The much-touted health benefits associated with super-food such as broccoli and blueberries do not reach past the gut, a new study has found.

Super-food may have been the mainstay of the health industry for a long time, but now researchers are questioning their much promised health promoting properties.

Researchers at London's Kingston University used an approach that allows them to delve deeper into the effectiveness of health-promoting 'super foods' and their elixir-giving ilk.

They found that foods such as broccoli, blueberries and whole grains do contain polyphenols - compounds that have antioxidant and anti-inflammatory properties - but they seldom 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," said the study.