University of Otago, Christchurch, researchers have found that a natural fruit source of vitamin C - kiwifruit - is vastly superior to a purified supplement form.

The researchers are studying kiwifruit as a source of dietary vitamin C and found that in mice eating kiwifruit, vitamin C uptake was five times as effective as taking a purified supplement form.

The study was recently published in the American Journal for Clinical Nutrition, the highest ranking journal for human nutrition research.

Lead researcher Associate Professor Margreet Vissers says people require vitamin C (ascorbate) in all body tissues and organs to be healthy. Our bodies cannot make the vitamin and we should obtain it from our food. It is also available in purified form and is arguably the most commonly consumed vitamin supplement.

In the experiment vitamin C-deficient mice were fed the vitamin over a month, either as kiwifruit or as an equivalent amount of pure vitamin C.

Mice fed the kiwifruit absorbed vitamin C much more efficiently than those given the purified supplement form, and they also retained it for longer. This suggests that there is something in the fruit that improves absorption and retention.

Vissers says: "The findings of the mouse trial have important implications for human nutrition".

To determine whether this situation also applies to people would require a human trial and an equivalent human study is now underway.

"The question that has often been asked is whether a supplement is as good a source of vitamin C as whole foods, but few studies have addressed this issue. We are uniquely placed to do that work.''

The mouse study was funded by Zespri and the University of Otago.