Daily doses of 400 micrograms of the B vitamin led to significant improvements in blood pressure and improved blood flow after 16 weeks of supplementation, according to results published in the British Journal of Surgery.
Furthermore, equal doses of 5-methyltetrahydrofolate (5-MTHF), the naturally circulating form of folate, produced the same results, leading the researchers to conclude that “5-MTHF may be a safe and effective alternative to folic acid”.
“Few studies have evaluated the efficacy of 5-MTHF compared with folic acid in increasing plasma folate indices and reducing plasma homocysteine,” explained the researchers. “Reports on the bioavailability of 5-MTHF compared with folic acid are not consistent.”
A range of studies has linked increased blood levels of the amino acid homocysteine to an increased risk of cardiovascular disease (CVD). It has been suggested that by lowering the levels of homocysteine in the blood with B-vitamins, people could cut the risk of CVD.
However, a number of high profile randomised intervention trials have reported negative or null effects, most notably the Women's Antioxidant and Folic Acid Cardiovascular Study (WAFACS), the Heart Outcomes Prevention Evaluation (HOPE) 2 trial and the Norwegian Vitamin (NORVIT) trial reported that B-vitamin supplements did lower homocysteine levels but did not reduce the risk of certain cardiovascular diseases.
The new study, by scientists from Norfolk and Norwich University Hospital NHS Trust, the University of East Anglia, and the Institute of Food Research, report that supplements of either folic acid or 5-MTHF could reduce homocysteine levels, and improve blood flow in people with PAD.
PAD is associated with decreased blood flow in the legs, and occurs when arteries in the legs become narrowed or clogged with fatty deposits. According to 2008 statistic from the American Heart Association, PAD affects about 8 million Americans and is associated with significant disease and death.
Dr N. Khandanpour and his co-workers recruited 133 people with PAD and randomly assigned them to receive daily supplements of folic acid (400 micrograms), 5-MTHF (400 micrograms), or placebo for 16 weeks.
At the end of the study, the researchers noted that, compared to the placebo group, that both the folic acid and 5-MTHF groups displayed significant reductions in homocysteine of 2.12 and 2.07 micromoles per litre, respectively.
Measures of blood flow, namely the so-called pulse wave velocity (PWV), decreased in the 5-MTHF group by 1.1 metres per second, and by 0.9 m/s in the folic acid group.
“Plasma homocysteine has a significant association with PWV in both healthy individuals and people with vascular diseases,” wrote the researchers. “The present study suggested that lowering plasma homocysteine was associated with an improvement in PWV.”
“This study found that folate supplementation substantially reduced plasma homocysteine and produced a statistically significant but clinically modest improvement in peripheral arterial circulation compared with placebo,” concluded the researchers.
Source: British Journal of Surgery
September 2009, Volume 96, Issue 9, Pages: 990-998
“Randomized clinical trial of folate supplementation in patients with peripheral arterial disease”
Authors: N. Khandanpour, M. P. Armon, B. Jennings, P. M. Finglas, G. Willis, A. Clark, F. J. Meyer