A sound nutritional strategy is a critical component of any athletes training program. Unfortunately, this is one aspect of a player’s game that is often overlooked. Over the years, research has examined the diets of both youth and professional male players (Click here for a recent SSO article). However, very few studies have focused on female athletes. Female players have unique influences on nutritional choices compared males. Increased risk of iron depletion, a need for calcium and vitamin D to support bone heath as well as social pressures to maintain a low body weight can all affect diet their choices. A recent study published in the International Journal of Sports Nutrition and Exercise Metabolism found that similar to their male counterparts, female diets are lacking in key components that could affect both health and performance on the field.
The study was conducted by researchers at the University of Victoria in British Columbia, Canada. It focused on junior female players who play at the highest regional competitive level in Canada. The ages of the players ranged from 14 to 17 years and they trained an average of 12 hours per week.
The investigators asked the players to record their food choices during four different days – two training days, one competition day and one rest day. All players and their parents attended a seminar to insure that they understood how to accurately record the types of foods eaten and the serving sizes. The diets were analyzed by the researchers to determine total calories eaten as well as the amounts of vitamins and minerals. The researchers also estimated the players’ energy expenditure on those same days.
The results are quite interesting. The average amount of foods and beverages consumed (total energy intake) amounted to slightly more than 2,000 calories per day. This was less that the estimated amount of energy expended, 2,546 calories per day. Thus, these players are not consuming enough calories to match the demands of training and other daily activities. They are left with a caloric deficit of more than 500 calories per day. It is important to point out that the players in the study are not considered over weight or overly lean. Thus, the caloric deficit recorded during the study period is probably being gained on other days so that weight is maintained. However, over the long-term, a daily reduction in energy intake (especially in lean players) can add up and eventually affect performance.
More than 50% of the players consumed fewer carbohydrates than recommended for female athletes. Fiber intake was very low with only one-quarter of those studied eating the recommended amounts. Fortunately, fat and protein intakes were within the normal range, with only a few players eating too few proteins or too many fats. Thus, the caloric deficit mentioned above probably results from inadequate carbohydrate intake.
As for vitamins and minerals, not a single player consumed the recommended amounts of vitamins D and E. Folate and calcium intake was also remarkably low with only one-third taking in the recommended amounts. Several players’ diets were also lacking in zinc, magnesium and vitamin A. On the other hand, a large number exceeded the recommended amounts of the B vitamins, iron and copper.
The authors of the study conclude that the female players’ diets are lacking in key components needed to fuel performance as well as support proper growth and development. As for performance, the total calories consumed do not match the energy expended. Also, the low amount of carbohydrates eaten may leave players with reduced muscle glycogen levels. Given that muscle glycogen depletion has a dramatic affect on performance, a diet lacking carbohydrates can hinder performance. This is especially true during the later stages of training or match play.
They also raise concern that the low intakes of vitamin D and calcium can impact bone growth. Both of these are essential for proper bone health. Low intakes of these components could lead to lower bone density and raise the risk of stress fractures. Vitamin E is a powerful antioxidant that is essential to preventing cellular damage aiding repair.
What can be done to correct the problems outlined in this study? The optimal strategy to counter these findings is to focus on a proper diet with adequate carbohydrates, vitamins and minerals. Lean meats, fresh fruits and vegetables as well as whole grain breads and pastas are the best approach. A daily multivitamin supplement can help insure that recommended amounts of vitamins and minerals are taken in. However, eating a proper diet can supply these key components.
The researchers also suggest that athletes should be taught the importance of a healthy diet, one that can meet the unique demands of soccer. Coaches often assume that players understand what types of foods to eat and when to eat them. However, that is often not the case (as suggested by this study). Because diet and performance are integrally linked, players should also closely monitor their daily nutritional habits. They can then compare the types of foods eaten with their performance on the pitch. By understanding how diet affects performance, players can begin to make both wise and healthy nutritional choices. Instilling habits that improve athletic performance will also set in place a health dietary routine that can last a lifetime.
Gibson JC, Stuart-Hill L, Martin S, Gaul C (2011) Nutritional status of junior elite Canadian female soccer athletes. International Journal of Sports Nutrition and Exercise Metabolism. 21: 507-514.