Transcript: Kiwifruit and DNA Repair
In 2003, a landmark study was published in the Journal Carcinogenesis. Now we've known "plant-based diets rich in fruit and vegetables can prevent the development of several chronic age-related diseases, including cancer," but why? "Consumption of fruits and vegetables is associated with decreased risk of cancer," but why? The mechanism behind this protective effect is not clear. We know these foods are rich in antioxidants, which are capable of decreasing oxidative damage to DNA, and thus might prevent mutation and cancer,” but what about the second line of defense against oxidative DNA damage, DNA repair? We’re going to get some DNA damage in our world no matter how healthy our diets, so it's critical to find ways to upregulate our DNA repair enzymes to better assist with stitching our DNA back together.
So, how about we give people some kiwifruits on and off for a few weeks and see what happens. Why kiwifruits? Because it was funded by the International Kiwifruit Organization. You got to get funding from somewhere.
First, what happened to the level of DNA damage? Each symbol represents the DNA damage measured in one person. So day zero, no kiwifruit, the "WO" means without kiwifruit and you can see they start out all over the map. Maybe some were smokers, or sat in traffic, who knows. But then here they go on one kiwi a day, then they go back to zero, then two a day, then zero, then three a day. It wasn’t completely consistent on every day for every person, but you can kind of get a sense that during the weeks without the kiwifruits, DNA damage tended to go up. And indeed that’s what the statistical analysis showed. Significantly less DNA damage on the days they were eating kiwifruits.
Note that it didn’t seem to matter how many kiwis they were eating, though. They seemed to get the same benefit whether they were eating one or three.
Kiwifruits have antioxidants, so no wonder there was less DNA damage, but once you already have DNA damage can kiwifruit help with the restoration? So this was our first line of defense, the antioxidants in plant foods. Now on to our second defense line of defense, DNA repair. This is measuring DNA repair rates. Level of DNA repair off kiwis, on kiwis, off kiwis, on kiwis, off kiwis, on kiwis,.
Now although it appears the three kiwis did better than one or two, statistically all three kiwi doses appeared pretty much the same, suggesting there’s some sort of plateau effect. Maybe there’s just some phytonutrient in kiwis that boosts this DNA repair enzyme system and it’s really just a matter of whether we have it in your bloodstream or not, rather than how much of it is there.
What would be interesting is if you added a different fruit or vegetable on top of the kiwi, with a whole different portfolio of phytonutrients; would they complement one another or would it just be a plateau across the board? We didn’t find out until recently.
We’ll look at this study in tomorrow’s video.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Serena.
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