biochemical

• Nutritional biomarkers

  are defined as biological characteristics that can be objectively measured and evaluated as indicators of normal biological or patho genic processes, or as responses to nutrition inter ventions.
• Nutritional biomarkers


  can be measure ments based on biological tissues and fluids, on physio logical or behavioral functions, and more recently, on metabolic and genetic data that in turn influence health, well-being and risk of disease
• Nutritional biomarkers


  are biological measurements (e.g., in blood or urine) that are used to indicate normal biological processes, pathogenic processes, or pharmacologic responses to therapeutic intervention
• Nutritional biomarkers


  are essential for assessing the nutritional status of an individual and/or population.
• Program managers and policymakers


  use population-level biomarkers for screening, surveillance, and monitoring and evaluation of interventions
• Clinicians


  use biomarkers mainly for diagnosis, prognosis, and treatment; and researchers use biomarkers for any or all of these purposes based on their needs
• Biomarkers of exposure


  classification of nutritional biomarkers (1)
• Biomarkers of status


  classification of nutritional biomarkers (2)
• Biomarkers of function


  classification of nutritional biomarkers (3)
• Biomarkers of exposure and Biomarkers of status


  body fluids (serum, erythro cytes, leuco cytes, urine, breast milk); tissues (hair, nails)
• Biomarkers of function


  measure the extent of the functional con sequences of a nutrient deficiency: serve as early bio markers of subclinical deficiencies.
• functional

  ____ biochemical: enzyme stimulation assays; abnormal metabolites; DNA damage
• Functional physiological/behavioral

  more directly related to health status or disease such as vision, growth, immune function, taste acuity, cognition, depression. These biomarkers impact on clinical and health outcomes
• Biomarkers of exposure

  Food or nutrient intakes; dietary patterns; supplement usage.
• dietary biomarkers

  Biomarkers of exposure can be based on direct measurements of nutrient intake using traditional dietary assessment methods, or indirect measurements using surrogate indicators termed
• Dietary biomarkers

  ____ _____ as objective indicators of dietary exposure.
• Dietary biomarkers 


  can be classified into three groups: recovery, con centration, and predictive — each has distinctive properties
• Recover biomarkers


  • Measure total excretion of marker over a defined time period
• Excretion


  is a fixed proportion of intake with only negligible inter-individual variation.
• Recover biomarkers


  • Best suited to measure absolute intake • Examples include: urinary N2  for protein, K and Na in 24hr urines; doubly-labeled water for short-term energy expenditure
• Concentration biomarkers


  • Based solely on the con centration of the bio marker • Provide no infor mation on physio logical balance and excretion • Cannot be translated into absolute levels of intake • Positively correlated with intake, so can be used for ranking • Examples include: total carotenoids (fruit + vegetable intake): plasma vitamin C; phenols
• Predictive biomarkers


  • Incomplete recovery • Stable and time-dependent, and a high correlation with intake • Used in medicine to predict who is likely to respond to therapy • Rank between con centration and recovery bio markers in terms of ability to estimate absolute intake • Examples include: urinary sucrose and fructose for sugar intake
• biomarkers of status

  Biomarkers based on nutrients in biological fluids and tissues are frequently used as ______, and in some cases, of exposure.
• whole blood


  Biopsy material most frequently used is ____ ____ or fraction of ____
• sampling, storage, preparation, and analysis


  Four stages are involved in the analysis of these biopsy materials
• Contamination


  is a major problem for trace elements, and must be controlled at each stage of their analyses
• Biomarkers of function


  • Measure the extent of the functional con sequences of a nutrient deficiency
• surrogate biomarkers

  They measure the extent of the functional con sequences of a specific nutrient deficiency and hence, have greater biological significance than the static bio markers, some functional biomarkers are also being used as substitutes for chronic disease outcomes, when they are termed
• True

  T or F: Biomarkers should be selected with care, and their limitations under con ditions of health, inflam mation, genetic and disease states understood.
• True

  T or F: • Biomarkers are affected by non-biological sources of variation arising from specimen collection and storage, seasonality, time of day, con tamination, stability, and laboratory quality assurance.
• True


  T or F: Both the biological (e.g., conditions of health, inflammation, genetic) and non‑biological sources of variation will impact on the validity, precision, accuracy, specificity, sensitivity, and predictive value of the bio marker.
• True


  T or F: Because almost all techniques are subject to both random and systematic measurement errors, personnel should use calibrated equipment and should be trained to use standardized and validated techniques which are monitored continuously by appropriate quality-control procedure.
• Validity


  refers to how well the bio marker correctly describes the nutritional parameter of interest.
• Valid biomarkers


  are ideally free from random and systematic errors and are both sensitive and specific.
• vitamin b12


  biomarkers: pernicious anemia
• Fat-soluble vitamins


  Steatorrhea: biomarker?
• precision 


  assessed by repeated measure ments on a single specimen or individual.
• Precision


  refers to the degree to which repeated measurements of the same bio marker give the same value.
• coefficient of variation


  as determined by the ratio of the standard deviation to the mean of the replicates (SD/mean × 100%) is the best quantitative measure of the precision
• Sensitivity


  refers to the extent to which the bio marker identifies individuals who genuinely have the con dition under investigation (e.g., a nutrient deficiency state).