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VITAMIN B9 (FOLIC ACID)

Vitamin B9 is also known as folic acid. In 1941, Henry Mitchell isolated a water-soluble nutrient from spinach leaves. This nutrient was essential for the growth of Streptococcus bacteria. He called it folic acid from the Latin word folium, meaning “leaves,” and found that it could cure megaloblastic anemia, a condition in which abnormally large red blood cells appear in the bloodstream. In the 1950s, scientists discovered that folic acid is involved in many enzymatic reactions. Recognizing its role as an essential nutrient, they named it vitamin B9.

Vitamin B9 participates in one-carbon metabolism involving the methylation of DNA and synthesis of methionine. A sufficient amount of vitamin B9 is needed to avoid incorrect synthesis of new DNA, which is of particular importance during the fetal and infant stages. Incorrect synthesis of DNA could lead to birth defects and growth retardation. The infants of pregnant women who are vitamin B9 deficient have a high risk of birth defects.

What Are the Symptoms of Vitamin B9 Deficiency?

 • Major symptoms. The major symptoms of vitamin B9 deficiency are lack of appetite, weight loss, weakness, headache, irritability, and anemia. Vitamin B9 deficiency could retard growth in infants and children. Vitamin B9 deficiency during pregnancy can lead to premature births and new babies with neural tube defects.

 • Megaloblastic anemia. Vitamin B9 deficiency can cause megaloblastic anemia, in which large, irregularly shaped red blood cells called megaloblastic cells circulate in the bloodstream.

What Are the Causes of Vitamin B9 Deficiency?

Insufficient dietary intake is the most common cause of vitamin B9 deficiency. Drinking alcohol and smoking could also lower the absorption of vitamin B9 in the intestines. Cancer and inflammation can deplete the stores of vitamin B9 in the body, resulting in vitamin B9 deficiency. Vitamin B9 is needed for the synthesis of DNA and production of new red blood cells in bone marrow. Vitamin B9 deficiency reduces the production of new red blood cells, leading to anemia.

Prevention and Treatment of Diseases

 • Prevention. Meta-analysis confirms that vitamin B9 can help prevent breast cancer (47), lung cancer (82), colorectal cancer (56), renal cell cancer (100), bladder cancer (44), and pancreatic cancer (95). In addition, meta-analysis shows that vitamin B9 is effective in preventing hypertension (78), depression (58), chronic kidney disease (52), stroke (108), coronary artery disease (57), venous thrombosis (110), atherosclerosis (39), glaucoma (69), oral cleft (92), neural tube defects (90), recurrent stroke (108), and age-related macular degeneration (84).

 • Treatment. Meta-analysis confirms that vitamin B9 can treat hypertension (78), depression (58), chronic pancreatitis (54), and atherosclerosis (39).

Which Food Items Are Vitamin B9 Rich?

Vitamin B9 is an essential nutrient for growth and regeneration in the body. Dark-green leafy vegetables like spinach, broccoli, kale, and asparagus and fruits—such as watermelons, oranges, and strawberries—are excellent sources of vitamin B9. Vitamin B9 supplementation curtails the risk of neural tube defects in infants. Therefore, since 1998, many governments have mandated domestic food manufacturing companies to fortify vitamin B9 in breakfast cereals, bread, spaghetti, rice, and the like.

This list of vitamin B9–rich food items is adapted from information provided by the NIH Office of Dietary Supplements.

Daily reference value of vitamin B9 is 400 mcg according to the 2013 FDA food-labeling guidelines.

What Are the Recommended Dietary Allowances for Vitamin B9?

The upper daily intake limit of vitamin B9 is 1,000 mcg.

Vitamin B9 Supplements

 • Dosage and types. The most common dosages of vitamin B9 supplements are 400–800 mcg. Folic acid and folate are the two major types of vitamin B9 supplements. Folic acid is a synthetic product, while folate is naturally produced. Both types are readily absorbed in the intestines.

 • Fortification. Worldwide, many countries fortify breakfast cereals, bread, and rice with vitamin B9. In the US, the fortification program has proven effective over the years and has successfully reduced vitamin B9 deficiency to only 1% of the population.

 • Pregnant women. Pregnant women should take a vitamin B9 supplement at a dose of 400 mcg daily immediately after confirming their pregnancies.

 • Hypertension. Folic acid could lower blood pressure and curtail the risk of stroke. The suggested dose is 800 mcg daily for four years.

 • Depression. Antidepressants are less effective in patients whose blood levels of vitamin B9 are too low. Supplementation with vitamin B9 at a daily dose of 500 mcg has been found to improve the efficacy of Prozac in patients with depression.

Safety Issues

 • Side effects. Long-term use of high-dose vitamin B9 could damage the kidneys and increase the risk of prostate cancer. The daily dose of vitamin B9 should not exceed 1,000 mcg.

 • Vitamin B12. Both vitamin B9 and vitamin B12 are required for the production of new red blood cells in bone marrow. Deficiency of either vitamin B9 or vitamin B12 can cause anemia. Vitamin B9 taken at a daily dose of 400 mcg alone can alleviate the symptoms of anemia. Thus taking vitamin B9 supplements could potentially conceal the hidden problem of vitamin B12 deficiency, leading to permanent damage to the nervous system.

What Types of Drugs May Interact with Vitamin B9?

 • Drugs like antacid medications, gallbladder juice inhibitors, diabetes drugs, anticonvulsant drugs, nonsteroidal anti-inflammatory drugs, and antibiotics may reduce the absorption of vitamin B9 by the intestines.

 • Methotrexate is a prescription drug that treats cancers and rheumatoid arthritis. Taking vitamin B9 supplements reduces side effects associated with methotrexate without affecting its efficacy.

 • Phenytoin is a medication used to treat epilepsy. Vitamin B9 can inhibit the efficacy of phenytoin. Patients who take phenytoin should consult with their physicians before taking vitamin B9 supplements.