Is folic acid good for everyone?

Oxford Project to Investigate Memory and Ageing, Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom.
American Journal of Clinical Nutrition (Impact Factor: 6.5). 04/2008; 87(3):517-33.
Source: PubMed

ABSTRACT Fortification of food with folic acid to reduce the number of neural tube defects was introduced 10 y ago in North America. Many countries are considering whether to adopt this policy. When fortification is introduced, several hundred thousand people are exposed to an increased intake of folic acid for each neural tube defect pregnancy that is prevented. Are the benefits to the few outweighed by possible harm to some of the many exposed? In animals, a folic acid-rich diet can influence DNA and histone methylation, which leads to phenotypic changes in subsequent generations. In humans, increased folic acid intake leads to elevated blood concentrations of naturally occurring folates and of unmetabolized folic acid. High blood concentrations of folic acid may be related to decreased natural killer cell cytotoxicity, and high folate status may reduce the response to antifolate drugs used against malaria, rheumatoid arthritis, psoriasis, and cancer. In the elderly, a combination of high folate levels and low vitamin B-12 status may be associated with an increased risk of cognitive impairment and anemia and, in pregnant women, with an increased risk of insulin resistance and obesity in their children. Folate has a dual effect on cancer, protecting against cancer initiation but facilitating progression and growth of preneoplastic cells and subclinical cancers, which are common in the population. Thus, a high folic acid intake may be harmful for some people. Nations considering fortification should be cautious and stimulate further research to identify the effects, good and bad, caused by a high intake of folic acid from fortified food or dietary supplements. Only then can authorities develop the right strategies for the population as a whole.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The impact of folate on health and disease, particularly pregnancy complications and congenital malformations, has been extensively studied. Mandatory folic acid fortification therefore has been implemented in multiple countries, resulting in a reduction in the occurrence of neural tube defects. However, emerging evidence suggests increased folate intake may also be associated with unexpected adverse effects. This literature review focuses on contemporary issues of concern, and possible underlying mechanisms as well as giving consideration the future direction of mandatory folic acid fortification. Folate fortification has been associated with the presence of unmetabolized folic acid (PteGlu) in blood, masking of vitamin B12 deficiency, increased dosage for anti-cancer medication, photo-catalysis of PteGlu leading to potential genotoxicity, and a role in the pathoaetiology of colorectal cancer. Increased folate intake has also been associated with twin birth and insulin resistance in offspring, and altered epigenetic mechanisms of inheritance. Although limited data exists to elucidate potential mechanisms underlying these issues, elevated blood folate level due to the excess use of PteGlu without consideration of an individual's specific phenotypic traits (e.g. genetic background and undiagnosed disease) may be relevant. Additionally, the accumulation of unmetabolized PteGlu may lead to inhibition of dihydrofolate reductase and other enzymes. Concerns notwithstanding, folic acid fortification has achieved enormous advances in public health. It therefore seems prudent to target and carefully monitor high risk groups, and to conduct well focused further research to better understand and to minimize any risk of mandatory folic acid fortification.
    Preventive nutrition and food science. 12/2014; 19(4):247-60.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Folate can be transported into the cell by the reduced folate carrier (RFC), the proton-coupled folate transporter (PCFT), or the folate receptor (FR), of which various isoforms exist. While the RFC and PCFT are expressed by many normal cells, the FR is present only in a small proportion of normal tissues. In these tissues, the FR expression level is often low and restricted to the apical surface of polarized epithelial cells. In contrast, FR is expressed on the blood-accessible basal and lateral membranes of many types of epithelial cancer. Considering that FR is expressed in few nonmalignant cell types on luminal membranes generally not accessible for molecules transported in the blood, FR is considered a promising antitumor target. As FR expression seems associated with tumor progression and prognosis, anticancer therapies targeting FR are currently being developed, such as farletuzumab (Morphotek, Exton, PA, USA), IMGN853 (ImmunoGen, Waltham, MA, USA), vintafolide, and EC1456 (both Endocyte Inc., West Lafayette, IN, USA). FR expression could be used as a response-predictive biomarker for these treatments. The ability to identify patients and treat them with an effective therapy based on the known expression of the tumor marker would, indeed, be the next step in predictive medicine for these patients. This review summarizes the role of FR in ovarian cancer and the value of FR as a prognostic biomarker for ovarian cancer and a response-predictive biomarker for folate-targeted therapeutics.
    Cancer and metastasis reviews 01/2015; · 6.45 Impact Factor
  • Neurology 01/2015; · 8.30 Impact Factor


Available from
May 22, 2014