. Author manuscript; available in PMC: 2018 Sep 1.

Published in final edited form as: J Nutr. 2017 Jul 19;147(9):1677–1685. doi: 10.3945/jn.117.247445

TABLE 1.

Blood concentrations of vitamins and total homocysteine in 30 healthy individuals at baseline and after the intervention with 5 mg FA/d¹

	Baseline	Intervention with 5 mg FA/d		P
	Baseline	45 d	90 d	P
Serum folate, ² nmol/L	17.1 (15.1–19.5)^a	81.7 (71.9–92,9)^b	84.5 (74.4–96.2)^b	<0.001
Serum total folate, ³ nmol/L	22.6 (20.2–25.4)^a	97.1 (86.6–108.9)^b	100.1 (89.2–112.2)^b	<0.001
Serum UMFA,³ nmol/L	0.57 (0.51–0.64)^a	3.86 (2.94–5.28)^b	2.21 (1.79–2.79)^b	<0.001
Serum 5-methyl-THF,³ nmol/L	22.5 (18.9–26.5)^a	75.8 (68.1–83.9)^b	83.8 (76.8–91.0)^b	<0.001
Serum THF,³ nmol/L	0.40 (0.32–0.49)^a	0.94 (0.69–1.22)^b	1.19 (1.02–1.32)^b	<0.001
Serum MeFox,³ nmol/L	0.70 (0.57–0.85)^a	1.67 (1.36–2.04)^b	1.65 (1.42–1.92)^b	<0.001
High serum folate, (>45.0 nmol/L), n (%)
Microbiologic assay	1 (3.3)^a	28 (93.3)^b	28 (93.3)^b	<0.001⁴
HPLC/MS-MS	2 (6.6)^a	30 (100)^b	30 (100)^b	<0.001⁴
High serum UMFA,³ (> 1.12 nmol/L)	2 (6.6)^a	29 (96.6)^b	26 (86.7)^b	<0.001⁵
Serum vitamin B₁₂,² pmol/L	376 (334–421)	364 (327–403)	387 (342–434)	0.332
Plasma total homocysteine,⁶ μmol/L	8.4 (7.6–9.3)	8.1 (7.4–8.9)	8.0 (7.2–8.8)	0.394

Values are means and 95% CIs of back-transformed values unless otherwise indicated. Serum 5,10-methenyl-THF and 5-formyl-THF were below the limit of detection (0.2 nmol/L). Numeric variables were transformed by Box-Cox, and the data are presented after reconversion.

One-factor repeated-measures ANOVA was used; when significant, Tukey’s test was performed. Labeled means in a row without a common superscript letter differ, P < 0.05. FA, folic acid; HPLC-MS/MS, HPLC–tandem MS; MeFox, oxidation product of 5-methyl-THF; THF, tetrahydrofolate; UMFA, unmetabolized folic acid.

Derived by using a microbiological assay.

Derived by using HPLC-MS/MS.

⁴

Derived by using likelihood ratios.

⁵

Derived by using chi-square.

⁶

Derived by using chemiluminescence.