NUTRITION FOR FEMALE ATHLETES

Over the years the number of females participating in various sports activities has skyrocketed. Today we can see female finishers outnumber male finishers in marathons. However, to truly embrace the obvious benefits of sport participation, it is essential that athletes and coaches alike understand the unique nutritional demands that face females during sports training and competition.

The most important nutritional consideration for women engaged in sport is an increased need for energy in the form of carbohydrates, fat, and protein to help fuel the working body. Inadequate caloric and macronutrient intake is a major problem among female athletes who tend to be much more concerned about their weight than male athletes, especially those engaged in sports where leanness is emphasized: gymnastics, dance, diving, and distance running, among others. The sad irony is that female athlete are far more likely to achieve an optimal performance physique by increasing their intake of appropriate nutrients than by enforcing unhealthy dietary restrictions. They will also perform much better in practice and competition and recover more efficiently due to reduced muscle breakdown and injury.

If an athlete’s energy (calorie) intake falls below 13 kcal/lb (13 kcal/0.45 kg) of fat-free mass/day, hormonal balance and functionality of other metabolic systems may significantly deteriorate, hurting both health and performance. A negative energy balance, whether it is a subconscious result of failing to consume enough calories to offset the deficit incurred during training or a conscious effort to achieve perceived ideal body weight, not only can compromise performance but is also a known risk factor for lower estrogen levels and amenorrhea, or the cessation of menstrual flow. In turn, low estrogen levels can hurt bone mineral density and predispose the female athlete to stress fractures as well as an increased probability for developing osteopenia and osteoporosis, also known as brittle bones. Further medical problems arise when weight-control behaviors become recognized diagnoses of eating disorders, including anorexia nervosa (severe energy restriction) and bulimia nervosa (binge and purge disorder). The combination of disordered eating, which conscious restriction of calories falls under, menstrual irregularities, and diminished bone health has been labeled the female athlete triad and is becoming an increasingly prevalent problem in sport.

Trigger Factors for Disordered Eating

  1. Prolonged periods of dieting or weight fluctuations
  2. Traumatic events such as illness or injury, new coach, causal comments about weight, leaving home (college), failure at school or work, family problems, relationship issues
  3. A large increase in training volume and significant weight loss associated with an increase in training volume
  4. A belief that menarche (first period) has been reached too early
  5. Early start of sport-specific training
  6. A large discrepancy between self-denied ideal weight and ideal weight
  7. Recommendation to lose weight without guidance
  8. Social influences for thinness
  9. Performance anxiety
  10. Negative self-appraisal, generally as it relates to performance

Beyond a heightened risk for altered hormonal status and diminished bone health, female athletes, especially those following restrictive diets, are vulnerable to both macro- and micronutrient deficiencies that can result in fatigue, stunted growth (for adolescent athletes), poor immune function, loss of motivation, inability to concentrate, and significant declines

in both strength and endurance. Several studies have found lower than recommended intakes for carbohydrate, which can significantly compromise glycogen stores and put an athlete at risk for the mental bonk and muscle-fatiguing wall, and for protein, which can inhibit strength gains as well as compromise muscle recovery and immune function.

Iron is one of the most prevalent micronutrient deficiencies found in female athletes, partially due to restrictive energy intake that may include the elimination of such iron-rich foods as red meat and dark meat (poultry). Also, blood loss during menstruation along with a phenomenon known as exercise-induced hemolysis (red blood cells rupture when the foot strikes the ground) can cause hemoglobin (the protein that carries iron) levels to drop and can increase the risk for iron deficiency. Declines in both physical and cognitive performance have been demonstrated in female athletes with poor dietary intake of iron and especially iron-deficiency anemia (blood deficiency). Female athletes are also at increased risk for calcium, vitamin D, and zinc deficiencies; these nutrients play a role in building bone and muscle as well as supporting immune function. Another practice commonly employed by women trying to suppress hunger while dieting is to sip on calorie-free beverages such as water, tea, and diet soda—and consume large volumes of these beverages. Drinking excessive amounts of any type of fluid, especially water, outside of or during exercise, can cause blood sodium levels to drop, triggering a potentially fatal condition known as hyponatremia, or water intoxication, marked by one or several of the following symptoms: clear urine, muscle fatigue, pressure headache, dizziness, confusion, nausea, and vomiting. Coupled with sodium losses during exercise, female athletes, especially those new to endurance sports who may be on a racecourse for a longer duration, seem to be at greatest risk for hyponatremia and associated symptoms. The vulnerability may be further heightened during menstruation since both estrogen and progesterone hinder the function of the sodium-potassium pump, which helps maintain sodium levels and protect against hyponatremia. Therefore, nutrition education for female athletes, especially during the formative preadolescent and adolescent years becomes of paramount importance for the prevention of health issues as well as success in sport.

Nutritional Recommendations

While the bulk of performance nutrition advice is not sex-specific, there are a few nutritional considerations that female athletes should pay particular attention to. For one, because women carry less metabolically active muscle tissue and, on average, 10% more body fat than their male counterparts, women’s resting metabolic rates tend to fall about 5%-10% lower than men’s. As a result, many health professionals believe energy and macronutrient calculations should focus on lean body mass (fat-free mass) versus total mass. The use of a body fat scale, even though error rate tends to be higher than other body fat–testing methods, can provide an estimate of fat-free mass for athletes and coaches to use to calculate needs. Nonetheless, for both sexes, and energy intake that matches both resting and training metabolic needs, which will vary daily especially when comparing in- and off-season training protocols, and includes appropriate amounts of carbohydrate and protein (see table below) is critical to performance success. 

 

 Daily training   <1 hour  1-2 hours  2+ hours

Calories per lb (per 0.45 kg)fat-free mass   

16-20    21-25  25-30

Carbohydrate g/lb (g/0.45 kg) fat-free mass 

2.7-3.0  3.0-3.5  3.6-4.5

Protein g/lb (g/0.45 kg) fat-free mass   

0.5-0.8   0.5-0.8  0.5-0.8 

 

Those athletes needing to drop body fat for health and performance reasons preferably will focus attention on this goal during the off-season. However, if an athlete wants to shed body fat during a competitive season, energy restriction should be limited to 500 calories/day, ideally outside of heavy training cycles. A registered dietitian can help determine a healthy body composition goal as well as develop a menu plan for achievement while maintaining peak performance during a competitive season. As a general rule, female athletes should aim at consuming 4-6 closely calorie-matched meals throughout the day. The three staple meals (breakfast, lunch, and dinner) should include a balance that incorporates 25% protein, 25% starch, and 50% color (fruits and vegetables) along with small doses of healthy fat. Avoidance of major food groups is highly discouraged as deficiency risks, including those common among female athletes (e.g., iron, calcium, vitamin D, zinc), tend to be heightened with food restriction. To improve iron intake, female athletes should include more animal protein or Plant sources of iron such as whole grains, fortified cereals, and legumes should be combined with foods rich in vitamin C (e.g., oranges) to aid iron absorption. To boost the intake of bone-building nutrients, calcium, and vitamin D, female athletes should aim to consume 3-4 servings of dairy or fortified dairy alternatives such as soy or almond milk, three-fourths cup yogurt, one-half cup 113 g cottage cheese. To avoid a zinc deficiency and better support immune function and metabolism, the inclusion of zinc-rich foods such as chicken breast, oysters, peanut butter, legumes, milk, yogurt, is encouraged. An additional calorie intake of about 100-250/hour is appropriate for most females and is warranted when training exceeds 90 minutes. Perhaps the most convenient method of replenishing lost fluids, electrolytes, and carbohydrate during prolonged sports, activity is through a sports drink containing these nutrients. For aerobic activities lasting longer than 4 hours (e.g., long-distance cycling, walking a marathon), the addition of small amounts of protein (up to 5 g/hour) can help offset the hunger that creeps into the calorie-deprived body as well as possible delay fatigue and speed recovery. It is estimated that two out of every three female athletes walk around chronically dehydrated, which is a definite cause for concern since dehydration tends to be the primary dietary-contributing factor to poor performance. On the other hand, some female athletes drink excessive amounts of water throughout the day, which can promote hyponatremia. To maintain fluid balance, athletes should aim at drinking approximately half their body weight in fluid ounces each day, or so urine runs a pale or straw-like yellow (not clear) color. For example, a 68 kg woman would aim to consume 2.2 L of fluid (not just water)/day. An additional 0.12-0.24 L of fluid should be consumed every 15 minutes or so that bodyweight losses stay under 2% (e.g., 3 lb [1.4 kg] for a 150 lb athlete) during training. For training sessions lasting longer than an hour, a sports drink that contains carbohydrate, sodium, and other electrolytes to enhance fluid uptake is preferable to water.

Supplement Options

Because there is no research suggesting that supplementation with vitamins and minerals is beneficial to performance (except when an athlete has a deficiency of certain nutrients), the first line of defense for the female athlete—and any athlete for that matter—should always be via whole food intake. If a deficiency is detected by a doctor, therapeutic levels of specific vitamins and minerals in supplement form may help blood levels normalize and allow the athlete to regain optimal health and peak performance. Female athletes without blood deficiencies yet who consistently fail to consume recommended daily intake amounts of key nutrients, especially iron, zinc, calcium, and vitamin D, through whole food intake may benefit from supplementation with a once-a-day multivitamin and multimineral supplement. Multivitamin and multimineral supplements generally provide lower doses (up to 100% of the current RDA) of nutrients and can serve as nutritional insurance for concerned athletes.