Collection of dietary-supplement data and implications for analysis

Area of Science:

• Nutritional Epidemiology
• Public Health Nutrition

Background:

• Epidemiologic studies frequently assess nutrient intake's impact on disease outcomes.
• Many U.S.-based studies omit fortified foods and vitamin supplements, crucial sources of certain vitamins.
• The significance of these nutrient sources varies across demographics like race, sex, and age.

Purpose of the Study:

• To highlight the impact of excluding fortified foods and supplements in nutrient intake assessments.
• To examine the consequences of nutrient misclassification on disease risk analyses.
• To inform statistical approaches in nutritional epidemiology.

Main Methods:

• Review of existing epidemiologic study methodologies regarding nutrient intake assessment.
• Analysis of nutrient sources (fortified foods, supplements, diet) and their contribution to total intake.
• Evaluation of the effects of misclassification on nutrient status and disease risk association.

Main Results:

• Excluding fortified foods and supplements leads to significant misclassification of total nutrient intake for vitamins C and E.
• Misclassification results in poor correlation between estimated intake and blood nutrient concentrations.
• This omission impairs the ability to detect associations between nutrient intake and disease risk, unlike for beta-carotene.

Conclusions:

• Accurate nutrient intake assessment in epidemiologic studies must include fortified foods and supplements.
• Failure to account for these sources introduces bias and reduces statistical power in etiologic research.
• Revised methodologies are needed to improve the reliability of findings on nutrient-disease relationships.