Glucose the simple sugar, from carbohydrate is the body’s preferred fuel for muscles during prolonged exercise. Glucose is stored in the muscles and liver as glycogen and converted to glucose when needed. There is a limited supply of glycogen in the body and most people will experience a complete depletion after 90 minutes, so it’s important to refuel stores during sessions over 90 minutes duration. See Race Day Nutrition
Fats are also a great source of fuel as they are the densest form of energy available to us (9kCal/g) and our bodies store them in far greater abundance than glycogen in our fat tissue or adipose tissue. In endurance sports, the body uses both carbohydrate and fats as fuel. Low fat consumption can result in fatigue by reducing the activity and production of fat burning enzymes, meaning you won’t use your fat supplies efficiently, in other words, lessening endurance.
Protein, in particular, the building blocks of protein – amino acids; are essential for muscle function, synthesis and repair. Runners need adequate protein to help muscle tissue recover from the damage caused by training. Animal protein, such as eggs, meat, dairy etc. contain all essential amino acids (the amino acids we can’t create ourselves); plant protein will be missing one or two, although soya and quinoa are plant proteins which contain all of the essential amino acids.
Hydration, hydration, hydration! Water will be your best friend during runs and is critical for replacing lost fluid from sweating, which is how your body cools itself. Topping up water levels while you run will help with performance by keeping blood volume stable. You’ll also lose salts in sweat called electrolytes, mainly sodium, potassium and magnesium, so drinking an electrolyte drink is a good idea on longer runs and on hot days.
Calcium is one of the most important minerals we need in our bodies. It has many functions, the most commonly thought of association is with bone density. The good news is that weight bearing exercise such as jogging and running has a positive effect on bone mass. Calcium also plays a critical role in the muscle contacting and relaxing through the nerve impulses from the brain. So, to have optimum muscle and nerve function as well as healthy bones, make sure to have calcium in your diet.
Iron is one of the most important minerals consumed by athletes. Regular intensive workouts can decrease your iron stores in the body, which can result in iron deficiency anaemia, a condition that impairs the body’s ability to transport oxygen. Iron is also lost through sweating and foot strike hemolysis, which is caused by repeated pounding of the feet on hard surfaces, destroying red blood cells, which causes iron losses. Iron is involved in many processes in the body, including the formation of red blood cells; oxygen and carbon dioxide transport and is also involved in energy production. Iron cannot be produced in the body, therefore, it must be supplied by the food we eat. Haem iron, which is easily absorbed, is found in animal sources particularly in lean red meat, such as beef, liver, pork, poultry and seafood. Non-haem iron is found in plant-based sources, such as cereal grains, nuts and certain green vegetables and is not as easily absorbed as haem iron. Vitamin C helps the absorption of iron from plant sources so, if you’re vegetarian, be mindful of the relationship.
Zinc is a trace element found in all tissues and fluids in the body. It is very important in enhancing a person’s immune function, by reducing the risk of the common cold and infectious diseases. It also has roles associated with growth and development, healing wounds and enhancing senses. Foods rich in zinc include beef, lamb, spinach, nuts and mushrooms, with the RDA for both males and females is 15mg/day
Magnesium also plays a role in muscle and nerve function and the creation of ATP (the energy currency which causes muscles to fire) and is also an electrolyte, which we mentioned in the water section. Low blood levels of magnesium can result in muscle fatigue. Sources of magnesium are dark green leafy vegetables, nuts, seeds and fish.
Sodium is also an electrolyte that works within the body to balance fluid levels. It transports nutrients into cells and also plays a role in muscle and nerve function. It is rare to see a sodium deficiency but loss of sodium through sweating and replacing fluid without replacing sodium can lead to too much fluid in your body, which is just as dangerous as too little. Using a sodium enriched drink during long (>1 hour) sessions is advisable.
Potassium is the third electrolyte that is critical for water/fluid balance in our bodies and in particular within our cells. It also plays an important role alongside Calcium in muscle contraction and a loss of potassium can result in fatigue. A popular snack food for runners is a banana, which is a great source of potassium, as are potatoes.
Vitamin B1 Thiamin, B2 Riboflavin, B3 Niacin, B5 Pantothenic, B6 Pyridoxin, B7 Biotin, B9 Folate and B12 all play a role in energy metabolism, which is what you need as an endurance runner. These nutrients help the release of energy from carbohydrates, proteins and fats, folate plays an important role in cell division and red blood cell production, which is how we transport oxygen, so you see, from an endurance runner perspective, these vitamins are pretty important.
Antioxidants play a very important role for your diet, particularly if you exercise frequently. They are vitamins minerals and enzymes, which can be either consumed or naturally produced by the body. The main role of antioxidants is to protect the body’s cells from the effects of free radicals. These are molecules produced as a by-product of energy production. Therefore, the amount of free radicals increases during periods of exercise. Free radicals can lead to oxidative stress, which strains muscle tissues, and can play a role in many diseases, such as cancer and heart-related diseases. By adding an intake of antioxidants to your diet, muscle damage and fatigue can be prevented, and can improve aerobic capacity after intense training sessions.
The best way to ensure you eat enough antioxidants, is to eat a wide variety of foods in a healthy, balanced diet. The best sources of antioxidants can be found in berries, dark, green, leafy vegetables, nuts, green tea and even dark chocolate!
Vitamin D plays a critical role in the absorption of calcium, so it is usually added to dairy products to aid absorption. Living in the northerly latitude of Ireland, Vitamin D deficiency is quite common. This important nutrient is actually a hormone and is synthesised by our skin through UV rays. Given that we don’t see the sun that often and when we do, we use sunscreen, it’s easy to see why we can be deficient. Vitamin D is not only beneficial for the absorption of calcium and bone health, more and more research is demonstrating its powerful effect on immunity and preventing illness. Good dietary sources of Vitamin D are eggs, oily fish and fortified dairy foods.
Nitrates are becoming increasingly popular for endurance athletes. These are ions, containing nitrogen and oxygen, which can either be produced in the body or ingested. Their consumption has grown interest in athletes, as studies have reported that they can be used as a potential aid to enhance exercise performance. Even small amounts digested have been shown to increase plasma nitrite/nitrate levels, and reduces the amount of oxygen lost during exercise. It has also been reported that nitrate consumption can aid to treat individuals with high blood pressure and oxidative stress. Vegetables, such as celery, beetroot, spinach and rocket have a large nitrate content of over 2,500mg per kg, which can be added to a wide variety of meals.