Experts challenge super food claims: Healthy-giving properties of broccoli, blueberries, may not make it past the gut

"Polyphenols may well work when cells are exposed to them directly, such as under laboratory conditions, but what needs to be established is how effective they are when consumed as part of a food. If they don't actually get through the gut membrane and into the rest of the body, then they're not a super food," Dr Lucy Jones, Deputy Dean of the University's Faculty of Science, Engineering and Computing, said.

Dr Jones and her colleague Dr Elizabeth Opara have taken a model developed in the early 1980s by US cancer research institute Sloane Kettering and adapted it to see if and how medicinal Chinese herbs, known to limit the growth of cancer cells, are absorbed in the body. Known as the Caco-2, the model mimics the action of the small intestine, the principal place where nutrients are taken up. The Kingston researchers have used it to assess what does and doesn't make it through the gut.

"The Caco-2 is a single layer of cells grown in a laboratory environment that develops the characteristics and functions of the micro-villi, the tiny hair-like projections that aid efficient absorption found mainly in the small intestine," Dr Opara said. "This method allows us to look at what nutrients pass through into the body and could be used to test food supplements, drugs and foodstuffs. We found that while some compounds may have a local effect in the gut itself, in terms of the rest of the body the impact could be negligible."

Products so far tested by the Kingston University research team include herbs such as parsley, rosemary, sage and thyme. "We are also looking into the possibility of using the model to test a dietary nitrate supplement which is currently being investigated for its impact on performance by Kingston University's sport and exercise scientists," Dr Opara said.

Beyond its use for debunking exaggerated health claims and benefits, the Caco-2 model could form a key part of a screening process to determine the effectiveness of a range of dietary compounds. "It can also be used to study compounds in combination," Dr Jones said. "For example, a cancer patient may want to take Chinese medicines in addition to their prescribed medication. The Caco-2 model would allow researchers to look at the pros and cons of this and provide an insight into the various interactions."