Antioxidants, Diet and Cancer

Cancer is on the rise. In 1988, the Surgeon General estimated that an American born in 1985 has a 30 percent chance of dying from this disease. This figure doesn’t take into account the individuals who will get cancer and survive. Cancer is a slowing growing disease (actually group of diseases) egged on by the cumulative effects of cancer promoting substances and activities. At least 80 percent of cancers are caused by lifestyle habits, including diet. Fortunately, diet, especially one rich in antioxidants, can protect you against cancer.

In the fall of 1989, a group of scientists from around the world met in London to talk about antioxidants. Everyday, normal metabolic processes as well as environmental pollutants, tobacco smoke, and rancid fats create highly reactive molecules called free radicals. Free radicals damage cells and may impede health. During their three day meeting, researchers reviewed the evidence and discovered that antioxidants reduce free radical damage and possibly cancer.

Antioxidants come in a variety of forms. Plants are a plentiful and powerful source of antioxidants in part because these botanicals often have an affinity for particular organs. For example, the antioxidant acting flavonoids in milk thistle target the liver. Those in ginkgo are attracted to the central nervous system, including the brain. Probably the most well known plant antioxidants are carotenoids, the yellow pigment found in many fruits and vegetables.

In addition, antioxidants can include vitamins such as C, E, and A, and minerals like selenium, zinc, copper, and manganese. Here are some of the findings from the London conference on a fraction of the antioxidants available to us.

Eat Your Fruits and Vegetables

The echo of motherly advice, “eat your vegetables”, is now being heard in scientific laboratories. In a paper presented by the National Cancer Institute, Regina Ziegler reviewed the relationship between vegetable, fruit and carotenoid intake, and cancer rates. Of the many hundreds of carotenoids found in our food–primarily fruits and vegetables–many are antioxidants. Beta-carotene is the most abundant and well known carotenoid.

Ziegler found a definite link between fruits and vegetables in the diet, and cancer. The strongest relationship was for lung cancer, although cancer of the stomach, cervix, neck, breast, and bladder were also reported. However, some of the studies Ziegler analyzed
lasted for only five years. Considering that cancer may take 20 or more years to develop, the association between vegetables and cancer may be even stronger. Ziegler also admits that when you eat your fruit and vegetables, fiber and other antioxidants such as vitamin C
may also protect against cancer.

Although we don’t know all the ins and outs of the vegetable-cancer connection, there is, without a doubt, a benefit. It is sad that most Americans neglect this portion of their diet. The Second National Health and Nutrition Examination Survey revealed that only 10 percent of the 12,000 adults it surveyed ate the recommended five servings of fruits and vegetables each day.

Remission with Beta-Carotene

One-quarter of the world’s population chews some type of drug-like plant whether it be tobacco, a tobacco mixture, betel leaves or coca leaves. While tobacco is the main cause of mouth cancer, other chewing substances may also contribute to this condition.

Research teams from Canada and India cooperated to study the effect of antioxidants on precancerous mouth tumors in Indian fishermen who chewed tobacco containing betel quids. Only six months of vitamin A therapy led to a complete remission of leukoplakia, a
precancerous lesion also known as smoker’s patch, in over half of the treated fishermen. Beta-carotene was less effective, helping nearly 15 percent of the subjects who took it. More encouraging news was that no new smoker’s patches developed during the test period in any of the fishermen taking vitamin A, and in only half of the beta-carotene group.

These exciting results have prompted a new idea in cancer research. Besides talking about chemotherapy, scientists are now speculating about chemoprevention using agents such as antioxidant vitamins. As investigators learn more about cancer and how nutritional intervention can halt or slow its progress, more precise treatment plans will be developed.

Protection with Vitamin E

Taking the cue from several animal and human studies that suggested vitamin E may also be protective against cancer, Finnish researchers began a study on over 36,000 adults. After eight years, these scientists confirmed their suspicions. Persons with low serum levels of vitamin E were at greater risk of developing cancer than those with more of this nutrient in their blood. Cancers of the gastrointestinal tract were protected the most.

These results point out an important connection between nutrition and cancer. Cancer is not caused by one incident or substance. The ground is first primed by some initiating factor.
Subsequent events then prompt cancer’s development. The more cancer promoting activities you endure, and the less protection you have against cancer such as antioxidants, the greater your chance of being diagnosed with this disease. Vitamin E is just one nutrient that has proven itself useful in guarding against cancer.

Cervical Cancer

It has been established that immunity not only operates systemically, but, at least in female reproductive organs, locally. We also know that low dietary intake and blood levels of
beta-carotene are associated with an increased risk of cervical dysplasia, a precancerous state, and cancer.

Naturopathic medical treatment for women with cervical dysplasia takes into account both of these scientific findings. In addition to other therapies, which vary depending on the patient’s specific diagnosis, beta-carotene is taken by mouth and vitamin A is applied directly to the cervix for these conditions. Beta-carotene is the precursor to vitamin A.

Cancer and Vitamin C

Over two decades ago, Linus Pauling and his colleagues concluded that vitamin C is effective in controlling cancer. In his book, Cancer and Vitamin C, Pauling and his Scottish associate and co-author, Ewan Cameron, are quick to point out that vitamin C is not a miracle cure. But in high doses it can increase both the quality and length of a cancer patient’s life.

Twenty years later, the National Cancer Institute is acknowledging vitamin C’s importance in cancer prevention. After reviewing 46 studies, Gladys Block found that most research showed twice as much protection from cancer when vitamin C consumption was high versus low. Vitamin C not only acts as the first line of antioxidant defense, but it spares vitamin E and other antioxidants.

Block criticizes much of the vitamin C research. She points out that errors in experimental procedure and interpretation may actually underestimate the beneficial effects of vitamin C and other nutrients. It is also important, she says, to understand that these nutrients work together not alone. We shouldn’t think about whether it’s vitamin C or beta-carotene that fights cancer and other diseases. We need to remember that vitamins and minerals are packaged in fruits, vegetables, and other foods to provide optimal protection in optimal amounts.

1. Tubiana M. Human carcinogenesis–introductory remarks. American Journal of Clinical Nutrition 1991; 53: 223S-5S.

2. Ziegler R. Vegetables, fruits, and carotenoids and the risk of cancer. American Journal of Clinical Nutrition 1991; 53: 251S-9S.

3. Block G. Dietary guidelines and the results of food consumption surveys. American Journal of Clinical Nutrition 1991; 53: 356S-7S.

4. Stich HF, Mathew B, Sankaranarayanan R, Nair MK. Remission of precancerous lesions in the oral cavity of tobacco chewers and maintenance of the protective effect of beta-carotene or vitamin A. American Journal of Clinical Nutrition 1991; 53: 298S-304S.

5. Knekt P et al. Vitamin E and cancer prevention. American Journal of Clinical Nutrition 1991; 53: 283S-6S.

6. Forrest BC. Women, HIV, and mucosal immunity. The Lancet 1991; 337: 835-6.

7. Sngh VN, Gaby SK. Premalignant lesions: role of antioxidant vitamins and beta-carotene in risk reduction and prevention of malignant transformation. American Journal of Clinical Nutrition 1991; 53: 386S-90S.

8. Cameron E, Pauling L. Cancer and Vitamin C. Menlo Park, CA: The Linus Pauling Institute of Science and Medicine, 1979.

9. Block G. Vitamin C and cancer prevention: the epidmiologic evidence. American Journal of Clinical Nutrition 1991; 53: 270S-82S.