These Underrated Nutrients Can Make or Break Marathon Performance, Sports Dietician Says
Carbs and salt: the two holy grails of pre-marathon fueling. Anyone with a few races under their belt knows that carb loading is essential for topping off glycogen stores, while salt helps your body retain fluid and maintain blood volume as the miles slowly tick by. But that’s not where race-day fuel preparation should stop.
Several key nutrients, including potassium, magnesium, and calcium, also support proper hydration and muscle function. Plus, eating nitrate-rich foods before the race can help promote better blood flow, a small but meaningful advantage when you’re chasing 26.2 miles.
"Keep it simple!" says Jennifer O’Donnell-Giles, M.S., R.D.N., endurance athlete and adjunct professor at Columbia University. "Don't do anything new, and always practice fueling during training. Focus on food as fuel to give you the energy needed to race."
4 Hidden Nutrients That Can Save Your Next Race
Potassium
There’s a reason bananas are basically the unofficial mascot of foot races! Potassium helps regulate fluid balance and works alongside sodium to manage hydration levels as you sweat. Maintaining steady fluid levels helps to support a steady heartbeat and prevents muscle cramps during strenuous physical activity.
Magnesium
Magnesium supports faster post-run muscle recovery, helps reduce cramps, and promotes better sleep. One study found that marathoners who got enough magnesium, along with unsaturated fats and potassium, performed better and showed improved cardiovascular health compared to those who didn’t.
"I have clients that are getting results, such as fewer muscle spasms, by making magnesium the priority of their evening meal," says David Zhong, a kinesiologist and certified personal trainer. "It relaxes your nervous system so that you get better sleep when the early morning alarm goes off."
Calcium
Calcium plays a key role in keeping your heart beating and your muscles contracting, which are both essential for running and other from physical activity. One study even found that eating calcium-rich foods before exercise can lower markers of bone breakdown during and after your workout.
Nitrates
Nitrate-rich foods, like beets and beetroot juice, have emerged as nature's preworkout. The nitrates in these foods are converted in the body to nitric oxide, which helps relax and widen blood vessels. The improved blood flow means more oxygen reaches your muscles, which enhances endurance during long runs.
"Eating nitrates in your diet will improve your aerobic output tomorrow. We often recommend drinking beet juice or eating cooked beets the night before a really big effort," Zhong explains. "These specific compounds help your body act with oxygen more efficiently by increasing the way that your mitochondria act under stress."
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