Folate intakes from diet and supplements may place certain Canadians at risk for folic acid toxicity

Abstract

To examine the prevalence of folate inadequacy and toxicity based on usual intakes from food and supplements, as well as biomarkers of folate, secondary data analyses were performed using cross-sectional, nationally representative data from the Canadian Community Health Survey, Cycle 2.2 (n 32 776), as well as biomarker data from the Canadian Health Measures Survey, Cycles 1, 2 and 3 (n 15 754). On the basis of unfortified food sources, Canadians would struggle to consume adequate amounts of folate. When folate intakes from all food sources were considered, the overall prevalence of folate inadequacy was low across all age/sex groups, with the exception of females >70 years. However, >10 % of supplement users were above the tolerable upper intake level, increasing to almost 18 % when overage factors were accounted for. In addition, between 20 and 52 % of supplement users had elevated erythrocyte folate concentrations, depending on the cut-off used. Results from this study suggest that insufficient dietary intakes of folate in Canadians have been ameliorated because of the fortification policy, although folate inadequacy still exists across all age groups. However, supplement users appear to be at an increased risk of folic acid (FA) overconsumption as well as elevated erythrocyte folate. As such, the general population should be informed of the potential risks of FA overconsumption resulting from supplement use. This study suggests a need for more careful assessment of the risks and benefits of food fortification, particularly fortification above mandated levels, and FA supplement use in the general population.

Trimester-Specific Dietary Intakes in a Sample of French-Canadian Pregnant Women in Comparison with National Nutritional Guidelines

“…For these reasons, our results should be combined with direct assessment of iron status to evaluate the adequacy of our participant’s iron intakes. Furthermore, results from a recent Canadian study suggest that although fortification policies improved the population’s dietary intakes of folic acid, supplement users may be at risk of folic acid overconsumption [ 44 ]. To date, the implications of high folic acid intakes on pregnancy and prenatal health outcomes are not well understood and should therefore be further investigated [ 40 , 45 , 46 ].…”

Erythrocyte folate, serum vitamin B12, and hearing loss in the 2003-2004 National Health And Nutrition Examination Survey (NHANES)

“…The reason for the increase in the odds of hearing loss in the topmost quartile is unclear but could be related to neurologic damage that has been associated with excess folic acid, a likely scenario in populations with increased use of folic acid supplements and fortified foods. 16 , 17 Excess folic acid from chronic use of supplements or food fortification leads to excess levels in the erythrocytes 17 and could lead to large levels of unmetabolized folic acid in the body, which has been associated with altered DNA methylation and reduced immune function. 18 , 19 Although side effects of acute overconsumption of folic acid are considered reversible, effects from long-term overconsumption are unknown and may be worse in individuals with low vitamin B12 levels which has also been associated with hearing loss.…”

Nutrients in Energy and One-Carbon Metabolism: Learning from Metformin Users

“…Folate deficiency in metformin users is rare, but a decrease in serum and red blood cell (RBC) folate concentration is common [ 117 ]. It is difficult to ascertain the effect of folate fortification in some foods due to discrepancies in results [ 118 ] and the lack of data regarding folate bioavailability in metformin users [ 34 , 119 ]. Favoring the consumption of foods that are endogenously high in folates is probably reminiscent of decades using folates with cytotoxic agents, but this empirical practice requires caution.…”