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. Author manuscript; available in PMC: 2016 Mar 29.
Published in final edited form as: J Nutr. 2013 Apr 17;143(6):1001S–1010S. doi: 10.3945/jn.112.172882

Table 1.

List of dependent and independent variables including stratification

Nutrient classes and biomarkers of diet and nutrition
(dependent variables)
Water-soluble vitamins (WSV) and related metabolites (RM):

  • Serum folate (S-FOL)

  • RBC folate (RBC-FOL)

  • Serum pyridoxal-5′-phosphate (PLP)

  • Serum 4-pyridoxic acid (4PA)

  • Serum total cobalamin (B-12)

  • Plasma total homocysteine (tHcy)

  • Plasma methylmalonic acid (MMA)

  • Serum ascorbic acid (VIC)


Fat-soluble vitamins (FSV) and micronutrients (MN):

  • Serum retinol (VIA)

  • Serum alpha-tocopherol (VIE)

  • Serum carotenes (CAR, sum of 3 analytes)

  • Serum xanthophylls (XAN, sum of 3 analytes)

  • Serum 25-hydroxyvitamin D (25OHD)


Fatty acids:

  • Plasma saturated (SFA, sum of 6 analytes)

  • Plasma monounsaturated (MUFA, sum of 7 analytes)

  • Plasma polyunsaturated (PUFA, sum of 11 analytes)

  • Plasma total fatty acids (tFA, sum of 24 analytes)


Trace elements:

  • Serum ferritin (FER)

  • Serum soluble transferrin receptor (sTfR)

  • Serum body iron (BI, calculated from the ratio of sTfR to FER)

  • Urine iodine (uI)


Phytoestrogens:

  • Urine genistein (GEN)

  • Urine daidzein (DAZ)

  • Urine equol (EQU)

  • Urine O-desmethylangolensin (DMA)

  • Urine enterodiol (ETD)

  • Urine enterolactone (ETL)


Acrylamide hemoglobin adducts:

  • Hemolyzed blood acrylamide hemoglobin adduct (HbAA)

  • Hemolyzed blood glycidamide hemoglobin adduct (HbGA)

Physiologic variables
(independent variables)
Fasting status:

  • <3 h

  • 3–<8 h

  • ≥8 h


Inflammation (based on C-reactive protein [CRP]):

  • No, CRP <5 mg/L

  • Yes, CRP ≥5 mg/L (57)


Renal function (defined by estimated glomerular filtration rate [eGFR] using the National Kidney Foundation classification system to determine stages of chronic kidney disease (CKD [58]):

  • Normal, eGFR ≥60 mL/(min·1.73 m2) and absence of albuminuria

  • Stage 1 or 2 of CKD, eGFR ≥60 mL/(min·1.73 m2) and presence of albuminuria

  • Stage 3–5 CKD, eGFR <60 mL/(min·1.73 m2)


Pregnancy (ascertained at the time of the health examination by the value from urine pregnancy test and from self-reported pregnancy status; for women who were interviewed but not examined, pregnancy status could not be determined):

  • No

  • Yes