athletes especially over the winter months (Close et al., 2012). Evidence suggests a link between adequate vitamin D status, immune health, skeletal muscle regeneration and athletic performance (Owens et al., 2015).

Role of the professional

Given these insights on sports nutrition and the need for a tailored nutrition strategy to the individual athlete, the role of (sports)dietitians and/or nutritionists is important. These professionals are key figures in optimizing the performance of an athlete through nutrition!