By Katherine A. Beals, PhD, RD, FACSM, CSSD and Breanne Nalder, MS —
The word “protein” is derived from the Greek word, “proteos” meaning first and, when it comes to reputation of this macronutrient in the diets of athletes, the name seems to fit. Surveys assessing the nutrition knowledge of athletes often find that they believe protein is more important than either carbohydrate or fat in athletic performance. But, is protein deserving of this position on the pedestal of the athlete’s diet? In this month’s nutrition article—the first of a three-part series– we will take a look at the role of protein in cycling performance as well as protein recommendations for endurance athletes, considering the amount and timing of protein intake around training. In subsequent articles we will address the topics of meeting protein needs on a vegetarian diet and protein supplementation.
The Importance of Protein
Protein serves a number of structural and functional roles in the body. Structurally, protein is required for the synthesis of muscle tissue, tendons, ligaments, and even bone. Functionally, protein is involved in nutrient transport, endocrine control, immunity, and metabolic regulation. While protein can be used as fuel (i.e. ATP) to support muscular work, using protein for energy severely compromises its structural and functional roles.
Protein is comprised of amino acids. There are twenty amino acids that have biological significance- eleven are non-essential, meaning that the body can synthesize them, while nine are essential, meaning that the body cannot synthesize them and, thus, they must be consumed as part of the diet. The essential amino acids include leucine, isoleucine, valine, phenylalanine, tryptophan, threonine, histadine, methionine, and lysine.
Unlike carbohydrate and fat, which can be stored in the body for later use, there is no inert storage of protein in the body; rather, all of the protein in the body is functional (i.e., muscles, tendons, ligaments, transport proteins, hormones, bones are all carrying out functions). Thus, it is important that athletes consume an adequate amount of protein on a daily basis to support the multitude of structural and functional roles.
How Much Is Enough?
Some controversy exists regarding the amount of protein athletes need to consume on a daily basis; however, there is a significant body of research to suggest that athletes do require slightly more protein than their sedentary counterparts. The current recommendation for protein intake among adults is 0.8 grams per kilogram of body weight. Most sport nutrition experts recommend endurance athletes consume between 1.2-1.6 grams per kilogram of body weight. Exactly how much protein within this range an individual athlete needs depends on the intensity, duration, and frequency of training as well as the athlete’s training status. So long distance rides, intense interval workouts, and how often you train or race all contribute to higher protein needs.
It should be emphasized, however, that while protein requirements are likely higher for endurance athletes compared to sedentary individuals, dietary intake surveys reveal that the majority of endurance athletes either meet or exceed the current protein recommendations, so there is no need to go crazy to get large boluses of protein. In fact, our bodies can only process about 15-30g at a time (depending on body size and digestibility). Aim for adequate amounts of protein spaced among each of your meals and snacks throughout the day. Nonetheless, there are certain athletic populations such as female endurance athletes, vegetarians, weight-class athletes, or those restricting energy intakes that may be at risk for inadequate protein intakes.
How Much is too Much?
If the body has no place to “store” excess protein, then what happens if an athlete consumes too much protein? The answer to this question depends largely on the rest of the athlete’s diet. If the diet is excessive in protein but inadequate in carbohydrate, then some of the excess protein will be used to synthesize carbohydrate—a process known as gluconeogenesis (literally the making of new glucose). If the athlete is getting adequate carbohydrate then the excess protein will be converted to fat and stored (yes as body fat).
What likely won’t happen as a result of excess protein consumption is kidney damage or brittle bones. In fact, excessive protein intake will only cause kidney damage if the athlete already has compromised kidney function. And, research suggests that higher protein intakes actually result in greater peak bone mass among adolescents and may actually reduce the risk of osteoporosis and related fractures in older individuals. Indeed the only real concern regarding consuming too much protein is the impact on the rest of the athlete’s diet (crowding out other important macronutrients like carbohydrate) and, perhaps, his or her waistline (as protein consumed in excessive will be stored as body fat).
Is Timing Everything?
Research suggests that there is an anabolic window—approximately 1 hour prior to and/or after resistance training– during which protein should be consumed to optimize strength gains and muscle hypertrophy (increase in muscle mass). However, whether consuming protein prior to, during, and/or after endurance exercise is more advantageous remains unclear. Protein digestion is a fairly complicated process; thus, consuming protein along with carbohydrate before endurance exercise will likely only delay gastric emptying (the time for the food to leave the stomach) and intestinal absorption, which would NOT be beneficial for performance.
There is some research suggesting that consuming protein along with carbohydrate during endurance exercise may provide performance benefits over pure carbohydrate. However, a closer look at that research highlights some major flaws in the methodology. For one, the studies failed to use isocaloric drinks, meaning the protein + carbohydrate drinks contained more total calories than the carbohydrate drinks. In addition, the “performance” measure used was time to exhaustion (that is, the length of time the athlete could cycle or run until fatigue). In real life there are no events in which the winner is the one who cycles or runs as long as possible until fatigue. Rather the goal of most endurance events is to go a set distance as fast as you can. Studies that have used isocaloric drinks and have tried to mimic real-life endurance events, have found no endurance performance benefits when protein is added to a carbohydrate solution consumed during endurance exercise.
When it comes to post exercise, cyclists are advised to consume a recovery drink with protein (i.e., chocolate milk) to minimize muscle damage and speed recovery.
But, is there any research supporting a recovery benefit from consuming protein along with carbohydrate post endurance exercise? The research is somewhat mixed on this topic. Early studies seemed to indicate that protein based recovery drinks/chocolate milk were superior to carbohydrate only replacement beverages post exercise. However, once again, these studies suffered from flaws in the methodology, most notably not equalizing the calories of the recovery beverages. More recent research in which the calorie levels of the recovery beverages are matched, have found little benefit from the added protein (assuming that total carbohydrate and calories is sufficiently high). Still, there is no disadvantage to consuming some protein along with carbohydrate post exercise and it may be more palatable to the athlete.
Remember that if you have another workout or race within 24 hours of finishing a hard training bout, you have a 30-minute window to get your recovery nutrition according to your body size and the effort you just finished and replenish depleted glycogen and repair tissues. If you keep your tank well fueled, you will be more equipped to perform to your optimal abilities in your next ride or race!
Examples of foods to help achieve adequate protein needs
- Animal sources: meat, poultry, fish, eggs, diary
- Plant sources: beans, lentils, nuts, seeds, soy products, whole grains
|Foods||Serving Size||Protein (grams)|
|Black Beans||1/2 cup (4 oz)||8g|
|Canned Tuna||3 oz||21g|
|Chicken Breast||4 oz||34g|
|Clif Bar||1 whole||10g|
|Deli Turkey||4 oz||16g|
|Milk||1 cup (8 fl.oz)||8g|
|Peanut Butter||2 Tbsp (1 fl.oz)||9g|
|Plain Yogurt||1 cup (8 fl.oz)||9-14g|
|Quinoa||1 cup cooked||8g|
|Tofu||1/2 cup (4 fl.oz)||16g|
|Whole Wheat Bread||1 slice||4g|
Stay Tuned! Part 2 will cover protein needs for athletes on a vegetarian/vegan diet.
Breanne Nalder, MS recently completed her master’s degree in nutrition with an emphasis in sports dietetics at the University of Utah and is a competitive Category 2 cyclist. For personal nutrition coaching, you can reach Breanne at 801-550-0434 or [email protected]
Katherine Beals, PhD, RD, FACSM, CSSD is an associate professor (clinical) in the Division of Nutrition at the University of Utah. She is a registered dietitian, a certified specialist in sports dietetics and a fellow of the American College of Sports Medicine.