MTHFR, gluten free diet, and arsenic seem unconnected, but there is a sneaky link. If you have replaced enriched bread, cereal, and pasta with gluten-free versions because of folic acid and MTHFR concerns, you may have traded one questionable ingredient for another. Many gluten-free packaged foods rely on rice as a base ingredient, which absorbs arsenic from soil and water more readily than many crops.