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A Runner’s Guide to Sugar

Confused about the role of sugar in your running diet? Here’s how to use the sweet stuff to your advantage.

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If you can’t seem to shave minutes or even seconds off your half-marathon time, or getting through what used to feel like an “easy” three miles suddenly feels like a slog, your diet might be to blame. Experts are realizing that it’s added sugar and refined carbs, not previously villainized healthy fat, that are wreaking havoc on the wellness of Americans young and old.

“Taking in too many empty calories in the form of added sugars and refined carbs can sabotage your progress, making you feel lethargic and slowing you down,” says Michele Promaulayko, author of the new book Sugar Free 3: A Three-Week Plan for More Energy, Better Sleep, and Surprisingly Easy Weight Loss.

Runners aren’t an exception to this rule. “They don’t need more sugar than anyone else when it comes to day-to-day living, and consuming too much is just as harmful to them,” says registered dietician Keri Glassman, founder of Nutritious Life.

There is one time, however, when athletes can use the sweet stuff to their advantage: “Runners can utilize sugar when they’re training for quick, immediate energy,” says Glassman. So what exactly does that mean? Here’s what female runners need to know about how sugar impacts the body, the different types, and exactly when to consume it for the biggest payoff.

“Good” versus “Evil”

“If you prioritize real food, you don’t need to worry so much about added sugar because Mother Nature naturally made certain foods sweet and tasty,” says Marni Sumbal, RD, an exercise physiologist and author of Athlete to Triathlete and Essential Sports Nutrition. So, yes, you’ll get sugar in potatoes, fruit, whole grains, and some dairy products, but these foods offer naturally-made sugar, not sugar added from a factory. And since these foods also contain fiber, protein, or vitamins and minerals, they are slower to digest, keeping you fuller longer and more satisfied. Even better, you can curb your sweet cravings with these naturally sweetened foods, which will help you reduce your intake of their sugary-rich processed counterparts.

Speaking of the “bad” stuff: Unfortunately, these days, many people eat more processed, packaged foods than the natural options lining the perimeter of the grocery store. And hidden sugar is everywhere. “Look closely at the nutrition labels of yogurt, cereal, granola bars, soups, marinara sauce, a lot of our condiments, and even salad dressings,” says Sumbal. You’ll see sugar or what Promaulayko calls “sugar AKAs” (rice syrup, dextrose, fruit juice, corn syrup, the list goes on …) in many of these options lining supermarket shelves.

That’s what you want to avoid, or at least limit, to optimize your health and running performance. The American Heart Association (AHA) recommends women take in no more than six teaspoons—about a hundred calories or about 25 grams—of added sugar a day.

The female factor

Turns out there’s a scientific reason to explain your sugar cravings when you’re about to get your period. When it’s that time of the month, your body’s carbohydrate needs spike, according to Sumbal. “Those cravings are like your body is telling you, ‘Hey, I need you to eat a little bit more,’ but unfortunately what your body craves may not be so healthy.”

One way to combat those cravings is to make sure you’re getting enough calories in general. “[Being too restrictive] will end up making you crave sugar more because you’re going to be starving,” says Glassman. “Instead, make sure you’re getting a combination of complex carbs, fats, and protein throughout the day. You need all three macros to be a healthy athlete, for reducing inflammation, for repairing damaged muscles, and for building your glycogen gas tank,” Glassman says.

The runner’s loophole

First, a quick science refresher: When we digest sugar, the enzymes in the small intestine break it down into glucose and then it’s released into the bloodstream before it’s transported to the muscles for energy, Sumbal explains. Once sugar is broken down, the body doesn’t care where it came from—it could be from an apple or an energy gel. But the sugar from an apple is going to be digested very differently than from the engineered sugar source, even though by the time it gets to your small intestine, it’s the same thing.

The “problem” (if you can even call it that) with real food is it’s packed with fiber. “Fiber is not a friend to athletes who need carbohydrates to be digested and absorbed very rapidly,” says Sumbal. Instead, runners need easy-to-digest simple sugar for that quick energy boost, per Glassman.

“Rather than the body having to digest it and break it down into a form that can be used, you’re basically taking sugar in a form that it can put to immediate use,” says Glassman. “You can think of your glycogen stores as your gas tank. You want to keep that tank topped up as long as possible—when it empties, that’s when you ‘hit the wall’ and run out of energy.”

What’s more, research shows that getting carbohydrates in during a workout can protect your immune system and help you maintain proper form, warding off injury: “When you start running out of energy, your form gets sloppy and that’s when niggles start to pop up,” Sumbal explains.

So, how much do you need?

For runs lasting 75 minutes or more, Sumbal recommends 25 to 30 grams of carbohydrates per hour. “Because sport nutrition is best absorbed in small amounts, consumed frequently, consider taking in about 5 grams of carbs every 10 minutes,” says Sumbal. That could be one shot block or simply nursing a packet of GU rather than downing it in one go. “Don’t forget that carbohydrates are easier to digest when consumed with water (about 2 to 3 fluid ounces for every 10 minutes of running. One gulp of water equals about 1 ounce),” Sumbal adds.

That can be in addition to that 25 grams of sugar per day recommendation from the AHA. “The guidelines are not produced for very active individuals so you can have your sports nutrition and then still have a cookie or scoop of ice cream.”