They come in all sorts of forms and concentrations: juices, tablets, capsules and powders made from cranberries, which are said to protect against urinary tract infections. Is this just gentle nonsense from the natural corner or is it a sensible prevention method? A new article by the Cochrane network concludes that there may actually be something to the effects of the fruit, also known as cranberries.
The authors evaluated 50 clinical studies with a total of almost 9000 patients on the benefits of berry products. Overall, study participants who consumed cranberry products had an approximately 30 percent lower risk of urinary tract infections than those who received a placebo or no treatment at all. The authors called the evidence for this result “moderate”.
Although there is a benefit, it is still largely unclear who benefits and how much
However, the effects are not consistently recognizable. According to the data, children, women with recurring bladder infections and people who are particularly susceptible to the inflammation due to previous treatment of the urinary tract, such as radiation, could probably benefit.
For older people in need of care and for pregnant women – two groups that are also more susceptible to the infections – the study data indicated that the effect of the berry products is small or non-existent. However, the authors write that more research is needed on the question of who benefits and how much.
No serious side effects were found in the studies. Stomach pain may occur after taking the juices, pills, and powders; however, these appear to be scarcely more frequent than after placebo administration.
However, the work leaves some questions unanswered. One of the biggest problems is that the cranberry market is confusing. There are no standardized products. And so the studies included very different products with different concentrations of the presumably active substance.
The proanthocyanidins contained in the berries, which occur in various plants, are considered effective. They are believed to prevent bacteria from attaching themselves to the bladder wall, preventing the germs from infecting the cells in the first place. The main cause of urinary tract infections are Escherichia coli bacteria, which are carried from the intestine into the urinary tract.
However, the great heterogeneity of the cranberry products examined makes it difficult to assess how reliable the results of the evaluated studies are. At the same time, they leave open the practical question of which of the many products made from red berries is the most helpful.
“There is currently insufficient evidence to recommend cranberry products across the board”
Studies that compare different concentrations of proanthocyanidins or different dosage forms are rare. Pills may be a little more effective than juice, but maybe only because the rather bitter-tasting drink isn’t consumed as reliably as pills, the Cochrane authors suspect. Ultimately, however, the question of the best form of berry products cannot be answered with certainty. The question of the optimal dose of the decisive ingredient also remains open.
Birgit Schindler, specialist pharmacist and research associate at Cochrane Germany, therefore draws the conclusion: “The evidence is currently not sufficient to recommend cranberry products across the board.” At the same time, it points to possible further problems. “It is not a good sign that six studies have been registered for a long time without results being published. This may indicate publication bias, i.e. studies that showed no difference between cranberries and a placebo were not published “.
In addition, Schindler draws attention to contradictions in the evaluated studies. Some studies in women with recurring urinary tract infections showed clear advantages of the products, but half of the studies showed no effect at all.
Many women in particular are likely to be able to take effective preventive measures. They are much more likely to be affected by urinary tract infections than men because the coli bacteria have to travel a much shorter distance from the intestines to the bladder. And while the women are just getting rid of the annoying symptoms, especially frequent urination and pain, many of them must expect the infection to return. About 30 percent of all women experience an average of two to three UTIs per year, some more.