Folate Intake and Markers of Folate Status in Women of Reproductive Age, Pregnant and Lactating Women: A Meta-Analysis

Table 4

Forest plot of the effects of total folate supply (i.e., supplement plus dietary folate), with the supplement provided in form of folic acid and [6S]-5-methyltetrahydrofolate [5-MTHF] on serum or plasma folate in childbearing age, pregnant and lactating women.

Study or subgroup	Beta	SE	Weight	Beta; IV, Random, 95% CI	Beta; IV, Random, 95% CI
Folic acid
Brouwer et al., 1999_1 [26]	0.35741049	0.04126697	12.5%	0.36 [0.28, 0.44]
Ellison et al., 2004 [33]	0.53050104	0.09332632	11.1%	0.53 [0.35, 0.71]
Fohr et al., 2002 a [31]	0.53023607	0.04406458	12.5%	0.53 [0.44, 0.62]
Green et al., 2005 [32]	1.00981877	0.06717076	11.9%	1.01 [0.88, 1.14]
Houghton et al., 2006 f [36]	0.57853113	0.09878823	10.9%	0.53 [0.38, 0.77]
Lamers et al., 2006 c [18]	0.7384753	0.06637089	11.9%	0.74 [0.61, 0.87]
Lira et al., 1989 [34]	0.37051554	0.06476415	12.0%	0.37 [0.24, 0.50]
Mackey and Picciano, 1999 [20]	0.13206921	0.10234828	10.8%	0.13 [−0.07, 0.33]
Nogueira et al., 2003 [35]	0.94291343	0.24037313	6.3%	0.94 [0.47, 1.41]
Subtotal (95% CI)			100.0%	0.56 [0.40, 0.72]
Heterogeneity: Tau^2 = 0.05; Chi^2 = 102.70, df = 8 (𝑃<0.00001); 𝐼^2 = 92%
Test for overall effect: 𝑍 = 6.68 (𝑃<0.00001)
5-MTHF
Fohr et al., 2002 b [31]	1.65921221	0.05130933	35.0%	1.66 [1.56, 1.76]
Houghton et al., 2006 g [36]	0.74857769	0.17130372	31.0%	0.75 [0.41, 1.03]
Lamers et al., 2006 e [18]	1.06897313	0.0904731	34.0%	1.07 [0.39, 1.25]
Subtotal (95% CI)			100.0%	1.18 [0.65, 1.71]
Heterogeneity: Tau^2 = 0.21; Chi^2 = 50.98, df = 2 (𝑃<0.00001); 𝐼^2 = 96%
Test for overall effect: 𝑍 = 4.35 (𝑃<0.0001)

*The Authors kindly requested us to cite both the publication in AJCN [18] and Lamers’ Ph.D. thesis for the raw data [37].
RCB: red blood cell.
^aSignificant differences between the baseline and the end of the treatment.
FA: folic acid.
MTHF: methyltetrahydrofolate.