Normality assessment and dietary data categorization

Golaleh Asghari, PhD 2019

How to approach nutritional factors

When relationships with disease are analyzed, nutritional factors may be examined in terms of absolute amount (crude intake) or in relation to total caloric intake

Depends on:

• • the nature of the biologic relationship
  • and the public health considerations
• If a nutrient is metabolized in approximate proportion to total caloric intake (such as the macronutrients and some vitamins), nutrient intake is most likely biologically important in relation to caloric intake.
• As body size is a major determinant of energy intake, adjustment for energy is usually appropriate because an absolute amount of nutrient have less effect for a larger person than for a smaller one.
• If a nutrient selectively affects an organ’s system uncorrelated with body size (e.g., central nervous system), or if physical activity does not affect its metabolism, absolute intake may be most relevant.
• For example: menstrual blood losses are not thought to increase with physical activity → iron requirements to prevent anemia might be related to absolute intake.
• If absolute nutrient intake rather than intake in relation to calories is biologically most relevant, caloric intake should be associated with disease, as intakes of all nutrients are ↑ with total caloric intake
• Ex: if ↑ absolute intake of a nutrient is a cause of disease, then those who consume more total food due to being large, active, or metabolically inefficient should be at higher risk of disease. We would expect a greater risk of iron deficiency anemia among women with ↓ total energy intake due to ↓ physical activity.
• Lack of association between total energy intake and disease: evidence against the importance of absolute nutrient intake, but not against the importance of nutrient composition of the diet.