Proper nutrition isn't simply about eating what's right; it's also about avoiding what's wrong. "Wrong," for most everyone, encompasses more than just the obvious nasties like processed foods, trans fats, and sugar.
"There are a lot of healthy foods that people can be sensitive to," says Pam Vagnieres, a Colorado-based nutritionist and exercise physiologist. "Strawberries, citrus fruits, corn, peanuts, and nightshades in particular can cause joint pain for some people." (Nightshades are a group of chemically linked plants that includes tomatoes, potatoes, bell peppers, and eggplants.)
For U.S. hockey player and four-time Olympian, Angela Ruggiero, knowledge of her own sensitivities has meant cutting out cherries, eggs, yeast, almonds, and black pepper, among others.
"I had a food-sensitivity test and came back sensitive to 14 foods," Ruggiero says. "The biggest for me was discovering that wheat and yeast make me feel lethargic. Even if you think something is healthy, it might not be right for you."
In addition to the tiredness that Ruggiero experienced, eating foods that the body is sensitive to can lead to aches, rashes, mood problems, and sleeplessness.
While lab tests are the best way to determine food sensitivities, it can also be done at home through what is commonly known as an elimination diet-a way of figuring out what foods work and don't work for individual bodies.
"Gluten, dairy, soy, and eggs are the big ones," says Vagnieres. "Some reactions are obvious, like coughing, congestion, and rashes. But some, like fatigue, are trickier."
For athletes like Ruggiero, who are frequently on the road and at the mercy of hotel restaurants, this sort of food flexibility becomes very important.
"It's hard to keep up with all this when you're traveling," says Ruggiero. "You don't always have the alternatives. I'm much stricter when I have complete control."