Kiwifruit and DNA Repair

In 2003, a landmark study was published in the journal Carcinogenesis. Now, we’ve known “Plant-based diets rich in fruits and vegetables can prevent the development of several chronic age-related diseases, including cancer.” But why? Well, the mechanism behind this protective effect is not clear. We know whole plant foods are rich in antioxidants, which are capable of decreasing oxidative damage to DNA, and thus might prevent mutation and cancer.

But what about our 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 again.

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, right? 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 kiwis a day. Now, it wasn’t completely consistent on every day for every person, but you can kind of get a sense that the times without the kiwifruits, DNA damage tended to go up. And indeed, that’s what the statistical analysis found: 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 DNA restoration? So, this is our first line of defense, right, 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 two kiwis, off two kiwis, on three.

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 just really a matter of whether we have it in our 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. And we’ll look at that 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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• Collins AR, Harrington V, Drew J, Melvin R. Nutritional modulation of DNA repair in a human intervention study. Carcinogenesis. 2003 Mar; 24(3):511-5.
• Bøhn SK, Myhrstad MC, Thoresen M, Holden M, Karlsen A, Tunheim SH, Erlund I, Svendsen M, Seljeflot I, Moskaug JO, Duttaroy AK, Laake P, Arnesen H, Tonstad S, Collins A, Drevon CA, Blomhoff R. Blood cell gene expression associated with cellular stress defense is modulated by antioxidant-rich food in a randomised controlled clinical trial of male smokers. BMC Med. 2010 Sep 16; 8:54.

Thanks to Moriori and LadyofHats via Wikimedia Commons.

• antioxidants
• cancer
• DNA damage
• fruit
• kiwifruit
• oxidative stress
• phytonutrients
• Plant-Based Diets
• vegetables