Cancer is a fact of life. Some studies suggest that most if not all of us have cancerous cells growing in our body at some time during our life. Fortunately, most of these cells do not form a tumor but remain as small, microscopic “nests” of tumor cells. In this form they do no harm and do not cause the group of diseases that we call cancer. Most cancers are diseases of old age and the increased numbers of patients who have cancer in our society are a reflection of increasing human longevity. Whereas it is true that risk factors can increase your chance of getting some types of cancer, like cigarette smoking and lung cancer and extended exposure to sunlight and melanoma, the causes of most cases of cancer are unknown.
The term “immune function” includes the activity of the white blood cells that can recognize and respond to foreign substances and invading organisms and to things that the immune system sees as “dangerous,” including tumor cells. Several types of these white cells participate the immune response to tumors. The most important are T-cells, B-cells, and natural killer cells, but many other types are involved. These cells work together to attack invading organisms as (e.g., bacteria and viruses) as well as tumor cells. The interaction of these cells, and others, is a very complicated “symphony” that is not completely understood and is still the subject of scientific research.
Until recently, it was thought that tumors were ‘invisible’ to the human immune system and that this allowed them to grow even though they are “dangerous.” We now know that the immune system does see tumors and the immune response does protect against many types of cancer. This has been shown in patients who have lost their immune function due to disease, like some viral infections, or from certain types of medical procedures; like radiation or chemotherapy. Patients who have lost their immune function have a much higher risk of getting certain cancers.
If your immune system can recognize tumor cells as “dangerous,” then how do these cells escape destruction? Although there are probably several ways that tumor evade or hide from the immune system, recent research shows that the environment within the tumor itself suppresses the function of the cells of the immune system. [1]. The immune system does its job of making the T-cell and B-cells and natural killer cells that should kill the tumor cells, but when these white cells reach the tumor, it “suppresses” them.
During the last decade, scientific knowledge has improved to the point where we can increase a patients’ immune response against their growing tumor. Many studies have shown that vaccines can stimulate the production of more immune cells that recognize the tumor [2]. Following such immunization, the patients’ blood will contain many more T-cells, B-cells and even natural killer cells that can recognize tumor cells as dangerous. In laboratory tests, these cells are able to kill the tumor cells. In most cases, however, increasing the number of these “anti-tumor” cells in patients does not seem to benefit the patient. Even patients who have been give billions of their own anti-tumor cells that were raised in the laboratory often fail to have a significant and lasting clinical response [3].
Many dietary supplements and diets are marketed with claims that they can fight cancers by boosting the number of circulating anti-tumor cells. These claims have never been scientifically tested and cannot be supported by any scientific evidence. Any such increases, if they occur at all, are several thousand times smaller than the ones described above, which means that it is inconceivable that diet- or supplement-induced increases will ever be proven effective.
Some nutrition-related claims are based upon scientific observations that a certain dietary component, such as vitamin, is necessary for proper immune cell function. The fact is then interpreted to mean that increeased consumption of this factor will increase immune function. This is like saying that by pouring three cups of coffee into a one-cup coffee mug will enable someone to drink more coffee—when, in fact, the extra coffee just overflows onto the table. This is exactly what happens to surplus nutritional components, such as vitamins. The cells can only use so much, and the rest is either excreted in the urine or stored in body fat but does not contribute to immune function.
The Bottom Line
No one will argue that eating a healthy, balanced diet is important for general health. However, there is no logical reason to believe that dietary supplements or special diets can improve immune system function in people who are not malnourished. Nor is there any evidence that dietary supplements can “boost” the immune system to produce cancer regression.
References
- Stewart TJ, Abrams SI. How tumours escape mass destruction. Oncogene 27:5894-903, 2008.
- Wang E and others. Antitumor vaccines, immunotherapy and the immunological constant of rejection. IDrugs 12:297-301, 2009.
- Rosenberg SA. Progress in human tumor immunology and immunotherapy. Nature 411:380-384, 2001.
Dr. Brooks, who specializes in immune therapy for cancer, iis Assistant Research Professor in the Department of Microbiology/Immunology, SUNY at Buffalo. IHis doctoral degree is in molecular immunology.
This article was posted on March 30, 2010.
