Jay Birmingham spent the summer of 1980 going across the country. On foot. In 71 days, 22 hours and 59 minutes.

A resident of Jacksonville, Fla., Birmingham spent the summer managing to break the cross-country record running from Los Angeles to New York.

What'd he eat? Cheeseburgers. Lots of cheeseburgers and lots of Mellow Yellow. He said a fear of food poisoning made him avoid tuna and chicken salads in small-town diners, and cheeseburgers seemed to offer the most nutrition with the least trouble to eat; Mellow Yellow (or any non-cola drink) offered quick sources of calories and were refreshing at the same time.

Listen, when you're running 50 miles a day you don't have a lot of time to shop around for haute cuisine.

And when you're tuning up for the Marine Corps Marathon this Sunday, it doesn't matter what you eat. Within reason. What really matters, Birmingham says and other runners agree, is training. Concerns about food, they say, are at best secondary.

Birmingham is quick to caution anyone against wonder foods. "I am reluctant to advocate anything in the extreme," he says. What's good for him may give someone else violent cramps. The only advice he gives about eating is to eat a balanced diet and not to make drastic changes in anything you eat right before a race. If a certain food works for you, that's all you need to know, he insists.

What's peculiar is the gamut of foods and food combinations people rely on for their pre-race meal plans. While spaghetti is a ubiquitous marathon dinner, many racers wouldn't dream of running without a bedtime banana split, or pancakes, or just about anything.

As a matter of fact, master runner Glenn Coleman doesn't eat anything at all before short races (up to 10 miles). He fasts two days before the race and consumes only fluids -- mostly fruit juices.

The 148-pound, 5-foot-9-inch computer specialist takes the traditional approach to carbohydrate loading before a marathon. A vegetarian (for all practical purposes), he'll eat high-protein foods, including yogurt, cheese and eggs on days six through four before the marathon, then switch to eating high-carbohydrate foods, like -- you guessed it -- spaghetti with tomato sauce. Then the two days before the race he might switch to fruit juices again.

Between races he follows Nathan Pritikin's advice for high-carbohydrate diets -- munching on raw vegetables through the day and eating steamed vegetables, boiled potatoes and salads (with low-calorie dressing) at night.

Running consistently for the last 10 of his 58 years, Coleman says, "If you're going to do well as a runner, you have to have all the fat out of your body. You have to eat a lot, but you have to watch what you eat."

Johnathan Miller, a congressional administrative assistant, does watch what he eats. All of it right, down to the pre-dinner Dutch pretzels he polishes off with two or three beers.

At 5-11 and 135 pounds, it's hard to believe the 29-year old has a weakness for sweets. While breakfast between races might be a glass of milk and lunch a carton or two of fruit-flavored yogurt, he says, "In the evening, I'm disgusting." After pretzels and beer, there is a "huge dinner" and always a double helping of ice cream.

Ed Demoney, whose preparation for Washington's Marine Corps Marathon is only a small step in the grand scheme to run 100 miles in June, says he is "continuously trying to lose weight."

The 5-foot-10, 145-pound Federal Reserve Board employe relies on modified carbohydrate loading (heavy consumption of carbohydrates the last days before a race), but succumbs also to the temptation of sweets such as pound cake and ice cream.

He belongs to an informal group of 12 runners at his job called the "Striders" who indulge in a ritual called an "end-cut meeting." Three days before the big race (today, in fact) they go to the Watergate pastry shop and share a bargain box of pastries -- the end cuts of sweets like Napoleans -- that costs $3.

A veteran of the 1976 Boston marathon, he says before that race he consumed fruit and fruit juices and kept his food intake "low for the few weeks before the race."

But Jay Birmingham warns that no amount or combination of food will deem a successful run. The only thing that guarantees that, he says, is training. No food in the world can make up for lack of it. Still, the night before he races, he usually has a plate of spaghetti and his wife's oatmeal cookies.