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Health Benefits of Citrus Zest

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.


Now you know why my favorite citrus fruit is kumquat—because you can eat the peel and all!

For other foods that may keep our DNA intact, see my Which Fruits and Vegetables Boost DNA Repair? video. Kiwifruit (Kiwifruit and DNA Repair), broccoli (DNA Protection from Broccoli), and spices (Spicing Up DNA Protection) may also fit the bill.

Interested in learning more about citrus? Check out:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling 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.


47 responses to “Health Benefits of Citrus Zest

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    1. Hello Ronald,

      Great question! The article indicates that whole citrus instead of juices is the optimal way to consume it; however, we may be able to boost effects even further by zesting the peel. It is my understanding that the white strands that are attached to the fruit after peeling also contain the DNA repairing phytonutrients, so it is not necessary to eat the peel, but why not zest a bit of the peel to further add to the DNA repairing effects?

      I hope this helps,

      Matt, Health Support

  1. Sir, does this mean that using lemon zest in green tea is a non-starter due to the heat factor and that we are better served by eating it straight off of the lemon’s back?

  2. I would be interested in knowing if there is any value (nutritionally) in consuming banana peels? I heard that it is customary in some parts of south asia to eat the peels. To me the taste is bitter, as is citrus peel and not apeeling lol

    1. Barb, I wonder if other primates (eg. chimps, etc) eat the banana peels? Sometimes, the other primates can give us an indication of what’s healthy for us human primates. :-)

      1. I did a quick search on the web on whether primates eat the banana peels and the answers vary across the whole spectrum. The only way to tell for sure whether the peels are good for humans is to :put it to the test” :-) (DBPC trials, but I think it would be very difficult to tease out any cause and effect relationships.

        1. Interesting Hal! And thanks for checking that idea. Often animals DO choose the healthier or more nutritious meals. I just wondered since my searches on blueberries and antioxidants revealed that the leaves of blueberries, raspberries, blackberries were much more potent antioxidant-wise than the fruits. Though I imagine there is a different array of specific antioxidants.. too complex for me. (thanks to Lonie, I am enjoying True Blueberry Tea now)

          Since Dr G is talking about citrus peel, thought I would ask about banana peel. I really enjoy marmalade, but maybe the good in the peels do not over-ride the bad in the sugar!

    2. Greetings…I have read that only in the “west” do people peal bananas + the “rest of the world” find it strange to do so. That said, I think the peels from only organic bananas should be used of course. For me it seems like an acquired taste. I cannot quite yet stomach the idea of eating the peel. In the same articles it also stated that the peels contain the most nutrients by far!
      Interesting is also, in all the countries I can think of where rice is the main staple they eat white refined rice only! It seems only in the “west” is whole grain rice consumed. I have asked a lot of Asians about this ant they told me that in their home countries people consider brown rich unhygienic and dirty. Go figure. Everything is relative.

      1. Yes William, I agree that if someone wanted to try banana peels, organic would definitly be the way to go. Cooking probably alters the taste a bit I imagine, bringing out some sweetness in the same way cooking does for onions. You remind me too about rice- I meant to pick up some forbidden rice to try. That’s the black/purple coloured rice that Dr Greger was saying contains anthocyanins. Thanks William!

  3. So is heat good or bad? Today I added lemon peel to Lemsip (before reading the article) but I’m none the wiser. Please clarify, Dr Greger.

    1. In the first sentence Dr Greger says the substance was found to be ‘heat sensitive’ , so yes, cooking destroys the effective substance. Raw citrus only would work.

  4. Am wondering if Zest is same as eating the peel. My lemons and oranges have a largely white stringier peel covered with a thin, easy to remove, colored zest all packaging a juicy pulp fruit. I would like guidance on most beneficial way to consume similar fruits.

  5. Yes, please clarify. Most pesticides can only be partially removed by intensive scrubbing. And even organic growers paint their citrus fruits so as to make them look more attractive….

  6. Any suggestion from research whether the peel looses its effectiveness if heated? Lovely in tea and might be nice even in coffee? Would an extract of citrus peel also be helpful taken internally?
    What foods would it taste good with?

  7. I add 1/2 lime, turmeric, ginger, and kale to my favorite green smoothie. The taste will make your head turn 180 degrees – invigorating.

  8. I question the orange juice melanoma connection. I imagine most nurses in the study cited used orange juice made from concentrate as that is what is commonly available in supermarkets. Concentrates are heated to pasteurize them. I wonder if fresh fruit were juiced what the results would have been. I certainly think adding zest is the way to go.

  9. Most fruits sold in grocery stores are waxed. Whole Foods Market claims that organic fruits are waxed with “natural waxes,” whereas conventional fruits can have all sorts synthetic waxes.

    “What about people who don’t want the wax anyway? Because the coating is formulated to be water-repellent, it won’t wash off, though it’s always a good idea to rinse fruit before eating.” https://www.theatlantic.com/technology/archive/2017/04/why-fruit-has-a-fake-wax-coating/524619/

    I never know what to do when a recipe calls for a zest from an unwaxed fruit; how do I find that here in the northeast?

    1. I have read that only the peels from organically grown fruits + vegetables should be eaten otherwise you will get untoward doses of pesticides. I think liquifying and mixing them in with other ingredients is the only way to consume them because they do not taste good in their own right.

  10. I like to soak orange and lemon peels in apple cider for a few days and then drink it. It’s delicious! Sometimes i remove the outer peel with a vegetable peeler to get rid of dyes and wax.

  11. I take an smaller organic navel orange, scrub it while washing, cut in half, remove visible seeds, cut about 6-7 slices ( the entire orange) and drop into heavy duty blender with what ever else if I feel like it, sometimes an ice cube. Refreshing OJ drink that lets me have the skin nutrients. I love the orange juice taste and most times I do not add anything in it. I occasionally use this as a salad dressing too. Easy A family member used it as a pancake syrup as he said too dry to eat but fine with oj. Y’all be well!

  12. What about (citrusy) bergamot? I cold brew my Earl Grey tea and add a splash of bergamot water to my other cold brewed teas.

    It’s my understanding the Queen of England drinks Earl Grey and she (and the Queen Mother before her) seem to fare well in the longevity race.

    1. But you can get all of them out (~ one year or less) and it is relative inexpensive to do so. Look in online articles, youtube, and try to learn. It will make a huge difference on you.

  13. Okay, I am in the grocery store and realized that I have wifi, so I could read this one without using data time.

    I have been doing Modified Citrus Pectin. Wondering if it still has the good stuff in it?

    Also, I use things like lemon pepper and Orange spice jar all the time, does that count?

    I know that I am a day behind so I will try to figure it out.

  14. Swanson sells a supplement called Pectipure, they say it is a modified citrus pectin. Any thoughts to the benefits of consuming citrus in a pill?

  15. What is the deal with orange juice? Should I avoid drinking it from a container? Should I just peel and eat it whole? Does it matter if I squeeze the juice out and then drink it and eat the left over portion of the fruit? I have Googled this issue and I get several highly different opinions. Some of them are doctors.

  16. Maria,

    The quote is from this study: https://www.ncbi.nlm.nih.gov/pubmed/12778065.

    The full quote: “Contrary to expectation, we observed higher risks of melanoma with greater intakes of vitamin C from food only (RR=1.43, 95% CI 1.01-2.00 for >/=175 vs <90 mg day(-1), P for linear trend=0.05) and a significant positive dose-response with frequency of orange juice consumption (P=0.008). Further research is needed to determine whether another component in foods such as orange juice may contribute to an increase in risk."

    Dr. Alan Kadish moderator for Dr. Greger http://www.Centerofhealth.com

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