Efficacy of Weekly Versus Daily Folic Acid Supplementation

460 women of a rural community in the western highlands of Guatemala were recruited for participation in the double-blinded study led by Emory University and the Institute of Nutrition of Central America and Panama (INCAP). The women were randomly assigned one of 4 vitamin treatments containing different levels of folic acid, Vitamin B12, iron and zinc. The treatments were as follows:

1. weekly dose of folic acid at 5000ug, iron at 120 mg, zinc at 30mg, and B12 at 16.8 ug;
2. weekly dose of folic acid at 2800ug, iron at 120mg, zinc at 0mg and B12 at 16.8ug;
3. daily dose of folic acid at 400ug, iron at 60mg, zinc at 15mg, B12 at 2.4ug; and
4. daily dose of folic acid at 200ug, iron at 50mg, zinc at 0mg, and B12 at 2.4ug.

The women, aged 15-49, received the vitamins daily for 3 months. Anthropometric data and blood samples were taken at baseline and post-supplementation. The participants also completed a series of dietary interviews at baseline and post-intervention. No pregnant or lactating mothers were admitted into the study, nor severely anemic females. Blood samples were sent to the National Laboratory in Cuernavaca, Mexico, for analysis of serum folate levels.