When it comes to endurance running, your physical fitness and mental fortitude are key — especially if you're training for a race.

But don't forget that performing at your peak also hinges on what you eat.

"Each runner's nutrition goals will vary depending on several factors, including your performance level (elite or recreational), your training intensity and duration, your weight and more," says Kylie Arrindell, a wellness dietitian at Houston Methodist. "Generally speaking, though, endurance runners need to emphasize eating more nutrient-rich carbohydrates than the average person, since this is the type of fuel the body predominantly uses during long runs."

Arrindell, who regularly advises people training for long-distance runs on the fuel their body needs, shares her expert advice below — including how to avoid common mistakes runners make.

Mistake #1: Eating the wrong foods (or at the wrong time) before a run

Endurance running and "carb loading" have become almost synonymous these days, but there are nuances to the carbohydrates you should choose and when you should consume them.

"For the most part, you don't want your pre-run fuel to be something like a donut or bag of chips — the less nutrient-rich types of carbohydrates," explains Arrindell.

Instead, she recommends a solid meal of nutrient-rich carbohydrates, including a little lean protein, two to four hours before your run.

"This gets tricky depending on when you run — especially if you're an early morning runner — but that's the goal if you can make it work," says Arrindell.

Nutrient-rich carbohydrates to add to your pre-run meal include:

• Whole grains, like whole wheat pasta or bread, quinoa and rice
• Starchy veggies, like corn, potatoes and peas
• Fruit
  
  

But that meal shouldn't be your last pre-run nourishment, Arrindell says.

"About 30 minutes before your run, top off your energy stores with about 30 grams of quick-digesting carbohydrates," Arrindell recommends. "You can even do this as close as five minutes before your run, but that's where your personal tolerance comes into play."

Some people's stomachs are more sensitive to eating just before a run. If so, try experimenting with the timing or the amount that works best — such as eating more than 30 minutes before a run or consuming less than 30 grams of carbohydrate. You might also need foods with less fiber, protein or fat with your pre-run meal, depending on your tolerance levels.

Examples of quick-digesting carbohydrates to top off your energy stores include:

• Fresh fruit, such as a medium banana
• A handful of dried fruit
• A glass of orange juice
  
  

"Orange juice, in particular, is a good option if you are someone who just can't stomach anything but liquid before an early morning run," says Arrindell. "It digests quickly, provides carbohydrates and fluids for hydration and the vitamin C in it can also be helpful for recovery."

And, as with earlier pre-run meal, highly processed carbohydrates aren't recommended for the snack shortly before the run.

"Fruits are better options because they're not just quick-digesting sources of energy, they also provide the micronutrients your body needs to function optimally," Arrindell adds.

Mistake #2: Not bringing fuel on longer training runs

Taking a snack with you on a run isn't always necessary, but for those training for a race, it's something to consider more often than you might think.

"If your run is going to last longer than 60 minutes, bring a small amount of carbohydrate for refueling purposes along with you," says Arrindell. "You may also need to do this if it's a slightly shorter run that includes sprinting or some other more intense activity."

For instance, a run incorporating hill training is an example of a high-intensity activity that likely warrants taking some fuel with you.

As for what to bring exactly, Arrindell recommends:

• A sports drink
• Energy gels
• Energy chews
• Peeled fruit
  
  

"These options are great because they provide carbohydrate in a simple and easy-to-digest form," explains Arrindell.

They're important to incorporate into your run not just on race day, but during practice leading up to it. More on that below.

Arrindell also stresses the importance of consuming your fuel at about the 60-minute mark, regardless of whether you feel hungry or not.

"Many endurance runners make the mistake of waiting until they feel fatigued or hungry to take in carbohydrates, and that can actually be a detriment to your performance," Arrindell says. "It's best to be proactive about when it's time to refuel on long training runs."

She adds that if your run is longer than two hours or you're running in extreme heat, you may need a sodium-specific item, like pretzels or pickle juice, to help replace electrolytes lost through sweat. This is important for anyone, but it's especially important for heavy sweaters.

Mistake #3: Forgetting that what you eat plays a role in exercise recovery

Your run may be over, but your fueling plan isn't yet complete. There are several nutrition-related goals to make time for afterward.

"First, you'll need to replenish your glycogen stores with a carbohydrate source," says Arrindell. "Second, taking in high-quality protein can help start the recovery and repair process of the muscles you just worked."

Lastly, Arrindell adds that it's important to rehydrate and replace the electrolytes lost during your run.

Outlining the ideal recovery meal and routine is complicated, though, since it hinges on many unique, personal factors. So does the ideal pre-run meal. That's why Arrindell recommends endurance runners training for a race meet with a dietitian for help formulating a nutrition plan.

"The gram by gram amount of each macronutrient a person needs is very individualized," says Arrindell. "It's also specific to your training schedule, which changes from week to week if you're preparing for a half marathon or marathon."

Though most of runners' nutritional needs are variable, Arrindell says the recommended protein intake for exercise recovery is fairly universal — about 15 to 25 grams of high quality protein post-exercise.

Mistake #4: Ignoring the importance of your overall diet (even on non-running days)

Sorting through the logistics of your pre- and post-run meals is a lot of work. So much so that many runners forget about what the rest of their diet should look like.

"A lot of times with endurance training, so much emphasis is placed on getting adequate carbohydrates and protein that we tend to not think about getting healthy fats and fiber as well," explains Arrindell.

For pre-run meals, this makes sense. These two nutrients are slower to digest and eating them can often lead to gastrointestinal issues during your run.

What this means, though, is that on days you're not training or you're just doing light training, a major emphasis should be placed on getting the healthy fats and fiber you've been limiting.

Mistake #5: Not practicing your fueling plan before race day

"For those training for a half marathon or marathon, you want to practice your fueling plan way before race day," Arrindell points out. "Most of the time, people forget about this until about a month or two before the race, or when they start getting to higher mileage, which can sometimes be too late."

After all, endurance running is an incredibly taxing pursuit.

"When you're running for longer periods of time, blood from your gut gets diverted into the muscles that are working," explains Arrindell. "This means you're not able to digest food as well while running."

Your body needs time to adjust to such a unique situation. That's the first reason to start practicing your fueling plan early.

"And when you're incorporating a new product or something you've never tried before, it can lead to bloating or gas if your body isn't used to it or if it includes a good amount of fiber or protein," says Arrindell.

This explains the second reason to give yourself plenty of time to practice your fueling plan — there are personal nuances to it.

"It is often a process of trial and error," Arrindell adds. "For instance, maybe when it comes to refueling during your run, you do best if you break up your carbohydrate intake into 15-minute increments, rather than consuming the full amount once per hour."

She adds that you won't know these things unless you practice well in advance.