South African Journal of Clinical Nutrition – A review of current research performed by Sunita Potgeiter illustrates that the International Society for Sport Nutrition (ISSN), American College of Sports Medicine (ACSM), and the International Olympic Committee (IOC) have redefined carbohydrate, fat, protein, and calorie guidelines for athletes who train and compete at moderate to high volume intensity levels.
This article’s purpose is to provide non professional and professional athletes with information to individualize their dietary intake to maintain optimal performance in training and competition settings. Energy, carbohydrate, fat, and protein guidelines were set for all ranges of activity: normal every day active individuals (30-40 min/day; 3 times/week), the moderate intense athlete (2-3 hrs/day; 5-6 times/week), and the high volume intense athlete (1-2 sessions of 3-6 hrs/day; 5-6 times/week). Proper nutrition in all areas is necessary to increase muscle mass, prevent injury and illness, avoid overtraining syndrome, and increase ultimate performance. The IOC, ACSM, and ISSN agree that additional supplements are not necessary as long as dietary needs are met through available food sources.
The ISSN found that calorie (kcals) requirements are more than doubled for athletes compared to regular active individuals (25-35 kcals/kg). Athletes who train at a moderate to high volume intensity should consume 50-80 kcals/kg of body weight (BW) equaling approximately 2,500-8,000 kcals/day. Adequate energy needs are vital to maintain skeletal, reproductive, and immune functions in the body. A well balanced diet that focuses on 4-6 meals scheduled at specific hours in the day is imperative to make sure the muscles are receiving energy when it is most needed. Waiting until you are hungry can decrease the amount of energy available and physical performance.
Blood glucose is the body’s primary source for muscle contraction and timing of carb intake for pre-exercise, duration, and post exercise should be done to enhance performance, recovery, and glycogen storage. Carb loading (8-12 g/kg BW for 36-48hrs prior to event) is a practice that maximizes glycogen use in activities that last longer than 90 minutes and is recommended by the IOC and ISSN. To avoid hypoglycemia, heavy legs, or “hitting a wall” during exercise and limit breakdown of liver glycogen, the IOC, ACSM, and ISSN agree that 30-60g/hour of carb be consumed via sports drink, snack, gel, etc. Post exercise is just as important to aid recovery and should be aimed at 1.5 g/kg BW within 30 min and repeated every 2 hours within a 24 hr period. The type of carb used is controversial, but all agencies seem to agree that majority of it should be glucose derived sources. Too much fructose can cause gastrointestinal complications and is contraindicated.
Protein intake is important to maintain muscle mass and daily requirements range between 1.2-2.0 g/kg stemming from sources of milk (whey & casein), eggs, and high biological value meat products (beef, chicken, etc.). Any level higher than this has shown to be detrimental by increasing amino acid and protein breakdown. Surprisingly, the 3 agencies differ on their recommendations regarding protein intake pre- and during exercise. The ACSM and ISSN recommend that a small portion (0.2 g/kg) of protein pre-exercise can help with muscle maintenance but the IOC refutes the statement and notes that duplicative studies have shown inconclusive. More research regarding protein prior to and during exercise is needed. All agencies agree that protein should be focused post-exercise (20g within 30 min) and flavored, low fat milk or meal replacements are the best sources. The IOC suggests that these sources increase energy intake helping the body store glycogen and recover muscles quicker.
According to the IOC, ACSM, and ISSN, fat intake for athletes should be similar for sedentary adults. Fat intake less than 20% are inefficient to maintain energy balance and to process essential fatty acids and fat soluble vitamins. Fat intakes >30% can be disruptive to training and competitive races by causing gastrointestinal distress.
Fluid and electrolyte balance should be carefully maintained to avoid excessive weight loss (>2%) during activity and provide adequate hydration to athletes. Salty snacks and sports drinks are suggested by the IOC, ACSM, and ISSN to consumed prior to and during exercise. The agencies also agree that regular meals and beverages post exercise are sufficient for rehydration. Nutrition supplements and vitamin & mineral status are not as critical in obtaining optimal athletic performance but can affect performance if deficiencies and toxicities occur. The IOC suggests that individuals be aware if they are at risk of any deficiencies and to work with a nutritional professional resolve any that might occur.