Skip to Content
Canadian Paediatric Society

Position statement

Folate and neural tube defects: The role of supplements and food fortification

Posted: Apr 1 2016

The Canadian Paediatric Society gives permission to print single copies of this document from our website. For permission to reprint or reproduce multiple copies, please see our copyright policy.

Principal author(s)

Noam Ami, Mark Bernstein, François Boucher, Michael Rieder, Louise Parker; Canadian Paediatric Society, Drug Therapy and Hazardous Substances Committee

Paediatr Child Health 2016;21(3):145-49.


Periconceptional folic acid significantly reduces the risk of neural tube defects. It is difficult to achieve optimal levels of folate by diet alone, even with fortification of flour, especially because flour consumption in Canada is slightly decreasing. Intermittent concerns have been raised concerning possible deleterious effects of folate supplementation, including the masking of symptoms of vitamin B12 deficiency and an association with cancer, especially colorectal cancer. Both concerns have been disproved. The Canadian Paediatric Society endorses the following steps to enhance folate intake in women of child-bearing age: encouraging the consumption of folate-rich foods such as leafy vegetables, increasing the level of folate food fortification, taking a supplement containing folate and B12, and providing free folate supplementation to disadvantaged women of child-bearing age. These recommendations are consistent with those of the Society of Obstetricians and Gynaecologists of Canada.

Key Words: Folate; Folic acid; Fortification; NTD; Supplementation

Folic acid (vitamin B9) is a water-soluble B group vitamin. It is present in foods as folate and in supplements as folic acid, which has greater bioavailability. Folate plays an essential role in DNA synthesis and repair, and in cell growth and division. Folate also has a major role in DNA methylation and is therefore important for epigenomic regulation.

Folate is found in foods such as leafy vegetables, legumes and red meat. Offal, such as liver, also contains high levels of folate. However, up to 70% of folate can be lost during cooking due to thermal degradation or dissolution in the water used for cooking.[1][2]

Adequate folate intake is important for protecting against neural tube birth defects (NTDs). NTDs result from malformation or failed closure of the neural tube during central nervous system development in the third and fourth weeks of gestation.[3]-[11] NTDs include anencephaly, a failed closure of the neural tube at the cerebral cortex, and spina bifida, a defect of closure at the lumbosacral region or, less frequently, at higher regions of the spinal cord.[3][6][10]-[14] NTDs represent one of the most common categories of birth defects in North America. In 1996, the birth prevalence of neural tube defects in Canada (excluding Quebec) was 8 per 10,000 live births, with 219 affected infants.[6][15] In the period before folate fortification, the highest rates were reported in Eastern Canada, with rates decreasing progressively toward the West Coast: rates varied from 10 per 10,000 births in the East versus 5 per 10,000 births in the West.[6][15]-[18] There is a 2% to 5% risk of recurrence in women who have previously given birth to an affected child.[6][19]

The etiology of NTDs is complex and multifactorial: genetics, chromosomal abnormalities and environmental factors have been implicated.[5][6][10][14][19]-[25] However, there is conclusive evidence that increased folic acid intake before conception is associated with a significant decrease in the birth prevalence of NTDs.[26] Optimal levels of total folate may also protect against congenital heart defects,[27] oral clefts,[28]-[29] and neurodevelopmental problems.[30] Current Health Canada recommendations are that women ingest at least 400 µg of folate per day to reduce the risk of bearing a child with an NTD. It is not commonly possible for most people to achieve this level of folate intake from natural foods and for this reason many countries, including Canada, the United States and the United Kingdom, have introduced initiatives to increase folate intake.[31]-[37] These initiatives include fortifying grain products with folic acid and promoting oral folic acid supplements.

Folic acid fortification of foods

To address the dietary insufficiency in folate in North America, the fortification of flour and grain products (including ready-to-eat cereals and pasta) at a rate of 150 µg of folic acid/100 g was made mandatory in 1998. The objective of folic acid fortification is to reduce the birth prevalence of NTDs by increasing total maternal folate, best estimated by a determination of red blood cell (RBC) folate. Food fortification aimed to increase the daily folic acid intake by about 100 µg on average, and one American study demonstrated a rise in RBC folate concentrations from 527 nmol/L to 741 nmol/L in 38,000 women of child-bearing age following the introduction of folic acid fortification. However, even this policy still leaves only 23% to 33% (depending on ethnicity) of North American women of child-bearing age meeting the daily recommended intake.[38] As a result, RBC folate levels in some women remain below the optimal estimated protective level of 900 nmol/L.[39] Moreover, a recent large study in China with pharmacokinetic modelling showed that even higher levels of RBC folate (up to 1500 nmol/L) might be additionally helpful.[40]

Despite the fact that for many women daily folate intakes remain lower than the 400 µg Health Canada recommends, fortifying food with folic acid has been highly effective in reducing the birth prevalence of neural tube defects. Following folic acid fortification, the birth prevalence of spina bifida in Canada fell by over 50% and that of other NTDs by approximately one-third.[41] Moreover, the East-West gradient in the rates of NTDs flattened significantly following the introduction of folic acid fortification.[41] There may, however, be some under-ascertainment of cases because terminations at <20 weeks gestation/500 g are not uniformly recorded across the country. Similar 50% to 70% reductions in infants born with an NTD have been reported elsewhere following increased maternal folic acid intake.[12][23][35][39][42]-[44]

More recent studies of Canadian women of child-bearing age have revealed that approximately one-quarter of this population do not have protective levels of RBC folate,[45] despite some acknowledged discrepancies among assay techniques.[46] Supplement use was the most significant predictor of optimal levels and correlated with higher socio-economic status.[47]

Oral folic acid supplements

Despite overwhelming evidence that folic acid fortification is effective in reducing NTDS, a significant proportion of women remain folate-deficient in early pregnancy. Health Canada and the Public Health Agency of Canada recommend that women of child-bearing years take a daily supplement of 0.4 mg of folic acid to reduce the risk of NTDs. This recommendation is supported by detailed guidelines from the Society of Obstetricians and Gynaecologists of Canada.[13][17]-[18] They recommend that women in good health eat a diet of folate-rich foods, along with daily supplementation with a multivitamin which includes folic acid (0.4 mg to 1.0 mg) for at least two to three months before conception and throughout the pregnancy and postpartum periods (for a minimum of four to six weeks and as long as breastfeeding continues). Factors known to increase the risk of NTDs in subsequent pregnancies include birth of a previous child with a NTD, a family history of NTDs, maternal obesity and maternal Hispanic origin, and the use of some anticonvulsants.[48][49] Pregestational or gestational diabetes is of low predictive value,[48] perhaps because the risk may vary with the level of glycemic control.[50] Since the etiology appears to be multifactorial, each risk factor is of similarly low predictive value, with the highest risk being for women with a previous affected child (at 2% to 5% before fortification [24]). Therefore, for women with a family history of NTD or other health complications, the SOGC recommends increasing dietary intake of folate-rich foods and daily supplementation with multivitamins (including 5 mg of folic acid) at least three months before conception and continuing 10 to 12 weeks postconception.[18]

Challenges with food fortification

While food fortification with folic acid has increased folic acid intake, it is estimated that only one-quarter of women of reproductive age take in a sufficient dietary total of folate to minimize the risk of having a child affected by an NTD.[32][51] When folic acid fortification began in Canada in 1998, fortification was estimated to supply an extra 100 µg of folic acid daily to the average diet.[52] By 2008, however, the annual per capita consumption of flour in Canada had dropped by 2.3 kg from the previous year to 43.7 kg. This decline may have been due, in part, to a 35% increase in the cost of flour from 2007 to 2008, as well as to an increasingly popular trend toward adopting gluten-free diets. The total amount of folate being ingested as a result of food fortification is likely to have declined further since 2008.[53]

In the United States, populations at particular risk include women of Hispanic descent, especially those who are less acculturated or who eat less wheat flour and use more corn-based flour. Their levels of folic acid are lower and their rate of NTDs higher than in the non-Hispanic Caucasian population. There is a proposal to fortify corn masa flour to increase folate intake for these women,[54] who also have a relatively high incidence of a methylenetetrahydrofolate reductase (MTHFR) gene polymorphism (TT) that renders them at greater risk of low folate status.[55]

The current level of folic acid food fortification is below that required to enable most Canadians to attain the recommended daily intake (400 µg) from diet alone. It is reported that up to 40% of women of child-bearing age in Ontario do not achieve folic acid intakes sufficient to prevent NTDs in their children.[13][17]-[18] One more recent study found that in Canada overall, 25% of women of child-bearing age have suboptimal RBC folate levels.[45] Consequently, there is considerable debate around the level of folic acid fortification in foods and whether it should be increased to afford better fetal protection. In their 2007 guidelines, the SOGC proposed that folic acid fortification be increased to 300 µg/100 g of flour to better prevent neural tube defects. They also noted a positive impact on maternal health during pregnancy due to folic acid supplementation.[17]-[18]

Challenges with supplementation

Oral folic acid supplementation offers a more targeted approach for women of child-bearing age, and has been widely promoted. However, even though reasonable awareness of folate has been achieved through extensive marketing campaigns and clinical education, the adoption of folic acid supplementation is generally poor. Only one-quarter of North American women of child-bearing age take folic acid supplements. Also, there is a significant socio-economic gradient, with only 16% of women of low socio-economic status reported to have taken folic acid supplements during their pregnancy.[56] Those with annual earnings <$25,000 USD cited the cost of folic acid supplements as an issue.[37] This statistic is especially important because low socio-economic status correlates with elevated risk for NTDs. It is women in these groups who are most in need of effective supplementation.[51][56]-[58] A recent small study from Ste-Justine Hospital in Quebec reiterated these findings, with only 4% of women who smoked and drank alcohol taking supplements in accordance with guidelines.[59] Alternative strategies include the use of oral contraceptives that contain a folic acid supplement, using tetrahydrofolate,[60] or recommending high-dose supplementation (5 mg daily). Counselling this higher dose assumes imperfect adherence, with only occasional supplements taken, but is safe and helps to achieve optimal RBC folate levels (

Concerns about folate supplementation: Vitamin B12 deficiency and cancer

There has been some hesitation to recommend increased levels of folic acid food fortification due to concerns around two issues: whether high levels of folate mask the symptoms of vitamin B12deficiency and whether they are implicated in the etiology of colon and other cancers.

Folate, B12 deficiency and pernicious anemia

Vitamin B12 deficiency is generally diagnosed following presentation with pernicious anemia. Ingesting adequate levels of folate partially treats the anemia and may ‘mask’ the appearance of vitamin B12 deficiency, possibly allowing neuropathy to progress and worsen.[7][35][39][62]-[64] However, more recent analysis of the effects of high folate intake has not confirmed the phenomenon of masking of symptoms of B12 deficiency.[33][65]-[67] Epidemiological analysis has revealed that the number of cases of pernicious anemia has decreased rather than risen since the introduction of food folic acid fortification.[33][67][68] High intake of folate combined with low serum vitamin B12 has been shown to actually exacerbate symptoms of B12 deficiency rather than masking them,[65][66] whereas normal serum vitamin B12 combined with high folate status demonstrated a protective effect against cognitive impairment.[67] These new findings suggest that increasing ingestion of folate at the level achieved with the current fortification standard poses no threat of masking vitamin B12 deficiency. Current recommendations have shifted toward vitamin B12 food fortification and finding more accurate ways to detect vitamin B12 deficiency via blood assays.[33][61][63]

Folic acid and cancer

Folate antagonists such as methotrexate are part of the chemotherapeutic arsenal used in the treatment of cancer. It is therefore reasonable that there has been some concern as to whether increasing the levels of folate in the population acts to either initiate or promote cancer, perhaps by providing a permissive environment for the growth of pre-existing cancers.

Several reviews have found either no increase or a slight decrease of cancer risk in people with the highest folate status, with individual studies variously controlling for possible confounding variables (eg, age, sex, caloric, fibre and alcohol intake, body mass index and family history). The cancers reviewed include colorectal, breast, prostate, pancreatic and lung cancer:

Breast cancer is by far the most common malignancy in women and in Canada, it is responsible for 27% of all incident cases and 15% of cancer deaths in women. One review and meta-analysis of breast cancer studies showed no association between breast cancer and the use of multivitamins, including folic acid.[68][69]

Prostate cancer is the most common malignant disease in men, and accounts for 28% of all incident cases and 11% of cancer deaths in men. A recent study presented findings of the largest case-control study of prostate-specific antigen test-detected prostate cancer to date, including a review and meta-analysis of prostate cancer risk and folate. Results were inconclusive, although study authors were unable to rule out some association between high folate status and increased prostate cancer risk.[70]

Pancreatic cancer is the fourth-leading cause of cancer death in both men and women, accounting for around 5% of all cancer deaths and a little over 2% of incident cases. One review suggests that for women, higher levels of folate protect against pancreatic cancer, while for men there is no effect.[71]

Lung cancer is by far the biggest single cause of cancer death in men and women, accounting for 27% of all cancer deaths. The European Prospective Investigation into Cancer and Nutrition (EPIC), a large cohort study with participants in 10 countries, published their main finding in this area: a substantive reduction in the risk of lung cancer in people with the highest folate status.[72]

Colorectal cancer is the third most common cancer in men and women, accounting for 14% and 12% of all incident cases, respectively, and a similar proportion of cancer deaths. One study proposed the hypothesis that increased folate intake heightened the risk of colon cancer in adults, acting as a cancer promoter.[36][73] A possible ‘dual modulatory’ effect has been noted in model systems, in which folate deficiency has an inhibitory effect while supplementation may promote cancer growth in already established colorectal neoplasms.[74] However, folate-deficient colorectal cells were protected from neoplastic changes by the addition of modest concentrations of folate in rodent models.[74] The epidemiological evidence for a relationship between colorectal cancer and folate has been extensively reviewed with the conclusion that high folate status reduces the risk of colorectal cancer.[73][75] A linear inverse relationship between folate status and colorectal cancer risk has been clearly demonstrated. The greatest difference found was between those in the highest and lowest quintiles. Individuals in the highest quintile were the most likely to take multivitamin supplements containing folate in an especially bioavailable form (as pteroyl-monoglutamic acid), as well as other potentially important micronutrients.[73]

Other concerns

Other concerns that have been raised but not supported by the evidence include an increased risk of bronchiolitis in the infants of supplemented mothers,[76] anorectal malformations,[77] preeclampsia,[78] acute lymphoblastic leukemia[79] and brain tumours.[80] Unmetabolized folic acid in supplemented patients has also been suggested as a possible cause of disease, but this concern has not withstood scrutiny.[81]


The impact of folic acid fortification and supplementation on reducing NTDs is well established and has led to mandatory food fortification in more than 50 countries, including Canada.

Despite flour fortification at current levels, the recommended daily intake of 400 µg is difficult to achieve for a variety of reasons, including relatively poor availability of folate in natural foods and its easy destruction during cooking. A lower general consumption of flour and a trending socio-economic gradient in folate intake from all sources leave many pregnancies underprotected against NTDs.

Currently, at least 25% of women of child-bearing age do not have folate intake sufficient to optimally protect their offspring from NTDs. Inequality remains, with women of lower socio-economic status being less well protected by folate. As a consequence, they bear the greatest burden of this serious congenital anomaly.

Concerns that folate supplementation increases the risk of cancer or masks vitamin B12 deficiency appear to be unfounded.


It is essential that women of child-bearing age maximize protection of their offspring from the risks of neural tube defects (NTDs) by ensuring adequate folate intake. Folate is available from three sources: natural diet, food fortification and oral supplementation. Folate intake from all sources should be promoted by policy makers and health professionals:

Natural diet: The significance of eating folate-rich foods such as leafy vegetables should continue to be a fundamental message delivered to all women of child-bearing age, especially those known to be contemplating pregnancy. This strategy is consistent with “Canada’s Food Guide” from Health Canada and with recommendations from the Society of Obstetricians and Gynaecologists of Canada (SOGC).

Food fortification: Flour and cereal products in Canada are supplemented at the level of 150 µg/100 g. This level was based on dietary intake of these products in the 1990s. In light of lower flour consumption, strong evidence that maternal dietary folate intake remains inadequate and a growing body of evidence to suggest a cancer-protective (rather than carcinogenic) effect of higher folate intake, the Canadian Paediatric Society strongly recommends increasing the level of folic acid food fortification.

Oral supplementation: Health Canada guidelines advise women of child-bearing age to take a daily multivitamin tablet containing 0.4 mg of folate as well as vitamin B12. The SOGC advocates a much higher intake for women at risk because of their current health status or a family history of NTD. The Canadian Paediatric Society supports this recommendation and, in addition, recommends supplementation with folate for all women during the child-bearing years. The Canadian Paediatric Society also strongly recommends providing free folate supplementation for women of child-bearing age, particularly those in less advantaged circumstances, for whom the risk of not achieving adequate prophylaxis is highest.


This position statement has been reviewed by the Genetics Committee of the Society of Obstetricians and Gynaecologists of Canada and by the Fetus and Newborn Committee of the Canadian Paediatric Society.

Members: Michael J Rieder MD (Chair), François Boucher MD (Board Representative), Christoph Fusch MD, Geert ‘t Jong MD, Philippe Ovetchkine MD, Shahrad Rassekh MD
Liaison: Doreen Matsui MD, Canadian Society of Pharmacology and Therapeutics
Principal authors: Noam Ami, Mark Bernstein MD, François Boucher MD, Michael Rieder MD, Louise Parker PhD


  1. McKillop DJ, Pentieva K, Daly D, et al. The effect of different cooking methods on folate retention in various foods that are amongst the major contributors to folate intake in the UK diet. Br J Nutr 2002;88(6):681-8.
  2. Eitenmiller RR, Landen WO. Folate. In: Eitenmiller RR, Landen WO, eds. Vitamin Analysis for the Health and Food Sciences. Boca Raton: CRC Press, 1999.
  3. Au KS, Ashley-Koch A, Northrup H. Epidemiologic and genetic aspects of spina bifida and other neural tube defects. Dev Disabil Res Rev 2010;16(1):6-15.
  4. Blencowe H, Cousens S, Modell B, Lawn J. Folic acid to reduce neonatal mortality from neural tube disorders. Int J Epidemiol 2010;39(Suppl 1):i110-121.
  5. Blom HJ. Folic acid, methylation and neural tube closure in humans. Birth Defects Res A Clin Mol Teratol 2009;85(4):295-302.
  6. Health Canada. Congenital anomalies in Canada: A perinatal health report, 2002. Ottawa: Minister of Public Works and Government Services Canada, 2002.
  7. McNulty H, Scott JM. Intake and status of folate and related B-vitamins: Considerations and challenges in achieving optimal status. Br J Nutr 2008;99 Suppl 3:S48-54.
  8. Centers for Disease Control and Prevention. CDC Grand Rounds: Additional opportunities to prevent neural tube defects with folic acid fortification. MMWR Morb Mortal Wkly Rep 2010;59(31):980-4.
  9. Kondo A, Kamihira O, Ozawa H. Neural tube defects: Prevalence, etiology and prevention. Int J Urol 2009;16(1):49-57.
  10. Bassuk AG, Kibar Z. Genetic basis of neural tube defects. Semin Pediatr Neurol 2009;16(3):101-10.
  11. Beaudin AE, Stover PJ. Folate-mediated one-carbon metabolism and neural tube defects: Balancing genome synthesis and gene expression. Birth Defects Res C Embryo Today 2007;81(3):183-203.
  12. Pitkin RM. Folate and neural tube defects. Am J Clin Nutr 2007;85(1):285S-288S.
  13. Koren G, Goh I. Increasing folate supplementation for selected groups of Canadian women. J Obstet Gynaecol Canada 2007;29(12):992-6.
  14. Beaudin AE, Stover PJ. Insights into metabolic mechanisms underlying folate-responsive neural tube defects: A minireview. Birth Defects Res A Clin Mol Teratol 2009;85(4):274-84.
  15. Liu S, Longerich L, Steel O, et al. Evaluation of food fortification with folic acid for the primary prevention of neural tube defects: Executive summary 1997-2003. Ottawa: Public Health Agency of Canada, 2004.
  16. Liu S, West R, Randell E, et al. A comprehensive evaluation of food fortification with folic acid for the primary prevention of neural tube defects. BMC Pregnancy Childbirth 2004;4(1):1-10,20.
  17. Wilson RD, Davies G, Désilets V, et al. The use of folic acid for the prevention of neural tube defects and other congenital abnormalities. J Obstet Gynaecol Can 2003;25(11):959-73.
  18. Wilson RD; Genetics Committee, Audibert F, et al. Pre-conception folic acid and multivitamin supplementation for the primary and secondary prevention of neural tube defects and other folic acid-sensitive congenital anomalies. J Obstet Gynaecol Can 2015;37(6):534-52.
  19. Heseker HB, Mason JB, Selhub J, Rosenberg IH, Jacques PF. Not all cases of neural-tube defect can be prevented by increasing the intake of folic acid. Br J Nutr 2009;102(2):173-80.
  20. Osterhues A, Holzgreve W, Michels KB. Shall we put the world on folate? Lancet 2009;374(9694):959-61.
  21. Bjorklund NK, Gordon R. A hypothesis linking low folate intake to neural tube defects due to failure of post-translation methylations of the cytoskeleton. Int J Dev Biol 2006;50(2-3):135-41.
  22. Padmanabhan R. Etiology, pathogenesis and prevention of neural tube defects. Congenit Anom (Kyoto) 2006;46(2):55-67.
  23. Van der Linden IJ, Afman LA, Heil SG, Blom HJ. Genetic variation in genes of folate metabolism and neural-tube defect risk. Proc Nutr Soc 2006;65(2):204-15.
  24. Grosse SD, Collins JS. Folic acid supplementation and neural tube defect recurrence prevention. Birth Defects Res A Clin Mol Teratol 2007;79(11):737-42.
  25. Copp AJ, Stanier P, Greene ND. Neural tube defects: Recent advances, unsolved questions, and controversies. Lancent Neurol 2013;12(8):799-810.
  26. Temel S, van Voorst SF, Jack BW, Denktas S, Steegers EA. Evidence-based preconceptional lifestyle interventions. Epidemiol Rev 2014;36:19-30.
  27. Jenkins KJ, Correa A, Feinstein JA, et al. Noninherited risk factors and congenital cardiovascular defects: Current knowledge; a scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young: Endorsed by the American Academy of Pediatrics. Circulation 2007;115(23):2995-3014.
  28. Wehby GL, Murray JC. Folic acid and orofacial clefts: A review of the evidence. Oral Dis 2010;16(1):11-9.
  29. Golalipour MJ, Vakili MA, Kaviani N. Reduction in non syndromic oral clefts following mandatory flour fortification with folic acid in Northern Iran. Med J Islam Repub Iran 2014;28:9.
  30. McGarel C, Pentieva K, Strain JJ, McNulty H. Emerging roles for folate and related B-vitamins in brain health across the lifecycle. Proc Nutr Soc 2015;74(1):46-55.
  31. Dary O. Establishing safe and potentially efficacious fortification contents for folic acid and vitamin B12. Food Nutr Bull 2008;29(2 Suppl):S214-24.
  32. Lawrence MA, Chai W, Kara R, Rosenberg IH, Scott J, Tedstone A. Examination of selected national policies towards mandatory folic acid fortification. Nutr Rev 2009;67(Suppl 1):S73-8.
  33. Oakley GP Jr, Weber MB, Bell KN, Colditz P. Scientific evidence supporting folic acid fortification of flour in Australia and New Zealand. Birth Defects Res A Clin Mol Teratol 2004;70(11):838-41.
  34. Cordero JF, Do A, Berry RJ. Review of interventions for the prevention and control of folate and vitamin B12 deficiencies. Food Nutr Bull 2008;29(2 Suppl):S188-95.
  35. Ray JG. Efficacy of Canadian folic acid food fortification. Food Nutr Bull 2008;29(2 Suppl):S225-30.
  36. Kim YI. Folic acid fortification and supplementation—Good for some but not so good for others. Nutr Rev 2007;65(11):504-11.
  37. Lindsey LL, Hamner HC, Prue CE, et al. Understanding optimal nutrition among women of childbearing age in the United States and Puerto Rico: Employing formative research to lay the foundation for national birth defects prevention campaigns. J Health Commun 2007;12(8):733-57.
  38. Bentley TG, Willett WC, Weinstein MC, Kuntz KM. Population-level changes in folate intake by age, gender, and race/ethnicity after folic acid fortification. Am J Public Health 2006;96(11):2040-7.
  39. Tam C, McKenna K, Goh YI, et al. Periconceptional folic acid supplementation: A new indication for therapeutic drug monitoring. Ther Drug Monit 2009;31(3):319-26.
  40. Crider KS, Devine O, Hao L, et al. Population red blood cell folate concentrations for prevention of neural tube defects: Bayesian model. BMJ 2014;349:g4554.
  41. De Wals P, Tairou F, Van Allen MI, et al. Reduction in neural-tube defects after folic acid fortification in Canada. N Engl J Med 2007;357(2):135-42.
  42. Tamura T, Picciano MF. Folate and human reproduction. Am J Clin Nutr 2006;83(5):993-1016.
  43. Ray JG, Wyatt PR, Vermeulen MJ, Meier C, Cole DE. Greater maternal weight and the ongoing risk of neural tube defects after folic acid flour fortification. Obstet Gynecol 2005;105(2):261-5.
  44. Wald N, Sneddon J, Densem J, Frost C, Stone R. Prevention of neural tube defects: Results of the Medical Research Council Vitamin Study. Lancet 1991;338(8760):131-7.
  45. Colapinto CK, O’Connor DL, Tremblay MS. Folate status of the population in the Canadian Health Measures Survey. CMAJ 2011;183(2): E100-6.
  46. Colapinto CK, Tremblay MS, Aufreiter S, Bushnik T, Pfeiffer CM, O’Connor DL. The direction of the difference between Canadian and American erythrocyte folate concentrations is dependent on the assay method employed: A comparison of the Canadian Health Measures Survey and National Health and Nutrition Examination Survey. Br J Nutr 2014:112(11):1873-81.
  47. Colapinto CK, O’Connor DL, Dubois L, Tremblay MS. Folic acid supplement use is the most significant predictor of folate concentrations in Canadian women of childbearing age. Appl Physiol Nutr Metab 2012;37(2):284-92.
  48. Agopian AJ, Tinker SC, Lupo PJ, Canfield MA, Mitchell LE; National Birth Defects Prevention Study. Proportion of neural tube defects attributable to known risk factors. Birth Defects Res A Clin Mol Teratol 2013;97(1):42-6.
  49. Agopian AJ, Lupo PJ, Tinker SC, Canfield MA, Mitchell LE; National Birth Defects Prevention Study. Working towards a risk prediction model for neural tube defects. Birth Defects Res A Clin Mol Teratol 2012;94(3):141-6.
  50. Correa A, Gilboa SM, Besser LM, et al. Diabetes mellitus and birth defects. Am J Obstet Gynecol 2008;199(3):237.e.1-9.
  51. Scholl TO, Johnson WG. Folic acid. Influence on the outcome of pregnancy. Am J Clin Nutr 2000;71(5 Suppl):1295S-303S.
  52. Sweeney MR, McPartlin J, Scott J. Folic acid fortification and public health: Report on threshold doses above which unmetabolised folic acid appear in serum. BMC Public Health 2007;7:41.
  53. Statistics Canada, 2008. Canada Food Statistics Database, Cat. no. 23F0001X, vers.1.12.
  54. Hamner HC, Tinker SC. Fortification of corn masa flour with folic acid in the United States: An overview of the evidence. Ann NY Acad Sci 2014;13(12):8-14.
  55. Botto LD, Yang Q. 5, 10-Methylenetetrahydrofolate reductase gene variants and congenital anomalies: A HuGE review. Am J Epidemiol 2000;151(9):862-77.
  56. Suitor CW, Gardner JD. Supplement use among a culturally diverse group of low-income pregnant women. J Am Diet Assoc 1990;90(2):268-71.
  57. Frey L, Hauser WA. Epidemiology of neural tube defects. Epilepsia 2003;44(Suppl 3):4-13.
  58. Wasserman CR, Shaw GM, Selvin S, Gould JB, Syme SL. Socioeconomic status, neighborhood social conditions, and neural tube defects. Am J Public Health 1998;88(11):1674-80.
  59. Richard-Tremblay AA, Sheehy O, Audibert F, Ferreira E, Bérard A. Concordance between periconceptional folic acid supplementation and Canadian Clinical guidelines. J Popul Ther Clin Pharmacol 2012;19(2): e150-9.
  60. Shere M, Bapat P, Nickel C, Kapur B, Koren G: The effectiveness of folate-fortified oral contraceptives in maintaining optimal folate levels to protect against neural tube defects: A systematic review. J Obstet Gynaecol Can 2015;37(6):527-33.
  61. Carmel R. Efficacy and safety of fortification and supplementation with vitamin B12: Biochemical and physiological effects. Food Nutr Bull 2008;29(2 Suppl):S177-87.
  62. Cornel MC, de Smit DJ, de Jong-van den Berg, LT. Folic acid – the scientific debate as a base for public health policy. Reprod Toxicol 2005;20(3):411-5.
  63. Johnson MA. If high folic acid aggravates vitamin B12 deficiency what should be done about it? Nutr Rev 2007;65(10):451-8.
  64. Koren G, Goh YI, Klieger C. Folic acid: The right dose. Can Fam Physician 2008;54(11):1545-7.
  65. Mills JL, Von Kohorn I, Conley MR, et al. Low vitamin B-12 concentrations in patients without anemia: The effect of folic acid fortification of grain. Am J Clin Nutr 2003;77(6):1474-7.
  66. Morris MS, Jacques PF, Rosenberg IH, Selhub J. Folate and vitamin B-12 status in relation to anemia, macrocytosis, and cognitive impairment in older Americans in the age of folic acid fortification. Am J Clin Nutr 2007;85(1):193-200.
  67. Qi YP, Do AN, Hamner HC, Pfeiffer CM, Berry RJ. The prevalence of low serum vitamin B-12 status in the absence of anemia or macrocytosis did not increase among older U.S. adults after mandatory folic acid fortification. J Nutr 2014;144(2):170-6.
  68. Larsson SC, Giovannucci E, Wolk A. Folate and risk of breast cancer: A meta-analysis. J Natl Cancer Inst 2007;99(1):64-76.
  69. Prinz-Langenohl R, Fohr I, Pietrzik K. Beneficial role for folate in the prevention of colorectal and breast cancer. Eur J Nutr 2001;40(3):98-105.
  70. Collin SM, Metcalfe C, Refsum H, et al. Circulating folate, vitamin B12, homocysteine, vitamin B12 transport proteins, and risk of prostate cancer: A case-control study, systematic review, and meta-analysis. Cancer Epidemiol, Biomarkers Prev 2010;19(6):1632-42.
  71. Oaks BM, Dodd KW, Meinhold CL, Jiao L, Church TR, Stolzenberg-Solomon RZ. Folate intake, post-folic acid grain fortification, and pancreatic cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Am J Clinl Nutr 2010;91(2):449-55.
  72. Bingham S, Riboli E. Diet and cancer – the European Prospective Investigation into Cancer and Nutrition. Nature Reviews: Cancer 2004;4(3):206-15.
  73. Kim DH, Smith-Warner SA, Spiegelman D, et al. Pooled analyses of 13 prospective cohort studies on folate intake and colon cancer. Cancer Causes Control 2010;21(11):1919-30.
  74. Sanderson P, Stone E, Kim YI, et al. Folate and colo-rectal cancer risk. Br J Nutr 2007;98(6):1299-1304.
  75. Kennedy DA, Stern SJ, Moretti M, et al. Folate intake and the risk of colorectal cancer: A systematic review and meta-analysis. Cancer Epidemiol 2011;35(1):2-10.
  76. Veeranki SP, Gebretsadik T, Dorris SL, et al. Association of folic acid supplementation during pregnancy and infant bronchiolitis. Am J Epidemiol 2014;179(8):938-46.
  77. Wijers CH, de Blaauw I, Zwink N, et al. No major role for periconceptional folic acid use and its interaction with the MTHFR C677T polymorphism in the etiology of congenital anorectal malformations. Birth Defects Res A Clin Mol Teratol 2014;100(6):483-92.
  78. Thériault S, Giguère Y, Massé J, et al. Absence of association between serum folate and preeclampsia in women exposed to food fortification. Obstet Gynecol 2013;122(2 Pt 1):345-51.
  79. Lupo PJ, Dietz DD, Kamdar KY, Scheurer ME. Gene-environment interactions and the risk of childhood acute lymphoblastic leukemia: Exploring the role of maternal folate genes and folic acid fortification. Pediatr Hematol Oncol 2014;31(2):160-8.
  80. Greenop KR, Miller M, de Klerk NH, et al. Maternal dietary intake of folate and vitamins B6 and B12 during pregnancy and risk of childhood brain tumors. Nutr Cancer 2014;66(5):800-9.
  81. Obeid R, Herrmann W. The emerging role of unmetabolized folic acid in human diseases: Myth or reality? Curr Drug Metab 2012;13(8):1184-95.

Disclaimer: The recommendations in this position statement do not indicate an exclusive course of treatment or procedure to be followed. Variations, taking into account individual circumstances, may be appropriate. Internet addresses are current at time of publication.

Last updated: Apr 4 2016