Folic acid is found in dark green, leafy vegetables (such as spinach and turnip greens), dried beans and peas (including black-eyed peas and lentils), and foods fortified with folic acid (including enriched grain products). Folic acid is also available from supplements.
Doctors in Italy recently studied folic acid's effects on laryngeal leukoplakia, which are precancerous lesions in the larynx. While more tests are needed, early results showed laryngeal leukoplakia didn't turn into cancer while patients were taking folic acid supplements, and - in some patients - the precancerous lesions disappeared.
The researchers included Giovanni Almadori, MD, who works at the Universita Cattolica del Sacro Cuore's Institute of Otolaryngology in Rome. Results appear in the early online edition of the journal Cancer.
Almadori's team had previously reported that people with laryngeal leukoplakia tend to have lower blood levels of folic acid than people without laryngeal leukoplakia.
Folic Acid Supplements
So the researchers gave folic acid supplements to 43 adults with laryngeal leukoplakia for six months.
The patients had lower blood levels of folic acid than people without laryngeal leukoplakia when the study started.
European countries don't fortify grain products with folate, according to the nonprofit European Food Information Council's web site. And the patients hadn't taken supplements of folic acid, or the closely-related vitamin B 12, in the previous six months.
The patients weren't heavy drinkers, but more than 80% were smokers. Smoking and heavy alcohol use can boost the risk of laryngeal leukoplakia, the researchers note.
Checking for Cancer
Every eight hours, participants took oral supplements containing five milligrams (mg) of folic acid.
Blood levels of folic acid rose in the patients during the study. Meanwhile, blood levels of homocysteine - an amino acid that at elevated levels has been associated with increased risk of cancer and heart disease-- fell, the researchers report.
Doctors checked the participants' laryngeal leukoplakia every 30 days.
The participants' laryngeal leukoplakia didn't progress to cancer during the study. In addition, 12 patients (28%) had a "complete response," meaning the laryngeal leukoplakia faded away, the researchers write.
Nineteen others had a "partial response," write Almadori and colleagues. In those patients, the laryngeal leukoplakia shrank but didn't disappear.
The remaining 12 patients had no change -- for better or worse.
During the follow-up period -- which lasted a year on average -- laryngeal lesions returned in three patients.
The researchers caution that "definitive conclusions are far from being drawn" since Almadori's team can't rule out the possibility that the laryngeal leukoplakia might have gone away on its own, with or without folic acid.
They plan a larger, longer study of folic acid supplements in people with laryngeal leukoplakia.
Upper Limit for Folic Acid Intake
Folic acid is water-soluble, which means excess amounts are usually excreted in the urine. However, the federal Office of Dietary Supplements (ODS) notes that the Institutes of Medicine has set an upper limit of 1 milligram per day for adults aged 19 and older. Almadori's study used a much higher dosage of folic acid, but it did not address any side effects.
Getting more than the upper limit of folic acid could trigger symptoms of vitamin B12 deficiency, states the ODS. Signs of vitamin B12 deficiency include anemia, fatigue, weakness, constipation, loss of appetite, weight loss, numbness or tingling in the hands and feet, and depression.
Such symptoms are also seen with other conditions, so check with your doctor about any concerns.