In the first article in this series, I describe the role of the immune system in fighting cancer. In this article, I address the critical role of diet in enabling optimal immune function. The final article reviews the value of exercise, sleep and stress management in the fight against cancer.
Eat a healthy diet high in fruits, vegetables, and whole grains, and low in saturated fat, and maintain a healthy weight.
My opening advice on this topic is to be skeptical. There is a great deal of misleading advertising out there. At best, people with good intentions promote a tenuous association between a nutritional supplement and alleged immune benefit beyond the strength of the underlying science. At worst, nutrition is a multi billion-dollar market in which the unscrupulous make preposterous claims about products for personal financial gain. Be particularly careful about products that claim that they “boost immunity”. The immune system is hard to study, and even top scientists are not in agreement as to which individual measures best represent overall immune strength. To make matters worse, certain products may actually interfere with important treatment you are receiving for your cancer. If you have cancer, you MUST consult your doctor on your diet, especially if you plan to start something new, or follow a new dietary program.
Having said this, leading scientists will all agree that there is sufficient evidence that a well-balanced diet is essential to your overall health and to your immune function. First, you need to be sure that you are getting the right macronutrients. These are the dietary substances you need in substantial volume for growth, metabolism and other important functions. Macronutrients provide you with energy (calories), something you need for healthy immune function, and belong to the three food groups of protein, carbohydrate and fat.
Achieving the right caloric balance when you have cancer can be more challenging. First, you may not feel like eating for emotional or physical reasons. On the other hand, you may actually have greater emotional hunger as a result of the stress you experience from your cancer. Thirdly, both the presence of cancer and some of the drugs used to treat it can modify your metabolic requirements. For most, the general guidance under Golden Rule #2 about counting and balancing your calorie intake remain entirely valid. I strongly recommend that your nutrition be a regular part of your discussion with your doctors.
It is probably fair to say that there is more public interest in the micronutrients in your diet, and their effect your immune function. Micronutrients, often referred to as vitamins and minerals, are only required by the body in small amounts, but are critical to health.
An exhaustive review is well beyond the scope of this article, but here are a few pointers that may be helpful.
Vitamin A, Vitamin B2, Vitamin B6, Vitamin C, Vitamin D and Vitamin E supplementation have received interest and are the subject of ongoing research due to potential immune benefits. To date, studies are inconclusive. Vitamin D has perhaps enjoyed the most attention do to the key role it plays in cell development. Vitamin C has been explored for its antioxidant benefits, but some experts worry that antioxidants can protect the cancer cells against radiation therapy and chemotherapy after a study reported in 2008 that vitamin C supplements blunted the effect of chemotherapy. Vitamins A and E also have antioxidant properties and experts are not in agreement that their immune benefit outweighs the risks of protecting cancer cells against radiation and chemotherapy. Antioxidants are found in abundance in fresh fruit and vegetables (and to a lesser extent in grains and nuts). A diet rich in fresh fruit and vegetables contains sufficient antioxidants to protect the body against free radicals that assist in the development and proliferation of cancer cells.
Trace elements selenium and zinc have evoked research interest, but unfortunately again, results are inconclusive and there is no agreement on the value of these supplements in strengthening the immune system or in fighting cancer.
The same is true for many other supplements (including herbal remedies), including Aloe vera, Astragalus, Echinacea, Garlic, Ginseng, Glycyrrhiza glabra (licorice root) and probiotics. Garlic has demonstrated favorable impact on immune elements and has been shown to suppress the growth of breast and lung cancer cells in the laboratory, but has yet to prove overall clinical benefit in humans. The processing of dietary garlic appears to be important to its functionality. Hopefully future research will illuminate value in garlic supplementation. In contrast, licorice has known side effects, and in the absence of proven immune benefit should be avoided.
Several natural products such as green tea contain substances called polyphenols that may have immune impact useful in fighting cancer. Tumors rely on rapidly growing blood vessels to supply their disproportionate growth. Polyphenols may inhibit the development of these new blood vessels that supply cancerous tumors. Some experts advocate their use in the hopes that this will strangle the hungry tumor, but the ultimate proof is outstanding.
I wish that there were more conclusive evidence for the clinical benefit in many of these micronutrients. I realize that there is risk that I sound like a conservative scientist, rejecting new ideas in favor of a stagnant body of knowledge. On the contrary, I have been involved in research into several hopeful natural candidates. Each time, like you, I hope we will find a valuable insight to help strengthen the immune system in its critical fight to prevent and defeat cancer. The best advice remains good advice. A balanced diet, rich in fruits, vegetables and whole grains and low in saturated fats is an excellent way to support your immune system. If you’re concerned that you’re not getting the right micronutrients in your diet, perhaps because you’re not a fan of vegetables or fruit, or your disease or treatment are impacting your appetite, then ask your doctor about taking a daily multivitamin and mineral supplement. And if you drink alcohol, do so in moderation. It has not been shown to enhance immune function in any way, but particularly red wine in moderation has been shown to enhance heart health. As we anticipate a positive outcome in your fight against cancer, we want your heart to live a long and healthy life too.