In many Asian countries, soybeans have been part of the traditional diet for thousands of years. Soy has also become increasingly more popular in the West, both in Asian-style cooking and in vegetarian foods, like meat substitutes and non-dairy milk products.
A diet rich in pulses, including soy, along with plenty of fruits and vegetables, seems to be one of the healthiest ways to eat. While it's important to eat a balanced overall diet, researchers have also wondered whether specific chemicals from soy can be beneficial when they're taken on their own.
A new study has looked at capsules containing soy extracts called isoflavones. The study, based in Hong Kong, looked at around a hundred people who had all had a stroke at some point in the past. The average age was 66 years.
Half the people took the supplements for 12 weeks, and the rest were given a placebo, for comparison. Everyone kept on taking their usual medications, too.
At the end of the study, 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 that didn't expand very well. After treatment, this dropped to 6 in 10 for people taking isoflavones, but barely changed for people taking a placebo. However, taking isoflavones didn't improve people's heart rates or blood pressure.
It's important to think about what this study doesn't tell us, as much as what it does. Although the study shows promise, we don't yet know if there are real-life benefits to taking isoflavones, like living longer or being less likely to have a stroke. All we can say at the moment is that these supplements helped improve the health of people's arteries.
It's also important to remember that the people in the study kept on with the drugs they'd been prescribed by their doctors. The researchers stress that isoflavones aren't a replacement for conventional medications.
The people were taking capsules containing an 80 milligram (mg) dose of isoflavones every day. We don't know whether eating foods containing isoflavones, like soy products and chickpeas, would have the same effects. However, these foods tend to have lots of fiber and vitamins, with low amounts of saturated fat, so they're unlikely to do you any harm.
What you need to know. 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.
—Philip Wilson, patient editor, BMJ Group
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Check out our Natural Medicine Ratings for soy (subscribers only), and read more about how to reduce your risk of a stroke (free).