Soya supplements may lead to healthy arteries
Publication Date:24/09/2008
Food supplements made from soya beans may improve the health of people's blood vessels following a stroke, according to new research. However, it's not clear yet if the supplements will help to prevent a further stroke or extend people's lives.
What do we know already?
People who've had one stroke are at a higher risk of having another. Doctors often prescribe drugs to lower people's blood pressure and cholesterol, to protect against a second stroke.
In countries where a typical diet is rich in fruits, vegetables and beans, people seem to have a lower risk of heart problems and strokes. This has led researchers to wonder whether specific chemicals found in these foods might be a useful way of preventing these problems.
For example, soya beans and chickpeas contain chemicals called isoflavones. Isoflavones act on the body in a similar way to the hormone oestrogen. They're sometimes called plant oestrogens or phyto-oestrogens.
Some studies have suggested that isoflavones may play a part in keeping blood vessels healthy, which could be helpful for people at risk of a heart attack or a stroke. Researchers have now looked at the effects of isoflavone capsules in people who've already had a stroke, to see if there are any benefits.
What does the new study say?
The researchers looked at about 100 people who'd all had at least one stroke at some point in the past. The average age was 66. About 50 people were given an isoflavone supplement for 12 weeks, on top of their usual medicines. Another 50 were given a placebo. A placebo is a dummy treatment (in this case a capsule) with no active ingredient, which is used in studies as a comparison with the "real" treatment.
At the end of the 12 weeks, researchers used an ultrasound scanner to see how well people's arteries could expand. If your arteries can widen easily to let more blood through, it's a sign that your blood vessels are healthy.
At the start of the study, about 8 in 10 people had blood vessels which didn't expand very well. After treatment, this dropped to 6 in 10 for people taking the isoflavones, but barely changed for people taking a placebo. However, taking isoflavones didn't improve people's heart rates or blood pressure.
An important thing to remember with this study is that it didn't look at whether isoflavones helped to prevent strokes. The researchers hope that isoflavones might do this, but the study was only able to look at how healthy people's blood vessels were. We still don't know whether isoflavones have important benefits, like preventing strokes or helping people live longer.
Where does the study come from?
The study was done by researchers based at the University of Hong Kong. It appeared in the European Heart Journal, which is published by Oxford Journals, part of Oxford University Press.
The research was paid for by several grants, including one from a company that makes food supplements. It's quite common for companies to fund research into their own products.
How reliable are the findings?
The study was fairly small, with only about 100 people taking part, but it seems to have been carefully carried out.
One slight problem is that, apart from having recovered from a stroke, most of the people in the study were in reasonable health. People were excluded from the study if they had problems like an irregular heartbeat, serious heart failure, or kidney or liver problems. People who've had a stroke are often older and suffering from several medical conditions. This means that the people in the study might have been healthier than a typical stroke patient, and more likely to benefit from treatment.
The study only lasted 12 weeks, so it doesn't tell us anything about the long-term benefits or possible side effects of isoflavones.
What does this mean for me?
We can't say yet whether isoflavone supplements are worth taking for people aiming to prevent a stroke. The latest research suggests the supplements can help keep blood vessels healthy, but we really want to know whether they can stop you having a stroke. We don't have an answer to this question yet.
The people in the study had all had a kind of stroke caused by a blocked blood vessel. There's also another type of stroke, caused by bleeding in the brain. A supplement that increases blood flow might not be helpful for people who've had a stroke caused by bleeding, and could even be harmful.
What should I do now?
You don't necessarily have to do anything. If you're interested in the idea of taking isoflavone supplements, it's a good idea to check with your doctor or pharmacist first. Natural supplements can sometimes cause side effects or react with other medicines you're taking, so it's best to get professional advice before you start.
The people in the study were taking capsules containing an 80 milligram (mg) dose of isoflavones every day. We don't know whether eating foods containing isoflavones, like soya products and chickpeas, would have the same effects. However, these foods tend to have lots of fibre and vitamins, with low amounts of saturated fat, so they're unlikely to do you any harm.
The study looked at people who were already taking medicines to protect them from heart attacks and strokes. The researchers stress that isoflavones should only be used in addition to the drugs your doctor prescribes. They're not a replacement for conventional medicines.
From:
Chan YH, Lau KK, Yiu KH, et al. Reduction of C-reactive protein with isoflavone supplement reverses endothelial dysfunction in patients with ischaemic stroke. European Heart Journal. Published online 23 September 2008.
To read more, see our information on preventing strokes.
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