From my earliest days as a runner, I’ve been deeply interested in the nutrition and hydration that produce peak performance. I’m not sure where this came from. Certainly not my days as a Little League baseball player. Then I believed the best diet should meet two requirements. Before a game I had to eat steak and baked potatoes. (In a pinch, hamburgers and French fries were an acceptable alternative.) After the game we had to stop at Dairy Queen for a large ice cream cone.

My high school cross-country coach, John J. Kelley, introduced me to a different world. He was an ovo-lacto vegetarian. He ate eggs and dairy products, but no meat or fish. I first encountered wheat germ at the Kelley breakfast table, and soon learned to enjoy its chewy texture. At seventeen I decided that vegetarian eating held the secret to great endurance running.

What I lacked in knowledge, I made up in stupidity. My diet was so restrictive—about 50 percent wheat cereal and milk—that I wonder how I survived. I knew almost nothing about nutrition then. Science never entered the picture. I plunged into vegetarianism with the same passion with which I pursued running.

Five years later, I had my first opportunity to be a running guinea pig. A young physiologist, David Costill, PhD, invited me to his lab. Costill had received a small grant to study how hydration affected distance runners. He wanted me to run a 20-miler on his treadmill on three successive days—once with no fluids, once with water, once with a new product named Gatorade.

I couldn’t say yes fast enough. I couldn’t imagine anything more exciting than gaining scientific insight into the way my body acted while I was running. Costill drove to Detroit, where I was competing in the NCAA indoor 2-mile championship with the likes of superstars Jim Ryun and Gerry Lindgren (and finishing far behind them). Then we headed south through the early-morning hours to Ball State University in Muncie, Indiana.

On each of the next three mornings, I ran 20 miles on a Ball State treadmill at a pace of just over 6 minutes per mile. The first time, I ran dry—with no fluids. The second, Costill and colleagues handed me a flask of water every 10 minutes and asked me to drain it. The third, I was handed an equal quantity of Gatorade, recently invented at Florida State University in Tallahassee, Florida.

The first couple of drinks during each run were refreshing, whether water or Gatorade. After that I developed a queasy, sloshy feeling in my stomach. Too much already. I looked beseechingly in Costill’s direction. Do I have to? He nodded. Yes. I had to keep drinking. This was science. We had to be consistent.

I grew tired from the running, sure. Ten miles. Fifteen miles. Eighteen. But the drinking was worse. I had grown accustomed, over five or six years, to running considerable distances with little or no refreshment. I had finished two Boston Marathons. Boston had no fluid stops. Now, in Costill’s lab, I was growing nauseous. I started to worry that I might vomit.

The worst was still to come. After I finished each 20-miler, Costill sat me on a bench and threaded a narrow plastic tube up my nose, down my throat and esophagus, and into my stomach. He needed to siphon out the contents of my stomach to determine how much fluid was left there, and hence not absorbed into my bloodstream.

I gagged. I felt as if I were being suffocated. “It’s OK. Just relax,” said Costill. “Pretend you’re swallowing spaghetti.”

Oh, sure. That’ll work.

While Costill was draining my stomach, his associates asked a series of questions about how I had felt during the run. They wanted to determine my RPE (relative perceived exertion) during each of the three treadmill runs. I pointed to numbers on their sheet that indicated effort. This part was easy. I’d felt best when I drank nothing, as was my custom. And worst when I drank the Gatorade, an entirely new and foreign experience.

Later, Costill sat me down to go over the results. According to his analysis, I had performed the best (consuming least oxygen) on Gatorade and the worst while drinking nothing. In other words, the exact opposite of how I had felt subjectively.

This brings up a very important point about sports research. Scientists are forever conducting experiments that yield results that should be associated with important health or performance outcomes. In theory. It’s far more difficult, and much less common, to link the experimental condition to an actual health or performance benefit.

I like to say that the measure is not the thing. Costill’s results did not constitute proof that I run faster with Gatorade than with nothing. In the spring of 1968, in his lab, in my first time drinking Gatorade, I could have guaranteed that would not have been the case.

One month later, on a warm day in April, I won the Boston Marathon without drinking anything en route. I weighed 138 pounds at the start line, and 129 at the finish. I know this because Costill was there to weigh me. I’m also quite sure that, if someone had given me Gatorade on the course, I wouldn’t have run as well.

Through the years I’ve enjoyed volunteering for other nutrition and physiology studies. Once I joined a group of runners consuming a diet consisting of 90 percent fats. I thought it would be yummy, like the Dairy Queen of my Little League days. Instead, after just two meals, I couldn’t stand the thought of eating another plate of near lard.

I’ve also run in a heat chamber cranked up to ninety degrees Fahrenheit. We wanted to see what this would do to my body temperature. No surprise, it spiked. Humans are better heat runners than shaggy, thick-haired bison, but we’re still better off in the cool and shade.

Here’s what science and various experiments have taught me about nutrition and performance. Don’t expect miracles. Secret foods and pills won’t make you faster. Only training and smart racing can do that. There is no one and only true path—not the vegetarian way nor vegan nor Paleo nor any other anointed diet. Rather, there are many healthy diet patterns.

Whole carbohydrates improve performance. So do caffeine and moderate amounts of water. Use Gatorade or another sports drink if you have tried it and liked it many times. Avoid most processed foods. Eat real fruits, real vegetables, eggs, dairy, whole grains, legumes, and healthy fish, fowl, and meat.

Don’t try to be perfect. Go to Dairy Queen from time to time. It feeds the child within, which is never a bad idea.