6 Misconceptions about Nutrition & Performance in Endurance Sports

6 Misconceptions about Nutrition & Performance in Endurance Sports

10 December 2019

By: Paula Mrowczynski; RD, CSSD, MED 

Hello Everyone! My name is Paula Mrowczynski (Mrow-chin-ski)-Hernandez. I am a Registered Dietitian and Certified Specialist in Sports Dietetics/Sports Dietitian as well as a Newton Running Ambassador (2019). I work with various athletes to help them improve their nutritional intake and help them achieve their performance goals as well as overall health.

Newton Running and I thought it would be a good idea to discuss some of the misconceptions in nutrition and Endurance sports we often see and discuss with my clients. 

1) Lighter or lower body weight = faster runner or triathlete. 

Actually focusing too much on achieving  a lower body weight, restricting or not eating enough to support training and daily activities can lead to decreased performance and injuries! If an athlete is losing weight quickly and not eating enough energy or nutrition this can lead to low energy availability or Relative Energy Deficiency in Sport (RED-S). Low energy availability occurs when an athlete’s energy intake is much less than the energy the athletes is expending during their training and daily physical activities. This mismatch in energy intake can lead to many potential performance consequences such as:

●       decreased performance

●       decreased coordination

●       decreased endurance

●        decreased muscle strength

●       decreased training response

●       increased irritability

●       increased risk of injury

●       increased illness

●       depression

●       impaired judgement

It is true that some athletes may see benefits from making healthy changes to their diet by decreasing intake of excessive high fat foods or fried foods or foods/fluids with large amounts of added sugars; however being obsessive about only having certain foods or restricting certain food groups or macronutrients (protein, fat and carbohydrates)  can lead to low energy availability. A well fueled athlete is more likely to see performance gains than an athlete restricting or in a state of low energy availability.

2) The more (vitamins/antioxidants) the better!

Actually taking too many supplements/antioxidants has been shown to inhibit training adaptations. Some athletes believe that because they are participating in long distance endurance exercise thus causing stress on their body and producing free radicals, that taking supplements such as antioxidants (vitamin C and E)  will help with recovery.  Actually studies have shown that taking megadoses of supplements such as antioxidants may blunt or inhibit the training adaptations. Eating food that naturally has vitamins and antioxidants throughout the day with meals and snacks is more beneficial than popping pills!  Having a well balanced diet that includes various fruits, vegetables, protein sources, dairy and grains is more beneficial to overall health, recovery and training adaptations than taking a supplement.

3) Carbohydrates and sugar are bad or should be restricted.

Actually carbohydrates are found in many nutritious foods and can  help improve athletic performance! Carbohydrates are stored in our muscles and liver and help provide our bodies with fuel when we are increasing our speed as well as running long distances.  Our bodies have a finite amount of carbohydrates they can store. When our bodies start to deplete their carbohydrate stores, performance may decrease. Restricting carbohydrates can leave a runner feeling low in energy, fatigued  and decrease their overall performance.

Carbohydrates are found in fruits, vegetables, grains, starch and dairy as well as  sugar, honey, syrups, sodas, juices, sweets and desserts. Eating or drinking excessive amounts of processed sugars can be unhealthy, however these forms of sugar and carbohydrates can have a place in a runner’s diet and can provide quick energy and actually enhance a runner’s performance. Not all athletes can tolerate whole foods or fruits during long runs or high intensity runs. Sports nutrition products or simple forms of sugar and carbohydrates serve as a good energy source for some runners and is tolerated well.

Including balanced meals and snacks that include grains, starch, fruit, vegetables and dairy can help with having good energy, overall health and performance benefits.

 Every runner is different and may benefit from different forms of sugar or carbohydrates. Some runners do better having lower fiber foods such as crackers, white rice or bread while other athletes can have fruits, whole grains or legumes. During runs or endurance exercise carbohydrate sources that are easy to digest and quickly absorbed are preferred and this is when different forms of sugar or added sugars may be beneficial and have performance improvements for athletes.  Some runners can tolerate eating food or  fruits such as dates or bananas when running while while other runners do better using sports nutrition products made with sugar such as glucose, fructose, honey or maple syrup. There are many different forms of carbohydrates and fuel that can be taken during runs. Each runner should practice fueling and hydrating during their runs to find what carbohydrate or fuel sources work best for them.

4) Fats are bad or will make you fat.

Fat is actually found in many different forms of food and food groups and has many health benefits. Food sources that include omega 3s, unsaturated and saturated fats can be very beneficial to the over health, fueling and strength of an athlete! Fat is responsible for satiety, vitamin absorption, immune and nerve cell function as well as energy. Food sources of fats include nuts, seeds, olives, coconuts, vegetable oils, avocado, fish and animal food sources. There are also man-made fat sources such as trans fatty acids (TFAs) or hydrogenated oils. These are usually found in foods such as pastries, cookies, donuts, chips or fried foods that can last a long time on the shelf or freezer. TFAs (transfats) are the types of fats that may have harmful effects on our overall health when consumed in large amounts often. Balancing meals with fat sources from a variety of food groups is healthy and beneficial for overall health and energy.

5) Protein sources are only important for muscles or muscle building.

Protein rich foods are important for maintaining lean muscle mass, recovery as well as hormones, antibodies and enzymes. Protein is found in many various foods and food groups. You can find protein in egg, beans, meat, fish, chicken, soy, tofu, dairy, grains, nuts and seeds. Athletes and older adults need more protein spaced out evenly throughout the day to maintain and gain lean muscle mass. Protein also helps with satiety, immunity, energy, healing and recovery. It is beneficial to include high quality protein food sources with each meal every 3-5 hours. Many athletes benefit from having 20-30 grams of protein per meal (examples: 3 eggs or 1 cup of Greek yogurt or 1.5 cups of cooked beans or lentils). Including a variety of protein sources also provides the body with vitamins and minerals such as B12, iron and zinc, which can be important for optimal sports performance.

6) For long runs hydrating with sugar free fluids or water are best for hydration.

For endurance activities lasting more than 60 minutes or intense training or in humid/hot temperatures, fluids with electrolytes and a small amount of carbohydrates are most beneficial for adequate hydration. If you are sweating a lot or running for a long time you are losing fluid, electrolytes (sodium and potassium -mostly). For adequate hydration it is best to have a sports drink that has a low level of carbohydrates/sugar (3-8%) and sodium and potassium to help with fluid retention. Sports drinks help to replenish and hydrate well because they have electrolytes and sugar or carbohydrates to help your body with replacing lost fluid. For shorter runs or runs in cooler temperatures water or sugar free fluids may be appropriate. However, sugar free fluids are those with artificial sweeteners may not digest well for some individuals and cause GI distress.

Paula Mrowczynski racing in Newtons


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