Nutrition-Related Considerations in Soccer: A Review

FUELING THE SOCCER PLAYER

Depending on the match fixture, proper fueling can be a challenge due to the number of matches, travel time, and limited recovery time. Macronutrients will provide the mainstay of fuel for a player, specifically carbohydrates and fats. Carbohydrates are the preferred source of fuel for the majority of the calories consumed. Using body weight (kg) is a more current and accurate method of recommending the amount of each macronutrient an individual player should eat as compared to using a percentage of total daily calories.

• Carbohydrates: 5–10 g/kg/day
• Protein: 1.2–2.0 g/kg/day
• Fat: 0.8–1.5 g/kg/day

CARBOHYDRATE AND SOCCER PERFORMANCE

Carbohydrates are a limited supply of fuel compared with fat stores. They are an important fuel source for soccer players, as muscle glycogen is vital to performance during high intense training and match play (Table 1). Yet current research shows that a high carbohydrate intake is not required to be followed every day due to varied energy demands.⁹ This newer strategy is referred to as “training low,” allowing the athlete to train at a low-moderate intensity in a low glycogen state. The glycogen status of the muscle can alter the training adaptations through cellular changes in the mitochondria. Therefore, carbohydrate needs should reflect the work required or demand for optimal performance. However, on high-training load days or 24 hours pre-match, carbohydrate intake should be increased to maximize muscle glycogen stores. Soccer players need to consume up to 8-10 g/kg body weight during the 24 hours before a match.¹⁰ On low or rest days, carbohydrate intake should be reduced to reflect the decreased training load. For example, recent research has demonstrated potential training adaptations when muscle glycogen stores are not consistently high¹¹ or intentionally kept low depending on the training load. Adjusting carbohydrate intake to the physical demands of an athlete is a strategy called nutrition periodization.

However, if glycogen stores are not well supplied before a match >90 minutes, then the muscles and the brain will become fatigued and lead to poor performance. Glycogen depletion contributes to fatigue toward the end of a match.¹⁰ In the early 1970s, Saltin and colleagues¹² showed that players with high muscle glycogen stores (~400 mmol/kg dry wt) achieve higher movement intensities and cover more total distance than those players who start the match with low glycogen stores (~200 mmol/kg dry wt). Another study examined pre-match diets of male soccer players (65% vs 30% daily carbohydrate intake) to determine the effect on performance outcomes and glycogen concentrations. Results showed high-muscle glycogen concentrations in the 65% carbohydrate diet and a significantly higher amount of intense exercise bouts. More acutely, studies have shown a meal containing 200 to 300 grams of carbohydrates 2 to 4 hours before exercise prolongs endurance.^13-15 Ideally, consuming fast-digesting carbohydrate sources during or at half time will help maintain blood glucose concentrations and spare muscle glycogen reserves. The majority of literature shows a 6% to 8% solution of combined fast-digesting carbohydrates (ie, glucose, fructose, sucrose, or maltodextrin) at a rate of 30 to 60 g/h enhances at least 1 aspect of performance in soccer.^16-18 These performance benefits include increased running time, improved time to fatigue, and enhanced technical skills. Regarding recovery, soccer players should begin consuming carbohydrate-rich foods and beverages immediately after exhaustive training or a match to optimize glycogen reloading. Ingesting post-exercise carbohydrates stimulates muscle and liver glycogen synthesis up to tenfold compared with post-intake of no carbohydrates.¹⁹ This recovery period becomes vital when there are <8 hours between training sessions or another match, such as in youth tournaments. The form of carbohydrate, solid or liquid, can be based on preference and tolerance, as long as the source provides a large glycemic and insulin response.

An easy way to adjust daily carbohydrate intake is to schedule carbohydrate-rich foods at meals or snacks around important training sessions or before/during/after on match day. Anderson and colleagues¹⁰ looked at training loads for 1, 2, and 3 matches per week, recommending high carbohydrate intake match day minus 1, on match day, and match day plus 1 for 1 and 2 matches per week and lower carbohydrate intake on the other days. During a 3-match week, lowering carbohydrates any day of that week is not recommended. More research is needed to determine the best strategy for performance regarding carbohydrate periodization in soccer.

PROTEIN AND SOCCER PERFORMANCE

Protein is important to soccer players for muscle tissue repair, strength, bone health, and the immune system (Table 2). The American College of Sports Medicine, the Academy of Nutrition and Dietetics, and the Dietitians of Canada recommend 1.2 to 2.0 g/kg/day.²⁰ Most soccer players meet the daily protein requirements; however, the key to optimizing the total daily amount is focusing on the source/amino acid profile, timing, and amount per feeding. Consuming divided doses of protein (20 g to 40 g) every 3 to 4 hours gives the body a continuous flow of amino acids to support muscle synthesis and recovery. In terms of body size, the recommendation is 0.25 to 0.4 g/kg every 3 to 4 hours, which includes pre-training/match and post-training/match. Protein/amino acids consumed around strength training and high-intensity sessions can promote muscle adaptations, minimize tissue breakdown, and speed recovery. Soccer matches lead to significant muscle damage²¹ especially at 2 sessions/day or multiple matches in a week. Protein is not a priority during training or matches, as its role is not to provide energy, and the primary goal during soccer activities is energy production. Research supports an intake of 30 to 40 g of casein, which is a slow digesting protein, at night before bed when a strength-training session has been performed that day.^22,23

Continue to: FAT AND SOCCER PERFORMANCE