From: A scheme for a flexible classification of dietary and health biomarkers
Criterion | Classification | Definition | Examples | References | |
---|---|---|---|---|---|
Sample type | Biomarker | ||||
Temporal relationship with dietary intake | Short-term biomarkers | Biomarkers that respond to dietary intake within hours | Breath | Hydrogen (lactose intolerance) | [4] |
Plasma | 13C–glucose (lactose intolerance) | ||||
Serum | Vitamin C (postprandial spikes) | ||||
Serum | Triglycerides (postprandial spikes) | ||||
Medium-term biomarkers | Biomarkers that respond to dietary intake over weeks or months | Red blood cell | Essential fatty acid (average of the previous 120 days of intake of essential fatty acids) Folate (average of the previous 120 days of intake of folate) | ||
Long-term biomarkers | Biomarkers that respond to dietary intake over several months or years | Hair Toenail | Trace element (long-term intake of a trace element, e.g. Se) | ||
Relevant functional outcomes | Markers of exposure to a food compound | Markers that are related to the exposure to the food compound being studied, such as a serum, fecal, breath, urine or tissue marker | Red blood cell Blood | Folate (exposure to folate in food) Tryptophan (exposure to tryptophan in food) | [5] |
Markers of target function/biological response | Markers that are related to the target function or biological response such as changes in body fluids, levels of a metabolite, protein or enzyme or changes in a given function | Plasma Physical | Reduction of homocysteine (response to dietary folate) Blood pressure (response to dietary caffeine) | ||
Markers of intermediate endpoint | Markers that are related to an appropriate intermediate endpoint of an improved state of health and well-being or reduction of risk of disease, or both, such as the measurement of biological processes that relate directly to the endpoint | Physical Bone | Extent of narrowing of the carotid artery (cardiovascular disease) Mineral density (risk of bone fracture) | ||
Association with intake | Recovery biomarkers | Biomarkers based on recovery of certain food compounds directly related to intake and not subject to substantial inter-individual differences | Urine Urine Urine | Doubly labeled water (metabolic rate and total energy expenditure) Nitrogen (protein intake) Potassium and sodium | |
Predictive biomarkers | Biomarkers that are sensitive, time dependent and show a dose-response relationship with intake levels but their overall recovery is lower than recovery biomarkers | Urine | 24-h sucrose and fructose (sugar intake) | ||
Concentration biomarkers | Biomarkers whose concentrations do correlate with intakes of corresponding foods or nutrients but the strength of the correlation is often lower (< 0.6) than that expected for recovery biomarkers (> 0.8) | Serum Blood | Vitamins (vitamin intake) Lipids (lipid intake) | ||
Replacement biomarkers | Biomarkers that are closely related to concentration biomarkers and refer specifically to compounds for which information in food composition databases is unsatisfactory or unavailable | Urine Serum Urine | Aflatoxin Isoflavonoids and lignans (phytoestrogen intake) Phytoestrogens (phytoestrogen intake) | ||
Biological endpoint | Biomarker of exposure | Accurately reflecting intake/exposure | Any biological specimen | Plasma vitamin C | [3] |
Biomarker of susceptibility | Accurately reflecting (an aspect of) susceptibility | Any biological specimen | Low plasma vitamin C (risk of scurvy); high serum cholesterol or blood pressure (susceptibility to myocardial infarction); low bone mineral density (susceptibility to fractures) | ||
Biomarkers of effect and efficacy | An established biomarker of efficacy is an indicator of an improvement of a physiologic function or a decrease in risk factors for a disease (it follows that effect biomarkers would also include the corresponding null or negative outcomes) | Any biological specimen | Changes in: serum cholesterol; blood pressure; bone formation, resorption or density; prostate specific antigen | ||
Purpose of the study | Biomarkers of dietary exposure | Biomarkers that are aimed at assessing dietary intake of different foods, nutrients, non-nutritive compounds or dietary patterns (recovery biomarkers, concentration biomarkers, recovery biomarkers and predictive biomarkers) | Urine | Nitrogen (protein intake) | [7] |
Biomarkers of nutritional status | Biomarkers that reflect not only intake but also metabolism of the nutrient(s) and possibly effects from disease processes | Plasma | Homocysteine (folate deficiency, one-carbon metabolic processes) | ||
Biomarkers of health/disease | Biomarkers related to different intermediate phenotypes of a disease or even to the severity of the disease | Plasma Plasma | Total cholesterol (cardiovascular diseases) Triglycerides (cardiovascular diseases) |