Health claims not berry well supported
I don’t usually bother with general nutrition stories that don’t contain any direct reference to research, but the Herald story about berries was irresistible. There are lots of biologically active compounds in berries, and many of them have been shown to have interesting properties in test-tubes or mice. As you know by now, this sort of interesting biochemistry is important because it occasionally translates to genuine health benefits, so you should be asking what the human clinical research shows.
If you go to the Cochrane Library (which is free to everyone in New Zealand), and look for clinical research in humans involving blueberries or cranberries you don’t find much. The only topic with enough information to draw any sort of conclusion is on cranberry juice to prevent urinary tract infections. Which it basically doesn’t. The plain-language summary says
Cranberries (usually as cranberry juice) have been used to prevent urinary tract infections (UTIs). Cranberries contain a substance that can prevent bacteria from sticking on the walls of the bladder. This may help prevent bladder and other UTIs. This review identified 24 studies (4473 participants) comparing cranberry products with control or alternative treatments. There was a small trend towards fewer UTIs in people taking cranberry product compared to placebo or no treatment but this was not a significant finding. Many people in the studies stopped drinking the juice, suggesting it may not be a acceptable intervention. Cranberry juice does not appear to have a significant benefit in preventing UTIs and may be unacceptable to consume in the long term.
As with many fruits and vegetables, eating more of them instead of other stuff is both enjoyable and probably healthy. As with pretty much any food, there might be some specific additional benefits (or harms), but if so we don’t yet have much evidence for them.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »