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Evaluation of Food Fortification with Folic Acid for the Primary Prevention of Neural Tube Defects
Table 1: Framework for a two-phase, multi-site study to examine the effects of food fortification with folic acid
| Content | Study objective | Sample** | Location |
| I. Knowledge and intake of folic acid supplements | Determine knowledge and consumption of folic acid supplements, pre- and post-fortification | Non-pregnant women of childbearing age (19-44 years) | St. John's Rural Newfoundland Kingston, Ontario |
| II. Dietary assessment* | Determine dietary intake of folate, pre- and post- fortification |
A) Non-pregnant women of childbearing age (19-44 years), not taking supplements containing folic acid; B) Seniors (65 years or older) not taking supplements containing folic acid or B12 supplements and not diagnosed with anaemia |
St. John's
|
| III. Blood analysis* | Determine blood folate and vitamin B12 status, pre- and post-fortification | St. John's only | |
| IV Rates of NTDs | Determine incidence of NTD-affected pregnancies, pre- and post-fortification | Provincial population | Province of Newfoundland and Labrador |
| * |
For each phase, the same sample of women and seniors were analyzed in Components II and III. |
| ** | Sampling was done separately for Phases I and II. |
Table 2: Knowledge and use of supplements containing folic acid
|
|
Newfoundland
|
Ontario
|
||
|
Phase I
|
Phase II
|
Phase I
|
Phase II
|
|
| Participants (n) |
469
|
443
|
481
|
451
|
| Knowledge (%) |
32.8
|
45.6*
|
35.6
|
51.2*
|
| Use of supplements (%) |
17.1
|
28.0*
|
33.0
|
38.8
|
| * | Increase from Phase I to Phase II is statistically significant. |
Table 3: Use of supplements containing folic acid by likelihood of pregnancy
|
Likelihood of
pregnancy
|
Newfoundland
|
Ontario
|
||||||
|
Phase I
|
Phase II
|
Phase I
|
Phase II
|
|||||
|
Number
|
% users
|
Number
|
% users
|
Number
|
% users
|
Number
|
% users
|
|
| Not using birth control |
50
|
18.0
|
33
|
54.5*
|
53
|
41.5
|
38
|
50.0
|
| Using birth control |
202
|
19.8
|
200
|
27.0
|
224
|
29.4
|
172
|
40.6
|
| No chance |
198
|
11.1
|
193
|
20.7
|
199
|
34.2
|
236
|
35.6
|
| Information not available |
19
|
47.4
|
17
|
70.6
|
5
|
60.0
|
5
|
40.0
|
| Total |
469
|
17.1
|
443
|
28.0
|
481
|
33.0
|
451
|
38.8
|
| * | Increase from Phase I to Phase II is statistically significant. |
Table 4: Laboratory data (geometric mean and 95% confidence interval) for young women participants (age 19-44 years) for Phase I and Phase II
| Characteristics |
Phase I
|
Phase II
|
p value*
|
| Total participants (n) |
322
|
305
|
-
|
| Serum folate (nmol/L) |
14.4
(13.9-15.0) |
19.0
(18.4-19.7) |
<0.001
|
| RBC Folate (nmol/L) |
647
(627-669) |
796
(769-824) |
<0.001
|
| Plasma HCY (µmol/L) |
10.0
(9.6-10.4) |
8.9
(8.6-9.2) |
<0.001
|
| Serum vitamin B12 (pmol/L) |
188
(180-197) |
199
(191-207)** |
0.02
|
| Plasma MMA (µmol/L) |
0.18
(0.17-0.19) |
0.20
(0.18-0.21)** |
0.169
|
| * | Significance test of difference between Phase I and Phase II is based on non-parametric Mann-Whitney U test. |
| ** | The distribution of log-transformed data failed when tested for normality by the Komogorov-Smirnov test for p <0.05. |
Table 5: Laboratory data (geometric mean and 95% confidence interval) for senior participants (age 65 or over) for Phase I and Phase II
| Characteristics |
Phase I
|
Phase II
|
p value*
|
| Total participants (n) |
202
|
186
|
-
|
| Serum folate (nmol/L) |
14.8
(14.0-15.6) |
23.0
(22.0-24.1) |
<0.001
|
| RBC Folate (nmol/L) |
745
(713-779) |
916
(873-961)** |
<0.001
|
| Plasma HCY (µmol/L) |
13.6
(13.0-14.2)** |
12.3
(11.7-12.9)** |
0.001
|
| Serum vitamin B12 (pmol/L) |
183
(173-194) |
216
(202-231) |
<0.001
|
| Plasma MMA (µmol/L) |
0.24
(0.22-0.27)** |
0.26
(0.24-0.28) |
0.229
|
| * | Significance test of difference between Phase I and Phase II is based on non-parametric Mann-Whitney U test. |
| ** | The distribution of log-transformed data failed when tested for normality by the Komogorov-Smirnov test for p <0.05. |
Table 6: Incidence of neural tube defects (NTDs) in Newfoundland before folic acid supplementation (1991-1993), prior to folic acid fortification (1994-1997) and after fortification (1998-2001)
|
Year
|
Number of cases of
NTDs
|
Total number of
births*
|
Average incidence per 1,000 births
per year
|
||
|
In live births and stillbirths
|
In terminated pregnancies
|
Total
|
|||
| Pre-supplementation 1991-1993 |
50
|
40
|
90
|
20,711
|
4.35
|
| Pre-fortification 1994-1997 |
53
|
50
|
103
|
23,592
|
4.37
|
| Post-fortification 1998-2001 |
8
|
11
|
19
|
19,816
|
0.96
|
| * | The total number of births includes live births, stillbirths and terminations for NTD. |
Figure 1: Incidence of NTDs in Newfoundland, 1976 to 2001 (3-year moving average rates)*
| * | The rate for 1976 is a 2-year average based on data for 1976 and 1977 and the rate for 2001 is a 2-year average based on data for 2000 and 2001. |
| ** | Live births, stillbirths and terminations for NTDs. |
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