Nutritional status of endurance athletes: what is the available information?

Nutritional status is a critical determinant of athletic performance. We question whether currently available studies can give adequate information on nutritional status of endurance athletes. This paper is a critical review of articles published from 1989 to 2003 that investigate nutritional status of endurance athletes. The terms, "nutrition", "diet", or "nutrient", were combined with "endurance athletes" to perform Medline and Pubmed electronic database searches. Two inclusion criteria were considered: (a) study subjects should be adults and (b) articles should report gender-specific values for total energy expenditure and intake of energy, macro and micronutrient from food. Only seven studies fulfilled inclusion criteria. In general, the conclusions of these studies are that endurance athletes have negative energy balance, low intake of carbohydrate, adequate to high intake of protein, and high intake of fat. A critical discussion of the articles' data on vitamins, minerals and trace elements adequacy is conducted using insights and methodology proposed by the newly published assessment and interpretation of Dietary Reference Intakes (DRIs). The studies evaluated give an inappropriate evaluation of the prevalence of adequacy/inadequacy of micronutrient intake among endurance athletes. In this work we indicate potential limitations of existing nutritional data, which reflects the misconceptions found in published literature on nutritional group evaluation. This review stresses the need for a comprehensive and well-conducted nutrition assessment planning to fulfill the existing gap in reliable information about micronutrient adequacy of endurance athletes.