Folic acid adverse effects
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Adverse Effects of Folic Acid: A Comprehensive Review
Introduction to Folic Acid and Its Importance
Folic acid, the synthetic form of folate, is essential for numerous bodily functions, including DNA synthesis and repair, and is crucial during pregnancy to prevent neural tube defects (NTDs) in newborns 12. However, while the benefits of adequate folate intake are well-documented, concerns about the potential adverse effects of excessive folic acid intake have emerged.
Potential Adverse Effects on Vitamin B-12 Deficiency
One of the primary concerns with high folic acid intake is its potential to exacerbate the clinical effects of vitamin B-12 deficiency. Elevated folate levels can mask the hematological symptoms of vitamin B-12 deficiency, leading to delayed diagnosis and treatment, which can result in irreversible neurological damage 14. Studies have shown that high plasma folate levels are associated with worsened clinical and biochemical signs of vitamin B-12 deficiency, such as anemia and cognitive impairment, particularly in the elderly .
Cancer Risk and Unmetabolized Folic Acid (UMFA)
Another significant concern is the potential link between high folic acid intake and increased cancer risk. Some animal and observational studies suggest that excessive folic acid intake may be associated with an elevated risk of certain cancers, although the evidence remains inconclusive 13. The presence of unmetabolized folic acid (UMFA) in the bloodstream, resulting from high intake, has also been implicated in potential adverse health outcomes, but strong biological and mechanistic evidence is lacking 13.
Adverse Pregnancy Outcomes
Excessive folic acid intake during pregnancy has been linked to several adverse outcomes. High maternal folate levels have been associated with an increased risk of gestational diabetes mellitus (GDM) and insulin resistance in offspring . Additionally, unbalanced intake of folate and vitamin B-12 during pregnancy has been linked to a higher risk of small-for-gestational-age (SGA) infants . These findings suggest that while folic acid is crucial for preventing NTDs, its excessive intake may pose risks to both maternal and fetal health.
Other Health Concerns
High folic acid intake has also been associated with other health concerns. For instance, studies have indicated a potential link between high folate levels and lower natural killer cell activity in elderly women, which could impact immune function . Additionally, there is evidence suggesting that excessive folic acid intake may increase the risk of unilateral retinoblastoma in offspring of women with certain genetic polymorphisms .
Conclusion
While folic acid is essential for preventing neural tube defects and other health issues related to folate deficiency, excessive intake poses potential risks, particularly concerning vitamin B-12 deficiency, cancer risk, and adverse pregnancy outcomes. The current body of evidence underscores the need for comprehensive research to clarify these issues and inform public health recommendations. It is crucial to balance the benefits of folic acid fortification and supplementation with the potential risks of excessive intake to ensure optimal health outcomes for all populations.
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