Risk factor pinpointed in high rate of strokes

PUBLISHED : Saturday, 25 February, 2006, 12:00am
UPDATED : Saturday, 25 February, 2006, 12:00am

Amino acid accelerates narrowing of blood vessels among southern Chinese

Eating a combination of vegetables and meat may help prevent stroke caused by narrowing of blood vessels in the brain, researchers said yesterday.

A joint study by Chinese University and the First Affiliated Hospital of Sun Yat-sen University in Guangzhou found elevated levels of a blood protein, homocysteine, was a major risk factor for the high incidence of stroke among southern Chinese.

Homocysteine, an amino acid, is harmful to artery linings because it accelerates narrowing of the blood vessels, said Lawrence Wong Ka-sing, head of the division of neurology at Chinese University's faculty of medicine.

The narrowing of blood vessels in the brain, called stenosis, doubles the risk of stroke. Stenosis is the most common cause of stroke in Hong Kong. Of 20,000 stroke cases each year, between 40 and 60 per cent are due to brain stenosis.

But vitamins in meat and vegetable work together to reduce levels of homocysteine.

The research is believed to be the first community-based study among Cantonese on the prevalence of cerebral stenosis.

A total of 1,068 people who had no previous history or symptoms of stroke were tested for their blood homocysteine levels. Using a second test, called transcranial Doplar, to determine narrowing of vessels, 63 were found to have cerebral stenosis.

To prevent stenosis that can lead to stroke, Professor Wong said, people should modify known risk factors, such as quit smoking, take up exercise and drink moderately.

'Second, we have to emphasise the importance of eating both vegetables and meat. Not just one or the other, but a combination,' he said. 'If they are vegetarian they should take vitamin B12 supplements. If they are Atkins or South Beach diet people, they should eat a lot of vegetables and fortified cereals that contain folic acid.'

The two vitamins, if taken together, work to reduce homocysteine levels.

Older men and those with diabetes and hypertension are known to have a higher stenosis risk, he said.

'Our findings suggest hyperhomocysteine has an important role in brain stenosis,' Professor Wong said.

'So remediation should begin at an early age, much before stroke symptoms become apparent.'

Earlier research by Chinese University among stroke sufferers in Henan found 7 per cent of patients aged 40 and above had stenosis.

'But never has there been a study in southern China, which is closer to Hong Kong. As most Hong Kong people are Cantonese, we wanted to find out the risk factors and prevalence of stenosis,' Professor Wong said.

He said the findings applied to Hong Kong people as they came from the same southern Chinese ethnic group.