Antioxidants and Cancer
by Jeremy Appleton, ND, CNS

Despite advances in modern medicine—including chemotherapy, radiation, hormone therapies, and surgery—cancer remains a worldwide killer and its causes are complex and only partially understood. Conventional medicine has many medicines and procedures to treat cancer, many of them highly toxic and damaging to normal cells and tissues. There is little consensus on how best to treat most forms of the disease.

Most experts can agree on one point, however: Prevention is the best cure. The answer to cancer may not be found in a pill, or in your fruit bowl, but recent research suggests that many types of cancer can be prevented with a healthy diet and lifestyle (e.g., regular exercise, not smoking). From a nutritional standpoint, antioxidants are vitally important adjuncts in the prevention of cancer, and in the reduction of side effects caused by chemotherapy and radiation treatments.

Fruits and vegetables are associated with cancer prevention because they are loaded with cancer-fighting natural ingredients: antioxidants, flavonoids, fiber, and phytochemicals, and other special substances unique to plants.

Despite a huge amount of published data in the medical literature supporting a role for antioxidants in the prevention of cancer, and in the reversal of adverse effects of chemotherapy and radiation, flawed studies continue to emerge (and continue to generate widespread, uncritical press) purporting that antioxidant supplements are harmful and may slightly increase the risk of death (Bjelakovic et al, 2007). The media seem to make a game of exploiting our fear of the disease on the once hand, and then playing up our hopes for its cure on the other. It may make for good press, but it leads the end-user into a state of confusion which often ends with taking no action at all in support of health.

Vitamin users should take these reports with a grain of salt. The basic value of eating well and supplementing with antioxidants and other nutrients in a judicious manner remains intact. Here are some of the key antioxidants that help protect against various types of cancer.

Natural Beta Carotene and Mixed Carotenoids
Most people, even many researchers, are not aware that there is an important difference between natural and synthetic beta-carotene. But when it comes to cancer prevention, especially prevention of lung cancer, the difference could hardly be more important. Natural beta-carotene has been shown to be protective against lung cancer whereas synthetic beta-carotene has not (Hennekins et al, 1996). In fact, smokers should definitely avoid synthetic beta-carotene, as studies indicate that it may actually increase the risk of lung cancer (Albanes et al, 1996; Omenn et al, 1996; Lee et al, 1999). The reasons why the two forms act differently in the body are beginning to be explained. One critical difference is that natural beta-carotene appears to have antioxidant activity that synthetic beta-carotene lacks (Bitterman et al, 1994; Ben-Amotz & Levy, 1996.) In one clinical study, pre-cancerous tissue changed back to normal tissue in those who took natural beta-carotene supplements, but not in those who took the synthetic equivalent (Yeum et al, 1995).

Natural Vitamin E
Like beta-carotene, vitamin E is also available in natural and synthetic forms. And like beta-carotene, the natural form appears to have benefits over the synthetic form. The natural for is also called the "d" form (or most correctly, RRR-alpha tocopherol). The synthetic form is called either dl-alpha tocopherol or all-rac-alpha tocopherol. In a nutshell, the natural form has more activity in the body and is better absorbed.

Compared to those who do not take vitamin E supplements, people who take such supplements appear to have a decreased risk of pre-cancerous colon polyps (Whelen et al, 1999; White et al, 1997; Neugut et al, 1996.)

Comparatively higher blood levels and dietary intake of vitamin E have been associated with a reduced risk of lung cancer in multiple studies (Menkes et al, 1986; Eichholzer et al, 1996; Knekt, 1993). In one study, non-smokers who took vitamin E supplements had a 45% lower risk of lung cancer compared with nonsmokers who did not take the supplement (Mayne et al, 1994). Some research has found non protective effect of vitamin E supplementation on lung cancer risk, but the amount used (about 50 IU per day) was likely insufficient to produce a measurable protective effect (ATBCC Prevention Study Group, 1994).

Selenium (Selenomethionine)
The trace mineral selenium is known to exert many different anti-cancer actions. (Medina, 1986; Beisel, 1982). Animal studies have confirmed an inhibitory effect of selenium on cancer (Medina & Morrison, 1988). In places where there is inadequate selenium in the soil, dietary intake of the mineral is affected. In such areas, we have long seen an increased incidence of cancer (Shamberger et al, 1973). People with a several different types of cancer have been found to have deficient levels of selenium in their blood (Burney et al, 1989; Toma et al, 1991; Willett et al, 1983; Helzlsouer et al, 1989; Jaskiewicz et al, 1988 ; Knekt et al, 1990; Yu et al, 1999; Scieszka et al, 1997). These cancers include pancreatic, oral, bladder, liver, esophageal, stomach, colon and others. Early reports showed that people with the lowest levels of selenium in their blood had between nearly 4 to 6 times the risk of dying from cancer compared with those with the highest selenium levels (Fex et al, 1987; Salonen et al, 1985).

In a particularly dramatic double-blind trial involving 1,312 Americans with a history of skin cancer, participants were treated with 200 mcg of yeast-based selenium (selenomethionine) or placebo every day for 4.5 years, then tracked for an additional two years. Although no decrease in skin cancers occurred, a dramatic 50% reduction in overall cancer deaths and a 37% reduction in total cancer incidence were observed. A statistically significant 58% decrease in cancers of the colon and rectum was reported (Clark et al, 1996).

Green Tea Catechins
Green tea contains cancer-fighting flavonoid antioxidants known as catechins. Several studies have shown an association between drinking green tea and reduced risk of several types of cancer, including gastric (Kono et al, 1988), esophageal (Gao et al, 1994), pancreatic (Ji et al, 1997), lung (Ohno et al, 1995) and colorectal (Ji et al, 1997; Fujiki, 1999; Yang et al, 2007).

In one study, green tea consumption was associated with increased survival time and decreased spread of cancer to lymph nodes in Japanese women with early-stage breast cancer; these benefits were not observed in those with more advanced cancer (Nakachi et al, 1998). Those who drank at least five cups per day had the lowest rate of recurrence. Despite these associations, however, no proof yet exists that green tea consumption helps breast cancer patients or helps healthy women prevent breast cancer.

Numerous preliminary studies have shown an association between drinking green tea and a reduced risk of several other types of cancer, including lung cancer (Ohno et al, 1995).

Can Antioxidants Be Safely Used
During Chemotherapy and Radiation?
There have been a few high-profile reviews published in mainstream medical journals that have come to the conclusion that cancer patients should not take antioxidant supplements while receiving chemotherapy or radiation treatment (D’Andrea, 2005). Such reports are promptly interpreted by major newspapers and often contend that antioxidants will block the beneficial effects of standard cancer therapies. In contrast to these reports, however, the best scientific evidence suggests something quite different.

Radiation therapy and some chemotherapy drugs produce free radicals, highly reactive chemicals that can damage both cancer cells and normal cells. Antioxidants, such as those discussed in this article, can quench free radicals and diminish their toxic effects. Therefore, the authors argue, they can also (theoretically) protect cancer cells in the same way they protect normal cells. On first glance, the argument seems compelling. However, while many cancer drugs create free radicals, they do not usually depend on this mechanism for their efficacy.

In animal studies, when antioxidants were given concomitantly with chemotherapy drugs, they actually enhanced the efficacy of the drugs rather than diminishing it. They also had the additional benefit of reducing the adverse effects of the drugs. In a study of women with ovarian cancer, selenium taken along with chemotherapy (cisplatin and cyclophosphamide) prevented adverse effects such nausea, vomiting, loss of appetite, hair loss, and depression of white blood cell production (Sieja and Talerczyk, 2004). In an older study, this one in women with cervical cancer, a combination of vitamin C and bioflavonoids was found to enhance the effects of radiation therapy (Cheraskin et al, 1968).

In men receiving radiation therapy for prostate cancer, concomitant use of "CAM-based antioxidant supplements designed to improve patient tolerance and quality of life" (such as green tea catechins) for as much as two years did not adversely affect radiation therapy-mediated tumor response or recurrence rates (Cain et al, 2007).

No blanket statement can be made that correctly assesses the safety and efficacy of antioxidants in combination with chemotherapy or radiation. The potential interactions are complex, and vary according to the type of cancer, the health status of the patient, which antioxidants are used, and how much is taken. However, the preponderance of evidence suggests that, under the most common circumstances, antioxidants probably decrease the adverse effects of these therapies without interfering with their efficacy. In some cases, efficacy may even be enhanced. When dealing with any disease, but especially cancer, it is strongly recommended to seek the counsel of a qualified health professional before taking any nutritional or herbal supplements.

How to Choose A Supplement Brand
Always select products from manufacturers that provide comprehensive proof and fully guarantee that their products are prepared utilizing the highest standards of manufacturing practice and laboratory quality assurance. Such companies will audit and verify their independent laboratories to insure that validated analytical methods and ethical lab practices for raw material and finished product testing are followed. They will take the time to validate the laboratory test methods as well. They will include testing for microbiologic contamination, authenticity, potency, heavy metals, and stability. Some companies also do additional testing, such as for chemical solvent residues, aflatoxins, markers of rancidity in oils, pesticide residues, dioxins, PCBs, and other contaminants. Finally, there is the matter of testing the finished products to assure they meet label claims for potency, purity and stability. Although most supplement companies do not go to these lengths, a few do and you should seek them out.