Die antioxydativ wirkenden Vitamine A und E können Herzerkrankungen doch nicht verhindern

Von Dr. med. Jochen Kubitschek

Die angesehene Medizin-Fachzeitung The Lancet räumt jetzt mit einem weiteren weit verbreiteten Vorurteil auf, das besagte, dass die antioxydativ wirkenden Vitamine A und E die Entwicklung einer Arteriosklerose verlangsamen und so der Entstehung von Herzinfarkten vorbeugen. In der jetzt in The Lancet publizierten Untersuchung wurden 7 Vitamin-E- und 8 Beta-Carotin (Vitamin A)- Studien analysiert, an der in der Vergangenheit jeweils mehr als 1.000 Menschen teilgenommen hatten. Die Teilnehmer wurden nach dem Zufallsprinzip mit den Vitaminen bzw. einem Scheinmedikament behandelt. Der Effekt der Tabletteneinnahme wurde in den jeweiligen Studien bis zu 12 Jahre lang verfolgt.

Eine Arbeitsgruppe um Marc S. Penn von der Cleveland Clinic Foundation, USA, kam jetzt zu dem für viele begeisterte Anhänger der Einnahme von Vitaminpillen ernüchternden Schluss, dass keine der untersuchten Großstudien den geringsten Hinweis erbrachte, dass die Antioxydantien Vitamin A und E Herzerkrankungen tatsächlich vorbeugen. Doch nicht nur das - es zeigte sich sogar, dass die Einnahme des Vitamin-A-Vorläufersubstanz Beta-Carotin mit einem leicht erhöhten Herz-Kreislaufrisiko einherging.
Marc S. Penn fordert daher die Beendigung all jener derzeit noch laufenden Herz-Kreislauf-Studien, bei denen einige Versuchsteilnehmer auch Beta-Carotin bzw. Vitamin A einnehmen.

The Lancet 2003; 361:2017-2023

FURTHER EVIDENCE THAT VITAMIN SUPPLEMENTS DO NOT PROTECT AGAINST CARDIOVASCULAR DISEASE (p 2017)

A meta-analysis of randomised trials in this week's issue of THE LANCET provides further evidence that antioxidant vitamins are not effective in reducing the risk of cardiovascular disease. Supplements containing vitamin A compounds could actually contribute to an increase in cardiovascular death and all-cause mortality.

Some previous studies have suggested that antioxidant vitamins could delay the progression of atherosclerosis and thereby offer protection against cardiovascular disease. However no such benefit has been shown in large randomised trials.

Marc S Penn from the Cleveland Clinic Foundation, USA, and colleagues analysed seven randomised trials of treatment with vitamin E and eight trials of treatment with beta carotene (a source of vitamin A). All the trials included over 1.000 participants, and follow-up ranged from one to twelve years.

Vitamin E was not beneficial in reducing death from cardiovascular causes, all-cause mortality, or in reducing the incidence of stroke compared with people given control treatment. Beta carotene led to a small (0.4%) but statistically significant increase in all-cause mortality and a 0.3% increase in cardiovascular death.

Marc S Penn comments: "Given the results of this meta-analysis, the use of vitamin supplements containing beta carotene and vitamin A, beta carotene's biologically active metabolite, should be actively discouraged because this family of agents is associated with a small but significant excess of all-cause mortality and cardiovascular death. We recommend that clinical studies of beta carotene should be discontinued because of its risks.

When used as secondary prevention, vitamin E did not reduce the risk of cardiovascular endpoints. Furthermore, given our results and the lack of mechanistic data supporting efficacy of vitamin E as a potent antioxidant in vivo, we do not support the continued use of vitamin E treatment and discourage the inclusion of vitamin E in future primary and secondary prevention trials in patients at high risk of coronary artery disease."

Contact: Alicia Sokol, Department of Public & Media Relations, Cleveland Clinic Foundation, W14, 9500 Euclid Avenue, Cleveland, OH 44195, USA, T)+1 216 445 9661, F) +1 216 445 3040, E) sokola@ccf.org

REUTERS

Antioxidants Don't Cut Heart Disease Risk: Study

Fri June 13, 2003 05:14 PM ET
By Keith Mulvihill and Karla Gale

NEW YORK (Reuters Health) - Antioxidants such as beta carotene and vitamin E don't cut the risk of dying from heart disease, and beta carotene may even slightly increase the risk, according to a new analysis of studies conducted in the past.

As a result, researchers at the Cleveland Clinic Foundation said the use of supplements containing beta carotene and vitamin A (a beta carotene metabolite) should be actively discouraged and that clinical studies using the antioxidant be discontinued.

In addition, they also discourage similar investigations involving vitamin E for heart disease treatment or prevention.

But the conclusions of the new study sparked criticism from one expert.

The conclusions are "unwarranted and very surprising," said Dr. Jeffrey Blumberg of Tufts University in Boston, Massachusetts, in an interview with Reuters Health.

"No new research has been conducted and this is why their conclusions are so surprising," added Blumberg, who is an antioxidant researcher.

In the study, Dr. Deepak P. Vivekananthan and associates reviewed seven previously published trials of vitamin E treatment and eight trials of beta carotene treatment, according to the report published in the June 14th issue of The Lancet. All of the trials included at least 1,000 patients and were trials in which patients were randomly assigned to take the supplements or a "control" treatment.

Vitamin E did not reduce the risk of stroke or dying of heart disease and made no difference in the risk of death due to any cause. Beta carotene users actually had a slight increase in the risk of death due to any cause and the risk of death due to heart disease.

The researchers note that the small harmful effect seen for beta carotene was largely due to two studies that included a lot of smokers.

"To suggest that there is some new danger is wildly out of proportion to the data," said Blumberg, noting that scientists have known the potential risks beta carotene poses to smokers for some time.

"Contrary to what the conclusions of this study state, beta carotene is quite safe to nonsmokers," he added.

Among the more than 80,000 patients included in vitamin E trials, the lack of efficacy leads the authors to say they do "not support the continued use of vitamin E treatment."

In fact, co-author Dr. Marc S. Penn told Reuters Health, one "trial showed that vitamin E blocked the effects of otherwise established good therapies with statins and niacin, so I think there's no evidence they're good and there is a hint that they may be harmful."

So he and his associates recommend that vitamin E be excluded in trials of patients at high risk of coronary artery disease.

However, Penn pointed out that ophthalmologists recommend large doses of vitamin supplements for the sight-robbing condition macular degeneration and that the antioxidants are being studied as treatment for other illnesses.

"Certainly if there is a risk for other diseases where beta carotene has been shown to be efficacious, they should still take those," he added.

Otherwise, "we should really be focusing on healthy diets," he said. "The concept of vitamin supplements to overcome bad dietary habits is not a valid thesis, at least with vitamin E and beta carotene."

But, according to Blumberg, there is a biological basis for vitamin E's potential role in heart disease prevention. He noted that several studies have shown that vitamin E appeared to help prevent heart disease in healthy people who took the antioxidant over a decade.

The Council for Responsible Nutrition, a group the represents supplement manufacturers and suppliers, called the analysis "irresponsible, over-interpreted, and old news disguised as something new for publicity purposes," in a press statement.

They note that the risk of beta carotene is associated primarily with smoking. They also said that vitamin E has potential benefits for vision, Alzheimer's disease and cancer.

SOURCE: The Lancet 2003;361:2017-2023.