NORVIT Trial- High dose B vitamins do not lower stroke or MI risk
Sep 8, 2005 - 12:02:38 AM
Researchers from Norway have found that treating patients who have had a heart attack with high doses of B vitamins does not lower the risk of getting another heart attack or stroke. Contrary to expectations, B vitamins may do more harm than good.
NORVIT, the Norwegian Vitamin Trial, is the first trial to examine whether high doses of B vitamins prevent recurrent heart disease in patients who have had a myocardial infarction. A total of 3749 patients were recruited from 35 Norwegian hospitals. The patients were assigned to take B vitamins or placebo for more than three years in addition to standard treatments after a heart attack. The NORVIT trial was conducted by researchers at the University of Tromsø, Norway, in cooperation with researchers at the University of Bergen, Norway, and doctors and nurses at 35 Norwegian hospitals. It was a low-budget trial financed by the Norwegian Research Council, the Council on Health and Rehabilitation, the Norwegian Council on Cardiovascular Research, and other non-profit organizations.
Professor Kaare Harald Bønaa MD, University of Tromsø, Norway, principal investigator of the NORVIT trial, comments, "The results of the NORVIT trial are important because they tell doctors that prescribing high doses of B vitamins will not prevent heart disease or stroke. B vitamins should be prescribed only to patients who have B vitamin deficiency diseases."
The participants in the NORVIT trial were divided at random into four groups that received either 0.8 mg folic acid (a B vitamin) per day, 40 mg vitamin B-6 per day, both 0.8 mg folic acid and 40 mg vitamin B-6 per day, or a placebo capsule per day. Those who took folic acid or vitamin B-6 alone had a small increase in the risk of cardiovascular disease. However, among those who took both vitamins the risk increased by 20 percent.
During the last 15 years interest in vitamin B research has rocketed worldwide because studies indicated that folic acid and vitamin B-6 could prevent heart disease and stroke. Researchers have believed that this was due to the ability of B vitamins to lower the blood level of an amino acid called homocysteine. It was thought that high levels of homocysteine may damage the lining of arteries and increase clotting of the blood. This can cause fatal blockages of arteries in the heart and brain.
"Some doctors have found the previous data so compelling that they have already started to treat patients with B vitamins to lower the homocysteine level. However, in the NORVIT trial, homocysteine levels were lowered by 30%, but this did not lower the patients' risk of cardiovascular disease", said Kaare Harald Bønaa MD.
There were no subgroups of patients in the NORVIIT trial who benefited from taking B vitamins. Harmful effects were seen in particular among those who had high levels of homocysteine at the start of the trial, among patients with impaired renal function, and among those who reported that they used other vitamin supplements in addition to the study medication.
The results of the NORVIT trial are supported by results of a recent, smaller study which used similar doses of B vitamins as those given in NORVIT. That study showed that B vitamins increased the risk of reocclusion of coronary arteries that had been opened by percutaneous revascularization.
One patient in every three who suffers a heart attack has a recurrent heart attack or stroke within three years after the first attack, even if they get the best medical treatment available. It was hoped that B vitamins could lower the risk of recurrence. The NORVIT trial showed, however, that B vitamins offer no protection against cardiovascular disease.
Commenting on the results Professor Peter Weissberg, Medical Director of the British Heart Foundation, said:
"People should not be taking folic acid and vitamin B6 to stop them having a heart attack because it wont. The study shows a significant increase in heart attacks and strokes.
"There is no reason for pregnant women and those hoping to conceive to avoid taking folic acid by itself. It has a proven track record in preventing birth defects and is very important.
"Coronary heart disease seldom affected women in their 30s and 40s, which had led to breast cancer becoming a bigger fear for young women. The problem is that women may have got into bad lifestyle habits such as smoking and taking too little exercise which become even more difficult to change later in life when they catch up with the risk faced by men.
"Men have probably become aware of the threat of heart disease from a much younger age than women and this may help them to seek and get help."
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