THE INTEGRAL ROLE OF NUTRITION IN CANCER TREATMENT
By Keith I. Block, MD, medical director of the Cancer Treatment Program at Edgewater Medical Center in Chicago, with private practice in internal medicine in Evanston, Illinois
While perhaps a third of all cancers are related to dietary factors, only a few people in contemporary American medicine realize that a well-structured nutritional regimen may be useful in the treatment of cancer as well as essential in cancer prevention. The scientific literature now emerging in this field confirms what I have seen in more than a decade of medical practice, in which I emphasize nutrition as an adjunct to conventional cancer treatment, with a multidisciplinary clinical approach.
Cancer treatment is concerned with more than just removing tumors by surgery, radiation, or chemotherapy. It also involves preventing recurrence of primary tumors; preventing or inhibiting the metastatic process; strengthening the immune system (a salient goal for cancer patients); and attenuating the noxious side effects of widely used therapies. Proper diet can usefully support all these areas of cancer treatment.
The role of diet in cancer prevention is now widely known. In one study, Willett and colleagues at Harvard University tracked the cancer rates of 80,000 American nurses while monitoring their diets. The study determined that colon cancer was closely associated with consumption of high amounts of animal fat, processed meats, and liver. Women who ate red meat every day had two-and-one-half times the colon cancer risk of those who ate it less than once a month.
Evidence suggests that high dietary fiber may also help lower colon cancer rates, as well as breast cancer rates, since the estrogen that promotes the growth of many breast cancers can apparently bind with and be excreted from the body by lignans, one of the chemical components of fiber. Studies comparing cancer rates in different countries suggest that breast occurrence is significantly related to fat consumption; and although causation of breast cancer is a complex issue, it seems that low fat consumption – less than 25 percent of total calories in the diet as fat – offers considerable protection against breast cancer.
Not just the amount of fat, but also the type of fat in the diet, affects cancer rates. Results of a large-population study relating diet and heart disease suggest that those who consumed the most omega-3 fatty acids (found in fish oils and canola oil) had lower cancer rates than those who consumed more omega-6 fatty acids (found in corn, safflower, and sunflower oils). Moreover, vegetables and fruits have a demonstratable protective against many cancers – most likely due to high concentrations of vitamins, carotenoids, indoles, and other anticarcinogens.
My personal observations with patients confirm much of the research on cancer prevention. In addition, however, it has become clear to me that many of the dietary patterns that prevent cancer can be helpful, even essential, therapeutic adjuncts as well. I have seen time and again how much better cancer patients tolerate and respond to therapy when their diets are truly healthy. The effects of diet seem to lie in four areas: boosting the body’s antioxidant status; restoring or stimulating the immune system; inhibiting metastasis; and modifying hormone levels. While we have no explicit experiments evaluating the efficacy of different diets in cancer therapy, both clinical observation and extensive research in laboratory animals offer compelling evidence for an important role for diet in cancer treatment.
Antioxidants are compounds that can neutralize electrically charged molecules, called free radicals, that are extremely destructive to the body. When combined with carcinogenic compounds, free radicals can begin the process of cancer formation through tumor "initiation." They also bind with DNA molecules, alter their structure, and cause initiated cells to form actual tumors, in a process called tumor promotion. Moreover, the versatile free radicals – the term is apt – can also cause extensive tissue damage, notably that seen in radiation therapy.
Free radicals emerge, in part, from adverse environmental factors, such as a poor diet, stresses that aggravate inflammatory diseases, and neglect of simple and obvious hygiene. Generated by the body’s internal processes as a result of poor conditions, they can wreak havoc. In areas of inflamed tissue, for example, immune cells called phagocytes undergo activation (a natural step in the immune process), giving off an army of free radicals that may help cause cancers that typically appear in the immune areas, such as colon and stomach cancers. Some free radicals are formed when prostaglandins (natural chemicals that mediate inflammation) are manufactured in the body. Other metabolic processes give off extra electrons that become part of the overall free radical force.
The other free radical source that is particularly relevant in cancer treatment is radiation. Radiation damage to body tissue is usually mediated by free radicals, since radiation generates still another army of free radicals to contend with. Certain chemotherapeudic drugs, notably cyclophosphamide, actually mimic radiation’s effects on the body, producing free radicals as the drug circulates in the body.
Despite their enormous destructive potential, free radicals can be countered effectively by substances – antioxidants – and processes – detoxification. Not surprisingly, many natural dietary antioxidants exist, primarily cartenoids (including beta carotene) and vitamins A, C, and E. Zinc, selenium, and the amino acids used by the body to make glutathione are all dietary sources of substances that help the body’s natural detoxifying processes.
These diet-supplied antioxidants can, however, be exhausted by the diminished and inappropriate nutritional habits we frequently see in cancer patients, and by vigorous cancer treatments. For instance, patients receiving bone marrow transplants are first plied with large doses of radiation and chemotherapy – a procedure called conditioning. In one study, the antioxidants vitamin E and beta carotene were monitored in blood plasma in a group of these patients before and after conditioning. After conditioning, vitamin E and beta carotene dropped 40 percent and 60 percent respectively, despite the vitamin E at Recommended Daily Allowance levels administered with conditioning treatments. Also, animal studies have shown that vitamin A can moderate toxicity from radiation of tumor-bearing animals without interfering with the anti-tumor activity of the radiation.
What becomes obvious is the potential of supplying extra vitamins A and E and beta carotene in the diet or as supplements to patients under radiation treatment. Since not all antioxidants that exist in plants appear in supplements, an antioxidant rich diet is preferable to supplements.
The versatile carotenoids seem to have other uses in cancer therapy, in what is sometimes called "secondary prevention." Patients whose primary tumor has been surgically removed often have an area of tissue remaining that has already been initiated by a carcinogen. Exposure to free radicals can possibly restart tumor-promoting processes and lead to recurrence of the primary tumor. Italian investigators have postulated that carotenoid supplements will boost the antioxidant levels of activity in the body, neutralize the free radicals, and thus delay or inhibit the recurrence of the cancer. In a pilot study, 11 patients with surgically removed primary cancers received carotenoid supplements for up to eight years in an effort to forestall recurrence of the disease. Ten of the patients did not experience any recurrence; the lone exception had his supplements interrupted for six months because of an auto accident. Normally, all patients would have recurrence within two years of the surgery.
The immune system
The immune system is one of the new frontiers in cancer treatment. Immune cells can attack tumors, suppress metastases, and resist infections. Unfortunately, many cancer patients have poorly functioning immune systems – and radiation and chemotherapy can reduce their effectiveness even further.
How best to equip the immune system? Maintaining high-quality nutrition, including responsible dietary levels of protein, carbohydrates, and especially vitamins A, C, E, and the B vitamins, is an important step to immune system enhancement.
Also important for the immune system is the choice of fats. Omega-6 fatty acids, found (you will recall) in corn, safflower, and sunflower oils, are used by the body to make prostaglandin E2, which suppresses many parts of the immune system. This is particularly true of linoleic acid, an omega-6 essential fatty acid far too plentiful in the standard American diet, largely in the form of corn oil and the many products in which it is found.
Omega-3 fatty acids, on the other hand, contribute to prostaglandins (not E2) that tend to reduce inflammation and activate the immune system’s vital T-cells. Also, since experiments indicate that immune-system suppression caused by radiation treatment is related to prostaglandins, consuming more omega-3 and less omega-6 fatty acid may help counter radiation-induced immune suppression.
The formation of metastases may also be affected by choice of fats. Mice fed a diet containing 5 percent fish oil, an omega-3 source, were found to have fewer lung metastases from lung carcinomas that were surgically implanted than did mice fed a standard diet containing 5 percent of mixed oils. Another study showed that mice fed 12 percent linoleic acid, the prostaglandin E2 promoter, had high rates of metastases for implanted mammary tumors, but this was overcome when they were given drugs that blocked the production of this prostaglandin. Linoleic acid also promotes the accumulation of free radicals, which are given off in making prostaglandins.
Clearly, choosing oils that contain omega-3 fatty acid instead of those high in linoleic acid (which we usually eat) makes eminent sense for cancer patients. Flax seeds, canola oil, and fish oils are high in omega-3 fatty acids.
Also relevant in cancer treatment is the amount of dietary fat, especially with cancers related to hormones. One study compared 10-year survival statistics for Japanese women receiving the same treatment for breast cancer as American women in Tennessee. The study separated results from pre-menopausal and post-menopausal women, as breast cancer proceeds very differently in the two groups. Pre-menopausal women in Japan had a 66 percent survival rate, pre-menopausal American women had a 61 percent survival rate. Post-menopausal Japanese women had a 60 percent survival rate, post-menopausal American women only 30 percent. Since the Japanese diet is much lower in fat than the American diet and since so much work indicates a possible link between fat and breast cancer, it is tempting to hypothesize that the survival difference in post-menopausal women is due to lower fat consumption.
There is solid evidence that excess body fat decreases survival in breast cancer patients: nine different studies have indicated that even following surgery removing the primary breast tumor, overweight patients had a worse prognosis than those of normal weight. Some studies found this for both pre- and post-menopausal women, although most did not examine the differences in the two.
A possible link between breast-cancer survival rates and body fat is the fact that for post-menopausal women at least, most production of estrogen occurs in fat cells. Estrogen is thought to promote the growth of breast cancers. For these women, losing weight might diminish the amount of estrogen in their blood – and restricting dietary fat is the best and easiest way to lose weight permanently.
Other foods might affect the amount of estrogens in the blood as well. Since estrogens seem to be bound to dietary fiber, which can be excreted from the body, increasing dietary fiber appears therapeutic as well. Similarly, indole, one of the anticancer compounds found in broccoli and other cruciferous vegetables, may be able to alter estrogen metabolism so that fewer highly active estrogen derivatives are found. Similar patterns may be found in other hormone-related tumors, such as prostrate cancer.
What kind of diet, then, would be most appropriate for cancer patients?
Both nutritious and practical is a diet centering on whole grains, vegetables, and legumes, one that supplies carbohydrate, protein, and vitamins. I recommend for frequent use those vegetables that are highest in vitamins, carotenoids, and cancer-preventive compounds such as broccoli, other cruciferous vegetables, like kale and collards, and winter squash. Protein sources should be mainly vegetarian, including tofu and other soy proteins, as well as beans (aduki beans, chickpeas, black beans, and lentils, to mention a few). Omega-3 fatty acids are supplied by small amounts of oily fish such as trout and salmon, or by using small amounts of canola oil or other omega-3-rich oils in cooking. The overall level of fat in the diet should be very low, with under 20 percent of calories coming from fat. Naturally all junk food, alcoholic overindulgence, nutritionally empty processed foods, and refined sugars are out!
On its own, a structured nutritional program probably cannot eradicate most cancers. Yet years of practice with courageous patients under the most strenuous conditions have shown me that it must not, and cannot be overlooked as an essential and decisive tool in both cancer treatment and prevention.
A multidisciplinary approach
As a clinician, I believe that nutrition must be seen in the overall context of my practice, which marshals a range of other services and support systems that have produced remarkable results for an array of ailments. Central to the practice is a fundamental knowledge of who the patient is, not merely what he or she has. Together with other specialists, I have developed a systemic stress-management program that includes group support work, biofeedback, cognitive work, and counseling in the reduction of life stresses and psychological vulnerability. We now know that the immune-suppressing effects of psychological stress are of major importance.
Exercise regimens, part of my physical conditioning program for the bedridden to the athletic, are designed to raise cardio-aerobic competence and maintain muscle mass. Where appropriate, selected nutritional and botanical supplements are given. We have begun an in-hospital program and a facility offering nutritious meals to be taken home or to the hospital, for patients and families who are incapacitated or under too much stress to cook at home.
The goal of all these programs is to arouse in each patient a life-affirming and healthy attitude. This is imperative in all medical care, but especially so in cancer treatment. My ongoing work and research in nutrition and diet, then, are part of a larger picture – that of fulfillment at the physical, biochemical, psychological, and emotional levels, both for people combating cancer, one of the most stressful medical experiences, and for those hoping to prevent it.
Article from NOHA NEWS, Vol. XVI, No. 4, Fall 1991, pages 3-6.