Functional medicine is experiencing an explosion in popularity due to its systems-based, personalized approach to treating disease. Where once we were forced to rely on pharmaceuticals to manage various disease symptoms, we now have the ability to look for and target the root causes. This type of medicine offers the hope of complete recovery for many, but it’s not limited to those with chronic, complex diseases. 

Functional medicine for athletic performance is becoming an attractive way to enhance and optimize physical function. A functional medicine approach focuses on the unique genetic, environmental, and lifestyle factors that affect an athlete's health and performance. Nutrition and lifestyle interventions are tailored to the individual to create a robust foundation for improving outcomes, preventing injuries and enhancing injury recovery, maintaining mental wellness, and supporting lifelong health. 

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Principles of Functional Medicine in Athletic Performance 

Performing at a high level as an athlete requires a body that works like a well-oiled machine. We’re living in a time when highly processed foods, stress, lack of sleep, and a ‘more is better’ attitude are commonplace. All of these factors can negatively influence an athlete’s ability to perform, as well as their long-term health—enter functional medicine.  

The principles of functional medicine in sports include viewing the athlete as unique and tailoring a plan based on the assessment of six core physiological processes:

• Assimilation (digestion, absorption, microbiota)
• Defense and repair (immune, inflammation, cellular renewal)
• Bioenergetics (mitochondrial function, cellular energy transport, tissue-specific energetics)
• Transport (cardiovascular, hematological, respiratory, and lymphatic functions)
• Communications (endocrine, neurotransmitters, signal transduction processes)
• Structural integrity (subcellular membrane barriers to musculoskeletal function

Functional medicine providers seek to prevent or address imbalances in these areas as a way to optimize an athlete’s physical function, mental wellness, and recovery. While all of these are vital, gut and hormone health are of the utmost importance when it comes to how an athlete performs. 

Gut Health and Athletic Performance 

Gut health in athletes can make or break physical and mental performance. Being able to create energy to consistently perform at a high level requires an athlete to not only consume nutritious foods but also to have the capability to digest and absorb nutrients from those foods. High level, this requires adequate digestive secretions like pancreatic enzymes, bile, and hydrochloric acid (which can be reduced in the context of high mental or physical stress), an intact intestinal barrier, and a balanced gut microbiome. Dysfunction in any of these areas can lead to malabsorption, fatigue, inflammation, poor immune system function, and mental health symptoms. In addition, gut health symptoms like gas, bloating, diarrhea, constipation, and pain can derail training.

A robust, diverse gut microbiome and athletic performance go hand-in-hand. Gut microbes help to maintain the health of the intestinal barrier to prevent leaky gut. Because they are subjected to high amounts of physical and mental stress, athletes are at an increased risk of gut barrier damage. The gut barrier helps the body decide what should be absorbed into the systemic circulation (like nutrients and fluid) and what should remain in the intestinal tract or exit the body in the stool. When this barrier becomes leaky (from dysbiosis, stress, toxins, food sensitivities, and inflammation), large food particles, microbes, and toxins can cross into the systemic circulation, triggering the immune system and upregulating body-wide inflammation. 

High levels of inflammation can increase fatigue, impair recovery, increase the risk of injury, and impact the mental health of athletes. Leaky gut is associated with sports injuries via altered immune responses in musculoskeletal tissues. Aside from maintaining gut barrier health, the gut microbiome also creates vitamins, neurotransmitters, and hormones, aids in calorie extraction from foods, protects against pathogens, modulates oxidative stress, and bolsters immune system function. 

Maintaining a healthy gut microbiome can be accomplished with a whole-food, nutrient-dense, anti-inflammatory diet, pre-and probiotics, adaptive training schedules that include adequate rest, routine stress management techniques, adequate hydration, and restorative sleep. 

Hormonal Balance and Sports Performance 

Hormones and athletic performance require a fine balance. After an exercise session there’s an increase in hormones like estradiol, testosterone, DHEA, and growth hormone to allow for adaptation, muscle growth, and better endurance. However, in the absence of adequate recovery and fuel, these hormonal elevations may be blunted. 

Cortisol is an important stress response hormone vital for exercise performance and recovery. Many athletes may have impaired hypothalamic-pituitary-adrenal (HPA) axis function related to inadequate recovery and excessive training. HPA-axis dysfunction contributes to altered cortisol regulation contributing to fatigue, reduced performance, and altered blood sugar control during exercise.

In female athletes, high-intensity exercise coupled with the lack of adequate recovery and insufficient fuel can reduce sex hormones like estrogen, progesterone, and testosterone and increase cortisol production. The result can be extreme fatigue, the inability to ovulate, and absent menstrual periods. Maintaining hormonal balance in athletes requires maintaining a healthy gut, practicing a daily stress management technique, adequate refueling, and prioritizing sleep.

Functional Medicine Testing for Athletes

Functional testing for athletes can help providers uncover the root causes of negative symptoms like fatigue and offer a way to better tailor nutrition and lifestyle recommendations for optimizing health and athletic outcomes. The following are some diagnostic tools to use in sports performance:

Comprehensive Metabolic Panel

The Comprehensive Metabolic Panel from Access Med Labs assesses an athlete's metabolism, kidney and liver function, electrolytes, blood sugar, and blood protein levels. This commonly run test can provide early warning signs of overtraining or poor recovery. 

Micronutrient Testing

The Micronutrient test from Spectracell Laboratories analyzes 31 vitamins, minerals, and other nutrients to provide an idea of an athlete’s nutrient status but also how well their body is utilizing nutrients. Identifying nutrient deficiencies allows the provider to further tailor meal plans and supplement recommendations. 

Comprehensive Gut Microbiome Testing

Poor gut health can result in nutrient malabsorption, increased levels of inflammation, leaky gut, and immune system dysfunction. In addition, if an athlete lacks adequate digestive secretions, it will be difficult to adequately absorb and utilize nutrients. The GI-MAP by Diagnostic Solutions uses qPCR technology to evaluate for the presence of pathogens, digestive function, microbial imbalances, inflammation, and immune system function. 

Comprehensive Hormone Testing

The Hormones Comprehensive Profile by Mosaic Diagnostics provides an assessment of sex and adrenal hormones, both of which can be impacted by undereating, overtraining, and inadequate recovery. Likewise, the Comprehensive Thyroid Assessment by Genova Diagnostics analyzes thyroid hormone metabolism to help determine if poor thyroid function could be limiting exercise capacity and endurance. 

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Nutritional Strategies for Enhanced Performance 

Nutrition is arguably one of the most impactful strategies for enhancing athletic performance; after all, nutrients allow your body to create adenosine triphosphate (ATP) to do the work. Dietary strategies for performance encompass the overall dietary pattern, pre- and post-workout feedings, and hydration. In addition, functional medicine providers should consider the high risk of disordered eating, especially among female athletes. 

Dietary Pattern for Athletes

There’s no single eating plan specifically for athletes, rather the diet needs to be personalized based on the type of athlete (i.e., endurance, strength, or speed) and the specific food intolerances or preferences of the individual. The following graphic depicts the many factors that impact an athlete’s food choices: 

In general, nutrition for athletes should include a whole-food, anti-inflammatory diet that includes adequate amounts of carbohydrates, fats, proteins, and micronutrients and ensures adequate hydration. 

Carbohydrates

Carbohydrates function as a main energy source and help to maintain blood glucose levels and maximize glycogen stores during and after exercise. Lack of adequate carbohydrates can lead to issues with endurance, fatigue, and muscle strength, as well as hormone creation and use. Carbohydrate needs vary but generally range from 2 grams per kilogram on light days to 10 g/kg on heavy training days or competition. Athletes may want to consume the following:

• 200– 300 grams of carbohydrates 3-4 hours before training or a competition
• 30–60 grams of carbohydrate (or 0.7g/kg body weight) during an event
• 1.0-1.5g/kg of carbohydrate after the event and every 2 hours for 4–6 hours.

Protein

Adequate protein intake is imperative for any type of athlete. Protein is critical for building and maintaining muscle mass, repair and recovery, and body composition. It’s also vital for the creation of hormones. Athletes should aim for 1.2–2.0 g/kg of protein spread evenly throughout the day. On training or competition days, consume the following:

• 0.3g/kg before 
• 0.25g/kg per hour (along with carbohydrate) during
• 0.3g/kg within 2 hours after

Fat

Healthy fats are an energy source; they allow for the absorption of various vitamins, and they assist in cell signaling and transport, as well as nerve function. While there aren’t specific recommendations for fat intake, it’s best for athletes to consume at least 20 percent of their calories each day from fat, being mindful to avoid high-fat, low-carbohydrate diets that tend to restrict the ability to train at high intensities. Lower intakes of fat may increase the risk of vitamin and essential fatty acid deficiency. Depending on tolerance, some athletes may want to limit fat immediately before training or during a competition to avoid gastrointestinal side effects. 

Micronutrients

While carbs, protein, and fat get most of the attention, micronutrients (vitamins and minerals) are just as crucial when it comes to athletic performance. Micronutrients don’t provide calories, but they’re intimately involved in the biological processes that ultimately allow the body to create energy. Athletes should be urged to consume a wide variety of plant and animal foods to provide sufficient micronutrient intake. 

Hydration

Both dehydration and overhydration can negatively impact athletic performance. Hydration needs vary based on the individual due to weight, sweat rate, sodium content of sweat, exercise intensity, and temperature. In general, athletes should consume 400–800 mL of water per hour during training or competition with 1.7–2.9 grams of sodium if the activity is intense. The addition of 1.3 grams of sodium per liter of water can aid in the recovery phase.

Disordered Eating

Many athletes, especially females, are at risk of under-consuming nutrients or have disordered eating practices, which can impact performance and raise the risk of injury. Disordered eating is especially problematic in sports that are dependent on weight or personal appearance, like wrestling, bodybuilding, and long-distance running. Disordered eating may be difficult to spot, but screening tools like the Eating Attitudes Test (EAT-26) can be helpful. If providers suspect disordered eating, athletes should be encouraged to seek treatment.

Supplement Use in Athletic Performance 

In competitive sports, less than 1% improvement in performance can be the deciding factor between winning and losing. Dietary supplements for athletic performance may offer a competitive edge and run the gambit from protein powders to caffeine. While personalized supplementation in sports is essential, a few safe evidence-backed supplements include:

Creatine Monohydrate

Creatine is an amino acid made by the body but also obtained from animal foods like beef and fish. Creatine functions to help replenish the body’s energy source, ATP, during demanding activities like exercise. Countless research trials have found creatine to be a safe, effective way to promote muscle mass and strength, improve athletic performance and body composition, preserve skeletal muscle during calorie restriction, support injury recovery, improve post-workout recovery, and improve immune system function. The International Society of Sports Nutrition advises a loading phase of 5 grams four times daily for 5–7 days, then 3–5 grams per day (5–10 grams/day for larger athletes) for maintenance. It’s likely best to take creatine with a source of carbohydrates or a combination of protein and carbohydrates.

Rhodiola Rosea

Strenuous exercise can increase the risk of viral infections due to transient immunosuppression. Rhodiola rosea is a medicinal herb with adaptogenic properties that’s been found to enhance physical and mental performance and reduce fatigue. Athletes who took 600mg/day for 30 days prior to, the day of, and for 7 days after a marathon were protected from exercise-induced viral infections.

Beetroot Juice

Athletic performance can be limited by VO2 max, ventilator thresholds, and energy efficiency. Beetroot juice may improve cardiorespiratory performance, power output, and time to exhaustion in endurance athletes. The optimal dose appears to be at least 500 mL of beetroot juice 90 minutes prior to a competition or training.

Mental and Emotional Factors 

While physical injuries are an accepted consequence of the rigorous training that accompanies being a high-level athlete, mental health in athletic performance has historically taken a back seat. Athletes often struggle with the symptoms of anxiety and depression, may be negatively affected by overthinking, and have a tendency toward perfectionism, all of which impact performance and quality of life. A mindfulness practice may help to reduce anxiety, promote relaxation, improve motor control, reduce the tendency to overthink, and help athletes attain the flow state (focused attention to the activity at hand).  

Focusing on the emotional well-being of athletes improves mental health but also serves to mitigate the negative health consequences of physical stress related to intense or prolonged physical activity, especially when the body hasn’t been prepared or rested appropriately. Mindfulness meditation can improve immune system function and sleep, lower inflammatory markers, support overall well-being, reduce injury risk, improve injury recovery, and enhance athletic performance. Athletes may benefit from a daily mindfulness practice like mindfulness meditation, yoga, or deep breathing.

Imagery for athletes can include mentally rehearsing their skill or imagining themselves in a relaxing setting like nature. Imagery may reduce muscle fatigue, improve strength, and enhance recovery after an injury. And, guided imagery is an effective tool for combating the symptoms of anxiety and depression in athletes. 

The Importance of Recovery and Rest 

Rest and performance enhancement go hand-in-hand. Many athletes deal with stressors and training that can interrupt their sleep, and they tend to report poor sleep as the number one cause of their fatigue and tiredness. Sleep-deprived athletes can experience reduced mental and physical performance, slower reaction times, mood changes, suboptimal immune system function, and altered metabolism, but they’re also at greater risk of injury and have a more difficult time recovering from an injury. Restorative sleep creates the foundation athletes need to not only perform at a high level but to also recover sufficiently, which helps to prevent injury, maintain proper immune system function, and reach training goals. 

Restful sleep helps to promote balance between stress, fatigue, and recovery, so it should be a priority for athletes. It may seem obvious, but creating a routine sleep schedule is the first place to start when it comes to rest and recovery. Athletes should try to go to bed at the same times each night and wake up at the same times each day. Many athletes will do well with 7–9 hours of sleep but may need up to 12 hours depending on their training regimen. One study found athletes who slept up to 10 hours per night for 5–7 weeks had improved basketball performance, specifically faster sprinting and better shot accuracy, along with better mood, less fatigue, and more alertness.  

Along with a healthy sleep schedule, additional recovery strategies for athletes include:

• Implementing 30-minute napping sessions – one study found a 30-minute nap after lunch improved sprint performance
• Avoiding big meals within 3 hours of bedtime
• Consuming a whole-food, anti-inflammatory diet
• Avoiding bright light in the evening (i.e., phone, computer, television)
• Seeking out bright, natural light upon waking
• Avoiding caffeine after noon
• Sleeping in a dark, cold, quiet environment
• Managing stress

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Enhancing Athletic Performance: Key Takeaways 

Performing as a high-level athlete requires optimal function in all physiological processes. Athletic performance is often limited by poor sleep, an inflammatory diet or disordered eating, unmanaged stress, and poor gut health. Functional medicine offers a holistic approach to athletic performance by considering the imbalances, genetics, nutrition, and lifestyle factors that could be hindering performance in a specific athlete. By tailoring a plan that includes an anti-inflammatory diet, dietary supplements, stress management, and sleep, functional medicine providers can help to optimize athletic performance, mental well-being, and the ability to recover more completely.