This is a randomised double-blind placebo-controlled trial to see whether giving a low dose of the vitamins folic acid and riboflavin is beneficial to women who have very low grade abnormalities of the cervical cells.

The overall aim of the study is to evaluate interactions between intakes of folic acid and riboflavin with a common polymorphism relevant to folate metabolism, in determining the risk of cervical cancer in women who carry high risk human papillomavirus.

We will test the following hypotheses:

Supplements of riboflavin and folic acid will increase the rate of regression of low grade cervical intra epithelial neoplasia (CIN1).

Effects of supplemental folic acid and riboflavin on CIN1 regression are modulated by a common polymorphism in the MTHFRC677T gene.

We will recruit women with biopsy-proven CIN1 and carrying high risk HPV infection, and randomise to a 12month intervention of 1.2mg folic acid and 5mg riboflavin or placebo. The primary outcome will be regression of biopsy-proven CIN1, and secondary outcomes will include measures of DNA stability.

Inclusion Criteria:

• biopsy-diagnosed CIN1 infection with oncogenic HPV

Exclusion Criteria:

Any other stage of cervical abnormality pregnant or planning a pregnancy diabetic taking B vitamin supplements taking anti-epileptic treatment taking methotrexate bleeding after intercourse abnormal GI function infection with chlamydia, HIV or other agent