The role of nutrition in the maintenance of good health and prevention of disease is well-established. Yet for the competitive or recreational athlete, proper nutrition is more than daily sustenance; it is the cornerstone of athletic performance. However, finding credible, evidence-based recommendations in the era of information overload can be tedious. The following is a breakdown of the Position Statement from the Academy of Nutrition and Dietetics (AND), Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM) on nutrition and athletic performance (1).
Energy and Macronutrient Needs
Although “macros” are a trending buzzword in various nutrition circles, the importance of calories or energy intake far outweighs that of macronutrient ratios. As an athlete, energy intake needs to match energy expenditure, which includes basal metabolic rate, the thermic effect of food, and the thermic effect of activity (planned activity, spontaneous activity, and activity associated with daily living). Energy intake below requirements can negatively impact several body systems and interfere with athletic performance by increasing the risk of injury or mood changes, as well as decreasing training response or muscle mass. Determining your energy needs as an athlete can be simple or complex. If weight is stable and training/competition goals are being met, energy balance is likely being achieved. Sophisticated equipment, like DEXA scans and bod pods, along with simple tools like skin calipers, can also be used to predict calorie needs. If these tools are unavailable, estimates of energy requirements can be approximated with various formulas. In your Cronometer account, the best way to determine your energy needs is to accurately track both structured and unstructured physical activity under the log exercise function, while monitoring weight and athletic performance.
Carbohydrates are an important source of fuel for athletes as they support essential functions of the brain and central nervous system and provide a readily available source of energy for active muscles as glucose. Unused Carbohydrate are stored in the muscles and liver in limited amounts as glycogen. While the exact amount of glycogen that can be stored in the body depends on an athlete’s diet and training, approximately 75-100 g and 300-600 g of glycogen can be stored in the liver and muscles respectively (2). An athlete will typically use up glycogen stores in 60-90 minutes, after which, carbohydrates need to be consumed in order to keep performing at the same intensity (2).
Recently, there has been increased interest in training in a fasted-state or ketosis to enhance the effects of training. However, according to the ACSM/AND/DC position statement, there is not enough evidence to support keto diets/carbohydrate-restriction on performance outcomes in athletes (1, 3). A detailed guideline on the recommended intake of carbohydrates for athletes training at different intensities may be found at the end of this post.
It is generally accepted that protein needs of athletes are far greater than recommendations set for the general, sedentary population. Total daily protein needs for athletes range from 1.2 to 2.0 g per kg per day, depending on the type of training (i.e. new or higher intensity requires more protein) and the conditioning of the athlete (well-trained athletes have lower protein needs).
When it comes to protein, it’s important to consider both timing and quality. Resistance training increases the synthesis of new muscle tissue for up to 24 hours following a single workout. As such, athletes are advised to include 20-30 grams of protein (containing ~10 g essential amino acids) in the immediate recovery period (0-2 hours) and every 3-5 hours after this point.
Protein sources can be either plant or animal-based, as essential amino acids can be easily obtained in both dietary patterns.
Recommendations for fat are not different for athletes compared to the rest of the population (i.e. a minimum of 20% of calories from fat; less than 10% of energy from saturated fat; include a sources of essential fatty acids). As mentioned, high-fat/low-carb diets do not appear to be superior to diets supplying adequate carbohydrates since they reduce the body’s ability to use carbohydrates effectively, leading to compromised exercise performance (1).
Athletes are not at a greater risk of nutrient deficiencies compared to the rest of the population, provided they are consuming a balanced, nutrition-rich diet. That said, nutrients such as iron, vitamin D, calcium, and antioxidants may be compromised with poorly-planned/restricted diets or at times of intense training. Meeting the RDA (or recommended intake) for these nutrients in your Cronometer diary is essential.
The maintenance of proper hydration is important for athletic performance and safety; losing 2% in hot weather (3-5% in cool weather) can result in decreased cognitive functioning, compromised athletic performance, and puts the athlete at increased medical risk. Proper hydration is necessary before, during, and after training/competition:
Fueling for Sport
In addition to proper hydration, what an athlete eats before, during, and after training/competition can influence athletic ability, risk of injury, overall nutrition, and general well-being. What is eaten before an event should be individually tailored to ensure gastrointestinal comfort and enjoyment. In general, carbohydrates and fluid are the most important considerations leading up to an event, while Intake of fibre, fat, and protein should decrease as an event approaches to prevent gastrointestinal distress.
During an event, carbohydrates and fluids continue to be the most important consideration, as they provide a readily accessible source of fuel for working muscles. Consuming protein along with carbohydrates during resistance training may be beneficial to muscle growth, but additional studies are needed before a recommendation can be put forth on the use of protein during an event.
Following activity, it’s important to consume adequate carbohydrates, protein, and fluid to replenish deleted glycogen stores, stimulate muscle protein synthesis, and maintain hydration status. Provided there is enough recovery time (i.e. > 8 hours) between events, athletes can be less specific about the types of foods that are chosen for recovery (although high quality protein sources are recommended in the first 0-2 hours post-activity).
What about supplements?
Erogenic aids, or supplements believed to enhance athletic performance, are very popular in sports and athletics. While a discussion of all the erogenic aids, and the evidence for or against them, requires a seperate post, there are a few, such as creatine, caffeine, sodium bicarbonate, beta alanine, and nitrate that may benefit to athletic performance (although negative side effects may mitigate the effectiveness of these supplements). To view available evidence on various erogenic aids used in sports, head to examine.com.
Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016 Mar;116(3):501-528. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26920240