Saturday Quack – Danger of Too Much Folate & Vitamin B12

Folic acid intake has risen dramatically since 1998, when fortification of flour and other grain foods with folic acid was instituted.  The purpose was to lower the risk of neural tube defects in unborn babies.  Subsequently, people began taking supplements of folate and vitamin B12 in the hope of preventing cardiovascular disease (people with cardiovascular disorders often have raised homocysteine blood levels, which are reversed by folic acid administration).  But there has been no evidence that such supplements work.  Meanwhile, anxiety has emerged that too much folate and vitamin B12 may cause an increased risk of cancer.  To test this, Norwegian scientists have analyzed combined data from two studies of the possible effects of these supplements in 6,800 patients with coronary heart disease.  The findings are published in the Journal of the American Medical Association.     

Cancer rates and mortality were determined in patients randomly given various combinations of folic acid (0.8 mg/day), vitamin B12 (0.4 mg/day), vitamin B6 (40 mg/day), or placebo, for 3 years. 

After an average of 6½ years, the risk for developing cancer in patients that were taking folic acid was 21% higher than in those that were not taking it.  And the risk for dying from cancer was 38% higher in the folic acid patients, while the risk for all-cause mortality was 18% higher.  Lung cancer was responsible for much of the difference from the non-folic acid taking patients.

The significance of Norway in these studies was important.  First, Norway does not mandate folic acid supplementation, so that basic serum folate levels were low;  they increased more than 6-fold during study treatment.  Second, more than 70% of the subjects were current or former smokers.  This means a known effect of folic acid – impaired immune surveillance of cancer cells – could have allowed stimulated growth of established lung cancers.  The differences in baseline folic acid levels could explain the negative results in earlier studies of cancer risk with folic acid supplementation.  The bottom line for USA inhabitants is that there is no need for folic acid supplements for most middle-aged or older adults.  On the other hand, there is no risk posed by food fortification – the levels are not in the “danger zone”.  In fact, cancer rates have dropped since the US began fortifying grains with folic acid.  Moreover, the doses of folic acid used in the Norwegian studies were about 5 times higher than the usual US intake.