What Is Folate?
Folate is a water-soluble B-vitamin that occurs naturally in foods such as spinach. Its synthetic form-folic acid-is found in dietary supplements and fortified foods – this form makes up a large part of the dietary intake in the United States.

The body absorbs and utilises folic acid twice as efficiently as it does food sources of folate. Because they play an integral part in making DNA and RNA, folate and folic acid are responsible for producing and maintaining red blood cells. Proper red blood cell production serves important functions, including the prevention of anaemia. Folate is also responsible for producing levels of homocysteine (an amino acid in the blood).

Food Sources of Folate
The best food sources of folate are green leafy vegetables such as spinach. Oranges and strawberries are also excellent sources of folate, as are some other fruits. Other foods that are rich in folate are legumes, such as dried peas and beans.

Folic acid was added to the U.S. food supply in the mid-1990s as a way to reduce the amount of neural tube defects in U.S. infants. These folic acid–enriched foods include dried cereal, white rice, and pasta; and the folic acid in these fortified foods is easier to absorb than the folate naturally present in other foods.

Daily Requirements of Folate
To prevent deficiencies in folate, a recommended daily allowance (RDA) has been established. Children between the ages of one and three need 150 micrograms (mcg) of folate per day. From ages four to eight, the RDA is 200 mcg. Teens ages nine to 13 need 300 mcg a day, whereas those 14 and older need 400 mcg. For women who are pregnant, the RDA is 600 mcg; if nursing, 500 mcg.

Taking large doses of folate or folic acid is not recommended because it may cause a lack of vitamin B12. The upper limit for folate in adults is 1,000 mcg per day unless instructed differently by a physician. A lack of vitamin B12 can present as another form of anemia and if not treated may result in permanent nerve damage.

Conditions Associated with Folate Deficiency
If one’s diet is lacking in folate or folic acid, the following may occur:

• Anemia induced by folate deficiency (which can occur as weakness), sore tongue, headaches, irritability, memory problems, and behavioral issues. 
• A lack of folate in the blood stream can also cause an increase in homocysteine, which increases the risk of developing heart disease.
• People who are pregnant, abuse alcohol, have malabsorption problems, or suffer from kidney or liver disease have an increased need for folate through diet or supplementation.
• Taking certain medications may also impair folate absorption, which can increase need. These medications include: Dilantin® (phenytoin), Mysoline® (primidone), Fortamet® (metformin), Azulfidine® (sulfasalazine), Dyrenium® (triamterene), Rheumatrex® (methotrexate), and some barbiturates.

Reducing Cancer Risk with Increased Folate Intake?
Research has shown that a diet lacking in folate may increase the risk of developing colon, and pancreatic cancers.1,2 The most confirmatory evidence of this was seen in the Nurse’s Health Study, where researchers followed the dietary habits of 88,000 women over a 14-year period. 

Researchers found that older women (ages 55 to 69) who consumed adequate amounts of folate through diet and a multivitamin had a lower risk of developing colon cancer. 

Another study found that Chinese women who consumed diets highest in folate or folic acid had a lower risk of breast cancer compared with their counterparts who consumed low amounts of folate. It’s also noted that alcohol negates the positive effect of folate in the diet. Researchers state that although these studies show promising results, more research needs to be done to establish a causal relationship.

Folic Acid and Methionine Intake may Affect Colon Cancer Risk
In a study involving almost 2,000 patients with colorectal cancer and over 4,000 disease-free patients (who were admitted to hospital for reasons not related to colorectal cancer), researchers in Italy concluded that a diet rich in folate and methionine – and containing little alcohol – may lower the risk of colorectal cancer. Incidence of colorectal cancer was 40% higher for patients who were both heavy drinkers and had diets deficient in folate and the essential amino acid methionine. 

The main sources of folate reported in the Italian diets were green leafy vegetables, whole grains, and liver. Methionine levels were studied because this amino acid plays a key role in regulating the availability of folic acid in the body. Previous studies have shown that high levels of methionine reduce colon cancer risk in people with a family history of the disease.

It is interesting to note that low levels of methionine were slightly associated with colorectal cancer, but the combination of low methionine and low folate had an even stronger association with cancer risk.

The researchers’ recommendations are to exercise regularly, eat a balanced diet with lots of fruit and vegetables and to avoid more than 2 alcoholic drinks per day.

References

Larsson S, Hakansson N, Giovannucci E, Wolk A. Folate Intake and Pancreatic Cancer Incidence: A Prospective Study of Swedish Women and Men. Journal of the National Cancer Institute.*2006; 98: 407-413.
La Vecchia C, Negri E, Pelucchi C, et al. Dietary folate and colorectal cancer. International Journal of Cancer. 2002;102:545-7.
Meta-analyses of Observational and Genetic Association Studies of Folate Intakes or Levels and Breast Cancer Risk. Journal of the National Cancer Institute. 2006;98:1607-22.