Nutrition for runners can feel overwhelming at times. Sports nutrition recommendations differ from general nutrition guidelines. Fad diets circulate and some social media influencers present misinformation. How do you know if your diet is supporting your running? Nothing can replace working with a credentialed professional such as a registered dietitian. However, these five basic principles of nutrition for runners can serve as a starting point.
1. Scale Carbohydrate Intake Based on Training Volume
Runners require carbohydrates in their diet. If you run more than a couple of 30-45 minute runs per week, you need more carbohydrates than the average person does. Carbohydrates are a vital source of energy production for any intensity of running.
Additionally, carbohydrates support immune cell function, brain function, and endocrine system function (amongst other body functions). Carbohydrates have a complex interaction with micronutrient absorption. Carbohydrates, especially whole grains, contain many essential micronutrients. Chronically low carbohydrate intake can upregulate hepcidin, which blocks iron absorption. (See this 2019 review in the European Journal of Applied Physiology). The fiber found in carbohydrates such as fruits, vegetables, and whole grains aids in digestive health and lowers the risk of various diseases.
However, your carbohydrate needs as a runner are not static. If you are training for a marathon, you need more carbohydrates than if you are running low mileage. Most runners change their training focus throughout the year. With each training cycle, off-season, and base-building phase, you want to scale your carbohydrate needs to support your training volume. The more you run, the more carbohydrates your body needs.
On a micro-scale, this means adjusting your carbohydrate intake for easy, moderate, and hard training days. For example, you will eat more carbohydrates on a long run day compared to a recovery run day. On a macro scale, you eat more carbohydrates in high-volume peak training compared to off-season training.
Carbohydrate choices can also be modified based on training load. When you are in a low-volume phase and eating fewer carbohydrates overall, you will choose more fruits and vegetables for carbohydrate sources. When your training requires high carbohydrate intake, you will likely include low-fiber, simple carbohydrates. Low-fiber carbohydrates can help meet daily goals without overdoing fiber. Additionally, high-volume athletes will eat more simple carbohydrates before, during, and after runs to support those training sessions.
The same principle applies to protein and fat intake. Every runner has a baseline requirement for those macronutrients. As training volume increases, protein and fat intake should both increase.
A simple guide to carbohydrate intake:
- Light (30-50 min, a few runs per week): 3-5 grams per kilogram of bodyweight
- Moderate: (~1 hour per day, several days per week): 5-7 grams per kilogram of bodyweight
- High: (1.5-3 hours per day): 6-10 grams per kilogram of bodyweight
- Heavy (>3 hours per day): 8-12 grams per kilogram of bodyweight
You will notice that these are wide ranges. Adapt within the range to find what feels best for you! Your needs may fluctuate daily. Some runners find they feel best with more fat in their diet, so they may eat carbs on the lower end of recommendations. (However, unless guided by a registered dietitian, stay within the recommended range due to risks of low carbohydrate diets and overtraining and endocrine dysfunction), Others thrive with more carbs on the higher end of the recommendations.
A simple way to visualize carbohydrate periodization is the Athlete’s Plate. The Athlete’s Plate provides a visual representation of how your plate should look based on your training volume. Easy days are <60 minutes; moderate days are 1-2 hours (across one or multiple workouts); and hard days more than two hours (across one or multiple workouts).
2. Eat Enough for Your Training Load
Undereating disrupts endocrine function in both male and female runners. When undereating occurs on a long enough scale, an athlete can develop relative energy deficiency in sport (RED-S).
Signs of undereating include loss of menstrual period (amenorrhea), libido loss, sleep disturbances, mood changes (including irritability), frequent soreness, frequent muscle pain/cramping, fatigue, and intense cravings. When undereating builds into RED-S, performance will decline. You are left with poor recovery, low energy in training, and increasing slower training and racing paces.
Undereating is linked to overtraining, according to a 2022 review in Sports Medicine. As outlined in this review, low energy availability and low carbohydrate intake are associated with overtraining symptoms across several studies. Additionally, overtraining symptoms often overlap with symptoms of RED-S, suggesting a link between the two.
Eating enough for your training load not only mitigates negative outcomes such as amenorrhea and injury; it also promotes training adaptations and supports performance. A well-fed athlete has the energy to perform to their potential. An underfed athlete may struggle with fatigue and have poor training quality, which leads to diminished training adaptations over time.
Eating enough for your training load means eating all three macronutrients. The higher your training volume, the more carbohydrates you need for energy production, the more protein you need for muscle repair, and the more fat you need for cellular and endocrine function. Additionally, eating enough for your training load helps you consume enough micronutrients (including antioxidants) to support your body’s recovery needs.
3. Eat a Variety of Colorful Fruits and Vegetables
A wide variety of fruits and vegetables supports micronutrient requirements. For example, leafy greens provide vitamin K, bell peppers and berries provide vitamins C and E, bananas supply potassium, and carrots and sweet potatoes provide vitamin A.
The antioxidants in fruits and vegetables are very beneficial for runners. The antioxidants include vitamins C, E, A, zinc, and various other compounds found in foods. Antioxidants reduce the oxidative stress that we accumulate as a natural result of training. While oxidative stress is essential for adaptation, too much can be detrimental. Antioxidants scavenge free radicals and reactive oxygen species. In addition to supporting overall health, antioxidant consumption may reduce delayed-onset muscle soreness, according to a 2020 review in Redox Biology.
It is worth noting that the evidence is not clear on whether antioxidant supplementation (which often has vitamin mega-doses) blunts training adaptations. Additionally, some recent studies suggest that excessive antioxidant consumption may actually turn the antioxidant into a pro-oxidant, thus increasing oxidative stress. Given that evidence, it is safest to rely on five to nine daily servings of vegetables and fruits over supplements for antioxidants.
For most runners, an appropriate goal is a minimum of five servings of fruits and vegetables per day. You can eat more. However, be mindful that you are not filling up excessively on vegetables and fruits at the expense of other foods. (Additionally, too many fruits and vegetables can lead to very high fiber intake, which can cause gastrointestinal distress in some runners.)
Fruits and vegetables alone will not provide all the vitamins and minerals you need. Be mindful to include other foods in your diet. Legumes and red meat provide iron. Dairy or fortified dairy substitutes supply calcium and vitamin D. Many nuts and seeds offer a plethora of micronutrients including vitamin E and magnesium. Unless you have medical reasons, eat from each food group and eat a colorful variety of fruits and vegetables.
4. Fuel Your Training for the Work Required
One of the primary goals of sports nutrition is to support performance via nutritional interventions. For long-distance runners, taking in supplemental carbohydrates during long runs or hard workouts supports performance. As outlined in the seminal 2014 review in Sports Medicine, carbohydrate intake during long runs should be scaled based on the duration. The longer the effort, the more muscle glycogen you will use, and the more exogenous (from food or supplement) carbohydrates you will need.
Fueling for the work required means that you adjust your carbohydrate needs to support the given effort. On shorter easy runs (<60-80 min), you do not need any carbohydrates due to the length of the session. These runs allow your body to improve fat oxidation rates. On medium-length efforts, you take enough carbohydrates to ensure adequate energy, but not so much that your gut feels overwhelmed. On very long efforts, extreme fueling approaches (as outlined in this Trail Runner Magazine article) support the extreme energy demands.
Additionally, fueling on long runs enhances recovery. I often see runners report that they no longer feel exhausted after their weekend long runs once they start fueling appropriately. This is demonstrated in the evidence repeatedly, such as in this 2020 study in Nutrients that saw higher intra-run carbohydrate intakes associated with better markers of muscular recovery in mountain runners.
A simple, general guide to fueling for runs:
- Easy runs <80-90min: no fuel required (can bring sports drink for hydration)
- Hard workouts <90 min: sports drink for hydration and carbs
- Runs (any intensity) 1.5-2.5 hours: 30-60 grams of carbohydrate per hour
- Runs (any intensity) >2.5 hours: 60-90 grams of carbohydrate per hour
Carbohydrates during long runs can come from a single type of sports nutrition or a combination. I recommend combining (such as gels and sports drinks) when you are aiming for 50 or more grams of carbohydrates per hour.
The evidence simply is not strong enough to support fasted running and withholding carbohydrates on long runs. Female athletes are particularly prone to negative ramifications of energy restriction around exercise, but male athletes are not immune to these ill effects. (Read here for more on fasted running and here on low-carbohydrate training.)
5. Supplement Cautiously and Deliberately
Supplements are not the magic bullet that social media presents them as. You won’t magically get faster from taking the newest supplement, even if another runner attributes their PR to it. Supplements are complex: each has its risks, not all contain what their labels claim, and supplements can interact with other supplements and medications.
That all said, not every athlete can meet their adequate micronutrient intake through food alone. For those athletes, supplements play a crucial role in supporting both performance and health. Additionally, some supplements (such as caffeine and sports drinks) have clear evidence supporting their benefits.
Certain micronutrient supplements (such as iron) should be taken only if bloodwork indicates a need. Vitamin toxicity is rare but can occur; even elevated levels of certain micronutrients can be detrimental. In the example of iron, high ferritin levels can produce similar symptoms to low iron levels, such as fatigue.
Every athlete can benefit from routine bloodwork to assess deficiencies and appropriate micronutrient supplementation. If you have been recently injured (especially with a bone stress injury) or feel tired often in training, you may want to have bloodwork done.
Performance supplements, such as pre-workout, creatine, and protein powder, should be taken based on individual needs. You may benefit from them or they may be a waste of money, depending on many factors.
For every supplement that you consider taking, perform a risk-reward analysis:
- What are the ingredients?
- Will this interact with any medications or other supplements you are taking?
- Does my bloodwork indicate I need this supplement?
- What are the benefits of this supplement for my specific goals?
- How strong is the evidence supporting the benefits of this supplement?
- Can I achieve the benefits through dietary changes?
- Is this supplement third-party tested?
- What are the risks to taking this supplement (including acute adverse reactions and chronic risks)?
Caffeine is one of the safest and most effective supplements for runners. However, it does not work for everyone. Some runners tolerate caffeine well. Others find it causes side effects such as anxiety, GI upset, jitters, or palpitations. If you do supplement caffeine, it is most effective before a workout or during a long run/race. Many gels and sports drinks contain caffeine for easy supplementation during runs. Before a run, you can use coffee, tea, or a pre-workout supplement. However, if using pre-workout, check the ingredients to see what it contains. Many pre-workout supplements are multi-ingredient, and not all ingredients benefit runners.
Other performance supplements, such as creatine, may or may not benefit runners. The overwhelming consensus from the research is that creatine is safe and highly effective for increasing muscle mass. For long-distance runners, the performance benefits are presently unclear, unless your goal is to increase muscle mass. (For more information on creatine for runners, reference this highly researched article.)
After completing several graduate-level classes in sports nutrition, the supplements I recommend are:
- Caffeine (if tolerated)
- Electrolyte/sports drink
- Protein powder
- A safely formulated probiotic (see this 2019 position stance from the International Society of Sports Nutrition)
- Micronutrients based on individual bloodwork (such as vitamin D or iron if bloodwork reveals low to sub-optimal levels)
If in doubt, work with a certified sports nutritionist or registered dietitian on supplements. Always assess your supplement intake as a whole, to avoid accidentally taking too much of any given vitamin or mineral. (For example, too much supplemental magnesium can cause diarrhea.)
Disclaimer: I have completed a MS in Applied Exercise Science with a concentration in Sport Nutrition. My education included various practicums under registered dietitians and I am preparing for the CISSN exam. However, I am not a registered dietitian. This article presents general advice, not individualized advice.