September 13, 2020
nutrition for athletes cover

Evidence-based Macronutrient Nutritional Considerations in the Athlete

Nutrition is a subject that should be important to every person, young or old, in order to have maximal functionality, health, and overall wellness. There are basic guidelines that should be followed regarding nutrition in terms of total caloric intake and division of diet into macronutrients which include predominantly carbohydrates, proteins, and fats. Along with the macronutrients, there are very important micronutrients, anti-oxidants, and vitamins that are essential for the human body. These requirements are absolutely essential for athletic success and needed in much higher quantities for athletes in comparison to the general public. In my experience working with many high-school aged athletes, the general trend is that our kids are not eating enough calories as well as not feeding their bodies with what they need for improved athletic performance, overall good health, and decreased injury risk. 

Kubik et al in 2009 reported a survey-based study of Minnesota area high school administration which showed trends of less policies regarding nutrition governing high schools than middle schools, more quality nutrition in private schools, and the use of foods high in fat and added sugars for fundraising activities (Kubik et al 2009). For the purposes of this review, we will only be discussing macronutrients. Future reviews will focus on micronutrients and other important aspects of dietary intake for athletic populations.
illustration of basic energy balance equation

Image 1. Illustration of basic energy balance equation (courtesy of awpnow.com)

There are many factors to consider in athletes when tailoring an individualized nutritional plan. The type of training, financial situation of the family, sex, specific sport of the athlete, weather conditions, genetics, stress levels, and premorbid medical conditions among others can all effect the metabolic intake and utilization of vital food resources for the athlete and should all be considered when advising athletes on dietary choices (Academy of Nutrition and Dietetics, Dieticians of Canada, and American College of Sports Medicine 2016 Position Statement). Basic dietary recommendations can be made by physicians and athletic trainers; however, it is recommended to consider referral to a sports nutritionist if the athlete is not making forward gains nutritionally after some basic recommendations.

Multiple methods have been utilized in the past to obtain data from athletes of what their diet entails and include measured food amounts for up to one week, food logs, 24 recall of foods, and cell phone applications such as myfitnesspal- all which have limitations on the accuracy of data provided (Deakin et al 2015). Additionally, nutritionists use mathematical equations to calculate energy balance using numbers considering the metabolic rate of the athlete, energy utilized, and the amount of food intaken. These are typically done using the Cunningham or Harris-Benedict equations (Cunningham et al 1980; Roza et al 1984). The details regarding the mathematics portion of these equations are beyond the scope of this review.

Carbohydrates are a vital source of energy for the athlete and are required in certain amounts for optimal athletic performance and overall energy during sports (Spriet LL,2014). Various fruits and whole grains are great, clean options for obtaining optimal amounts of carbohydrates. Additionally, carbohydrate stores are very sensitive to changes in dietary intake and change on nearly a daily basis (Spriet LL. 2014). Amounts of recommended carbohydrates are variable and change from daily athletic needs to various strategies for acute refueling after intense athletic performance or training. (Academy of Nutrition and Dietetics, Dieticians of Canada, and American College of Sports Medicine 2016 Position Statement). 

Typical recommendation ranges are in the 5-12 g/kg per day range with higher levels required for more intense, longer athletic endeavors (Academy of Nutrition and Dietetics, Dieticians of Canada, and American College of Sports Medicine 2016 Position Statement). Finally, for sports such as football and basketball where there are multiple aspects of quick movements followed by a short break it is recommended that the athlete intake 30-60 grams per hour of carbohydrate to optimize performance and body refueling with persons participating in ultra-marathons needing up to 90 grams per hour of competition (Spriet JJ 2014).

Image 2. Illustration of some examples of the three macronutrients (courtesy of avitahealth.org)

Finally, the last of the critical macronutrients are fats. Fats are also utilized as a fuel by the body and are used extensively by the body in athletes that are endurance competitors (Spriet 2014). As with proteins and carbohydrates, it is extremely important to tailor the amount of fats on an individualized basis for the athlete with recommendations that no more than 10% of energy should be obtained from saturated fats (Health Canada. Eating Well with Canada’s Food Guide). 

Approximately 20% of the diet has been recommended by various organizations historically such as the Institute of Medicine, Food and Nutrition Board due to literature suggesting lower values may impair the body’s ability to absorb other vital nutrients such as fatty acids and fat-soluable vitamins (Institute of Medicine, Food, and Nutrition Board 2005). Fat in excess has also been shown to impair utilization of carbohydrates as an energy source; therefore, making adherence to established guidelines important, although in some cases short periods of high fat diets may be beneficial (Burke 2015). Individualized sports may also require fat restriction depending on the athlete you are caring for, for example, in a bodybuilding athlete to reach aesthetic, body fat, and strength goals.

Nutrition is an incredibly important and often overlooked aspect of sports medicine, especially in our high school athletes. This is from a myriad of reasons that range from financial issues to medical conditions that predispose athletes to injury due to improper caloric and nutrient intake. Although many years of research have been completed regarding optimal nutrition of the athletic person, there is still much we do not know about nutrition in regards to optimizing performance, wellness, and overall health. 

Additionally, the importance of individualized sport-specific athlete plans should be utilized when possible and consultation with a sports nutritionist considered for optimal results. Further research efforts should be geared towards evaluating different protocols and the effects on the athlete’s biophysiological and sport performance profile. Meanwhile, specific guideline on both macro and micronutrients as well as vitamin supplementation are available from entities such as the Academy of Nutrition and Dietetics, American College of Sports Medicine, the International Olympic Committee, among others and should be utilized by sports medicine physicians to optimize athlete health, function, and wellness.

REFERENCES

Academy of Nutrition and Dietetics, Dieticians of Canada, and American College of Sports Medicine 2016 Position Statement: Nutrition and Athletic Performance
Burke LM. Re-examinaing high-fat diets for sports performance: Did we call “the nail in the coffin” too soon? Sports Med. 2015;45(1):33-49.
Beelen M, Burke LM et al. Nutritional strategies to promote postexercise recovery. Int Sport Nutr Exerc Metab. 2010;20(6):515-532.
Cunningham JJ. A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr. 1980;33(11):2372-2374.
Health Canada. Eating Well with Canada’s Food Guide. http://www.hc-sc.gc.ca/fn-an/food-guide-ailment/index-eng.php.
Josse et al. Body composition and strength changes in women with milk and resistance exercise. Med Sci Sports Exerc. 2010;42(6):1122-30.
Kubik et al. Food use in middle and high school fundraising: does policy support healthful practice? Results from a survey of Minnesota school principals. Am Diet Assoc. 2009 Jul; 109(7):1215-9.
Mettler S et al. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010;42(2):326-337
Phillips SM, Van Loon LJ. Dietary protein for athletes: From requirements to optimum adaptation. J Sports Sci. 2011;29(suppl 1):S29-38.
Phillips SM. Dietary protein requirements and adaptive advantages in athletes. Br J Nutr. 2012;108(suppl 2):S158-167.
Roza AM, Shizgal HM. The Harris – Benedict equations reevaluated: Resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-82.
Spriet LL. New insights into the interaction of carbohydrate and fat metabolism during exercise. Sports Med. 2014;44(suppl 1):S87-96.