Limitations and resolutions for dietary assessment of micronutrient intakes.

Micronutrients (vitamins and minerals) are present mostly in small amounts, or concentrated in certain foods. Traditional Asian diets are very diverse and consist largely of foods of plant sources, including several herbs and spices. Challenges in assessing dietary intake include difficulties in collecting information on ingredients in dishes as well as in meals shared by family members, and cooking effects. Variations in intakes of micronutrients are determined by frequency of consumption, and how common or concentrated the nutrients are in specific foods. Moreover, assessing only nutrient intake is inadequate, since other food components affect its bioavailability. Non-nutrient food constituents, such as, phytate and polyphenols interfere with the bioavailability of iron and zinc. Bioconversion and bioefficacy of precursor nutrients, such as, carotenoids, also affect the estimated intake of vitamin A in its active form. Different strategies are required to deal with these challenges in assessing dietary intakes of micronutrients in order to establish the prevalence of inadequate intake, as well as the association between intake and nutritional status.