A global loss of cytosine methylation in DNA has been implicated in a wide range of diseases. There is growing evidence that modifications in DNA methylation can be brought about by altering the intake of methyl donors such as folate. We examined whether long-term daily supplementation with 0.8 mg of folic acid would increase global DNA methylation compared with placebo in individuals with elevated plasma homocysteine. We also investigated if these effects were modified by MTHFR C677T genotype. Two hundred sixteen participants out of 818 subjects who had participated in a randomized double-blind placebo-controlled trial were selected, pre-stratified on MTHFR C677T genotype and matched on age and smoking status. They were allocated to receive either folic acid (0.8 mg/d; n = 105) or placebo treatment (n = 111) for three years. Peripheral blood leukocyte DNA methylation and serum and erythrocyte folate were assessed. Global DNA methylation was measured using liquid chromatography-tandem mass spectrometry and expressed as a percentage of 5-methylcytosines versus the total number of cytosine. There was no difference in global DNA methylation between those randomized to folic acid and those in the placebo group (difference = 0.008, 95%CI = ？0.05,0.07, P = 0.79). There was also no difference between treatment groups when we stratified for MTHFR C677T genotype (CC, n = 76; CT, n = 70; TT, n = 70), baseline erythrocyte folate status or baseline DNA methylation levels. In moderately hyperhomocysteinemic men and women, long-term folic acid supplementation does not increase global DNA methylation in peripheral blood leukocytes. ClinicalTrials.gov NCT00110604
Kim YI, Pogribny IP, Basnakian AG, Miller JW, Selhub J, et al. (1997) Folate deficiency in rats induces DNA strand breaks and hypomethylation within the p53 tumor suppressor gene. Am J Clin Nutr 65: 46–52.
Jacob RA, Gretz DM, Taylor PC, James SJ, Pogribny IP, et al. (1998) Moderate folate depletion increases plasma homocysteine and decreases lymphocyte DNA methylation in postmenopausal women. J Nutr 128: 1204–1212.
Axume J, Smith SS, Pogribny IP, Moriarty DJ, Caudill MA (2007) The MTHFR 677TT genotype and folate intake interact to lower global leukocyte DNA methylation in young Mexican American women. Nutr Res 27: 1365–1317.
Kim YI, Christman JK, Fleet JC, Cravo ML, Salomon RN, et al. (1995) Moderate folate deficiency does not cause global hypomethylation of hepatic and colonic DNA or c-myc-specific hypomethylation of colonic DNA in rats. Am J Clin Nutr 61: 1083–1090.
Bagley PJ, Selhub J (1998) A common mutation in the methylenetetrahydrofolate reductase gene is associated with an accumulation of formylated tetrahydrofolates in red blood cells. Proc Natl Acad Sci U S A 95: 13217–13220.
Ozturk H, Durga J, van de Rest O, Verhoef P (2005) The MTHFR 677C>T genotype modifies the relation of folate intake and status with plasma homocysteine in middle-aged and elderly people. Nederlands Tijdschrift voor Klinische Chemie en Laboratoriumgeneeskunde 30: 208–217.
Friso S, Choi SW, Girelli D, Mason JB, Dolnikowski GG, et al. (2002) A common mutation in the 5,10-methylenetetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status. Proc Natl Acad Sci U S A 99: 5606–5611.
Durga J, van Boxtel MP, Schouten EG, Kok FJ, Jolles J, et al. (2007) Effect of 3-year folic acid supplementation on cognitive function in older adults in the FACIT trial: a randomised, double blind, controlled trial. Lancet 369: 208–216.
Marsit CJ, McClean MD, Furniss CS, Kelsey KT (2006) Epigenetic inactivation of the SFRP genes is associated with drinking, smoking and HPV in head and neck squamous cell carcinoma. Int J Cancer 119: 1761–1766.
Kok RM, Smith DE, Barto R, Spijkerman AM, Teerlink T, et al. (2007) Global DNA methylation measured by liquid chromatography-tandem mass spectrometry: analytical technique, reference values and determinants in healthy subjects. Clin Chem Lab Med 45: 903–911.
van Driel LM, Eijkemans MJ, de Jonge R, de Vries JH, van Meurs JB, et al. (2009) Body mass index is an important determinant of methylation biomarkers in women of reproductive ages. J Nutr 139: 2315–2321.
El-Maarri O, Becker T, Junen J, Manzoor SS, Diaz-Lacava A, et al. (2007) Gender specific differences in levels of DNA methylation at selected loci from human total blood: a tendency toward higher methylation levels in males. Hum Genet 122: 505–514.
Basten GP, Duthie SJ, Pirie L, Vaughan N, Hill MH, et al. (2006) Sensitivity of markers of DNA stability and DNA repair activity to folate supplementation in healthy volunteers. Br J Cancer 94: 1942–1947.
Cravo ML, Pinto AG, Chaves P, Cruz JA, Lage P, et al. (1998) Effect of folate supplementation on DNA methylation of rectal mucosa in patients with colonic adenomas: correlation with nutrient intake. Clin Nutr 17: 45–49.
Figueiredo JC, Grau MV, Wallace K, Levine AJ, Shen L, et al. (2009) Global DNA hypomethylation (LINE-1) in the normal colon and lifestyle characteristics and dietary and genetic factors. Cancer Epidemiol Biomarkers Prev 18: 1041–1049.
Cravo M, Fidalgo P, Pereira AD, Gouveia-Oliveira A, Chaves P, et al. (1994) DNA methylation as an intermediate biomarker in colorectal cancer: modulation by folic acid supplementation. Eur J Cancer Prev 3: 473–479.
Kim YI, Baik HW, Fawaz K, Knox T, Lee YM, et al. (2001) Effects of folate supplementation on two provisional molecular markers of colon cancer: a prospective, randomized trial. Am J Gastroenterol 96: 184–195.
Ingrosso D, Cimmino A, Perna AF, Masella L, De Santo NG, et al. (2003) Folate treatment and unbalanced methylation and changes of allelic expression induced by hyperhomocysteinaemia in patients with uraemia. Lancet 361: 1693–1699.
Guerreiro CS, Carmona B, Goncalves S, Carolino E, Fidalgo P, et al. (2008) Risk of colorectal cancer associated with the C677T polymorphism in 5,10-methylenetetrahydrofolate reductase in Portuguese patients depends on the intake of methyl-donor nutrients. Am J Clin Nutr 88: 1413–1418.
van Engeland M, Weijenberg MP, Roemen GM, Brink M, de Bruine AP, et al. (2003) Effects of dietary folate and alcohol intake on promoter methylation in sporadic colorectal cancer: the Netherlands cohort study on diet and cancer. Cancer Res 63: 3133–3137.