REVIEW - High-dose vitamin B may do more harm than good for heart disease

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MedPage Today

Review

STOCKHOLM, Sept. 5-High-dose vitamin B may do more harm than good for heart

disease, and homocysteine, billed as a heart disease risk factor, isn't one

after all, researchers reported here today.

" The homocysteine hypothesis is dead, " declared Kaare Bonaa, M.D., of the

University of Tromso in Trondheim, Norway. In terms of heart disease risk, "

homocysteine is an innocent bystander, " he said at the European Society of

Cardiology Congress 2005.

And that wasn't the only bad news for believers in simple helpers in heart

disease and prevention. Fish oil capsules did not reduce cardiac events in

patients with implanted cardioverter defibrillators (ICDs), a team of Dutch

researchers reported.

In the vitamin B-homocysteine arena, Dr. Bonna and colleagues enrolled 3,749

myocardial infarction patients in the Norwegian Vitamin Trial (NORVIT).

Patients were randomized to high dose vitamin B, high dose folic acid, or

placebo for up to three years.

As expected the high doses of vitamin B lowered circulating homocysteine by

30%, but rather than decreasing heart attack risk, " there was a 20% increase

in risk of cardiovascular events, " Dr. Bonaa said.

In the past high levels of homocysteine have been associated with heart

disease, but attempts to treat the patients by lowering levels of the

hormone, especially with folic acid and other B vitamins have had

disappointing outcomes.

In NORVIT, the participants took doses of 40 mg of Vitamin B-6 or 0.8 mg of

folic acid per day. Dr. Bonaa said that the doses are prescribed at that

level in Europe and represent two tablets of the vitamins that are

sold-over-the-counter in the United States.

He said that the risk of suffering heart attacks or strokes was no different

if the patient was taking either vitamin or placebo. However, patients

taking both vitamins had about a 20% increased risk of having a heart attack

or stroke (IP=0.029).

In addition there was a non significant trend for an increased risk of

cancer among those on the high doses of vitamins.

" 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. " Dr. Bonaa said. " B vitamins should be prescribed only to patients

who have B-vitamin deficiency diseases. "

He noted that in the trial measurements of homocysteine were made before and

during treatment and showed that the vitamins dramatically reduced levels of

homocysteine. However, the lowering effect did not translate into a clinical

benefit.

Gibbons M.D., professor of medicine at the Mayo Clinic, who is

president-elect of the American Heart Association, was not surprised by the

negative results for vitamin B. " Taking something with no proven beneficial

effect is a bad idea, " he said.

He said that in addition to possible harm that could occur to the person

taking such substances as vitamins, taking the substances " wastes resources

and most patients can only take so many pills. " Moreover, he boasted that in

his career in cardiology, he has " never ordered a homocysteine test.

But others said it is too early to count out either vitamin B or

homocysteine. For example, Lampros Michalis, M.D., of the University of

Ioannina, Greece, who moderated a press conference where the study was

discussed, said " every time we have tried to find a connection between

homocysteine and lowering it with vitamins we never find anything. But it

[homocysteine] is so appealing that a natural substance such as a vitamin

that can reduce homocysteine levels that investigators will again try to see

if there is a connection. "

In the second study, which was also presented at today's late-breaking

clinical trials session, researchers with the Study on Omega-3 Fatty acid

and ventricular Arrhythmia (SOFA) reported that omega-3 fatty acids

contained in fish oil capsules reduced arrhythmias by 15% in patients with

implanted cardioverter defibrillators, as measured by the firing of the

devices, but that reduction was not statistically significant.

Ingeborg Brouwer, Ph.D., project manager at the Wageningen Center for Food

Sciences in The Netherlands, said, " The SOFA trial does not indicate a

strong beneficial effect of n-3 polyunsaturated fatty acids from fish on

life-threatening cardiac arrhythmia. "

But she said that patients with a history of myocardial infarction " may

still benefit from fish oil. " Dr. Brouwer said that in investigating

subgroups in the trial she noticed that patients who had a previous MI

appeared to show a trend toward a protective effect (p=.086). She said that

group of patients might be subjects for another trial.

But even if fish oil didn't help, she said the study confirmed that it

doesn't hurt either.

The researchers enrolled 546 patients and randomized 273 subjects to receive

fish oil while the other 273 received a common cooking oil with no known

cardiac effects, Dr. Brouwer said. After 12 months of monitoring 30% of the

patients taking fish oil had experienced a heart attack or stroke compared

with 33% of those taking the placebo oil. That difference was not

significant (P=O.24).

Primary source: European Society of Cardiology Congress 2005

Source reference:

Hot Line II Bonaa K.H. " NORVIT: Randomized trial of homocysteine-lowering

B-vitamins for secondary prevention of cardiovascular disease after acute

myocardial infarction " Brouwer IA " SOFA: Study on Omega-3 Fatty acid and

ventricular arrhythmia "

http://www.medpagetoday.com/2005MeetingCoverage/2005ESCCongress/tb/1674

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Mayo Clinic in Rochester

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s Hopkins Medicine

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