By: Micheal Greger, MD, Director of Public Health and Animal Agriculture at the Humane Society of the United States.
The traditional model of how fruits and vegetables protect against cancer is that their antioxidants prevent the buildup of free radicals (also known as reactive oxygen species) which would otherwise go on to damage our cellular DNA, membranes, etc, which can lead to the transformation of healthy cells into damaged, diseased, or dying cells. But in that landmark 2003 kiwifruit study, we learned that there’s a second pathway as well. Phytonutrients actually modulate gene expression and can increase our cellular defenses such that even if there is some damage to our DNA our cells may recover instead of being irreparably lost.
The kiwi study look at one of those defenses, one DNA repair enzyme, but there are many. Many ways our cells repair our DNA—we don’t mess around when it comes to protecting our genes. So question number 1, what affect does kiwifruit consumption have on all these other defences, and question number 2, what if we branch out and test multiple fruits and vegetables at the same time?
You’ll remember that there did not seem to be a dose response with the kiwis. As far as this DNA repair enzyme was concerned, you were either eating kiwis or not, it didn’t really matter how many. But man cannot live on kiwis alone. What if you did a mix of fruits and veggies? Could you break through that ceiling?
Now studies are expensive, particularly if the kiwi people withhold funding because you have the audacity to test other fruit. So they wanted to make this study count. So when they designed their plant portfolio they went all out. Check it out. Green tea. Rosehip juice, Berries, berries, berries, berries, berries, berries, berries, berries, pomegranate, dark blue grapes, brussel sproinds, broccoli, red cabbage, kale, blue potatoes, dark chocolate walnuts rosemary oregano. This study, is making me hungry.
I don’t know if anyone noticed but this is that same amazing research group that blessed the world with that study of thousands of different foods. So they knew what they were doing.
OK long story short: “Plant-based diets can prevent development of several chronic age-related diseases,” blah blah blah we know that. This is what they did: three groups, the antioxidants-to-the-teeth group, compared to a 3 kiwi a day group, compared to control. Tool blood from everyone, and for then for the first time ever reported did this microarray analysis where you can measure the effects of a plant-based diet on expression of hundreds of different genes at a time. The first to investigate the influences of healthy diets on gene expression in whole blood.
The kiwi group was able to significant regulate not just one gene as I showed in the 2003 study but a total of 5. Meanwhile the very berry group significantly regulated 5 times more, 25 genes. Conclusion: The observed changes in the blood cell gene expression profiles suggest that the beneficial effects of a plant-based diet on human health may be mediated through optimization of defence processes.
This is the final video of a three-part series about the latest discoveries on kiwi fruit. See also yesterday’s NutritionFacts.org video-of-the-day Kiwifruit and DNA Repair and Kiwifruit for Irritable Bowel Syndrome. The results of this follow-up study support the previous work on the importance of dietary diversity that I profiled in Apples and Oranges and Garden Variety Anti-Inflammation. The study of thousands of foods I mention is referring to Antioxidant Content of 3,139 Foods, and Antioxidant Power of Plant Foods Versus Animal Foods. Note this study is measuring so-called “epigenetic” changes, meaning differential gene expression. Just because we have a certain set of genes doesn’t mean you can’t turn them on and off with changes in your diet. See Mitochondrial Theory of Aging and Convergence of Evidence and the other thousand plus nutrition and health topics I address.
Michael Greger, M.D., is a physician, author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous “meat defamation” trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.