Plasma concentration of folate as a biomarker for the intake of fruit and vegetables: the Hordaland Homocysteine Study.
BACKGROUND
Nutritional biomarkers may be used to assess dietary exposure without the errors commonly associated with self-reported dietary data.


OBJECTIVE
The objective was to examine the association between plasma folate and intake of folate, fruit, and vegetables in a large cohort of healthy adults consuming foods that had not been fortified with folic acid.


METHODS
The present study population included 5533 middle-aged (47-49 y) and old (71-74 y) subjects from the Hordaland Homocysteine Study. The participants completed a food-frequency questionnaire and provided blood samples for chemical analyses.


RESULTS
We observed a significant difference in plasma concentrations of folate across increasing quartiles of fruit, vegetable, and orange juice consumption. The difference in plasma folate between the highest and lowest quartiles was 1.97 (95% CI: 1.86, 2.07) nmol/L for fruit intake, 1.79 (95% CI: 1.69, 1.89) nmol/L for vegetable intake, and 2.69 (95% CI: 2.51, 2.87) nmol/L for orange juice intake. A significant inverse relation was observed across increasing quartiles of milk and bread intakes. The difference between the highest and lowest quartiles was -1.03 (95% CI: -1.13, -0.92) nmol/L for milk and -1.60 (95% CI: -1.69, -1.50) nmol/L for bread.


CONCLUSIONS
Plasma folate concentration may be a useful biomarker for the intake of fruit and vegetables in populations consuming unfortified food products. The association can be attenuated by and should be corrected for individual intake of folic acid supplements.
Brevik
Asgeir
A
Department of Nutrition, School of Medicine, University of Oslo, Oslo, Norway. asgeir.brevik@medisin.uio.no
Vollset
Stein Emil
SE
Tell
Grethe S
GS
Refsum
Helga
H
Ueland
Per Magne
PM
Loeken
Elin Bjorge
EB
Drevon
Christian A
CA
Andersen
Lene Frost
LF
D000368:Aged; D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers / Q000097:blood; D001939:Bread / Q000009:adverse effects; D015331:Cohort Studies; D004034:Diet Surveys; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000097:blood*; D005638:Fruit; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008892:Milk / Q000009:adverse effects; D015596:Nutrition Assessment; D011795:Surveys and Questionnaires; D014675:Vegetables
D015415:Biomarkers; D006710:Homocysteine; D005492:Folic Acid