NEW YORK (Reuters Health):

Plant antioxidants called flavonoids may not offer the protection against heart disease that some research has suggested, according to a large study of United States women.

Flavonoids are compounds found in fruits, vegetables, wine and tea that act as cell-protecting antioxidants. Lab studies have also found that they may inhibit blood clotting and maintain healthy blood vessel function, which in theory could lower a person's risk of heart disease.

Studies in people have come to mixed conclusions, however. Some, but not all, have found that people with a relatively high flavonoid intake have a lower risk of heart disease.

NO LINK

The new study, which followed more than 66,000 U.S. women, is much larger than most of those earlier studies. The results, reported in the American Journal of Epidemiology, show no link between a woman's overall intake of flavonoids and her risk of suffering a heart attack or dying of heart disease over the next 12 years.

Still, the findings should not deter people from consuming flavonoid-rich foods, according to the study's lead author.

Fruits and vegetables, tea and moderate amounts of wine remain good choices for overall health, Dr. Jennifer Hsiang-Ling Lin told Reuters Health.

"These foods and beverages contain many important health-promoting nutrients, in addition to flavonoids," said Lin, of Brigham and Women's Hospital and Harvard Medical School in Boston.

She and her colleagues based their findings on data from the Nurses' Health Study, which began in 1976, enrolling more than 120,000 female nurses between the ages of 30 and 55. Lin's team focused on 66,360 women who answered detailed questionnaires on their diet habits in 1990, 1994 and 1998.

Based on those responses, the researchers were able to estimate study participants' intake of two major flavonoid subtypes - flavonols and flavones. They found no association between the women's overall intake of these compounds in 1990 and their risk of suffering a heart attack or dying of heart disease over the next 12 years.

There was one exception, however. Women who consumed higher amounts of a particular flavonol called kaempferol were less likely to die of heart disease than women with the lowest intakes.

Kaempferol is found in foods such as tea and broccoli, and Lin's team found that women who ate the most broccoli had a relatively lower risk of dying from cardiovascular disease than their peers who shunned the vegetable.

It's possible that among flavonoids, kaempferol has a particular cardiovascular benefit, according to Lin. For now, though, she said, the finding on kaempferol is an 'interesting' one that warrants further study.

SOURCE: American Journal of Epidemiology, June 1, 2007.