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The Spice of Life

Unlocking the Power of Curcumin

September 2001

By John C. Martin


Imagine if the key to disease prevention was as close as your kitchen shelf. It's not the product of someone's imagination, but the product of years of medical research. Scientists are beginning to take notice of a well-known spice as a potent new preventive therapy against disease, especially cancer.

Cancer takes the lives of more than 1,500 people a day—over 5 million since 1990—and is the second leading cause of death in the United States.1

While those statistics are staggering, the medical community is maintaining its focus on mechanisms behind the disease and discovering new, potentially effective methods of treating it. A similar emphasis is placed on prevention, as more and more scientists attempt to uncover the mystery behind ‘carcinogenesis,’ particularly at the genetic level.

What is drawing the attention of medical oncologists and researchers these days is a substance known as curcumin, a naturally occurring yellow pigment found in the spice turmeric, which is part of the ginger plant family. Turmeric is widely consumed in its countries of origin not only as a spice, but as a medicine for the treatment of a variety of illnesses. It was long ago used as an anti-inflammatory among Indian practitioners.2

Today, curcumin is showing a much broader potential. Not only does the extract work as an antioxidant and anti-inflammatory, but a series of studies in the past four years, focusing on cancer at the cellular level, reveals some exciting findings. For one thing, research is discovering that curcumin is a powerful carcinogenic inhibitor, slowing cancerous cell proliferation by inducing apoptosis, a pre-programmed set of processes within a cell that results in its death.

Curcumin as an antioxidant

Curcumin, the extract found in a common household spice, is common no longer. It’s been drawing more and more attention among medical experts the last several years for its antioxidant and anti-inflammatory qualities.

When the body responds to a physical injury, a series of changes occurs through which free radicals are released. These free radicals, or “oxidants,” protect the body from foreign invasion, such as infection. However, in the process of killing invading bacteria, oxidants can also harm our cells. Such oxidants can include superoxide, hydrogen peroxide, hydroxyl radicals and lipid peroxides. Over time, as our cells continue to be affected by these free radicals, or oxidants, organs begin to degenerate. The result can be such diseases and conditions as chronic inflammation, heart disease, aging acceleration and chaotic cell growth leading to cancer.

The body does have built-in defense mechanisms to protect itself from free radical damage, but eventually, aging and disease deplete the body’s ability to keep oxidants at bay. Studies show that curcumin can inhibit, or possibly even reverse this process by scavenging or neutralizing free radicals and breaking their subsequent oxidative chain reaction.

Research as early as 1995 has shown that a diet that includes curcumin can restrict this oxidative stress. Scientists in India found curcumin inhibited lipid peroxidation, superoxides and hydroxyl radical.

Two more recent studies were published last year. In the first analysis, scientists found that prolonged exposure by curcumin to endothelial cells of the bovine aorta resulted in “enhanced cellular resistance to oxidative damage.”

Doctors in a separate investigation discovered that curcumin suppressed oxidative stress induced by trichloroethylene in mouse liver. The researchers concluded that curcumin’s benefit seems to be derived from its ability to inhibit increases in cellular levels of peroxisome, a component associated with oxygen utilization in cells.

The oxidation of LDL, the “bad” cholesterol, plays an important role in the development of atherosclerosis. Based on that knowledge, medical researchers have also examined the effect of curcumin on LDL oxidation and plasma lipid levels. In one investigation, doctors in Spain fed 18 rabbits a high cholesterol diet to induce atherosclerosis. The rabbits were divided into three groups; one group was given 1.66 milligrams of curcumin per kilogram of body weight, the second group was given 3.2 mg, and a third group was designated as a control. After seven weeks, the investigators found that the group fed the lower curcumin dosage decreased LDL’s susceptibility to lipid peroxidation, and both dosage groups had lower cholesterol levels.

  • Motterlini R, Foresti R, Bassi R, Green CJ. Curcumin, an antioxidant and anti-inflammatory agent, induces heme oxygenase-1 and protects endothelial cells against oxidative stress. Free Radic Biol Med 2000 Apr 15;28(8):1303-12.
  • Ramirez-Tortosa MC et al. Oral administration of a turmeric extract inhibits LDL oxidation and has hypocholesterolemic effects in rabbits with experimental atherosclerosis. Atherosclerosis. 1999 Dec;147(2):371-8.
  • Ruby AJ et al. Anti-tumour and antioxidant activity of natural curcuminoids. Cancer Lett 1995 July 20;94(1):79-83.
  • Watanabe S, Fukui T. Suppressive effect of curcumin on trichlorothylene-induced oxidative stress. J Nutr Sci Vitaminol 2000 Oct;46(5):230-4.

Curcumin targets cancer proliferation

In two recent studies, scientists at New York’s Columbia University researched curcumin’s therapeutic potential against prostate cancer. In one case last year, the scientists discovered that curcumin had a powerful ability to induce apoptosis and inhibit prostate cell proliferation in vitro by interfering with the cells’ protein signaling pathways that typically begin the growth process.3 Just recently, the researchers extended those findings to determine if they could achieve similar results in an animal model.4 In their latest study, the researchers found that prostate cancer cells that had been injected subcutaneously into mice, which had been fed a diet of 2% curcumin for six weeks, were unable to develop extensively and underwent significant apoptosis. “Curcumin could be a potentially therapeutic anti-cancer agent, as it significantly inhibits prostate cancer growth… and has the potential to prevent the progression of this cancer to its hormone refractory state,” the study authors concluded.

Yet prostate cancer is not curcumin’s only target. Other cancer investigations have drawn similarly powerful conclusions about this intriguing substance.

A study this past spring at Wayne State University investigated the effect of curcumin on certain gastrointestinal and colon cancers in the lab.5 Several immunoblot analyses demonstrated that curcumin blocked cell proliferation and induced apoptosis in both gastrointestinal and colon cancer cell lines.

A Chinese study published five years earlier found apoptosis is the result when curcumin is introduced to certain skin, colon, kidney and liver cancer cells, either in cultures or in mouse embryo fibroblasts—large, flat oval cells found in connective tissue and inherent in the formation of fibers.6

Other studies using rodents found curcumin is effective in reducing skin inflammation, inhibiting formation of edemas—an abnormal accumulation of cellular fluid, resulting in swelling—and inhibiting skin tumors when the substance is applied topically7 or orally in concentrations of either 0.2% or 1%.8

Curcumin has had similar effects on other types of cancer. When Polish researchers last year assessed the potency of the extract on lymphoid cells—those found in tissues comprising the lymph nodes— apoptosis resulted, although apoptotic symptoms were uniquely different in the various cells tested, the scientists reported.9

To determine just how effective curcumin might be as an anticarcinogenic agent, it was compared to other compounds and plant extracts in fighting human oral squamous carcinoma.10 Cell lines were grown in vitro for 72 hours, then the number of cells were counted to determine proliferation and growth. The researchers found that curcumin was “considerably more potent” compared to plant phenolics genistein and quercetin in inhibiting this type of cancer. Only cisplatin, a platinum-based substance also tested in the study, was found to be more effective.

Still more research focused on the effect of curcumin on the development of pulmonary fibrosis by testing a group of rodents.11 Scientists in India induced the lung disorder in rats, while giving them dosages of curcumin both 10 days prior and then daily throughout the experiment. Remarkably, curcumin demonstrated its powerful anti-inflammatory and anti-fibrotic effect in each rat studied.

Even breast cancer apparently cannot avoid the power of this extract, which inhibits the growth of breast tumors that result from exposure to environmental estrogenslike chemicals and pesticides, when used in combination with isoflavonoids. Scientists found the curcumin combination inhibited the growth of estrogen receptor-positive cancer cells in a test tube up to 95%.12

Treating eye disorders

Curcumin is apparently more than your typical kitchen spice. It’s the substance that gives ginger its yellowish color, and it has been implicated in the treatment of certain eye diseases and conditions. One of those is known as chronic anterior uveitis (CAU), an inflammatory condition of the vascular layer of the eye, particularly the area comprising the iris. In one small study, curcumin was given orally to 32 chronic anterior uveitis patients who were divided into two groups. The first group received curcumin alone, whereas the second group received a combination of curcumin and antitubercular treatment. Amazingly, all of the patients treated with curcumin alone improved, compared to a response rate of 86% among those receiving the combination therapy. The researchers concluded that curcumin was just as effective as corticosteroid therapy, the only available standard treatment for chronic anterior uveitis at present, adding that “the lack of side effects with curcumin is its greatest advantage compared with corticosteroids.”

Similar research using rats and rabbits found that curcumin effectively inhibited chemically induced cataract formation, even at very low dietary levels. The same study also found, for the first time, that this type of induced cataract may be accompanied by apoptosis of epithelial cells in the eye and that curcumin may lessen the apoptotic effect.

In one of the earliest studies examining curcumin as a potential cataract therapy, researchers fed two groups of rats diets that included corn oil, or a combination of curcumin and corn oil for 14 days. Afterward, their lenses were removed and examined for the presence of lipid peroxidation. The scientists discovered that “the lenses from curcumin-treated rats were much more resistant to… induced opacification than were lenses from control animals.”

  • Awasthi S et al. Curcumin protects against 4-hydroxy-2-trans-nonenal-induced cataract formation in rat lenses. Am J Clin Nutr 1996 Nov;64(5):761-6.
  • Lal B et al. Efficacy of curcumin in the management of chronic anterior uveitis. Phytother Res 1999 Jun;13(4):318-22.
  • Pandya U et al. Dietary curcumin prevents ocular toxicity of naphthalene in rats. Toxicol Lett 2000 Jun 5;115(3):195-204.

The how’s and why’s

What exactly is the mechanism behind curcumin’s ability to counteract such a wide array of cancer progression? For several years, medical research focusing on cancer causation has centered on the notion of angiogenesis, the natural blood vessel growth that accompanies metastases. The new blood vessels literally provide nutrition and sustenance to new and growing tumors throughout the body. That may be one basis, medical researchers contend, for curcumin’s efficacy. In 1998, Harvard researchers tested the substance for its ability to inhibit the growth of endothelial cells; those which line the interior of blood vessels, as well as the growth of new blood vessels in the corneas of mice.

“Curcumin effectively inhibited endothelial cell proliferation in a dose-dependent manner,” they wrote. “Curcumin and its derivatives [also] demonstrated significant inhibition of …corneal neovascularization in the mouse…These results indicate that curcumin had direct antiangiogenic activity in vitro and in vivo. The activity of curcumin in inhibiting carcinogenesis in diverse organs such as the skin and colon may be mediated in part through angiogenesis inhibition.”13

Other studies, such as one by Taiwanese scientists four years ago, examined the molecular mechanisms behind curcumin. They concluded, after studying curcumin’s effect on mouse fibroblast cells, that it directly suppresses the expression of nuclear oncogenes, the genetic mutation that launches the process of cancer cell growth, among other things.14 Other studies have examined the possibility that the mechanisms behind curcumin may lie in its ability to block the activity of specific oxidants, and halt signal transduction pathways between cells during the initial tumor growth process.15