Flavanoids provide cardiovascular protection

Grape Shot

Once again, scientists are doing their best to sell us some candy bars with a study that “reveals” the cardiovascular protection offered by eating dark chocolate.

The results of this new study from the Athens Medical School in Greece shows that aortic flexibility and blood flow improved when 17 “young, healthy volunteers” ate about four ounces of dark chocolate over a three hour period.

Last year in the e-Alert “You Can Call Me Hal” (6/17/04) I told you
about a similar study that sang the praises of dark chocolate. A peek at the details, however, quickly revealed that the cardio benefits of chocolate are almost certainly the work of flavanoids, the antioxidant and anti-inflammatory chemicals that give fruits and vegetables their color.

In other words, if you’re looking for genuine nutrition, skip the chocolate bar and go with an apple instead.

Or grapes. Because another recent study offers evidence that the flavanoid content of certain grapes may inhibit an enzyme that helps
cancer cells multiply.

Hold it back

The enzyme goes by the catchy name “topoisomerase II.” We’ll call it topo2 for short. Previous studies have shown that some cancer cells have topo2 levels hundreds of times higher than levels in normal cells. Based on this evidence, scientists believe that topo2 may be partly responsible for the prolific cell division in some cancers. Likewise, an agent that would inhibit the enzyme might help check cancer cell division.

In a recent issue of the Journal of Agriculture and Food Chemistry, researchers at the University of Illinois at Urbana-Champaign (UIUC) report on a laboratory study in which flavonoid-rich extracts from seven different types of red grapes were tested on topo2.

Results showed that several specific components of the seven extracts significantly restrained topo2 activity. Most impressive was the discovery that these components appeared to be more effective than either quercetin or resveratrol, two antioxidant flavonoids that are well-known chemopreventive topo2 inhibitors.

Further studies will be needed to determine the amount of grapes (or grape juice or wine) that would need to be consumed in order to inhibit topo2 activity and stall cancer cell division.

The Helsinki cohort

As HSI members are already aware, dietary flavonoids provide plenty of health benefits.

For instance, in the e-Alert “A Cell’s Best Friend” (5/1/03) I told you about a large study from the National Public Health Institute in
Helsinki, Finland, that examined the effects of different flavonoids on chronic diseases.

The Helsinki researchers used questionnaires and interviews to determine dietary history for more than 10,000 men and women. Flavonoid intakes were estimated based on the known flavonoid concentrations in specific foods. The health of each subject was tracked through national prescription and disease registries for an average of 28 years.

When researchers examined the data they found that subjects who consumed more flavonoid-rich foods were less likely to suffer from a number of chronic diseases, including heart disease, lung cancer, stroke, asthma,and type II diabetes.

Prevention for dinner

In addition to the broad conclusions of their study, the Helsinki researchers reported some useful specifics about which flavonoids may work best to help prevent certain diseases.

The stars of the group were quercetin and another flavonoid called kaempferol. Quercetin is most abundant in apples, but is also found in onions, citrus fruits, parsley, green tea and red wine. Kaempferol is also found in onions, as well as in broccoli. Subjects who had high levels of both of these flavonoids in their diets were found to have a 21% lower risk of heart disease than those who ingested small amounts of the two. In addition, subjects with kaempferol-rich diets lowered their risk of stroke by 30 percent.

Diets that include good amounts of quercetin may also provide protection against lung cancer, asthma and type II diabetes. And another flavonoid called myricetin, found in cranberries, has been shown to have a preventive effect on prostate cancer.

Results of the study also indicate that antioxidant activity is more effective when many different flavonoids are consumed.