From the long-distance runner who “carbs up” the night before a race, to the protein-shake drinking weightlifter, to the tennis player who downs an energy drink between sets, athletes are known for using food to boost their performance.

But desk-jockeys, too, can use diet and nutrition to increase their energy, focus and mental agility. And that means there are three opportunities a day to be your best self at the office.

Dr. Judith Wurtman, a nutrition expert who wrote the book “Managing Your Mind and Mood Through Food” and a regular Huffington Post blogger, has made a career of telling people how to eat to their best advantage. Luckily, her advice falls well within the realm of “normal” daily diets – and the offerings of most office cafeterias. Even luckier still, she has good news for the java junkies among us.

“There are two components of food that have a proven effect on mental performance: protein, and caffeine,” says Wurtman. “For any situation where you need mental alertness – say you’re a lawyer arguing a case, or a negotiator sitting down with opposing parties to find a solution – you need protein,” she says. As for the java jolt, “of all foods, caffeine has been shown to be the most potent stimulant of mental acuity, alertness, and reaction time for problem solving.”

In other words, people who are used to starting their day with a strong cup of joe should keep at it. And drinkers of caffeinated cola or tea, which has a substance similar to caffeine, can relax in the knowledge that their stimulant of choice is delivering the goods, as well.

So, let’s say that, like an athlete, you’re watching your diet. You’re eating proteins at breakfast and lunch, and carbs at night. You’re drinking water all day long (and no alcohol at lunchtime), and you’re avoiding fat-laden snacks. You’re good to go, right? Focus, energy, and attention, here we come?

Almost. There is one more factor we need to keep in mind, and it’s the most important of all, Wurtman says. In fact, it could mean the difference between winning the race, and not crossing the finish line at all.

Get your shuteye

“A lack of sleep has an incredibly powerful effect of decreasing cognitive ability,” Wurtman says. “You can’t eat your way out of it.”

Seven hours of sleep at night is considered a miniumum, and sleep is especially important for the modern global executive, who may be on-the-job nearly round the clock, working in many time zones at once.

“You wouldn’t want an airline pilot to fly you if hadn’t had sufficient sleep, would you,” Wurtman asks. “Well I wouldn’t someone in that condition to pilot my financial situation either.”