Long ago, Olympians in ancient Greece believed that certain foods would provide strength and power during training and competition. While our knowledge of nutrition has certainly advanced, the basics remain the same — successful athletes recognize that what they eat affects their training performance and overall health. Without proper fuel and fluids, athletes may not reach their potential.
How can athletes eat to ensure optimal performance?  Competitive swimmers have different nutrient needs than the average person and should consume:
Carbs – which provide the main source of energy to the working muscles. Compared to protein and fats, stored carbs are very limited in the body and become depleted during a single training session.  Athletes who limit carbs will experience poor practices and performances. A diet rich in low fat, complex carbs is recommended to help maintain these stores.  Good sources of carbs include whole grains, cereals, fruits, starchy vegetables, fruit juices, dried peas and beans and low-fat dairy products.
Protein helps repair, helps growth and maintenance of muscle.
Good sources of protein include meat, fish, poultry, eggs, nuts, beans, and low-fat dairy products.  Protein should be eaten at every meal and including a small amount of protein before exercise may reduce muscle soreness.  Adding a small amount after exercise will stimulate muscle repair and growth.
Although workouts are spent exercising in the water, fluid loss is the greatest risk to a swimmer’s performance. Warm and humid air temperatures further increase the risk.  Maintain adequate fluid status by consuming fluids (water, sport drinks, 100% fruit juices, smoothies, soups, and fruits) before, during and after exercise.

Kathleen Woolf, registered dietitian, Splash Magazine