Endurance Athletes: Dietary Recommendations
by Melinda Burris Willms
It is not uncommon to find conflicting information on the type of diet and nutritional regimen that is most effective for athletes seeking to optimize their general health and elevate their performance in competition. This article examines this question through analysis of recent scientific investigations into the best approach not only to diet but also the timing of nutritional intake for competitive athletes.
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[/am4guest][am4show have=’g5;’]It is accepted fact among serious athletes, coaches, and trainers that what you take into your body prior to workouts or competition, during the exercise, and for recovery once the exercise is complete is paramount in maintaining peak physical and mental conditioning. However, a 2016 scholarly literature review conducted by Carlsohn reveals that “obsolete recommendations and dietary myths are still widespread among recreational and elite athletes, coaches and health care professionals” in regard to best practices for dietary and hydration needs.1
Carlsohn’s research highlights the fact that nutritional and hydration requirements vary depending on the level of athletic exercise and specifically, the total energy expenditure (TEE) required. In essence, the more energy used, the higher the nutritional and hydration needs of the participating athlete to refuel and rehydrate the body. Obviously, elite athletes are going to expend more energy than recreational athletes who will exert energy at a higher rate than the general public. The primary takeaway from Carlsohn’s research is that endurance athletes must customize their dietary plans to meet their individual energy requirements.1
Some general guidelines apply: the amount of energy available should never go below 30-45kcal/kg fat-free mass/d. The need for carbohydrates (the body’s primary source of fuel) fluctuates between 3-5g/kg/d when participating in low-intensity exercise to a high of 8-12g/kg/d for athletes taking part in high-intensity training or competition over an extended period of time. Examining protein needs provides insight into how the nutritional needs of athletes classified as “elite” differs from those of the general public. Elite athletes require double the amount of protein in their diets than what is needed for individuals who are not physically active or are recreational athletes.1
FACTORS THAT IMPACT THE NUTRITIONAL NEEDS OF HIGH-ENDURANCE ATHLETES
The dietary needs of high-endurance athletes fluctuates based on multiple factors including the type of sport engaged in, the individual person and their bodily requirements, and the physical demands being placed on the athlete in their present training regime. Likewise, calculations of total energy expenditure (TEE) for athletes involved in high-endurance sports will vary depending on the individual’s body mass, their body type and makeup, age, gender, activities engaged in when not training, and the type of exercise, regularity, intervals, and intensity level required to complete that exact form of exercise.1
SPECIFIC RECOMMENDATIONS FOR PROTEIN AND CARBOHYDRATE INTAKE FOR COMPETITIVE ATHLETES
Athletes who are classified as competitive but not elite (professional, Olympic) require varying amounts of carbohydrates depending on their level of exercise. Competitive athletes engaged in moderate or high-intensity exercise at a regular rate of between one and three hours daily require 6-10g/kg/d. In contrast, competitive athletes who train for longer periods or at increased levels of intensity for four to five hours daily need 8-12g/kg/d. Carbohydrate intake should be increased prior to competition that is sustained for more than an hour and a half at a rate of 10-12g/kg/d in the 36-48 hours immediately prior to competition. This increase in carbohydrate intake in the hours leading up to competition is commonly known as “carbohydrate loading.”1 For athletes in competition, training at a moderate level of intensity at a rate of four to five times each week for 45-60 minutes per workout, protein requirements range from1.2-1.4g/kg/d.1
RECOMMENDED DAILY ALLOWANCES FOR ATHLETES
Carlsohn points to recent research demonstrating that the recommended daily allowances (RDA) for the general public are not adequate to meet the demands of competitive athletes. The exception to this rule is iron requirements, which remains consistent. It is important that Carlsohn notes recent trends claiming that competitive athletes need to supplement their intake of vitamins C and E in response to “exercise-induced production of re-active oxygen species.”1 Carlsohn warns that no scientific data supports the theory that such peripheral deficiencies significantly impact general health or performance levels.1 In fact, the scientific study discussed below suggests that vitamin C and E supplementation can actually impede training and negatively impact performance.
THE NEGATIVE IMPACT OF VITAMIN C AND E SUPPLEMENTATION ON STRENGTH TRAINING
A 2014 investigative study examined how supplementation with vitamin C and E affected acute response rates and variations of strength training in recreational athletes. The study involved 32 participants, make and female, who met the classification of recreational athletes experienced in strength training. A control group was selected at random and given 1000 mg/day of vitamin C and 235 mg/day of vitamin E. The second group received a placebo and the study was conducted over a ten-week period. Over the course of the study, all subjects participated in heavy-load resistance exercise at a frequency of 4x/week. To compare muscle growth between the two groups, researchers collected biopsies from a thigh muscle, the m. vastus lateralis, and compared results of a 1 repetition maximum (1RM), observations of “maximal isometric voluntary contraction force, body composition”, and measurements of muscle cross-sectional area, which was determined through the use of magnetic resonance imaging (MRI) prior to and after completion of the study.2 The research concluded that vitamin C and E supplementation was not effective in increasing muscle mass. In fact, the study showed that supplementation with the vitamins actually hindered strength increase training involving the biceps curl. The final study findings observed that supplementation with vitamin C and E demonstrated a possible long-term negative impact on the athletes’ ability to adjust to strength training.2
CONCLUSION
Current research shows that athletes have elevated needs for certain nutrients based on the intensity and frequency of the exercise in which they participate. However, the findings of the scientific study into the effects of supplementation with vitamin C and E offers a caution against increasing recommended daily allowances (RDA) for nutrients when it is not necessary.
References
- Carlsohn A. Recent Nutritional Guidelines for Endurance Athletes. 2016.
- Paulsen, G. et al. Vitamin C and E supplementation alters protein signaling after a strength training session, but not muscle growth during 10 weeks of training. 2014.
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