 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 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 in 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 diet. So it's critical to find ways to up-regulate our DNA repair enzymes to better assist with stitching our DNA back together again. So how about we give people some kiwi fruits on and off for a few weeks and see what happens? Why kiwi fruits? Because it was funded by the International Kiwi Fruit Association. You've 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 kiwi fruit. The W-O means without kiwi fruit. 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 to 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, you know, the times without the kiwi fruits, DNA damage tended to go up. And indeed that's what the statistical analysis found, a significantly less DNA damage on the days they were eating kiwi fruits. 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. Kiwi fruits have antioxidants, so no wonder there was less DNA damage. But once you already have DNA damage, can kiwi fruit help with DNA restoration? So this is our first line of defense, right? The antioxidants and plant foods. Now on to our second 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 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 boost this DNA repair enzyme system. And it's just really a matter of whether or not you have it in your bloodstream, 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.