A new study by European and U.S. scientists shows that increased consumption of flavonoid-rich foods such as certain citrus fruits may help reduce the risk of stroke in women.
In the study published last Thursday in Stroke, a journal of the American Heart Association, researchers analyzed the flavonoid intake of 69,622 women from the U.S.-based Nurses’ Health Study, which has followed nurses since 1976 to assess risk factors for cardiovascular disease and cancer. The total flavonoid intake of the 69,622 women was calculated after they completed food intake questionnaires collected every four years using a U.S. Department of Agriculture database. They found that during 14 years of follow up surveys beginning in 1990, 1,803 incidents of strokes were confirmed from the women.
On analysis it was seen that women who ate high amounts of citrus products, which contain a specific class of flavonoid called flavanones, had a 19 per cent lower risk of ischemic (blood clot-related) stroke than women who didn't consume as much. Women with the lowest intake of flavonoids took in about 150 milligrams a day or less, compared to more than 470 mg a day by women consuming the highest level. A piece of citrus fruit normally contains 45 to 50 mg of flavanones.
There have been previous studies that have shown increased consumption of flavonoid-rich fruits and vegetables (preferably five servings a day) may help protect against stroke, researchers conducting the study released Thursday found most of the antioxidant-rich products consumed by the women with lower stroke risk were oranges, grapefruit and their juices.
“This study adds absolutely nothing to the relationship between fruit and strokes,” said ABC News’ chief health and medical editor Dr. Richard Besser. “The conclusions of the study go beyond the data.” However researchers note that women with higher total flavonoid intake also tended to smoke less, exercise more, take in more fibre, folate, fruits and vegetables and have low amounts of caffeine and alcohol. “The things we know that are important for stroke prevention remain,” said Besser.
Aedín Cassidy, the study's lead author and professor of nutrition at Norwich Medical School in the University of East Anglia in the United Kingdom, said flavonoids are thought to provide protection against stroke through several mechanisms, including improving blood vessel function and having an anti-inflammatory effect. “Studies have shown higher fruit, vegetable and specifically vitamin C intake is associated with reduced stroke risk,” said Cassidy.
Researchers are more likely to find a connection the deeper they dig into the data, but the findings are not necessarily significant for women, said Keith Ayoob, director of the nutrition clinic at the Rose F. Kennedy Center at the Albert Einstein College of Medicine. Previous studies have suggested that vitamin C and potassium, both found in citrus fruits, can also protect against heart disease and stroke, which may have also been figured into the findings. “It is impossible to disentangle the relative influence of all the constituents of citrus fruit,” the researchers wrote.
The researchers caution that further studies, which may include randomized trials of citrus-based foods, are needed to confirm their findings. The U.S. Department of Agriculture recommends eating two to four servings of any type of fruit a day.