Dr. Andrew Collins of the respected Rowett Research Institute in Aberdeen, Scotland, in the United Kingdom, conducted research to look at the ability of kiwifruit to prevent damage to DNA, which is an early step in the process that leads to cancer.

Dr. Collins is an internationally respected research worker in this field who has been working on a method to measure DNA damage inside cells.  Called the comet assay, it is a technique involving electrophoresis that is a very sensitive and reliable method for measuring DNA breaks and base oxidation. In addition, the levels of a number of anti-oxidants were measured, including vitamin C, various carotenoids and vitamin E, in blood plasma.

The results of the work were published in the authoritative journal,  Carcinogenesis, in March 2003 and show that eating kiwifruit daily can provide substantial protection against the kind of DNA damage that may cause cancer. This was shown by significantly lower levels of oxidized bases in DNA after consumption of kiwifruit, and an increased anti-oxidant capacity, with elevated levels of vitamin C in the plasma.

There are several novel findings from this work that makes it significant.

A significant increase in DNA repair was seen even after eating just one kiwifruit a day.  However, after three kiwifruit per day, the rate increased by two-thirds.  Dr. Collins was extremely excited by this new finding to such an extent that he has become a daily kiwifruit eater!

Study Methodology

Large-scale trials using humans have given variable results when looking at the protection afforded by individual micronutrients, including anti-oxidants. These compounds, in isolation, may behave differently from mixtures of anti-oxidants and other phytochemicals that would be found naturally in fresh fruits and vegetables.

Dr. Collins therefore decided that he would investigate the effects of kiwifruit as a particularly rich source of nutrients, including vitamin C, and other potentially active phytochemicals on oxidative DNA damage in human lymphocytes, using the comet assay technique, as well as measuring plasma levels of antioxidants.

Volunteers took different amounts of kiwifruit over 3-week periods. Concentrations of dietary anti-oxidants were measured in their plasma as well as the resistance of lymphocyte DNA to oxidative attack as measures of anti-oxidant status. The second line of defense against oxidative DNA damage is DNA repair so this was also investigated.

The volunteers were healthy non-smokers who were not taking anti-oxidant supplements or medication. Each volunteer consumed 1, 2 or 3 kiwifruit a day for successive three week periods separated by 2-week washout periods. Otherwise they maintained their normal diet. They were allocated randomly to three groups, each of which was given a different order of kiwifruit doses. Early morning, fasted, blood samples were taken at the start of the study, at the end of each washout period and at the end of each 3-week phase. The blood samples were then separated into different components for the different tests.  link to the study.


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