A comprehensive scientific review has concluded that a range of popular vitamin and antioxidant supplements fail badly in showing any evidence that they can help cut the risk of heart disease.
Cardiovascular disease (CVD) is a major cause of death in developed countries and is largely influenced by food and lifestyle choices. CVD is an umbrella term which includes heart attacks, heart disease, stroke and claudication (tiredness in the legs) of the peripheral blood vessels. Taking antioxidant supplements has been promoted for many years as being a valuable aid in helping someone prevent CVD, but just how effective are these supplements?
Antioxidants such as vitamins C, E and beta-carotene are part of the body’s defence system and their main role is to mop up damaging free radicals. Free radicals are a normal by-product of body metabolism, but high levels can be found in people who are smokers or have a poor diet.
Free radicals can oxidise important parts of the cellular machinery and can interfere with DNA replication and repair. Oxidation is thought to be an important part of the process in the development of heart disease where fatty plaques can build up in the lining of arteries.
Several well-designed clinical trials have found little evidence to support a benefit of antioxidants in preventing CVD, with some even pointing to a harmful effect. Now a group of researchers have conducted the most comprehensive review in this area ever done by looking at all of the published evidence for a range of popular vitamin and antioxidant supplements to see if they can prevent CVD.
Amassing the evidence
Published in the British Medical Journal, 50 randomised-controlled trials involving a combined total of almost 300,000 people fed into the conclusions from the meta-analysis.
The findings were clear cut: there was no benefit from the antioxidant supplements in reducing the risk of CVD regardless of the type of study design, duration of taking the supplement, number of people in the study and even if the study was funded by a pharmaceutical company or not.
The results pointed to a slightly higher risk of angina from taking supplements, and a lower risk of major CVD outcomes with low doses of vitamin B6, but all of these outcomes disappeared if analysis was restricted to only the high quality studies.
Rather than a normally long-winded, qualified conclusion as is the case in most research studies, the authors’ summary was refreshingly succinct and clear in its conclusion: vitamin and antioxidant supplements do not prevent CVD. They also noted other research analysis that similarly found that vitamin and antioxidant supplements have no preventative benefit in lowering the risk of cancer, and in some cases can actually elevate risk.
What it all means
Health claims made by suppliers of vitamin and antioxidant supplements include benefits in reducing heart disease; however, the scientific evidence simply doesn’t back this up. What does work and is supported by good science is maintaining a healthy body weight, keeping cholesterol levels in check, quitting smoking, and eating plenty of fruits and vegetables.
Confused about the mixed soup of nutrition messages being stirred through the media? Tim maintains an active nutrition blog at www.thinkingnutrition.com.au where you’ll find the latest nutrition research and controversies discussed in straight forward language, distilling out what you need to know for your better health.