For several decades now there has been a health rumour circulating that cranberry juice can cure urinary tract infections (cystitis) or have a preventative effect in those who tend to suffer multiple attacks. Such health rumours are extremely popular with the “health columns” of many newspapers and magazines. There is an obvious appeal in the idea that something natural and fruity will act like a medicine. But is there any evidence to back these claims?
If you want to know the answer to questions like this, the oracle is Cochrane. Many scientists publish reviews of literature. Sometimes they are thorough. Sometimes they are biased in support a particular theory. The Cochrane Collaboration, on the other hand, publish systematic reviews. These are exhaustive examinations of the literature carried out by volunteers from the ranks of medical scientists. They leave no stone unturned in their search for studies. Then they select the studies that involve well-conducted trials (randomised, controlled trials with a placebo) on human beings. They look at these carefully and determine whether the sum of the results tend to show any clear evidence.
The fact that they look at human studies is important. Lab data from cells in dishes or from mice are often cited but neither of these tell you whether something works in a human being. In the case of cranberries there is some lab evidence that cranberry juice contains a chemical that can discourage bacteria from sticking to the wall of the bladder. But does this translate into practice?
In a recently updated Cochrane review the authors failed to detect any clear effect of cranberry products in preventing cystitis in susceptible people. In a review in 2010 the Cochrane team found no well-conducted studies on cranberry products as a treatment.
There was a problem with a high drop-out rate from the studies. Consuming cranberry juice in sufficient quantities, every day, to maintain a high level of cranberry chemical in your urine is not easy. The juice is acidic and sugary. The implications for dental health are obvious and as I posted previously, consuming a lot of juice is not necessarily a Good Thing.
If you don’t want to read scientific reviews and you’re wondering whether some food or drink has a proven health benefit, I suggest you read the packaging carefully. It may refer vaguely to something that sounds healthy – but does it clearly say there is a proven benefit to a specific aspect of health? If not, you can be confident that no convincing case has been made to the regulatory agencies.
There is a long list of food products that would dearly love to prove they have health benefits but the list of those that do is an extremely short one.