A recently published study has suggested that fruits and vegetables that are rich in
anthocyanins--such as blueberries, strawberries, and blood oranges--may help prevent the development of high blood pressure, new research suggests.
It seems like every week we hear about a new food that is good, or bad, for your health and even the same foods have sometimes been linked with both good and bad data. What is most important is to see HOW the scientists performed the study and what their actual conclusions were. In other words, you must take these news snippets with a grain of salt (pun totally intended).
The media is very fond of stories like this because they are widely applicable to the general public and everyone can relate to eating berries, etc. However, just because a newspaper or Yahoo! publishes a study, it does not mean that it was well done or even clinically relevant. Sometimes, it's just interesting.
In this most recent food-for-therapy study, the subjects, who did not have high blood pressure at baseline, were asked to complete health questionnaires every two years, and their dietary intake was assessed every four years through a food frequency questionnaire. But this does not account for so many factors that also may have contributed to their blood pressure or health changes, e.g. drinking, smoking, social factors, other illnesses etc. In scientific lingo, these are known as confounding variables, ie factors that may impact the results of a study that cannot be controlled. There are ways, in a questionnaire-based study to try and make up for these variables but inevitably the study becomes less accurate because of it.
The most accurate studies are those that analyze 2 groups of patients, one which uses the treatment and one that does not - and neither group, nor the scientists are aware who is getting what. This is known as a randomized, double-blinded, control trial.
This is not to say that the results culled from thousands of questionnaires and analyzed by very smart people should be completely discounted but what we do with the results and how we interpret them and integrate them into recommendations for patients is very important. Here's what the author of the trial, Dr. Aedin Cassidy, stated - which often gets buried under a bold, sexy headline:
"Our findings are exciting and suggest that an achievable dietary intake of anthocyanins may contribute to the prevention of hypertension."
OK. That's a fair statement. Weekly intake of these blueberries, strawberries and foods high in anthocyanins
MAY prevent development of high blood pressure.
"In terms of guidance to patients, I think this can help us give a little bit more targeted advice. Rather than just telling them to eat more fruit and vegetables--which they are tired of hearing--we can try to refine messages about which dietary components are beneficial in terms of cardioprotective effects," she says.
She cautions, however, that these findings come from an
observational study and so will require confirmation in interventional trials.
Dr. Cassidy concludes by nothing that the next stage of the research will be to conduct randomized controlled trials with different dietary sources of anthocyanins to define the optimal dose and sources for hypertension prevention, enabling the development of targeted public-health recommendations on how to reduce blood pressure.
So are the red and blue berries good for high blood pressure? The take home message is that they might be, but more refined studies would need to be performed to say this with any certainty.
