Nutrition and Supplementation for Endurance Athletes

Nutrition and Supplementation for Endurance Athletes



Endurance athletes are a unique breed of athlete. Their specific energy system used during exercise requires them to eat differently than their peers. They also need to maintain adequate levels of electrolytes—before, during, and after exercise—and thus, need the support of targeted supplementation. As a sports nutritionist and Functional Medicine practitioner, I work with both competitive and amateur endurance athletes. Let’s take a closer look at what endurance athletes need to know about nutrition and supplementation.

Ketogenic diet and the endurance athlete

Ketogenic diet and the endurance athlete While “carb loading” has long been synonymous with endurance athletes and nutrition, a diet low in carbohydrates and high in healthy fats–such as the ketogenic diet (“keto”)–has proven advantages for performance athletes. For example, marathon runners that burn ketones instead of glucose experience increased cognitive and physical performance. Cognitively, the brain operates better on ketones versus glucose from sugar or carbs–leading to heightened levels of concentration and longer periods of focus.

Physically, keto-adaptation–the body’s transition to burning fat instead of glucose for energy–improves endurance exercise capacity in athletes, as well as improves fat mobilization and oxidation during exercise performance.1 Keto-adaptation also improves aerobic and anaerobic exercise capacity in endurance athletes.2 The keto diet minimizes the breakdown of lean muscle tissue and increases the body’s ability to maintain lean body mass while burning fat, which is beneficial for performance athletes’ body composition. Additionally, ketones increase mitochondrial glutathione levels, subsequently feeding the mitochondria better and leading to more rapid recovery between exercise sessions.3

The greatest physical outcome of keto-adaptation for athletes is improved endurance capacity during competition. Performance athletes, like ultra-runners or soccer players, that are keto-adapted will experience increased endurance and less central fatigue during the course of their competition or match.4 On the keto diet, the body taps into slow-burning fat storage, which prevents athletes from ‘hitting the wall.’1 This is especially beneficial to those athletes who can’t easily digest foods while exercising–e.g. a tennis player between sets. During keto-adaptation, liver and muscle glycogen deposits are maintained, attenuating the glycogen depletion observed in athletes consuming high-carbohydrate diets. With the absence of glucose to burn, athletes won’t experience the peaks and valleys of varying blood sugar levels.

Meal prep for endurance

When planning meals for the week, it’s important for endurance athletes to choose foods that will not only sustain their active lifestyle and athletic performance, but also ones that aid in maintaining a healthy body composition. I recommend starting with grass-fed, pasture-raised, and organic proteins, such as lamb, pork, bison, elk, chicken, turkey, or duck. If you prefer to eat fish or seafood, choose wild salmon, mackerel, anchovies, sardines or haddock, as well as wild clams, scallops, mussels, oysters or shrimp. For sides, choose ancient grains, such as quinoa, amaranth, or sorghum, and any organic green vegetables. Choose oils from avocados, walnuts, almonds, macadamia, flaxseed or hemp seed to both consume and cook with. You should also include fatty fruits in your diet—like avocados, coconuts, and olives—as well as wild organic berries, cherries, and the occasional apple. When it comes to milk, skip the dairy and choose an alternative like almond, coconut, hemp seed, or cashew—but make sure you choose one without large amounts of added sugars. If you desire a little sweetness in your food, a non-nutritive sweetener such as monk fruit extract can be used as an alternative to added sugars. Finally, include raw nuts and seeds to complement healthy fats.

Stay hydrated

Athletes should drink up to one ounce of water per pound of body weight every day. And while it’s important to stay hydrated during workouts, endurance athletes should plan to drink water throughout the day to make rehydrating easier post-workout. Also, athletes should never wait until a match to see how their body responds to other liquids like sports drinks. I recommend athletes sip on the same beverage during competition as they do during training to avoid any potential stomach troubles. As with most health-related issues, an individualized hydration plan is prudent for improving performance outcomes.5

Refuel properly post-workout

While nutrients serve different purposes, what endurance athletes put into their bodies post-workout is just as important as any pre-workout meal. Post-workout meals should focus on replenishing what has expended while exercising. To start, replenish lost electrolytes as soon as possible. Many sports drinks are high in sugar, instead  water mixed with electrolytes (e.g., tablets, powders) is an excellent rehydration option. While there isn’t a one-size-fits-all approach to replacing electrolytes—as individual sweat rates and lengths of exercise differ—the need to replace the sodium and water lost through sweat applies to all athletes.

In addition to rehydrating, endurance athletes should consume a mix of protein and carbs, like a whey protein shake, within the first 30 minutes after finishing a high-intensity or endurance workout. Doing so will help reduce muscle soreness and aid in muscle recovery. As for a healthy post-workout snack, avoid processed carbs, which increase inflammation, and opt for anti-inflammatory foods, like cherries, walnuts, or kale. Athletes should also consider including medium-chain triglyceride (MCT) oil in their post-workout regime, as it is one of the fastest sources of clean fuel to replenish the body and brain.


Take care of yourself in the off-season

As I mentioned earlier, the keto diet is an excellent choice for endurance athletes. It’s also a suitable diet to adopt during the off-season, too. Athletes looking to improve their fat to muscle ratio, especially those who are required to meet certain weight goals for their sport, benefit from an off-season keto diet. The keto diet benefits athletes’ off-season training, as well. Exercising while glycogen storage levels are low is a training technique popular for improving mitochondrial function and a key strategy athletes can utilize if they’re looking to improve endurance. By reducing oxidative stress and inflammation, gut and immune functions are better maintained–helping athletes sustain their health while they rest. Ketones also provide substrates to help repair damaged neurons.4

Consider targeted supplementation for rehydration

Intentional and personalized fueling—and refueling—often requires more than just food and fluids. Endurance athletes should know that many of their bodily functions depend on maintaining adequate levels of electrolytes, especially in muscle and nervous system tissue. Therefore, consistent electrolyte support is key at all stages—from preparation to performance. Targeted supplementation considerations for rehydration may include, but are not limited to: macro- and microminerals (e.g., sodium, potassium, chloride, calcium, phosphorus, magnesium, chromium), key amino acids (e.g., glutamine, L-carnitine, L-carnosine), and essential nutrients involved in cellular energy production from carb, proteins, and fat (e.g., B vitamins) or with antioxidant actions in the body (e.g., vitamins C, E). Individualized rehydration strategies should consider pre-exercise hydration status, as well as fluid, electrolyte, and substrate needs before, during, and after exercise.6

By eating smart, being intentional about hydration, and incorporating personalized and targeted supplementation to support rehydration, endurance athletes can be set up for success—not only sustaining performance during competition, but also extending the longevity of their sports career over the long run.


This information is for educational purposes only. The statements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease. Consult your physician if you have any question regarding a medical condition