Vitamins and Minerals

Vitamins and minerals are essential for metabolizing energy substrates, for aiding in tissue building, for fluid balance in the intercellular and extracellular environments, and for carrying oxygen and other elements needed for metabolic work. In addition, vitamins and minerals play a role in reducing the exercise-induced oxidative stress experienced by athletes. Because of their higher rates of energy metabolism and higher muscular and skeletal stresses, athletes need more of many of the vitamins and minerals than do nonathletes. However, the amount of individual vitamins and minerals needed and the optimal delivery systems for ensuring adequate tissue levels are not well understood by most athletes, who often err on the side of providing an excessive vitamin and mineral load through high-dose supplementation. In addition, some companies now include selected vitamins in sports beverages without sufficient thought to their impact on increasing fluid osmolality and reducing the rate of fluid delivery to working muscles. The end result of this strategy is excess vitamin and mineral intake plus inferior fluid delivery.

This chapter discusses vitamin and mineral requirements for exercise, the functions of these nutrients, and the optimal delivery strategies to ensure athletes obtain what they need without adding to the cellular stress associated with excess or deficiency. Standards for nutrient intake adequacy have been established by the Institute of Medicine. These standards, referred to as the Dietary Reference Intakes (DRIs), are based on the assessment of the Estimated Average Requirement (EAR), the Recommended Dietary Allowance (RDA), the Adequate Intake (AI), and the Tolerable Upper Intake Level (UL). Although the focus of the Recommended Dietary Allowance (the earlier standard for nutrient intake adequacy) was based on lowering the risk that someone would suffer from a nutrient-deficiency disease, the focus of the DRI is to lower the risk of developing chronic disease by ensuring a properly balanced nutrient intake.

Table 2.1 Dietary Reference Intakes Definitions

The Dietary Reference Intakes (DRIs) are quantitative estimates of nutrient intakes to be used for planning and assessing diets for healthy people. These values include both recommended intakes and tolerable upper intake levels. The DRIs are determined by the Institute of Medicine, a nonproï¬nullt group that provides health policy advice to the National Academy of Sciences. The DRIs are based on the scientiï¬nullc evaluation of the Recommended Dietary Allowance, the Adequate Intake, the Tolerable Upper Intake Level, and the Estimated Average Requirement.

• Recommended Dietary Allowance (RDA): the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.
• Adequate Intake (AI): a recommended intake value based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of healthy people that are assumed to be adequate-sed when an RDA cannot be determined.
• Tolerable Upper Intake Level (UL): the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects increases.
• Estimated Average Requirement (EAR): a daily nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a life stage and gender group-sed to assess dietary adequacy and as the basis for the RDA.

Vitamins

Minerals