The goal of proper diet during endurance training is to promote recovery of damaged muscle tissue that results from training, replenishment of energy stores for the next training session, and most importantly, the promotion of new muscle growth. To accomplish all of these things, it is essential the diet be balanced, and attentive to the body’s needs.
For all of the processes above, our body uses energy measured in calories. The intake of carbohydrate, fat and protein are our main sources of calories. Especially now, with so much attention on low carbohydrate diets, it is important to realize the population those diets apply to. To promote optimized performance and recovery of the body in endurance athletes, all three nutrients are beneficial. Carbohydrate, which is found in foods such as grains, breads, pastas, fruits, starchy vegetables, and dairy, are what we consider active fuel. During physical activity your body increases reliance on carbohydrate, in turn becoming less reliant on fat. Carbohydrate fuels the muscles so they can continue to contract under stress. Since they are our dominant form of energy during activity, intake of these foods should increase as exercise intensity and duration increase. This is very important for marathon and half-marathon runners, who should be eating far more carbohydrates on their long run training day compared to a day with little to no running.
Carbohydrate during races can also be necessary. We can only store a small amount of carbohydrate in the muscle and liver for use during activity. As soon as these reserves run out, the body will “Hit a Wall”. To maintain performance during a long distance race (longer than 90 minutes), intake of simple carbohydrate is needed to maintain blood sugar, preserve energy stores in the muscle, and continue delivery of fuel traveling to the brain. Foods such as fruit, dried fruit, sports drinks, gels, sports beans, and even dry cereals and pretzels are often used to keep energy levels high during the race. My favorite is dried apricots. Only 5 are needed for 25g of Carbohydrate. Not only are they convenient to carry, they are not overly sweet or sour. This convenient, neutral tasting source is the ideal combination for use during an event. Rule of thumb: pack what pleases your tongue and your stomach!
While carbohydrate is often the limiting factor during exercise due to the small reserves, fat remains a dominant fuel during low- to moderate-intensity activities. While the typical person has enough fat stored to run over 500 miles without stopping, it is still vital to keep fats in the diet. Aside from energy, fat is used in the body to create and balance hormones as well as maintain skin and other organs. Sources of fat include nuts, seeds, oils, avocado, olives, meat, dairy and fish. It is best to include a variety of sources throughout the day, as different fats are needed for many of the bodily processes. Personally, I use nuts, avocado and fish as my primary sources, and rotate canola oil, coconut oil, and olive oil in my cooking to find the right balance.
While protein is also a calorie containing nutrient, it is quite different than our first two. In an appropriately fed athlete, protein is rarely used for energy. It is often considered a secondary energy source, as our body only resorts to it when it lacks carbohydrate or fat. The importance of protein is less for energy and more for recovery of the body. Protein is used to repair damaged muscle tissue, create new muscle tissue, and maintain balance of hormones and other systems. There should be a protein source at most meals, especially those following training and in the evening. The most common protein foods include meat, poultry and fish, with other sources including nuts, beans, lentils, dairy, soy products, and whole grains.
Aside from the increase in macronutrient intake, the body of someone exposed to the stress of endurance training also needs adequate intake of vitamins and minerals. While most of these needs do not increase, it is more important than ever to make sure they are present in the diet. Including dark green vegetables such as broccoli, spinach and kale in the diet frequently, along with the other colors of fruits and vegetables, nuts, grains, and meat, is a great way to ensure proper intake of these nutrients. Many will use a multivitamin to cover these needs. There is no direct need for a multivitamin in a diet that is properly balanced, but in clients with inconsistent intake of vegetables, or without access to a Registered Dietitian, they can serve as an insurance policy for your micronutrients. The diet should always be the first source, but if the first line misses some nutrients, you have a way to cover your bases.
Hydration is the final and often most under-represented category for nutrition during training. Water, sodium, potassium and chloride intake are invaluable for proper function of muscles, including the heart. An active female should have at least 90oz of fluid per day, and a male should have at least 125oz per day. The values are conservative and will be low for most runners on days with long runs. I encourage all of you running to start drinking these amounts daily, with extra water added on training days. Sodium is usually not an issue for residents of United States, but its partner Potassium has a tendency to be low. Oranges, bananas and avocado are all great sources of potassium, with dairy, dark greens and other produce assisting to achieve an optimum intake.
More information about hydration and intake for performance will be provided closer to race day. For more information about these topics during training, I encourage you to contact a Registered Dietitian in the area. Not only can an RD help create a plan for specific nutrients you might be underconsuming, they can also help you find sources of foods that are convenient, taste great, and effectively fuel your body!