Shuaibi AM, House JD, Sevenhuysen GP. Folate status of young Canadian women after folic acid fortification of grain products. J Am Diet Assoc. 2008 Dec; 108 (12): 2,090-2,094.
PubMed ID: 19027414
The purpose was to determine folate status and the contribution to total folate intake from natural food folates, folic acid added to food and folic acid from supplements in women of childbearing age from a convenience sample from one Canadian province, Manitoba, in the post-folic acid fortification era.
Healthy women aged 17 to 25 years from the University of Manitoba and women who were taking oral contraceptives or folic acid supplements.
Women were excluded if they were currently pregnant, had a pregnancy lasting more than 20 weeks in the year before the scheduled clinic visit, were lactating and or used medications known to interfere with folate metabolism.
University of Manitoba campus-wide advertisement.
Dietary Intake/Dietary Assessment Methodology
Folate intake was assessed by the Food Choice Map by trained interviewers. The Food Choice Map nutrient analysis program was designed for collecting data on quality, quantity and preparation of foods and beverages in a standardized way. The Food Choice Map–nutrient analysis program calculations are made with food composition data from 1,462 food items that represent most of the foods reported by this population. Adjustments were made to correct for the bioavailability of folic acid. Food sources and contributors for folate were determined by grouping food items. Twenty-four food groups and subgroups were selected in this attempt. The total amount of folate in each of the selected groups or subgroups was estimated for each participant then divided by the total folate intake from all foods. Foods were ranked by percentage contribution to dietary folate intake.
- Biomarker, nutrient and food intake data were analyzed by Number Cruncher Statistical Software (2000 edition, 1999, Kaysville, UT)
- Mean, 10th, 50th and 90th centile values were determined for serum and red blood cell folate and total homocysteine
- Normality of the data was checked by using the Kolmogorov-Smirnov test. Log transformations were used to normalize skewed data. To assess for differences in vitamin intake between supplement users and non-users independent sample T-tests were used. A probability level of 5% was chosen to reflect the level of significance.
Timing of Measurements
Fasting blood samples measurements were take once after a 12-hour fast.
- Total folate concentration from ascorbic acid-stabilized serum with a competitive protein binding assay (Quantaphase Folate/B12 Radioassay, Bio-Rad Laboratories, Mississauga, Ontario, Canada). [Negative folate balance equals serum folate concentration of less than 3.1ng/ml (7nmol/L). Adequate red blood cell folate status equals values greater than or equal to 134.2ng/ml (304nmol/L)].
- Total homocysteine from plasma obtained from ethylenediaminetetraacetic acid-treated blood samples according to the reverse phase–high-performance liquid chromatography method of Araki and Sako, with modifications as suggested by Gilfix and colleagues. (Hyperhomocysteinemic was a total homocysteine concentration greater than 12 micromoles/L).
Total folate intake from:
- Natural food folates
- Folic acid added to food
- Folic acid from supplements.
- Initial N: 95 women
- Attrition: 0%
- Mean age: 20.5 years (range 17-24 years)
- Ethnicity: Not described
- Other relevant demographics: None were described
- Anthropometrics: None were described
- Location: The women were from the University of Manitoba, Canada. Subject characteristics were described in a previous publication: Shuaibi AM, Sevenhuysen GP, House JD. Validation of a food choice map with a three-day food record and serum values to assess folate and vitamin B12 intake in college-aged women. J Am Diet Assoc. 2008; 108: 2,041-2,050.
The mean intakes of folate, as natural food folate, dietary folic acid and folic acid from supplements and Dietary Folate Equivalents (DFEs) of the 95 women, as well as the difference in the intakes between supplement users and non-users, are shown in Table 1.
Sources of folate were determined and the dietary folate equivalents were determined. Table 2.
Table 1. Intakes of natural folate, folic acid from food, folic acid from food and from supplements.
mcg per day
|Supplement Users and Non-users (N=95)||Supplement Non-users[a] (N=70)||Supplement Users (N=25)||Supplement Users and Non-users
|Supplement Non-users [a] (N=70)||Supplement Users (N=25)||Supplement Users and Non-users (N=95)||Supplement Non-users[a] (N=70)||Supplement Users (N=25)|
|Natural folate from food||314.4±134.3||294.5||84.1-875.5||317.9±135.6||290.6||124.4+875.5||304.3±132.8||314.4||84.2-662.4|
|Folic acid from food||95.7±63.9||83.1||4.1-311.6||94.9±57.8||86.34||4.1-311.6||97.9±79.8||65.4||16.4-302.2|
|Folic acid from supplements||94.9±189.3||0||0-1,000||0||0||0||360.8±201.0||400.0||43-1,000|
a Means compared using independent T-test between supplement non-users and users
b SD=standard deviation
c DFE=dietary folate equivalent.
yz Values with different superscripts (y,z) in row differ significantly
Table 2. Mean, median and range for serum folate.
|Variable||Serum folate (nmol/L)||Red blood cell folate (nmol/L)||Plasma total homocysteine (micromol/L)|
|Range (10th and 90th percentile)||10.0 to 19.3ng/ml (33.0±7.9,32.0 and 22.6 to 43.8nmol/L)||180.5 to 462.9ng/ml (707±311, 650 and 409 to 1,049nmol/L)||3.5 to 7.5mol/L|
- Folate status was 2.3 times higher than the level deemed acceptable for all women
- 14% of women had a red blood cell folate concentration greater 400ng/ml (906nmol/L), which is the value associated with very-low neural tube defect risk
- Mean daily folate intake from food, fortified foods and supplements was 645.7± 368.4mcg DFE per day
- The contribution of folic acid from supplements to total folate intake, when calculated with the use of the bioavailability correction factor for supplemental folic acid, was 51%. The dietary folate intakes of supplement users from food alone were similar to those of non-users, a finding reported by others.
- With the use of folic acid-containing supplements and the 1998 folic acid fortification program, 79% and 91% of women in this study met the Recommended Dietary Allowance and Estimated Average Requirement for folate.
- Only 17% of study participants met the special recommendation for women capable of becoming pregnant (400mcg folic acid per day). No one met this recommendation unless they used folic acid supplements.
- One percent of participants exceeded the Upper Limit for folate intake and this was due to use of supplements containing 1,000mcg of folic acid
- The mean increase in folic acid consumption due to fortification reported in our study was 96mcg per day, which suggest that the fortification program is reaching women of reproductive age
- Vegetables contributed in total 17.7% of the folate consumed by these women. The top folate contributors were breads and bakery products, vegetables, juices, pasta, rice and ready-to-eat cereals.
- 4.2% of women were classified as hyperhomocysteinemia, which was defined as greater than 12.0micromoles/L
- No woman was found to have compromised serum folate status.
Data suggest that women of childbearing age are achieving positive folate status in the post-fortification era, but it may not be sufficient to achieve red blood cell folate concentrations associated with a significant reduction in neural tube defect risk.
It is unclear how many women they initially enrolled in their study.
Limitations noted by the authors
- Data may not truly reflect the folate intakes of all women of childbearing age since the data was taken from a convenience sample of women attending a post-secondary educational institution in one Canadian province (Manitoba)
- Lack of a pre-folic acid fortification control group and comparisons of serum and red blood cell folate results obtained from different laboratories and methods may not be directly comparable
- The potential exists for existing nutrient databases to underrepresent the amount of folic acid in fortified foods due to overfortification.
Research Design and Implementation Criteria Checklist: Primary Research
|1.||Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)|
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|1.||Was the research question clearly stated?|
|1.1.||Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?|
|1.2.||Was (were) the outcome(s) [dependent variable(s)] clearly indicated?|
|1.3.||Were the target population and setting specified?|
|2.||Was the selection of study subjects/patients free from bias?|
|2.1.||Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?|
|2.2.||Were criteria applied equally to all study groups?|
|2.3.||Were health, demographics, and other characteristics of subjects described?|
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|3.||Were study groups comparable?|
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|6.7.||Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?|
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