Welcome to the Sports Nutrition module in the Goldring Center for Culinary Medicine continuing medical education series.

For most people, a balanced diet is sufficient to provide the nutrients needed to sustain a regular exercise program but for endurance athletes more rigorous attention to nutrition is key to performance.

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The goals for nutrition in sports include:

Better performance, energy, endurance, and strength

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Achieving desired body type (increasing muscle mass and flexibility, meeting weight requirements, decreasing fat mass)

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Adequate and balanced nutrient intake (calories, carbohydrates, protein, fat)

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And minimizing fluid and electrolyte imbalances

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Specialized diets, with varying quantities of carbohydrates, protein, and fat, are usually tailored to individuals with specific performance goals.

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It is important to characterize the types of activities your patients are engaging in when making specific sports nutrition recommendations

Strength vs. Endurance exercise; Examples of strength sports include weight lifting, track and field (javelin throw, shot put) and sports that involve resistance training. Endurance exercise is what we think of for marathon runners, cross country skiers, Ironman competitors. Power sports usually combine both strength and endurance and involve team sports (football, soccer, basketball, tennis).

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The other two considerations are whether the athlete participates in Consistent vs. Intermittent activity

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And determination of their Training cycles to tailor nutrition to pre-competition vs. post-competition recovery.

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In order to make nutrition recommendations, it helps to know how athletes utilize different energy sources.

Movement, sports, and exercise are performed with force generated by skeletal muscle. There are three muscle fiber types are differentiated by their shortening velocity, metabolic profile, fatigability – which affects their predominance in different sports. Slow twitch muscle fibers use oxidative metabolism. That is, they use oxygen to generate ATP and can be used over long periods of time without fatiguing, as long as oxygen is being replenished from the environment. Note that several pathologic processes can diminish exercise capacity by decreasing amount or efficiency with which oxygen is delivered to the muscles.

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Fast twitch fibers use glycolytic (or anaerobic metabolism) to extract energy from carbohydrates – whether dietary or endogenous stores.

As a result, muscle glycogen decreases and lactic acid increases, which leads to muscle fatigue. These fibers are predominant in exercise that requires short bursts of strength or speed (as is often seen in team and power sports).

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Normally, we have about 50/50 ratio of slow to fast twitch muscle fibers. With specific training exercises, this distribution can change.

Endurance exercise causes a shift towards muscle fibers with greater oxidative capacity, while resistance exercise produces more muscle fiber hypertrophy. There is little research to support dietary effects on muscle fiber types.

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Increased anaerobic metabolism (when the cardiovascular system is unable to provide sufficient oxygen) produces lactic acid.

Acidification of the muscle environment impairs enzyme activity and muscle function.

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The intake of protein and carbohydrates within a certain window (usually 1 hour) post-exercise has been shown to enhance muscle protein synthesis as well as inhibit muscle protein breakdown.

The mechanisms are thought to involve provision of amino acids as well as the inhibitory effect of insulin on muscle protein breakdown.

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VO2 Max is calculated by the Fick equation as an estimation of the amount of oxygen delivered to and extracted by the skeletal muscle during exercise. This value is higher in trained athletes than in sedentary individuals due to both higher cardiac output (stroke volume x heart rate) as well as increased efficiency of oxygen extraction from arterial blood. Patients with lung disease, heart disease, and peripheral vascular disease have a low VO2 max. Increases in aerobic fitness is associated with a decrease in death from all causes. Understanding basic principles of exercise physiology is important for sports nutrition and determining the best sources for energy. Note that carbohydrates are the primary fuel for exercise intensities that are above 75% of VO2 max and are utilized in both aerobic (oxidative) and anaerobic (glycolytic) metabolism. Fat, in contrast, is utilized exclusively in oxidative metabolism. Works Referenced Atherton PJ and Smith K. Muscle protein synthesis in response to nutrition and exercise. Journal of Physiology 2012;590.5:1049-1057.

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Body composition includes water, protein, minerals, and fat.

There is no optimal value for body composition, lean body mass, or body fat percentage for any sport. Body mass index can be misleading and considering the two compartment model can help.

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Body fat can be divided into:

Essential fat, that which is necessary for normal bodily function. This is higher in women than in men.

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And storage fat that is found around internal organs and subcutaneously. This functions to provide cushion protection and insulate against heat loss.

Body fat ranges for optimal health (18-30% for women and 10-25% for men).

Optimal values are lower for athletes and those engaged in performance sports and exercise.

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Lean body mass measurements are used to determine ideal weight and subsequent caloric needs.

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Most methods for calculating lean body mass have at least a 3-4% margin of error when measuring body composition.

Skinfold Measurements are inexpensive but are dependent upon both the user and caliper accuracy.

Ideally measurements should be taken from 3-5 sites on the right side of the body (biceps, triceps, subscapular, suprailiac, abdominal)

Other measures are expensive and stationary as well as offering a wide range of accuracy.

Moon JR. Body composition in athletes and sports nutrition: an examination of the bioimpedance analysis technique. European Journal of Clinical Nutrition 2013;67:S54-S59.

*NOTE on BIA: BIA machines are actually inexpensive, not expensive compared to other machines such as Bod Pods. BIA is familiar in the

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The NATA Statement of Safe Weight Loss and Maintenance has a good review of the calculations and how Lean Body Mass, Basal Metabolic Rate, and Caloric Needs are determined.

Molnar D, Jeges S, Erhardt E, and Schutz Y. Measured and predicted resting metabolic rate in obese and nonobese adolescents. The Journal of Pediatrics 1995;127(4):571-577.

Thompson J, Manore MM. Predicted and measured resting metabolic rate of male and female endurance athletes. Journal of the American Dietetic Association 1996;96(1):30-34.

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Basal Energy Expenditure from the harris benedict equation is multiplied an activity factor to determine caloric needs.

Activity factor ranges from 1 to 2.2 for baseline needs and it is key to add the calories burned during exercise to determine nutrition needs during athletic activity.

BEE x AF = TEE or total energy exposure, i.e. the total calories burned in a day. If a person needs to gain weight or is hypermetabolic due to disease or injury, then a ‘stress factor’ can be added too. BEE x (AF+SF) = TEE

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For the general population, the daily CHO/PRO/FAT requirements are:

-CHO 5-7 g/kg of body weight

-PRO 0.8-1 g/kg of body weight

-FAT 15-35% of total daily caloric intake

Remember that protein intake can affect muscle protein synthesis and recovery.

Also, endurance athletes reach higher VO2 max values, utilize more Type I muscle fibers, and engage in aerobic metabolism – carbohydrate supplementation is also needed to prevent depletion of muscle glycogen stores and subsequent fatigue.

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Protein requirements are generally greater for athletes at up to 1 gram per kilogram per day. In endurance or power athletes the need is even higher.

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The amount of proteins in plant foods may not be enough. Plant proteins are generally less digestible than animal proteins. However, there is no evidence to support recommendations for separate protein requirement for vegetarians who consume complementary mixes of plant proteins.

On the other hand, overconsumption of protein is common, especially in power athletes especially in the form of protein supplements (whey powder, etc.) can result in up to 4 times the daily recommendations. Excessive intake can lead to kidney stones, dehydration, and generally decreased performance.

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Daily requirements for carbohydrates vary by on the intensity of exercise and recovery after intense exercise is an important part of planning in sports nutrition.

Sources of carbohydrates vary widely with athletes consuming sports drinks, gels and other convenient products. The quality varies widely and the source and quantity can lead to GI distress.

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Current recommendations suggest that dietary should be between 35 percent of energy intake, however, may be a lower percentage on exercise or recovery days when carbohydrate requirements increase.

Few studies support deviation from this percentage for ergogenic or sports performance related purposes. There is evidence to show that the types of fat consumed can affect health and well-being.

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Athletes have special needs and considerations regarding dietary fat.

Because fat is high in calories, it is an important energy source and can help with glycogen sparing as well as prevention of fatigue.

Making smart fat choices can also affect joint and soft tissue inflammation, important for injury and recovery in sports.

Diets high in saturated fats and trans fat have been associated with increased heart disease risk and inflammation.

Western diets also tend to be too high in linoleic (omega-6) fatty acids.

When making decisions about fat choices, the ratios of fats is more important.

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Exercise in all but especially hot conditions leads to increased demand for evaporative heat loss, increased sweat secretion, and subsequent hypo-hydration and dehydration.

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Note that self-selected hydration strategies (e.g. hydration ad libitum) does NOT result in adequate hydration even during low-intensity exercise.

Fluids for rehydration include water and supplemented sports drinks. Rehydration with only water in the context of electrolyte losses may lead to hyponatremia.

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Heat illness is a leading cause of death and disability among US high school athletes (highest among football players and during the month of August – primetime for preseason sports training).

Note that obesity is a risk factor for heat illness because fat decreases heat loss.

It is key to share the warning signs of dehydration with your patients during every sports nutrition consultation.

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For you patient who is the weekend warrior or exercises moderately there is no reason to make significant change in their diets.

They do not need sports drinks and a good rule of thumb is to recommend Gatorade and the like only for vigorous exercise that lasts for greater than 90 minutes.

The routine athlete should not deviate significantly from standard protein requirements of 0.8 g/kg/day. The standard American diet often exceeds this protein requirement.

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There is a tremendous amount of mis-information in the athletic world and many fad diets without significant foundation in science can impede performance.

The paleo diet, for example, restricts quality complex carbohydrates with out sufficient evidence of any potential boost in performance. Likewise the amounts of excess proteins is both unnecessary for most athletes as well as potentially harmful.

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Likewise, carbo-loading the night before an event is not necessary as many endurance athletes believe and a more sustained and balanced approach optimizes performance.

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Devotees of protein supplements often take much more than the recommended dosage – sometimes as much as 6x the recommended amount. Protein manufacturers use this habit to their advantage, and recommend a larger than necessary serving size; the increased rate of use means supplements are bought more frequently, and jugs of powder can cost $70!

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Creatine is a chemical normally found in the body, mostly in skeletal muscles where it functions in metabolism in the resynthesis of ATP.

It is endogenously produced in the body and consumed through the omnivore diet, especially fish and meats   Many athletes consume creatine as supplementation since studies have shown a positive relationship between muscle creatine uptake and exercise performance. The increase in creatine storage promotes faster regeneration of ATP and when combined with heavy resistance training, supplementation has been shown to lead to enhanced physical performance, greater fat free mass, and muscle hypertrophy. Some studies have also suggested that creatine supplementation can improves recovery from injury, muscle damage and oxidative stress induced by exercise. Dosing recommendations differ by protocol, but recent studies recommend 0.1g/kg body weight for best training adaptations at the cellular and sub-cellular level. Although studies have shown greater retention of creatine when simultaneously ingested with carbohydrates and/or protein, there has been no conclusive evidence of any further enhancement in performance

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There have been reports of renal damage secondary to creatine supplementation, however further history of these patients have revealed previous renal disease, concurrent nephrotoxic home medication, or use greater than the recommended amount. Although creatitine levels are raised, the increase is not significant to cause negative consequencs to renal function in a baseline healthy adult consuming the proper recommended dosage. Contrary to anecdotal claims, studies have shown creatine supplementation does not cause muscle cramp or injury.

Despite what we know about creatine supplementation, more research is still needed for different populations, different supplement forms, different dosing protocols and the effect in combination with other sports supplementations

Furthermore, recall that creatine is consumed from foods. Supplementation is not necessary, is a costly addition to your budget and holds risk of improper use

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Some physically active women are at risk for a group of symptoms known as the Female Athlete Triad. It is a combination of three conditions:

Disordered eating Amenorrhea Osteoporosis

Intentional under consumption of calories leading to health problems. This can occur both as a function of poor eating habits and as a function of too intense exercise. This in turn causes estrogen levels to drop. Athletes should be encouraged to think of food as fuel for performance. Consult with a Registered Dietitian can provide personalized recommendations for healthy weight and athletic performance.

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Hyperhydration is uncommon among athletes. Most reported cases are in the context of game show prizes or when employees try to flush out chemicals in their bodies in preparation for a random urine drug test.

Symptoms are secondary to the resulting hyponatremia and can be as minor as headaches and nausea.

However, at extremely low levels of sodium, patients can present with life threatening conditions such as seizures secondary to cerebral edema.

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This concludes the video lecture for this module.

Study guides, readings and the quiz are available online.

Thank you.

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