What a downer. Pre-race illness seems like a cruel case of Murphy’s Law, but you're not the first person to get sick while logging miles for an upcoming endurance event, and there certainly is a connection. While exercise in moderation does boost immunity, intense training tends to wear it down—at least temporarily.
Previous studies have shown that between 10 and 30 percent of pro athletes exhibit "negative physiological signs indicative of increased training volume" in the weeks leading up to championship events, including fatigue, inflammation, and compromised immune function.
"Training to maximize performance is an art, where nutrition, recovery, and stress on the body all need to be balanced," says Joel Fuhrman, M.D., author of Super Immunity. Exercise causes breakdown in the body and the release of free radicals, he explains, but it also allows the body to rebuild, stronger than it was before.
Training too hard, or without proper nutrition and recovery, however, leaves you vulnerable. "It's like taking from the bank and not allowing your deposits to build back up before you make another withdrawal," he says.
More important than any one supplement is your overall diet. Fuhrman advises his patients to make 90 percent of their diets "GBOMBS": greens, beans, onions, mushrooms, berries, and seeds. "They need much more colorful produce and plant protein—stuff that's rich in antioxidants and valuable nutrients the body needs to repair itself," he says.
Sleep is important too: New research says seven hours a night may be the sweet spot, but runners may need more when they're training hard, Furhman says. Also focus on active recovery: Be sure you're following a plan that schedules in rest days, easy runs, and cross-training, so your body's not being stressed in the same way, day after day.
Bottom line: Get enough shuteye, take days off when you're feeling run down, and eat better: more colorful produce and plant-based protein, less animal fat and processed foods.