What “Growing Evidence?”

One More Baseless Attack on Herbs and Chemotherapy!

By Keith I. Block, MD

Recently a colleague of mine emailed me a media report issued by Northwestern Memorial Hospital titled “Popular Herbal Supplements May Adversely Affect Chemotherapy Treatment.”  The first line of the article states: “Acai berry, cumin, herbal tea, turmeric and long-term use of garlic – all herbal supplements commonly believed to be beneficial to your health – may negatively impact chemotherapy treatment, according to a new report presented at the recent American Society of Clinical Oncology (ASCO) meeting in Chicago.”

The Northwestern Memorial report goes on to note that researchers have uncovered “growing evidence that these popular supplements may intensify or weaken the effect of chemotherapy drugs and in some cases, may cause a toxic, even lethal reaction.”  June M. McKoy, MD, a geriatrician at Northwestern Memorial and lead investigator on the ASCO presentation, urged cancer patients to discuss supplements with their doctors before beginning treatment—and to stop taking all herbal supplements while receiving chemotherapy.

The phrase “lethal reaction” caught my eye.  I had to wonder, exactly what was this claim based on?  In early May of this year, in a LOC blog article titled "How Supplements Can Help Protect Against the Toxic Side Effects of Chemotherapy,” [http://www.lifeovercancerblog.com/life-over-cancer-blog/2011/05/how-supplements-can-help-protect-against-the-toxic-side-effects-of-chemotherapy.html#more] I highlighted a number of herbals and other supplements that may be useful when taken during cancer treatment.  Among these was curcumin, the main substance in turmeric, and one of the herbs cited in the ASCO report as problematic.  So while I have reviewed many studies in the past, I decided to revisit curcumin, while also researching the other herbs mentioned as potential no-no’s for people receiving chemotherapy.

Here is what I found.  First of all, it is abundantly clear that most of the concern about herb-drug interaction in chemotherapy is not based on actual studies involving humans, or even animals for that matter.  As confirmed by a 2010 paper in Explore titled “Evidence-based management of herb-drug interaction in cancer chemotherapy,” the concern is almost entirely theoretical, with very little direct evidence of adverse reactions.  On the flip side, there is considerable preclinical evidence for therapeutic benefit when these herbs are combined with chemotherapy.

Let’s start with curcumin.  Dozens of laboratory studies have found that this botanical enhances the effectiveness of chemotherapy drugs in treating various types of tumors.  What’s really remarkable is that most of the interactions are synergistic, meaning that curcumin actually multiplies the effectiveness of various chemotherapy drugs (cisplatin, 5-FU, Taxol, and Gemzar). In many reports, in fact, curcumin has been shown to sensitize the cancer cells to the effects of the chemotherapy drug, while also eliminating cancer cells that were resistant to chemotherapy.

One of the most recent reports, published in the 24 May 2011 European Journal of Cancer, notes that in mice, curcumin not only reduces toxic side effects of the chemotherapy drug mitomycin-C (MMC), but also increases the drug’s tumor-killing potential.  The researchers propose that “the combination treatment of MMC and curcumin may be of significant therapeutic benefit in treating breast cancer.”  Green tea is thought to further enhance the anti-cancer punch of curcumin.  A February 2011 report in Cancer Science boldly proposed that green tea, together with curcumin, may improve all chemo regimens going forward.  While this has yet to be demonstrated in a clinical trial, current evidence suggests this potential exists.  Quite a contrast with Dr. McKoy’s dire warning of a possible “toxic, lethal reaction!”

My research team and I examined the list mentioned in the Northwestern Memorial report: Acai berry, Cumin, and long-term use of garlic (“herbal tea” is too imprecise a term to research).  We checked on both studies that gave theses herbs with chemo drugs, as well as studies of how these supplements might cause levels of chemo drugs to increase or decrease in the body because of enzyme effects.  No studies of Acai berry have shown any adverse effect; instead, they indicate that Acai can help prevent carcinogenesis and inhibit tumor growth.  As for Cumin, there appears to be no research at all on the common spice cumin that links it with chemo drugs.  For a relative of cumin called black cumin, the research is overwhelmingly favorable, with at least five studies reporting that the herb renders cancer cells more vulnerable to the killing effects of chemotherapy.  None of these studies showed any evidence of interference with chemotherapy.

There have been some contradictory studies about the interactions of garlic with chemo drugs and its capacity to alter drug levels in the body.  One possible concern is that large amounts of garlic may have a blood-thinning effect; this means it should not be taken in large amounts by patients with low platelet levels due to chemotherapy, or patients taking certain anticoagulant drugs.  Whether garlic affects drug levels was reviewed by Stacy Shord of the University of Illinois at Chicago in a recent article in Integrative Cancer Therapies.  Dr Shord found little evidence to indicate that garlic had negative interactions with chemotherapy, although it has a well-known interaction with some AIDS drugs, which has not been reported yet to carry over to chemo drugs.  In one of the relatively few actual clinical trials of herb-drug interactions, researchers found that in women with advanced breast cancer, taking a garlic supplement during chemo caused blood levels of Taxotere (docetaxol) to be somewhat elevated, though the result was not found to be statistically significant.  This would suggest increased efficacy, with the possibility of increased toxicity, although the lack of significant results casts doubt on the reality of the effect.  Lab studies also show that garlic may protect normal cells in the heart and intestines from adverse chemo drug effects. 

One botanical that can be problematic in the context of chemotherapy is St. John’s wort (SJW), which has a strong effect on enzymes that both activate drugs and excrete them from the body.  Clinical studies indicate that taking SJW at a daily dose of 900 mg may significantly reduce the effectiveness of the anti-cancer drugs Camptosar (CPT-11, irinotecan) and Gleevec (imatinib).  Since SJW is a popular herb for reducing depression—a common problem among people with cancer—such interactions ARE A CONCERN and should be watched for.  Given these facts, until we have more definitive data, I would certainly recommend avoiding SJW during chemotherapy.  Also, to be on the safe side, patients should not take large amounts of garlic supplements when they are suffering from or at considerable risk for low platelet levels during chemotherapy, or when they are taking anticoagulant drugs for blood clots. (Note: I consider a small routine amount of garlic use in cooking is safe and would only be a concern with a marked thrombocytopenia - platelets below 40,000).

In Conclusion:

There is no doubt that some particular interactions between herbal medicines and chemotherapy drugs exist and can have serious clinical consequences.  The problem is that the media’s sensational coverage of these interactions usually leads to a blanket rejection of all herbs and supplements during chemotherapy—as was the case with the Northwestern Memorial report.  This is truly unfortunate, because most of these plant substances have a very wide margin of safety and moreover, may improve treatment outcomes, as suggested by the vast majority of evidence to date.  Here are just a few examples of the herbs that show beneficial potential based on clinical studies:  ginger, for countering nausea caused by chemotherapy, milk thistle for repairing liver damage from specific chemo drugs, astragalus (demonstrated in multiple randomized controlled trials) for improving chemotherapy response, outcome and for offsetting immunosuppresion, and ginseng for overcoming fatigue during chemotherapy. 

As always, I encourage patients to discuss any herbal supplement use – in fact, all supplement and vitamin use – with their healthcare practitioner, not only to help avoid any potential interactions with medications, but to also make sure they are taking what is right for them.  It’s important to keep in mind that most supplements are designed for general health, not specifically for cancer patients.  Supplement quality will vary not only from brand to brand, but if a company manufactures multiple supplements, not all of them will necessarily pass independent testing.  And when it comes to treating cancer or preventing a recurrence, the need for a personalized program is a must. 

 

Comments

[Noah Berkowitz]

Just in the title you catch my attention. Thanks for the great sharing of superb information, I really appreciate your effort, bravo!

[arif]

my dad is suffering from brain cancer. it is anaplastic astrocytoma grade 3.since dec 2011. he is been treated by chemotherapy capsules

i have started giving garlic to my father since 2nd feb 2012, but the recent MRI dated 15th march 2012 shows an increase in cancer cells by 25 %.. i am giving him curcumin since 17th feb 2012. i have also started giving him grape seed extract and vitamin b17 tablets since 2nd march 2012