Vitamin B12 is not found in any plant food sources and is produced almost solely by bacteria, such as streptomyces griseus . Rich sources of B12 include liver, meat, egg yolk, poultry and milk. Folic acid, also known as folacin and pteroylglutamic acid , is one of the B-complex vitamins that interacts with vitamin B12 for the synthesis of DNA, which is important for all cells in the body. Folic acid is also essential to virtually all biochemical reactions that use a one-carbon transfer and is produced by bacteria in the stomach and intestines. Folic acid is present in nearly all natural foods but can be damaged, or weakened, during cooking.
Folic acid is found in yeast, liver, green vegetables, whole grain cereals and many other foods.
The need for folic acid increases during pregnancy, due to high requirements of the vitamin from the fetus. Doctors often suggest a 300 mg. Many nutritional requirements change during pregnancy, and vitamins are no exception. The daily intake of folic acid should be increased from 180 mg. Mega-doses of folic acid can produce convulsions, interfere with the anticonvulsant medication used by epileptics, and disrupt zinc absorption.