WATER
It’s the most essential of all nutrients, especially if you’re muscular: Muscle contains almost three times more water that fat. (The average man’s body is 40 percent muscle, while the average woman’s is 23 percent.) Water lubricates joints, regulates temperature and provides the body with minerals and essential fluids. The average man should get at least two quarts a day, or about eight glasses. “If you’re physically active, you could easily need to double that,” says Georgia Kostas, a registered dietitian and director of nutrition at the Cooper Clinic. You also get water from food: Bread is about 36 percent water; a potato, 80 percent.