Recent studies focussing on the reduction of plasma homocysteine as a risk factor for vascular disease showed that vitamin B(6) reduces plasma folate levels.
- Ann Nutr Metab 2001;45(6):255-8 -- Plasma folate but not vitamin B(12) or homocysteine concentrations are reduced after short-term vitamin B(6) supplementation. -- Bosy-Westphal A, Holzapfel A, Czech N, Muller MJ.
Paper reviews possible hazards associated with high intake of folic acid in the general population. Among the potential safety issues are interaction between folic acid and zinc, interaction between folic acid and drugs (phenytoin, methotrexate etc.) and hypersensitivity to folic acid. Of main concern are adverse effects of folic acid in cobalamin deficiency.
- Schweiz Rundsch Med Prax 2002 Jan 9;91(1-2):7-16 -- Safety aspects of folic acid for the general population -- Eichholzer M, Luthy J, Moser U, Stahelin HB, Gutzwiller F.
Folic acid antagonists, which include such common drugs as trimethoprim, triamterene, carbamazepine, phenytoin, phenobarbital, and primidone, may increase the risk not only of neural-tube defects, but also of cardiovascular defects, oral clefts, and urinary tract defects.
- N Engl J Med 2000 Nov 30;343(22):1608-14 -- Folic acid antagonists during pregnancy and the risk of birth defects. -- Hernandez-Diaz S, Werler MM, Walker AM, Mitchell AA.
Oral folic acid (pteroylglutamic acid) is generally regarded as not toxic for normal humans but it may cause neurological injury when given to patients with undiagnosed pernicious anemia. The vitamin should be given with caution to drug-treated epileptic patients because seizure control may be affected. Because antifolate medications are now being used to treat a wide range of malignant and nonmalignant disorders, further investigation is needed concerning folate metabolism and the safety of supplements in patients with these disorders.
- Am J Clin Nutr 1989 Aug;50(2):353-8 -- Folic acid safety and toxicity: a brief review. -- Butterworth CE Jr, Tamura T.
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