About 40 per cent of Canadians show high levels of folate, while fewer than one per cent were deficient, a new study finds.
Since 1998, some Canadian flour and grains have been fortified with folic acid. The naturally occurring form of the vitamin is folate, which can reduce the prevalence of birth defects such as spina bifida, congenital heart disease, oral clefts and neural tube defects in which the brain and spinal cord don't fuse properly.
For the first time in more than three decades, Cynthia Colapinto of Children's Hospital of Eastern Ontario Research Institute in Ottawa and her co-authors looked at the folate status of the general population.
Blood tests of 5,248 Canadians aged six to 79 years showed 40 per cent with high folate concentrations, after taking age, sex and socio-economic status into account.
Less than one per cent of Canadians showed folate deficiencies, Cynthia Colapinto of CHEO Research Institute in Ottawa and her co-authors found.
Among women of childbearing age — the population that fortification is meant to benefit — 22 per cent were below the level considered safe to guard against neural tube defects. Average levels among women of childbearing age did not differ by income or education in the study.
No need to fortify more
Some doctors have argued that many women of childbearing age need high-dose folic acid supplements and that doubling the level of folic acid fortification in the food supply should be considered, the researchers noted.
The findings, however, offer little rationale for doubling folic acid in the Canadian food supply, the study authors concluded.
"Since we've had that 46 per cent reduction in neural tube defects [since fortification in 1998], I don't believe that hard-fought battle to get folic acid into our flour should be taken away," Colapinto said. "But maybe we need to refine our recommendations."
Further attempts to improve the folate status of women of childbearing age by increasing fortification "should be approached cautiously," the study's authors concluded.
People can have too much folate, said Prof. Karin Michels of the department of epidemiology at Harvard Medical School in Boston.
"There have been reports that individuals with underlying cancer, in particular with colon cancer, may actually experience a faster growth of their underlying cancer," said Michels.
For elderly populations, there are also concerns that too much folate may make it harder to detect vitamin B12 deficiency, Michels noted.
Folate may also prevent some cancers and heart disease.
The study's authors called for ongoing monitoring of Canadians' folate levels and research into the relation between red blood levels and health.
Health Canada said its scientists are reviewing the study, noting there are still questions about whether the folate levels measured in the blood test came from foods or supplements.
The department continues to consider mandatory fortification of flour with folate an effective public health intervention.
"Health Canada scientists continue to follow the latest research on the possible health impacts of folic acid and will not hesitate to recommend changes to the department's position, should the scientific evidence available warrant such change," a spokesperson added in an email.
The study was funded by fellowship awards from the Canadian Institutes of Health Research and Statistics Canada.