In briefSports nutritionists generally think an athlete's increased mineral requirements can be satisfied by a greater but well-balanced caloric intake. This study supports that concept, demonstrating that 12 male runners who consumed an unrestricted, isocaloric diet maintained normal plasma mineral levels without using mineral supplements during a 500-km (312-mile) road race. None of the nine minerals tested (calcium, phosphorus, sodium, potassium, chloride, magnesium, iron, copper, and zinc) showed tendencies to become persistently reduced over the 20-day period.