Nutritional epidemiology: Nutritional assessment and analysis

Abstract

Dietary assessment is used to determine the amounts of intakes of foods, nutrients, energy, and other dietary components consumed by individuals. Different methods are employed to obtain quantitative data on usual intake patterns that reflect long-term eating habits. These include the 24-h recall, diet record, food frequency questionnaire, and others. After data are collected and checked for reliability, linkage with nutrient databases and statistical analyses are used to generate estimates of actual intake of individuals or populations. Nutrient consumption patterns vary with age and current studies using these tools focus on specific age categories, such as children, older adults, or those with one or another chronic disease. Diet-bone linkages have been advanced by assessment techniques, but only a few nutrients have been investigated in depth. For example, calcium, phosphorus, and vitamin D have been extensively investigated, whereas other micronutrients have been given little attention. Two forms of vitamin K are now receiving greater attention because the menaquinones (vitamin K2) may have greater effects on bone than phylloquinone (vitamin K1). The skeletal effects of phytochemical intakes from foods, i.e., chemicals made only by plants, are receiving more attention because of potential benefits. Both cross-sectional and longitudinal studies of the skeleton have used assessment methods to determine if any benefits accrue from defined diets or from single or multiple nutrient supplements. Further randomized controlled trials for one or more years designed to test nutrients besides calcium are needed for advancing our knowledge of skeletal effects and recommending dietary intakes of nutrients across the life cycle.