Pre- and Post-season Dietary Intake, Body Composition, and Performance Indices of NCAA Division I Female Soccer Players

Transcription

1 International Journal of Sport Nutrition and Exercise Metabolism, 2003, 13, Female Soccer Players / Human Kinetics Publishers, Inc. Pre- and Post-season Dietary Intake, Body Composition, and Performance Indices of NCAA Division I Female Soccer Players Mandy Clark, Debra B. Reed, Stephen F. Crouse, and Robert B. Armstrong Little published data describe the dietary and physiological profiles of intercollegiate female soccer players; therefore, the purpose of this investigation was to report baseline dietary data, anthropometrics, and performance indices of soccer women during rigorous pre-season training (2 sessions/day) and then during the post-competitive season. Members of a NCAA Division I women s soccer squad completed 3-day diet records, anthropometrics, and physical tests, including VO 2peak. Average body mass was 62 kg with 16% body fat, and no significant pre to post differences were observed. Total energy, carbohydrate (CHO), protein, and fat intakes were significantly greater during the pre-season. Pre-season energy intake met the DRI for females with an active lifestyle (37 kcal/kg). While CHO intake failed to meet minimum recommendations to promote glycogen repletion (7 10 g/kg), protein and fat intakes were above minimum recommendations. Pre- and post-season intakes of several micronutrients were marginal (<75% of the DRI) including vitamin E, folate, copper, and magnesium. VO 2peak significantly improved from pre- to post-season (42 and 50 ml/kg/min). In this study female soccer players appeared to meet caloric needs during periods of training but failed to meet minimum CHO and micronutrient recommendations. Foods higher in protein and fat displaced more CHOrich and nutrient-dense foods within athletes energy requirements and satiety limits. Key Words: dietary assessment, energy, carbohydrate, micronutrients, soccer The link between nutrition and athletic performance is well established in the scientific literature; therefore, optimal nutrition is widely accepted as a means to enhance physical activity, athletic performance, and recovery from exhaustive exercise (1). Athletes undergoing strenuous training often have energy expenditures two to three times greater than untrained individuals. Competitive athletes require sufficient M. Clark is with Notre Dame Strength and Conditioning, Loftus Sports Center, Notre Dame University, Notre Dame, IN D.B. Reed is with the Department of Animal Science, and S.F. Crouse and R.B. Armstrong are with the Department of Health and Kinesiology all at Texas A&M University. 303

2 304 / Clark, Reed, Crouse, and Armstrong energy to achieve and maintain energy balance an essential condition for both the maintenance of lean tissue and immune function and the promotion of optimal athletic performance. Nutrition for athletes participating in team sports, such as soccer, seems especially important when considering both the metabolic and energy demands warranted to fuel competitive soccer training. Soccer can be described physiologically as intermittent, high-intensity exercise (6); additionally, metabolic demands are further increased by accelerating and stopping, turning, jumping and tackling, as well as by irregular and feigned movements (34). Over the past 30 years, female participation in sports has dramatically increased, especially in competitive soccer, attributable to greater opportunities and awareness of women s sports. Simultaneously, the rising global popularity of women s soccer has coincided with the widespread acknowledgment of sport nutrition counseling as being a functional element of athletic training. As a result, nutrition intervention has been further integrated as a component of the overall training and health of female competitive athletes. Sport nutrition has somewhat developed a specialization for female athletes because of the growing questions concerning gender-specific needs for optimal performance (9). The majority of dietary research involving soccer players has included only elite male soccer players (12, 35). Little published research exists to describe either the dietary habits of soccer women or the physiological demands placed upon them by their sport and lifestyle (2). Despite the limited information describing the nutritional intake of intercollegiate female soccer players (17), dietary surveys have been conducted on a multitude of female collegiate teams (2, 16, 25, 38). Marginal intakes of several nutrients have been reported among female collegiate lacrosse, basketball, field hockey, and track-and-field athletes, including: iron (16, 31, 38, 43), calcium (23, 25, 31, 43), phosphorous (43), folate (43), vitamins A and D (43), vitamin B 6 (16), magnesium (16, 43), zinc (16, 43), energy (31), carbohydrate (13, 31,32, 43), and fiber (25). A number of investigations suggest that female athletes fail to compensate for the increased energy demands of training and competition (31) or that despite varying degrees of exercise intensity and energy expenditure, dietary intake remains constant (18). Dietary assessment of female athletes commonly demonstrates low carbohydrate intakes that are insufficient for adequate glycogen resynthesis (18, 31, 39). While achieving the recommended level of CHO may require an increase in total energy intake, female athletes typically consume less than 2000 kcal/day during training and competition (38, 43); thus, deriving even 60% of kcal from carbohydrate (allowing for 4 to 5 g/kg in a 60-kg athlete) will not support recommendations to maintain optimal muscle glycogen stores. Nutritional intervention by means of an overall assessment of pre- and postseason eating practices has been suggested to help guide soccer athletes towards improved nutrition (20). Therefore, the purpose of this investigation was to compare the pre- and post-season dietary intake, body composition, and performance indices of intercollegiate female soccer players in order to: (a) report baseline dietary data, anthropometrics, and performance indices of intercollegiate female soccer players; (b) determine if soccer women meet minimum energy, macronutrient, and micronutrient requirements recommended for athletes during training and competition; and (c) identify dietary components that should be addressed in nutrition counseling.

3 Female Soccer Players / 305 Methods Subjects Members of a NCAA Division I women s soccer squad at a university in the southwestern United States participated in this investigation. After being fully informed regarding the nature of the study and the risks involved, subjects were asked to sign an informed consent approved by the university s Institutional Review Board for Research with Human Subjects (IRB). Dietary Collection The subjects dietary intake was collected both pre- and post-season. Pre-season data collection occurred during rigorous two-a-day practices consisting of anaerobic activity intermittent running, skills, drills, and game-play. Three months later, the post-season data collection began approximately a week and a half after the close of the competitive season. Subjects recorded the amounts of all food and beverages ingested for 3 days (13, 38, 43). The 3-day food record consisted of 2 weekdays and a weekend day (Sunday, Monday, Tuesday) for both collection periods. At least 3 days, including 2 weekdays and 1 weekend day, are necessary to obtain valid information on a group level (26). This method additionally offers a reliable estimate of food intake for the entire week without over-burdening the subjects, which may potentially cause a decline in the subjects interest and accuracy of recording (43). The participants were given verbal and written instructions for completing food records during an educational session prior to the pre-season data collection period. The educational session focused on proper methods to accurately assess and record food intake (39). The instruction included visual aids on serving sizes (e.g., a serving of meat, pasta, and other commonly consumed foods) using standardized food models (16, 31) and a review of all household measures (i.e., teaspoon, tablespoon, cup) (31). Following the visual instruction, each subject completed a modified, multipass 24-hour recall with the guidance of the first author (19). This innovative method was designed to obtain information about food intake during the past 24-hour period while providing respondents with multiple cues and opportunities to report their food intake using three passes (quick list, detailed description, and review). The subjects received feedback at this time concerning tactics to improve the accuracy and quality of their food records. The subjects were instructed to follow their customary eating habits during the prospective recording days. The subjects received handouts of the same information presented during the instructional session to aid in recording all diet records. The handouts included a checklist (10, 31) to ensure the following: that information on all consumed foods and beverages was recorded in the correct units; brand names were specified and locations where all recorded items were eaten (whether at home, in the dining hall, or at a restaurant) were additionally included (36). The subjects were provided with a handout describing serving sizes of food in relation to common household objects to allow for better estimation of portion sizes. If applicable, subjects were encouraged to record the names of specific restaurant menu items to allow for the most accurate nutrient analysis of their diet records (21). To further ensure accuracy, the restaurants that subjects reported patronizing were called and/or visited to deter-

4 306 / Clark, Reed, Crouse, and Armstrong mine ingredients, food preparation methods, and serving sizes. Each subject received blank food records (10), where they could record their intake, in addition to a sample record to use as a model for specificity and detail (31). Each day s food record contained a separate sheet on which subjects were asked to record all supplement use during the 3-day period (39). Each subject was given these forms in a pocket folder to encourage easy transport and access at all times, thus allowing for the most accurate recording and recall of their dietary intake (39). Group messages were sent out to reiterate previously taught information concerning methods to record food intake. The first author collected the records daily in the subject s training area as a means of quality control (35). Subjects were contacted by phone or by if any food record entries were unclear. All subjects were informed that failure to comply with these standards rendered their food records invalid and not usable in data analysis. To ensure consistency, the first author gave all instructions and coded the dietary records under the guidance of a registered dietitian and nutrition researcher (second author). All diet records were analyzed using the computerized nutrient analysis program Nutritionist V (v. 2.3, 2000, First DataBank, San Bruno, CA, USA). A 3-day average for total energy, macronutrients, micronutrients, and alcohol consumption was determined for each subject. Results were compared to both the 1989 Recommended Dietary Allowances (RDAs; 29) and the new Dietary Reference Intakes (DRIs) released in 1997, 1998, 2000, and 2001 (45), thus allowing the present investigation to be viable when comparing results with both past and future research in the dietary assessment of athletes. Anthropometrics The anthropometric measurements included height, weight, and percent body fat. Each subject s percent body fat was determined by hydrostatic weighing (3). Underwater weight was determined in a rapid-drain tank while the subject sat in a tare connected to an overhead scale. The subject was asked to expel all air from her lungs as she submerged herself and remained submerged for 3 to 5 s while an underwater weight was recorded. This procedure was repeated several times, and the heaviest weights were averaged. Performance Testing Performance testing coincided with the collection of the dietary data. The subjects performed specific exercise performance tests typical of their training regimen. Peak oxygen uptake was assessed on a motor driven treadmill (Quinton Q-65) utilizing the standard Bruce protocol (33). Respiratory gas exchange (VO 2 and VCO 2 ) was measured continuously and averaged over 15-s intervals via opencircuit spirometry utilizing an automated metabolic cart (Medical Graphics CPX/D System) calibrated with gas mixtures of known composition. The peak oxygen uptake achieved during exercise was recorded as VO 2peak (ml/kg/min). In addition, the vertical jump and 20-yard shuttle were tested. These physical tests generally display speed, agility, and muscle explosiveness. First, the subject stood with her side to a marked wall while reaching her arm up, shoulder to ear, and a standing reach measurement was recorded (in inches). The vertical jump was measured using a Vertec (Sports Imports) machine. The final value was calculated

5 Female Soccer Players / 307 by subtracting the standing reach measurement from the height measured on the Vertec machine. The 20-yard shuttle is a timed sprint beginning from the middle of a marked 10-yard distance. The subject sprints 5 yards to a touch point, turns, and sprints the full 10-yard distance to a touch point, turns, and then sprints a final 5 yards to the starting point, for a total of 20 yards. Descriptive statistics, including the mean, standard deviation, and standard error of the mean, were determined for all variables. Paired t tests were performed between pre- and post-season values for each dependent variable. All statistics were determined using SAS software (v. 8.1, SAS Institute Inc., Cary, NC, USA). Statistical significance was defined as p.05. Results Physical Characteristics The physical characteristics of the subjects are presented in Table 1. There were no significant differences in body weight or body fatness from pre- to post-season. Energy and Macronutrients The 3-day average energy intake during the pre-season was significantly greater than the post-season average (Table 2). The pre-season value (37.0 ± 5.0 kcal/kg of body weight) met the minimum energy recommendation for active to very active females (based on kcal/kg body weight), while the post-season value (30 ± 18.0 kcal/kg of body weight) only corresponded to energy requirements for sedentary to low activity (29 32 kcal/kg; 44). Energy intake ranged from a low of 1750 kcal/day to a high of 2880 kcal/day during the pre-season, and a low of 830 kcal/day to a high of 2890 kcal/day during the post-season. Considering a physical activity level ranging from active to very active, these athletes had an estimated energy requirement of kcal/day for pre-season (44). Furthermore, postseason estimated energy requirements for these athletes would be comparably lower ( kcal/day), with a level of physical activity categorized as sedentary to low. Table 1 Pre- and Post-season Subject (n = 14) Characteristics Variable Pre-season Post-season Age (yr) 19.7 ± ± 0.9 Height (cm) ± ± 5.1 Weight (kg) 62.0 ± ± 4.7 Body fat (%) 16.4 ± ± 2.8 Note. Values expressed as mean ± standard deviation. No pre- to post-season differences were significant (p >.05).

6 308 / Clark, Reed, Crouse, and Armstrong Table 2 Female Soccer Players (n = 13) Pre- and Post-Season Mean Intakes of Total Energy, Macronutrients, and Fiber Variable Pre-season Post-season p value Energy Total kcal 2290 ± ± 530*.0012 Carbohyrdrate Total g 320 ± ± 71*.005 g/kg 5.2 ± ± 1.2*.006 % total kcal 55.0 ± ± Protein Total g 86.5 ± ± 16.9*.0001 g/kg 1.4 ± ± 0.3*.0002 % total kcal 15.0 ± ± 2.3*.021 Fat Total g 75.2 ± ± 28.7* <.0001 % total kcal 29.0 ± ± Fiber (g) 14.5 ± ± Note. Values expressed as mean ± standard deviation. *Significantly different from the preseason value (p <.05). From pre- to post-season, significant changes were observed in energy consumed as carbohydrate, protein, and fat when expressed in terms of grams/day (Table 2). However, neither the pre- or post-season carbohydrate intake (5.2 ± 1.1 and 4.3 ± 1.2 g/kg of body weight) met the recommended 7 10 g/kg body weight to accommodate repletion of muscle glycogen stores during repetitive days of training (4). In addition, pre- and post-season fiber intakes were only 58% and 53% of recommendations (30). No significant change was observed in percentage of energy consumed as carbohydrate or fat, but a significant change was observed in the percentage of energy derived from protein. Nonetheless, both the pre- and postseason protein intakes were well above the DRI (1.4 ± 0.3 and 0.96 ± 0.3 g/kg of body weight; Table 2). In addition, the pre-season value met the increased protein requirements recommended for female strength and endurance athletes ( g/ kg of body weight; 28). Although the percentage of energy consumed as fat during the post-season (31.0 ± 6.6%) was slightly above the recommended 25 30% of total energy intake, the absolute amount (65.9 ± 28.7 g) was actually less than that reported during the pre-season (75.2 ± 13.3 g, 29.0 ± 5.7% of caloric intake), which fell into the recommended range. Five athletes reported alcohol consumption during the pre-season, while only 1 athlete reported consumption during the post-season. Calories from alcohol constituted < 1% of daily calories consumed for those who reported alcohol use.

7 Female Soccer Players / 309 Micronutrients Average micronutrient values < 75% of the DRI were considered marginal for a particular nutrient. Tables and figures represent vitamin and mineral intakes without supplements. The 1989 RDAs for females, ages 19 to 24 years, and the DRIs for females, ages 19 to 30 years (Table 3), were used to compare mean (Tables 4 and 5) and individual values (Table 5). For simplicity of discussion, the athletes mean intakes are discussed here as they relate to the current DRIs, with reference to nutrients whose requirements have changed since the 1989 RDAs (29). Mean intakes of several vitamins and minerals (Table 4) were significantly lower during the post-season compared to pre-season, including calcium, copper, iron, magnesium, selenium, zinc, vitamin E, vitamin C, and several B-complex vitamins (thiamin, riboflavin, niacin, vitamin B 6, vitamin B 12 ). Biotin and vitamin D were the only micronutrients whose post-season average intake exceeded that of the pre-season. Mean intakes of copper, magnesium, vitamin E, vitamin D, folate, biotin, and pantothenic acid were marginal (<75% DRI) during the pre-season. The same nutrients were marginal during the post-season, in addition to calcium, chromium, iron, selenium, zinc, and vitamin C (Tables 4 and 5; Figures 1 3). Table 3 RDAs for Females Ages 19 to 24 and DRIs for Females Ages 19 to 30 Nutrient RDA DRI Calcium (mg) * Chromium (mcg) ** 35* Copper (mg) ** 0.9 Iron (mg) Magnesium (mg) Selenium (mcg) Zinc (mg) 12 8 Vitamin A (RE) Vitamin E (ATE) 8 15 Vitamin D (mcg) 10 5* Vitamin C (mg) Thiamin (mg) Riboflavin (mg) Niacin (mg) Vitamin B6 (mg) Folate (mcg) Vitamin B12 (mcg) 2 2.4* Biotin (mcg) ** 30* Pantothenic Acid (mg) ** 5* Note. Figures as established by the National Research Council, *Adequate intakes. **Estimated safe and adequate daily dietary intakes provided in a range.

8 310 / Clark, Reed, Crouse, and Armstrong Table 4 Female Soccer Players (n = 13) Pre- and Post-season Mean Intakes of Selected Micronutrients Micronutrient Pre-season Post-season p value Minerals Calcium (mg) 931 ± ± 289* a,b.005 Chromium (mcg) 34 ± 23 a 21 ± 17 a,b.1 Copper (mg).66 ± ±.26*.049 Iron (mg) 17.3 ± ± 5.2* b.008 Magnesium (mg) 178 ± 43 a,b 127 ± 71* a,b.03 Selenium (mcg) 69 ± ± 16* a,b.001 Zinc (mg) 10.4 ± ± 2.5* a,b <.0001 Vitamins Vitamin A (RE) 894 ± ± Vitamin E (ATE) 7.2 ± 3.7 b 3.3 ± 3.3* a,b.003 Vitamin D (mcg) 2.4 ± 1.7 a,b 2.5 ± 2.6 a,b.91 Vitamin C (mg) 100 ± ± 32* b.03 Thiamin (mg) 1.5 ± ± 0.4*.006 Riboflavin (mg) 1.8 ± ± 0.7*.007 Niacin (mg) 24.5 ± ± 6.3*.006 Vitamin B6 (mg) 1.8 ± ± 0.6* a.003 Folate (mcg) 271 ± ± Vitamin B12 (mcg) 4.5 ± ± 1.7*.001 Biotin (mcg) 11.3 ± ± Pantothenic Acid (mg) 3.1 ± 2.2 b 2.0 ± 1.3 a,b.17 Note. Values expressed as mean ± standard deviation. *Significantly different from the preseason value (p <.05). a Marginal nutrient intake (<75%) in comparison to the 1989 RDAs. b Marginal nutrient intake (<75%) according to the DRIs. Supplement Use Nutritional supplement use was reported both pre- and post-season. Supplements reported included multi-vitamin and/or mineral supplements such as Women s One-A-Day, Centrum, and iron supplementation (28 mg). Nutrients provided through supplements were not included in nutrient analysis for the following reasons: (a) The intention of this investigation was to observe nutritional intake obtained solely from food sources, and (b) consumption of a supplement was not consistent among those individuals who indicated their use, thus suggesting only sporadic use. Performance Indices VO 2peak was observed to significantly increase from pre- to post-season (Table 6). No significant changes were observed for the 20-yard shuttle or vertical jump.

9 Female Soccer Players / 311 Table 5 Female Soccer Players (n = 13) Intake of Selected Micronutrients Relative to the RDAs and DRIs Mean % of RDA Mean % of DRI Micronutrients Pre Post Pre Post Minerals Calcium (mg) 78 (8) 58 (9) 93 (2) 70 (9) Chromium (mcg) 68 (7) 42 (10) 97 (5) 60 (10) Copper (mg) 44 (13) 32 (13) 73 (9) 53 (10) Iron (mg) 115 (2) 81 (8) 96 (4) 68 (8) Magnesium (mg) 64 (11) 45 (11) 57 (12) 41 (11) Selenium (mcg) 125 (1) 62 (8) 125 (1) 62 (8) Zinc (mg) 87 (5) 43 (12) 130 (1) 64 (8) Vitamins Vitamin A (RE) 112 (2) 106 (5) 128 (1) 121 (2) Vitamin E (ATE) 90 (6) 41 (12) 48 (12) 22 (12) Vitamin D (mcg) 24 (13) 25 (12) 48 (9) 50 (11) Vitamin C (mg) 167 (2) 77 (7) 133 (3) 61 (8) Thiamin (mg) 136 (2) 91 (6) 136 (2) 91 (6) Riboflavin (mg) 138 (2) 92 (6) 164 (1) 109 (4) Niacin (mg) 163 (0) 101 (4) 175 (0) 109 (4) Vitamin B6 (mg) 113 (2) 69 (9) 138 (1) 85 (8) Folate (mcg) 68 (8) 47 (10) 68 (8) 47 (10) Vitamin B12 (mcg) 225 (1) 105 (7) 188 (1) 88 (8) Biotin (mcg) 38 (11) 44 (12) 38 (11) 44 (12) Pantothenic Acid (mcg) 78 (8) 50 (10) 62 (10) 40 (12) Note. As established by the National Research Council, 1989, and by the Food and Nutrition Board of the Institute of Medicine, The National Academies, 1997, 1998, 2000, and Numbers in parentheses denote the number of subjects who are marginal (<75%) in selected nutrients. Discussion To the knowledge of the authors, the present investigation is the first to establish baseline pre- and post-season dietary assessment, anthropometric, and performance profiles of female intercollegiate soccer players. Additionally, this is the first reported study to utilize the multi-pass 24-hour recall method during dietary instruction on recording food intake (19). The use of this method may have elicited a better understanding by the subjects, particularly because this technique addresses the specificity required in order to accurately record food intake. Because the results of this study demonstrated energy intakes consistent with recommended levels, the 3- day food record in combination with dietary instruction using the multi-pass 24- hour recall method appeared effective in obtaining valid information.

10 312 / Clark, Reed, Crouse, and Armstrong Figure 1 Female soccer players average pre- and post-season intake of selected minerals relative to the Dietary Reference Intakes (DRIs; N = 13). Figure 2 Female soccer players average pre- and post-season intake of selected vitamins relative to the Dietary Reference Intakes (DRIs; N = 13). According to the 2002 Dietary Reference Intakes (DRIs) (44), estimated energy requirements (EER) for women 30 years of age who are of similar height, weight (Table 1), as well as physical activity level to the present investigation s subjects should consume approximately kcal per day to remain in energy balance (44) or at a rate of kcal/kg body weight/day. In addition to age and gender, consideration of the many factors lending to metabolic stress is important

11 Female Soccer Players / 313 Figure 3 Female soccer players average pre- and post-season intake of the B-complex vitamins relative to the dietary reference intakes (DRIs; N = 13). Table 6 Female Soccer Players Pre- and Post-season Performance Values Variable Pre-season Post-season p value VO 2peak (ml/kg/min; n = 9) 42.2 ± ± 4.5* < yard shuttle (s; n = 7) 4.92 ± ± Vertical jump (in.; n = 12) 19.7 ± ± Note. Values expressed as mean ± standard deviation. *Significantly different from the preseason value (p <.05). to establish individual energy requirements, including: genetic disposition; body size; fat-free mass; and the intensity, frequency, and duration of exercise training (1). The subjects in the present investigation reported energy intakes during rigorous pre-season training that met minimum energy requirements (37 kcal/kg of body weight) for females with a physical activity level categorized as active to very active (44). While an actual means of measuring energy expenditure (EE) was not used in this investigation, the athletes pre-season reported caloric intake (2290 kcal/day) was equivalent to their estimated caloric needs based on the average body weight of the subjects (2300 kcal/day). Likewise, post-season caloric intake (1865 kcal/day or 30 kcal/kg of body weight) was equivalent to the estimated energy requirements for a more sedentary to low activity level ( kcal/day or kcal/kg of body weight; 44). Moreover, the stable body mass of these soccer

12 314 / Clark, Reed, Crouse, and Armstrong women from pre- to post-season suggests that the reported energy intakes were accurate. This is in contrast to previous researchers who observed that female athletes do not necessarily make changes in dietary habits to match changes in energy expenditure (i.e., failing to accommodate a greater energy expenditure with a greater energy intake; 31). Elite female soccer players, of similar age (18.5 ± 2.3 years), height (167 ± 5.0 cm), and weight (60.8 ± 5.9 kg) to athletes in the present study demonstrated a reported energy intake (EI) that matched estimated energy expenditure (EE) as determined through a factorial EE assessment (11). Attributed to their post-competitive season status, the elite soccer women s caloric intake was statistically similar to the energy intake of sedentary controls in the same study. These results suggest that female soccer players not only engage in lighter activity during their off-season but that they also maintain a state of energy balance. Therefore, the decrease in postseason caloric intake observed in the present study by collegiate players likely reflected a change in physical activity, and under-reporting of actual food intake was not suspected to have occurred. Accordingly, analyses of all nutrients were concluded to be equally valid. The Joint Position Statement issued by the American College of Sports Medicine, the American Dietetic Association, and the Dietitians of Canada (1) maintains that a diet providing 500 to 600 g of CHO (approximately 7 to 8 g/kg for a 70-kg athlete) is adequate to sustain muscle glycogen stores during training and competition, although Burke (4) supports a level as high as 10 g/kg for certain endurance athletes. These soccer women met guideline standards for dietary CHO, based on percent of kcal, both pre- and post-season (55% and 57% of energy intake), yet absolute values failed to support recommendations for optimal glycogen storage and resynthesis during repetitive days of training: Pre- and post-season values were only 5.2 and 4.3 g/kg of body weight. A recent review by Tarnopolsky (40) suggests the need for more gender specific nutritional recommendations and exercise training prescriptions based on data demonstrating greater lipid and lower carbohydrate oxidation in women compared to men during endurance exercise at 65 70% VO 2max (41). Nonetheless, a more recent investigation by Tarnopolsky (42) concluded that trained females overall may demonstrate similar increases in muscle glycogen stores compared to trained males, given that CHO recommendations are expressed in terms of body weight (8 g/kg) rather than as a percentage of energy intake (55 75%) because of the overall lower energy intake typical of females. Certainly future research is warranted to address more gender-appropriate macronutrient recommendations for athletes. While the debate in support of advocating higher protein requirements for athletes continues, athletes in this investigation consumed protein in excess of the DRI both pre-and post-season. The current DRI for protein for all healthy individuals is 0.8 g/kg body weight (29). However, experts in sports nutrition are currently advocating that competitive female athletes require protein intakes in the realm of 1.2 g/kg body weight in order to maximize performance potential (9), while levels as high as 1.7 g/kg body weight are recommended for female strength athletes (24). However, few data actually exist that document increased requirements for both female strength and endurance athletes (1). Despite the lack of a definitive consensus, the habitual diets of athletes have been reportedly sufficient to meet not only the current DRI for protein, but also to accommodate the increased recommendations suggested by some experts (13).

13 Female Soccer Players / 315 Moderate fat consumption (20% to 25% of energy from fat) is advocated as appropriate to facilitate an adequate caloric and CHO intake that permits for maintenance of body weight, as well as to provide the essential fatty acids and fat-soluble vitamins (1). These athletes pre- and post-season values (29% and 31%, respectively, of total energy intake) were close to recommendations. Currently, no data exist to support that athletes diets should vary considerably from the recommendations maintained by the Dietary Guidelines for Americans regarding fat intake (25 30% of total energy intake; 1). Although protein and fat in excess of recommendations does not interfere with glycogen storage given adequate CHO intake (5), the consumption of foods high in protein and fat may displace CHO-rich foods within players energy requirements and satiety limits. Hypothetically, a diet providing 20% fat, 9% protein (providing the RDA), and the remainder from CHO (but of identical caloric value to our investigation s pre-season intake) would increase CHO intake to 6.6 g/kg body weight, a 1.4-g/kg increase from the observed level. However, meeting CHO recommendations while providing adequate dietary fat and protein may necessitate an increase in overall energy consumption for athletes with greater nutrient needs. In addition, these soccer players caloric values demonstrated that an exercise-enhanced energy intake will not necessarily ensure adequate intakes of all nutrients. Accordingly, despite the soccer women s greater pre-season energy consumption, intakes of copper, magnesium, vitamin D, vitamin E, folate, biotin, and pantothenic acid were marginal. Furthermore, post-season intakes of calcium, chromium, iron, selenium, zinc, and vitamin C were additionally marginal with a lower caloric intake. Calcium and iron intakes are commonly marginal in female athletes who restrict caloric intake and/or who follow low-fat diets (39), particularly due to the avoidance of foods of animal origin, such as meat, fish, poultry, and dairy products. While caloric and dietary fat restrictions, per se, were not suspected among these athletes, the significantly lower post-season caloric intake resulted in marginal (<75% of the DRI) intakes of these micronutrients. Because iron is essential for oxygen delivery to the tissues as a component of hemoglobin and myoglobin, and acts as an enzyme cofactor involved in energy production (37), adequate iron status is crucial to the optimal physical performance as well as immune function of athletes. Optimal bone mineral density necessitates adequate dietary calcium, especially for female athletes with chronically low intakes (25). Moreover, sufficient intake of calcium is required to maximize the development of peak bone mass within an individual s genetic potential and to prevent osteoporosis later in life. In addition, vitamin D enables adequate calcium absorption, regulation of calcium levels, and promotion of bone health (1). Consequently, if the post-season calcium intake exhibited by these female players (only 70% of the DRI) was typical as well as longterm, calcium may become a risk nutrient for these athletes during times of lower energy intake. Due to evidence linking folate intake with neural tube defects in the fetus, it is recommended that all women capable of becoming pregnant consume 400 µg/day (45). The soccer women s folate intake was only 68 and 47% of the DRI during the pre- and post-season, suggesting a low intake of folate-rich and folate-fortified foods. Explanations for poor micronutrient intake in these athletes may include: (a) low intake of nutrient-dense foods, such as fruits, vegetables, and whole grains, and/

14 316 / Clark, Reed, Crouse, and Armstrong or (b) high intake of processed foods and foods high in empty calories, including sports drinks and soda. Such reasoning is further supported by the low fiber intakes observed both pre- and post-season (14.5 ± 4.9 and 13.3 ± 5.7 g/day, respectively). Female athletes have demonstrated fiber intakes averaging as low as 4 and 6 g/day (25), compared with members of the general population, who reportedly consume an average of 12 g/day (29). The Dietary Guidelines for Americans, in fact, suggest at least 25 g of fiber/day for a 2000 kcal/day diet (30). Some athletes may find that practical issues associated with their exercise schedule challenges their ability to meet daily energy and nutrient requirements. Certainly, the mode and intensity of exercise during pre-season training may have effectively prevented consumption of foods other than sports drinks (15). The fear of gastrointestinal discomfort and the reduced access to foods and fluid may limit intake both during the exercise session and also for up to 3 hours before the session. Many individuals have also reported diminished appetite in the 2 to 3 hours immediately after strenuous exercise (15). Alcohol consumption was rarely reported in previous dietary studies that described female athletes nutrient intakes. Perhaps alcohol use by athletes is not reported, or researchers may fail to report its consumption. While some athletes reported alcohol use in the present study, the majority (8 of 13 subjects pre-season, 12 of 13 subjects post-season) appeared not to consume alcohol during the recording days. This may be attributed to the actual days used in dietary analysis (Sunday, Monday, Tuesday). Nevertheless, a NCAA survey, including a broad spectrum of male and female sport teams, reported alcohol use by 80.5% of respondents the most widely used drug among student athletes in the past year (14). Additionally, although nutritional supplement use was insignificant for this investigation, vitamin and mineral supplement use among university athletes in a Division I institution was reported by over half the subjects, including 145 females from 22 varsity teams (22). The most common supplement reported was multivitamins/-minerals, with females more likely to take calcium and iron. Although body weight and body fatness were not correlated to diet or performance in this investigation, a high body fat is associated with a decrement in athletic performance in those sports in which body weight must be supported and transferred either horizontally or vertically (7). In a group of international female soccer athletes, body fat accounted for 21 22% of body mass (8), while Canadian intercollegiate players reportedly have values around 16% (27). A group of 12 soccer players from the Finnish National League (age, 18.5 ± 2.3 years) was reported to have an average body fat of 25.8 ± 3.0% (11). Certainly, the female athletes in this investigation appear leaner compared with reports of other soccer women. Metabolically, less body fat may offer better energy efficiency (11); thus, these female players lower body fat may prove conducive to enhanced physical performance. Accordingly the soccer women s post-season aerobic capacity (50 ml/kg/min) of the present investigation was similar to reports of other collegiate players (47 49 ml/kg/min) (27). Summary and Applications Nutritional intervention could strengthen the dietary intakes of intercollegiate athletes. Athletes require awareness of the interrelationship between physical activity and diet in that optimal adaptation to the stress of exercise training requires a diet

15 Female Soccer Players / 317 that is likewise optimal in all nutrients. Dietary assessments of athletes should be utilized to recognize potential nutritional weaknesses and then to provide nutritional advice accordingly that will allow athletes the opportunity to strengthen dietary behaviors. Encouraging athletes to base their diets on nutrient-dense, high-carbohydrate foods, while getting adequate, but not excessive, protein and fat will best accomplish the balanced nutrition that these athletes require during training and competition. In terms of a pie chart, athletes should strive to fill over half the pie (~60%) with calories derived from whole grain cereals, breads, pasta, and rice, as well as a variety of fruits and vegetables. Intake of quality protein foods such as lean meats, poultry, fish, eggs, beans, nuts, and low-fat milk products should fill the rest of the chart, providing adequate protein (12 15%) and fat (<30%) calories. However, availability and convenience are large factors in the food choices of a college athlete, which may cause a greater intake of convenience and fast food. Overcoming such obstacles is a challenge for sport nutritionists, especially because these foods are often high in fat and sugar and commonly replace more nutrient-dense foods. Sport nutrition counseling, including education on food selection, could assist female athletes in achieving micronutrient requirements during periods of intense training and competition, and also during phases of tapered training or lower activity when caloric intake may likewise decrease. Even with high-caloric intakes, athletes may fail to consume adequate carbohydrate to optimize glycogen stores. Surplus dietary protein and/or dietary fat may displace carbohydrate in the diet, thus making it difficult to meet minimum CHO recommendations. Accordingly, strategies to optimize CHO intake within an athlete s energy requirements and satiety limits may be valuable to females as well as males participating in sports of a multiple sprint nature, where performance may be influenced by low glycogen availability. Sport nutrition counseling will be most beneficial if it is based on accurate assessment of the athlete s diet. The use of the multi-pass 24-hour recall method as a training technique for keeping a 3-day diet record appeared to produce accurate results in this athletic population. Further use of this method should be explored. References 1. American College of Sport Medicine, the American Dietetic Association, and the Dietitians of Canada. Joint position statement: nutrition and athletic performance. Med. Sci. Sports Exerc. 32: , Brewer, J. Nutritional aspects of women s soccer. J. Sports Sci. 12:S35-S38, Brozek, J., F. Grande, J.T. Anderson, and A. Keys. Densitometric analysis of body composition: revision of some quantitative assumptions. Ann. N.Y. Acad. Sci. 110: , Burke, L.M. Practical issues in nutrition for athletes. J. Sports Sci. 13:S83-S90, Burke, L.M., G.R. Collier, S.K. Beasley, P.G. Davis, P.A. Fricker, P. Heeley, K. Walder, and M. Hargreaves. Effect of coingestion of fat and protein with carbohydrate feedings on muscle glycogen storage. Int. J. Sport Nutr. 78: , Coyle, E.F. Effects of diet on intermittent high intensity exercise. In: Intermittent High Intensity Exercise, D.A.D. McLeod, R.J. Maughan, C. Williams, C.R. Madeley, J.C.M. Sharp, and R.W. Nutton (Eds.). London: E & FN Spon, 1993, pp

16 318 / Clark, Reed, Crouse, and Armstrong 7. Davis, J.A., and J. Brewer. Applied physiology of female soccer players. Sports Med. 16: , Davis, J.A., and J. Brewer. Physiological characteristics of an international female soccer squad. J. Sports Sci. 10: , Dolins, K.R. Rethinking sports nutrition advice for women. ACSM Health Fitness J. 4:8-13, Faber, M., and A.J. Spinnler Benade. Mineral and vitamin intake in field athletes (discus-, hammer-, javelin-throwers and shotputters). Int. J. Sports Med. 12: , Fogelholm, G.M., T.K. Kukkonen-Harjula, S.A. Taipale, H.T. Sievanen, P. Oja, and I.M. Vuori. Resting metabolic rate and energy intake in female gymnasts, figure skaters, and soccer players. Int. J. Sports Med. 16: , Giada, F., G. Zuliani, E. Baldo-Enzi, S. Palmieri, S. Volpato, E. Vitale, P. Magnanini, A. Colozzi, L. Vecchiet, and R. Fellin. Lipoprotein profile, diet and body composition in athletes practicing mixed anaerobic activities. J. Sports Med. Phys. Fitness. 36: , Grandjean, A.C. Macronutrient intake of US athletes compared with the general population and recommendations made for athletes. Am. J. Clin. Nutr. 49: , Green, G.A., F.D. Uryasz, T.A. Petr, and C.D. Bray. NCAA study of substance use and abuse habits of college student-athletes. Clin. J. Sport Med. 11:51-56, Hawley, J.A., and L.M. Burke. Effect of meal frequency and timing on physical performance. Br. J. Nutr. 77(Suppl. 1):S91-S103, Hickson, J.F., J. Shrader, and L.C. Trischler. Dietary intakes of female basketball and gymnastics athletes. J. Am. Diet. Assoc. 86: , Horvath, P.J., R.G. Genovese, B. O Reilly, R.A. Melton-Bork, L. Gelchrist, and J. Leddy. The effect of peanuts or carbohydrate-rich energy bars on performance of female collegiate soccer players. FASEB J. 13(Part 1):A542, Imbeault, P., S. Saint-Pierre, N. Almeras, and A. Tremblay. Acute effects of exercise on energy intake and feeding behaviour. Br. J. Nutr. 77: , Jonnalagadda, S.S., D.C. Mitchell, H. Smicklas-Wright, K.B. Meaker, N. Van Heel, W. Karmally, A.G. Ershow, and P.M. Kris-Etherton. Accuracy of energy intake data estimated by a multiple-pass, 24-hour dietary recall technique. J. Am. Diet. Assoc. 100: , 311, Kirkendall, D.T. Effects of nutrition on performance in soccer. Med. Sci. Sports Exerc. 25: , Kopp-Woodroffe, S.A., M.M. Manroe, C.A. Dueck, J.S. Skinner, and K.S. Matt. Energy and nutrient status of amenorrheic athletes participating in a diet and exercise training intervention program. Int. J. Sport Nutr. 9:70-88, Krumbach, C.J., D.R. Ellis, and J.A. Driskell. A report of vitamin and mineral supplement use among university athletes in a division I institution. Int. J. Sport Nutr. 9: , Leinus, K., and V. Oopik. Habitual nutrient intake and energy expenditure of students participating in recreational sports. Nutr. Res. 18: , Lemon, P.W.R. Dietary protein requirements in athletes. J. Nutr. Biochem. 8:52-60, Lloyd, T., J.R. Buchanan, S. Bitzer, C.J. Waldman, C. Myers, and B.G. Ford. Interrelationships of diet, athletic activity, menstrual status, and bone density in collegiate women. Am. J. Clin. Nutr. 46: , Marr, J. Individual diet surveys: purpose and methods. World Rev. Nutr. 13: , 1971.

17 Female Soccer Players / McCay, L., and R.J. Shephard. Standardized Tests for Canadian Soccer Players. Ottawa, ON: Canadian Soccer Association, Meredith, C.N., M.J. Zackin, W.R. Frontera, and W.J. Evans. Dietary protein requirements and body protein metabolism in endurance-trained men. J. App. Physiol. 66: , National Research Council. Recommended Dietary Allowances (10 th ed.). Washington, DC: National Academy Press, Nutrition and Your Health: Dietary Guidelines for Americans (5 th ed.). Washington DC: U.S. Departments of Agriculture and Health & Human Services, Nutter, J. Seasonal changes in female athletes diets. Int. J. Sport Nutr. 1: , Ousley-Pahnke, L., D.R. Black, and R.J. Gretebeck. Dietary intake and energy expenditure of female collegiate swimmers during decreased training prior to competition. J. Am. Diet. Assoc. 101: , Pollock, M.L. A comparison of four protocols for maximal treadmill stress testing. Am. Heart J. 92:39-46, Reilly, T. Energetics of high intensity exercise (soccer) with particular reference to fatigue. J. Sports Sci. 15: , Rico-Sanz, J., W.R. Frontera, P.A. Mole, M.A. Rivera, A. Rivera-Brown, and C.N. Meredith. Dietary and performance assessment of elite soccer players during a period of intense training. Int. J. Sport Nutr. 8: , Schokman, C.P., H.E. Rutishauser, and R.J. Wallace. Pre- and postgame macronutrient intake of a group of elite Australian football players. Int. J. Sport Nutr. 9:60-69, Shils, M.E., J.A. Olson, M. Shike, and J.C.M. Sharp. Modern Nutrition in Health and Disease (9th ed.). Philadelphia: Lippincott, Williams, & Wilkins, Short, S.H., and W.R. Short. Four-year study of university athletes dietary intake. J. Am. Diet. Assoc. 82: , Tanaka, J.A., H. Tanaka, and W. Landis. An assessment of carbohydrate intake in collegiate distance runners. Int. J. Sport Nutr. 5: , Tarnopolsky, M.A. Gender differences in metabolism; nutrition and supplements. J. Sci. Med. Sport. 3: , Tarnopolsky, M.A., S.A. Atkinson, S.M. Phillips, and J.D. MacDougall. Carbohydrate loading and metabolism during exercise in men and women. J. App. Physiol. 78: , Tarnopolsky, M.A., C. Zawada, L.B. Richmond, S. Carter, J. Shearer, T. Graham, and S.M. Phillips. Gender differences in carbohydrate loading are related to energy intake. J. App. Physiol. 91: , Tilgner, S.A., and M.R. Schiller. Dietary intakes of female college athletes: the need for nutrition education. J. Am. Diet. Assoc. 89: , Trumbo, P., S. Schlicker, Y. Allison, and M. Poos. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. J. Am. Diet. Assoc. 102: , Trumbo, P., A.A. Yates, S. Schlicker, and M. Poos. Dietary reference intakes. J. Am. Diet. Assoc. 10: , 2001.