Wedge of lemon and peel slices on black background

New data demonstrating a DNA-protective agent present in at least some fruits and vegetables found that the agent was heat-sensitive and determined it was not vitamin C. This was confirmed in a study that tried vitamin C directly and found no effect on DNA protection or repair of DNA strand breaks.

If not vitamin C, what could the DNA-protective agent be?

The carotenoid beta-cryptoxanthin, found primarily in citrus, seems to be at least one candidate, as I discuss in my video Citrus Peels and Cancer: Zest for Life? If you expose cells to a mutagenic chemical, you can cause physical breaks in the strands of DNA. However, in less than an hour, our DNA repair enzymes can weld most of our DNA back together. What happens if we add some of that citrus phytonutrient? We can effectively double the speed at which DNA is repaired. But, this was determined in a petri dish. What about in a person?

In one study, subjects drank a glass of orange juice and their blood was drawn two hours later. The DNA damage induced with an oxidizing chemical dropped, whereas if they had just had something like orange Kool-Aid instead of orange juice, it didn’t help.

So, do people who eat more fruit walk around with less DNA damage? Yes, particularly women.

Does this actually translate into lower cancer rates? It appears so: Citrus alone is associated with a 10 percent reduction in odds of breast cancer.

Given to newly diagnosed breast cancer patients, citrus phytonutrients were found to concentrate in breast tissue, though many complained of “citrus burps” due to the concentrated extract they were given. So, researchers evaluated topical application as an alternative dosing strategy, recruiting women to apply orange-flavored massage oil to their breasts daily. This request was met with excellent compliance, but it didn’t work. We actually have to eat, not wear, our food. 

Why not just take carotenoid supplements to boost our DNA repair? Because it doesn’t work. Although dietary supplements did not provoke any alteration in DNA repair, dietary supplementation with carrots did. This suggests that “the whole food may be important in modulating DNA repair processes…”

Though orange juice consumption was found protective against childhood leukemia, it was not found protective against skin cancer. “However, the most striking feature was the protection purported by citrus peel consumption.” Just drinking orange juice may increase the risk of the most serious type of skin cancer. Daily consumption was associated with a 60 percent increase in risk. So, again, better to stick with the whole fruit. We can eat citrus extra-whole by zesting some of the peel into our dishes.

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NUTRITIONFACTS.ORG is a strictly non-commercial, science-based public service provided by Dr. Michael Greger, providing free updates on the latest in nutrition research via bite-sized videos. There are more than a thousand videos on nearly every aspect of healthy eating, with new videos and articles uploaded every day. NutritionFacts.org was launched with seed money and support by the Jesse & Julie Rasch Foundation. Incorporated as a 501c3 nonprofit charity, NutritionFacts.org now relies on individual donors to keep the site alive.

Dr. Greger is a physician, New York Times bestselling author, and internationally recognized speaker on nutrition, food safety, and public health issues. A founding member and Fellow of the American College of Lifestyle Medicine, Dr. Greger is licensed as a general practitioner specializing in clinical nutrition. Currently he proudly serves as the public health director at the Humane Society of the United States. Dr. Greger is a graduate of the Cornell University School of Agriculture and the Tufts University School of Medicine.

His latest book, How Not to Die, became an instant New York Times Best Seller. 100% of all proceeds he has ever received from his books, DVDs, and speaking engagements has always and will always be donated to charity. Dr. Greger receives no compensation for his work on NutritionFacts.org.

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