Component Summary

Dietary components include macronutrients [12, 13] (carbohydrates, protein, and fat) and micronutrients (fluids, electrolytes, vitamins, and minerals). Specific requirements are presented in the Table in the Summary of Nutritional Requirements and Sources section.

Macronutrients

Carbohydrates

Carbohydrates are necessary to meet energy needs, more so in endurance athletes than in strength athletes.

Carbohydrate needs are commonly based on the athlete's body size and activity level. Individuals engaged in moderate-duration, low-intensity exercise require 5-7 g of carbohydrates per kilogram of body weight. [14] By contrast, those participating in long-duration and high-intensity exercise require 7-12 g of carbohydrates per kilogram of body weight (see the Table).

Fruit, vegetables, brown rice, enriched whole-grain breads, whole grain cereals, rolled oats, beans, legumes, and sweet potatoes are good examples of healthy carbohydrate foods.

Protein

Active individuals have a heightened protein requirement because they have a high percentage of lean muscle mass to support, they need protein to repair muscle tissue that is damaged during exercise, and they require additional protein for energy during exercise.

The amount of protein required depends on the type of activity being performed. Researchers recommend protein intakes of 1.2-1.4 g/kg/d for individuals participating in endurance sports and 1.6-1.8 g/kg/d for those involved in anaerobic activities (see the Table). [15, 14]

Benefits of substituting carbohydrates with protein include the following:

Enhanced weight loss

Reduction in truncal adipose tissue

Optimal maintenance of blood glucose levels

Improved lipid profile

Protein-rich foods include lean pork and beef, poultry, fish, eggs, beans, tofu, and low-fat dairy products. Women at risk for having a low protein intake are those who restrict their energy intake to achieve weight loss or those who eat a vegetarian diet.

In the past, some investigators expressed concerns that a high-protein diet can cause renal damage. However, no conclusive evidence suggests that a high-protein diet negatively affects healthy adults with normal renal function. [16] In addition, some researchers have raised questions about whether a high-protein or low-carbohydrate diet may increase the all-cause mortality risk in women. [17] Further research is necessary to determine if this is the case.

Fat

Fat provides essential elements for the cell membranes and is essential for the absorption of fat-soluble vitamins. Fat should account for 25-30% of a person's energy intake. [15] Diets should be limited in saturated and trans-fats, while providing adequate amounts of essential fatty acids (linoleic and alpha-linoleic acid). In women, the following intakes are advised (see the Table):

Linoleic acid intake 11-12 g/d

Alpha-linoleic acid intake 1.1 g/d

Functions of essential fatty acids include regulation of blood clotting, blood pressure, heart rate, and immune responses.

Dietary fatty acids should come from naturally lean protein foods, nuts, seeds, nut butter, fatty fish (eg, salmon, trout), fish-oil supplements, flaxseed oil, safflower oil, canola oil, sunflower oil, corn oil, avocados, and egg yolks. [16] Women should avoid consuming fats found in processed foods because of their highly saturated nature.

Low-fat diets are not recommended for active individuals. [15] Low-fat diets decrease energy and nutrient intake, reduce exercise performance, and decrease oxidation of body fat stores. Fat provides the most energy per gram of all the macronutrients and can help in achieving a positive energy balance. Dietary fat maintains concentrations of sex hormones and may prevent menstrual disturbances. [18, 19]

Micronutrients

Fluids and electrolytes

Dehydration impairs performance; therefore, athletes must remain well hydrated. Adequate fluid intake is approximately 2.2 L/d for women aged 19-30 years, and increased drinking is required for active individuals or those in hot environments (see the Table). [15]

Athletes should consume 400-600 mL of fluid 2 hours before exercising. During exercise, 150-350 mL (6-12 fluid ounces [fl oz]) should be ingested every 15-20 minutes. For exercise lasting longer than 1 hour or occurring in hot environments, the fluid should be a drink containing carbohydrates and electrolytes. [15] Postexercise meals should include fluids and foods containing sodium, because diuresis occurs with the ingestion of plain water. [20]

Vitamins and minerals

Female athletes are at increased risk for iron, calcium, vitamin B, and zinc deficiencies. These nutrients are vital for building bone and muscle and for energy production. Vegetarians are particularly at risk for developing deficiencies in these vitamins and minerals. [6, 21]

Iron insufficiency is one of the most prevalent nutritional deficiencies among the female athlete because of menstrual losses (see the Table). Iron deficiency may lead to fatigue. [22, 23] Ferritin values are commonly used to reflect iron stores; however, their reliability in the female athlete is questioned.

Excessive iron ingestion may also cause problems, including gastrointestinal distress, constipation, and iron toxicity.