Citrus for Cancer

Citrus flavonoids, or naturally occurring plant compounds that function as antioxidants, may be effective anticancer agents, a new study reports.

Researchers from Lawson Health Research Institute in Canada explained that tangeritin and nobiletin are citrus flavonoids that are among the most effective at inhibiting cancer cell growth in vitro and in vivo.

Tangeritin is a flavone that is found in tangerine and other citrus peels. Tangeritin is commercially available as a dietary supplement. Nobiletin is one of the citrus bioflavonoids and can be found in citrus fruits such as lemon, orange, tangerine, grapefruit, etc.

The study investigated the antiproliferative activity of tangeretin and nobiletin in human breast cancer cell lines and a human colon cancer line.

Researchers found that both flavonoids inhibited proliferation in a dose- and time-dependent manner, and blocked cell cycle progression in all three cell lines. At concentrations that resulted in significant inhibition of proliferation and cell cycle arrest, neither flavonoid induced cell death in any of the tumor cell lines.

To test the ability of arrested cells to recover, cells that were incubated with tangeretin and nobiletin for four days were then cultured in a flavonoid-free medium for an additional four days. Cells resumed proliferation similar to untreated control within a day of flavonoid removal. Cell cycle distribution was similar to that of control within four days of flavonoid removal.

The study authors concluded that in cell lines at concentrations that inhibit proliferation up to 80 percent over four days, tangeretin and nobiletin stop cell growth and significantly suppress proliferation by cell cycle arrest without cell death. Based on this evidence, tangeretin and nobiletin may be effective anticancer agents.

Integrative therapies with strong or good scientific evidence for the treatment of various aspects of cancer include vitamin A, probiotics, psychotherapy and selenium.

For more information about the integrative therapies mentioned above or for information about the medicinal uses of citrus fruits, please visit Natural Standard's Herbs & Supplements and Health & Wellness databases.

Comments

[Paul]

The quest for the magic bullet for cancer is still a long way off I fear. There are so many natural products that have good activity against cancer cells, but it’s a very big step to become a drug. It has happened, and paclitaxel (Taxol) is a great example of a natural product that has done wonders for cancer patients. Hopefully there will be a few animal models on the way to see if it is tolerated and safe. It is interesting that these compounds didn't induce cell apoptosis, but whether that is good or bad I have no idea.

[Emily P.]

Paul, wouldn't it be a good thing that no apoptosis occurred? A cancer treatment is hardly effective if it eradicates your cells along with the cancer, especially in cases of severe metastasis when healthy cell counts are so low.

I'm always in favor of incorporating these compounds into my diet instead of taking supplements. For some reason supplements seem unnatural to me even, if they come from natural products. This study specifically cited the peels of these various citrus fruits as containing tangeritin. Does that mean people are not getting this compound in their diets if they only consume the fruit?

[Jo]

To answer Emily's question, apoptosis is actually something you want generally when talking about supplements and their effects on cancer because it typically refers to *cancer* cell death, which is the point. Many of these studies are done in vitro on cell lines and the researchers just test whether or not the extract/supplement/etc is able to kill the cancer cells (aka create cell apoptosis).

Hope that helps!

[W. Thomas]

In response to Emily's comment: Even if you were to eat the peels of tangerines, who knows what happens to tangentin after it has been subjected to stomach acids, digestive enzymes and colonic bacteria before entering the bloodstream? These studies involve applying highly concentrated tangentins directly to cells in laboratory media, and are generally performed in an attempt to identify potential compounds that can be processed into drugs. While eating citrus fruits has obvious nutritional benefits, I think it is highly unlikely that consuming them would stop cancerous growths from proliferating. Perhaps a diet high in flavanoids helps prevent cancers from forming in the first place, but it would take a long-term study in humans, comparing those who regularly consumed citrus fruits (or in this case, their peels) with those who did not and measuring cancer rates over time.
So often hopes get raised over in vitro studies suggesting anticancer benefits of a certain food or supplement, only to find in human studies that there is no clear benefit. I would wait for results of humans studies before choking down citrus fruit peels in hopes of warding off cancer.

[Caren]

As an old saying goes, "Mom knows best," and my mom surely has told me to eat plenty of fruits for better health! However, as this study has shown, we have not found the cure for cancer from eating citrus fruits. But I suppose, researchers should keep experimenting with fruits, while we continue to eat them... I'd say it is a win-win situation.

[Karen]

I didn’t see anything in the study about citrus fruits aiding in cancer prevention. Of course, they have plenty of other health benefits, but the link between my morning grapefruit and fewer cancer cells still seems weak. Even in the in vitro study, cancer cells weren’t dying, and the results faded soon after the flavonoids were removed. I’m still confident that citrus fruits help strengthen my immune system, but I agree with other bloggers that we need a lot more research to establish a relationship between citrus and cancer.

[Tim P.]

Whenever I hear anything about new findings concerning a diet, I am weary because I feel like it is difficult to tell whether these results will be achieved in humans and how. I think it is obvious that antioxidants are good for us and should be included in our diets, but I wonder how effective they are in directly treating cancer. Maybe it could be more of a preventative method or it could be manipulated into a drug and become more potent that way. Nevertheless, we should all take the time to incorporate more fruits and vegetables in our diets because we will definitely get some good out of it.

[Sally]

I think that rather than getting caught up in the details about the exact mechanism of action behind how citrus fruits are healthy for people, we should just trust what we have already been told/known for years- eating fruit is GOOD FOOD FOR YOU- for many reasons. Even if the antioxidants in the fruit don't have much, if any, anti-cancer activity, the fact that you are consuming fruit rather than fatty foods reduces your risk for cancer. People who eat well-balanced diets that are rich in fruits, such as oranges or tangerines, are going to lead much healthier, longer lives. No debate necessary.

[J. Keats]

Whoa... my head is spinning! Here, this study is saying that the flavonoids in citrus help stop cancer from growing, and another study posted on this site is saying that taking antioxidants may actually cause skin cancer! What gives here? I don't know whether to eat a diet high in antioxidants or avoid them! All this conflicting data is too confusing! Can anyone shed some light here?

[dalz]

Even though the study shows that cell death does not occur, it does say that growth was decreased, which is a light at the end of the cancer tunnel no matter how small. This could theoretically lead to an increase in the time to metastasis.

Flavonoids have long been believed to help with antiviral, anti-allergic, anti-platelet and anti-inflammatory effects, so what's the harm in looking deeper at research that shows some hope of promise.

[Audrina]

Interesting study. So many studies show that fruit and vegetables help prevent various types of cancer.

There's also recent evidence that supplementation with Lactobacillus casei (a type of probiotic) may help reduce the recurrence of colorectal tumors in patients who have previously undergone surgery for colon cancer.