How Curcumin Targets Cancer
By Virginia Chen
Despite clinical successes using new immunotherapy drugs, cancer is still killing over 560,000 Americans each year.
Conventional medicine recognises prevention as an essential element in today’s “War on Cancer.”
Curcumin is a natural compound extracted from the spice turmeric. An accumulation of evidence indicates its cancer-preventive effects, leading one scientist to call curcumin:
An ideal chemopreventive agent with its low toxicity, affordability, and easy accessibility.
Curcumin has emerged in this role after 30 years of research at the National Cancer Institute, which has been testing various substances for their potential preventive effects.
According to the National Cancer Institute, after testing more than 1,000 candidates, just 40 indicated promise. Curcumin is one of the leading members of that elite group.
Curcumin has reached the stage of clinical trials, although it has been in use since ancient times as a remedy for many illnesses in different cultures.
Used alone or in combination with other therapies, curcumin has an impressive track record in prevention and treatment.
Here is a brief review of the research indicating the benefit of curcumin in the prevention of common malignancies, its potential to help treat certain cancers and to minimise the side effects associated with radiation and chemotherapy.
Curcumin’s Unparalleled Cancer-Fighting Abilities
For those who have been diagnosed with cancer, it can seem as though cancer developed practically overnight. In reality, the development of cancer is a lengthy process that may take years or even decades to play out.
The initiation and progression of a cell into a malignancy involves multiple steps. At each step, there is a disruption in at least one pathway that controls normal cellular processes.
The good news about this complex process is that it represents a potential point of intervention to delay or prevent a malignancy from forming.
Curcumin has now been shown to have an impact on virtually all of the major targets involved in the cancer development process. These effects give curcumin potent preventive and therapeutic properties against many different kinds of cancer.
In general, chemopreventive substances (those used to inhibit, delay, or reverse cancer development) are grouped by their general mechanism: those that slow the proliferation of cancer cells, those that reduce oxidative stress, and those that block carcinogens from forming. Curcumin is a member of all three groups, giving it unparalleled cancer-fighting abilities.
Curcumin’s Multiple Mechanisms of Action
Curcumin’s actions involve various combinations of mechanisms, including:
Survival signalling. Cancer cells early on develop the ability to proliferate and survive in environments that normally would not support cell replication.
Curcumin modulates a host of survival signals through multiple pathways, thereby putting a halt to out-of-control replication.
Apoptosis. This is the programmed cell death that eliminates dysfunctional cells. Cancer cells lose their ability to die off naturally, which plays a major role in the development of cancer, and in its resistance to conventional treatment. Curcumin switches back on the apoptosis signalling pathway, encouraging over-proliferating cells to die gracefully, rather than continue to grow and spread.
Growth Factors. A wide variety of growth factors and other molecules can promote cancer cells’ replication. Curcumin directly inhibits many of those molecules, stopping cancer growth in a multi-targeted fashion.
Inflammation. Low-grade inflammation is a powerful promoter of cancer cell growth and survival. Curcumin blocks the pro-inflammatory process at several different points, reducing the overall state of inflammation and slowing cancer development. By blocking the inflammatory master molecule nuclear factor-kappaB (or NF-kB), curcumin blunts cancer-causing inflammation, slashing levels of inflammatory cytokines throughout the body.
Cancer stem cells. Cancer stem cells are an unusual population of cells within tumours. These cells, like all stem cells, can develop into many different types of mature cells—including new cancer cells. Cancer stem cells are responsible both for new tumour formation and for failures of conventional chemotherapy because they can survive drugs that kill normal cancer cells. Curcumin has been shown in multiple lab studies to suppress the growth of cancer stem cells. This has the dual benefit of possibly reducing the risk of recurrence after treatment, and also of improving response to therapy of existing malignancies.
Immune system. The healthy immune system constantly patrols the body, seeking out and destroying incipient cancer cells. As we age, however, the immune system becomes less functional, in a process called immunosenescence. Curcumin supports the body’s immune system by preventing the loss of immune cells that destroy tumour's. It also helps overcome tumour-induced resistance to immune destruction, thereby slowing or stopping early cancers naturally.
Curcumin and Cancer
Cancer still kills one in four Americans, despite years of waging the “War on Cancer.”
Mainstream medicine has little to offer in terms of cancer prevention, though it has won some important battles in the area of treatment.
The natural compound curcumin has been called “an ideal chemopreventive agent” because of its ready availability, low cost, and low toxicity.
Studies of curcumin and cancer now number in the hundreds and demonstrate the compound’s versatile cancer-preventive and even cancer treatment properties.
Anyone with a personal or family history of cancer, and in fact anyone with major concerns about cancer in their own lives, should begin supplementing with curcumin, ideally in a form designed to enhance its absorption from the intestinal tract.
Curcumin in Cancer Treatment
Curcumin has shown promise as a treatment for gastrointestinal cancers. This is because pure curcumin has a low rate of absorption, which is especially beneficial for these cancers because it means that higher levels of the compound stay in the intestinal tract for longer periods of time.
In one study of patients with colorectal cancer, for example, curcumin was administered at a dose of 1,080 mg per day during the period between initial biopsy and surgery (a range of 10 to 30 days). At the time of surgery, the supplemented patients experienced numerous benefits, including an increased number of dying tumour cells, an increased expression of a gene that suppresses cancer (called p53), a reduction in blood levels of inflammatory TNF-alpha, and an improvement in body weight.
In another series of colorectal cancer studies, curcumin was shown to improve intracellular free radical scavenging activity (a highly-protective effect), reduce DNA damage, and suppress inflammatory changes.
Curcumin has now gone through essential Phase I drug studies, which are aimed at determining the safety and ideal dose of any new therapeutic agent. In a group of patients with high-risk or premalignant cancerous lesions, curcumin was found to be tolerable without significant side effects at doses up to 12,000 mg per day. Beyond its obvious safety, curcumin led to numerous improvements in these patients as well. And in 33% of subjects, the tumours didn’t progress—even when they had not responded to chemotherapy previously.
Curcumin has made unprecedented headway in attacking a usually lethal type of malignancy: pancreatic cancer. This was seen in a study in which 8,000 mg per day of curcumin treatment produced favourable changes in markers of cancer progression.11 One patient in this study remained stable for 18 months without progression—a nearly unheard-of outcome. Another showed a temporary reduction of the existing tumour size by 73%.
Due to the poor absorption of standard curcumin and turmeric powder, very high doses are needed to achieve therapeutic blood levels. Enhanced absorption technologies today enable consumers to use curcumin supplements that provide the equivalent of over 2,000 mg a day of curcumin in just one 400 mg enhanced-absorbing curcumin capsule. Cancer patients often take several 400 mg enhanced-absorbing curcumin capsules daily.
Curcumin and Chemotherapy
Some exciting studies are emerging on curcumin’s potential role as a therapy in addition to standard treatments such as a radiation and chemotherapy. Studies show that not only can it help protect against the damage caused by these treatments, but it can also enhance their effect.
In a laboratory model, when curcumin was given in combination with the chemotherapy drug cisplatin, it significantly reduced the growth of surgically-implanted human head-and-neck tumours in mice. And, in the human breast, oesophagal, and colon cells in culture, curcumin increased the malignant cells’ sensitivity to chemotherapy drugs and to the effects of radiation treatments.
In a study of patients with chronic myeloid leukaemia (CML), subjects received either the chemotherapy drug imatinib alone or imatinib plus curcumin-rich turmeric powder (15 grams per day). After six weeks, the subjects receiving curcumin-plus-imatinib had a significantly greater reduction in a cancer growth factor than the patients treated with the cancer drug alone. Reduction of this growth factor as a result of combined therapy of imagine and turmeric powder may help in the treatment of chronic myeloid leukaemia.
Curcumin’s ability to help protect against the side effects of these treatments was seen in a study of breast cancer patients receiving radiation therapy. The patients were randomly assigned to receive 2,000 mg of curcumin or a placebo three times daily throughout their course of radiation therapy. At the end of the treatment, the patients taking curcumin had significantly less severe radiation damage to their skin and a reduction in skin sloughing. Both of these benefits demonstrate curcumin’s radioprotective effects.
Curcumin Prevents Cancer
It is extremely difficult to design and conduct human studies of cancer prevention. We cannot ethically induce cancer in a group of people and directly study the impact of preventive compounds, as is done in animal studies. Similarly, given the length of the human lifespan, it is not practical to study large groups of people for their entire lives to examine the impact of specific nutrients.
However, two particular kinds of studies—studies of slow-moving cancers or precancerous conditions,17 and studies of biomarkers, which are natural molecules that identify various stages of the transition from normal cells to malignant cells 2 —give us important insight into human cancer prevention strategies. Curcumin has been found to be beneficial in both of these kinds of studies, demonstrating its benefit in human cancer prevention.
Curcumin’s impact on precancerous conditions can be seen in a study of people with “monoclonal gammopathy of undetermined significance,” and “smouldering multiple myeloma. ”Both of these conditions are disorders of antibody-producing cells (these are immune cells that help to identify and neutralise pathogens), and both can progress to a potentially fatal blood cancer called multiple myeloma. A strong predictor of the likelihood of these conditions progressing to multiple myeloma is found through the detection of an abnormal ratio of certain proteins produced by the premalignant cells.
By the end of the study period, supplemented subjects showed a significant decrease in the abnormal protein ratio, and also in the presence of other “useless” proteins produced by premalignant cells.17 Treated subjects also showed a significant reduction in markers of bone resorption (bone breakdown), a problem that occurs as multiple myeloma progresses and erodes into bony areas. This shows that curcumin could have the potential to slow the disease process from a premalignant to a malignant state.
In a remarkably similar finding in prostate cancer, a supplement of curcumin plus soy isoflavones was effective at decreasing levels of prostate-specific antigen (PSA, a biomarker of prostate cancer activity) in men with the highest levels at baseline, but with no detectable cancer yet.18 These two studies together suggest that curcumin’s cancer-preventive effects may be most evident in more advanced precancerous conditions.
Colon cancer is another malignancy in which prevention can be studied because it is frequently first detectable as precancerous polyps or collections of abnormal cells called aberrant crypt foci. These represent one of the earliest changes seen in the colon that may lead to cancer.
In a study of patients with familial adenomatous polyposis (an inherited condition in which people develop multiple polyps that progress to cancer), taking curcumin (480 mg) and quercetin (20 mg) three times a day reduced the size and number of polyps by more than half. Another study demonstrated that taking 4,000 mg of curcumin per day for 30 days significantly reduced the number of aberrant crypt foci by 40%, again demonstrating curcumin’s power to prevent cancer progression.
Finally, a number of other studies have shown that curcumin reduces cancer-associated biomarkers, such as inflammatory molecules and oxidative damage, in patients having head-and-neck cancers, skin cancers, and tropical pancreatitis, an inflammatory disorder that can lead to pancreatic cancer.
Choosing the Right Curcumin Supplement
Curcumin has been called “an ideal chemopreventive agent” because of its multiple mechanisms of action that fight cancer development at every step. But curcumin does have an Achilles heel of sorts—it is relatively poorly absorbed from the gastrointestinal tract, reaching the circulation at only low levels after oral ingestion even of a large dose.
This is not a problem (and may be an asset) in gastrointestinal cancers since poor absorption causes it to remain in the gut at higher levels for a longer period of time. And, while there is good evidence for oral curcumin’s effects even at low blood levels in certain cancers, curcumin’s poor bioavailability may reduce its effectiveness in fighting cancer in other parts of the body.
Scientists have discovered that it’s possible to increase the bioavailability of curcumin by reconstituting purified curcumin with some of the natural oils and other components of the turmeric root.
When the curcumin-plus-turmeric complex is administered orally in healthy adults, the absorption of curcumin into the bloodstream is nearly 7-fold that of curcumin alone, and 6.3-fold greater than that of a curcumin-lecithin-piperine formula designed to enhance absorption.
In order to get the most out of this valuable supplement, it is important to select one that has proven high absorption characteristics.