Cancer Research Update
Chester J. Zelasko, Ph.D. | July 22, 2003

The American Association for Cancer Research recently held its annual meeting in Washington, D.C. This Newsletter is a summary of some of the research presented at the meeting that deals with the use of dietary supplements. At the end of the summary, I'll discuss the implications of the findings.

In several studies, vitamin E inhibited the ability of cancer cells to replicate including prostate, breast, and oral cancer cell lines (1-2). In all, 15 studies were presented that examined the potential benefits and mechanisms of action of vitamin E.

Conjugated linoleic acid appears to be beneficial in inhibiting breast cancer replication in test tubes. Several studies examined the possible mechanisms for this effect (3).

The herb milk thistle is effective in inhibiting the replication of prostate cancer cells. Researchers are attempting to find the specific phytonutrient in milk thistle responsible for this effect (4).

Echinacea purpurea inhibits breast cancer cells from replicating in test tubes. Researchers speculate that further study will result in additional treatments for breast cancer (5).

Two presentations indicated that black cohosh may have negative effects on breast cancer and breast cancer treatments. In the first study, black cohosh inhibited breast cancer cells in a test tube from responding to chemotherapy and radiation (6). In the second, mice genetically engineered to develop breast cancer may have had more invasive cancer when their diet was supplemented with black cohosh (7).

Overall, the research appears to show the potential benefits of some popular dietary supplements, with room for caution. What do the findings means in the real world?

First, most of this research tested the effects of the supplements on certain strains of cancer cells in test tubes. That may or may not mean anything when the supplement is used by human beings. The body consists of many systems and organs which regulate what goes in and out of cells. The supplement may or may not reach the target cells in the body. Potential benefits? Yes. More research to be done? Absolutely, but things look promising.

Second, while the results were overwhelmingly positive, especially for vitamin E and conjugated linoleic acid (CLA), should the black cohosh studies be a cause for concern? Yes and no, for the same reason outlined above. What happens in test tubes and in rodents may or may not mean anything in humans.

What it does mean is that we should respect the use of all food supplements. Know what you're taking. Know why you're taking it. Don't take it if you don't need it. Stop taking it if your healthcare professional tells you to stop--especially when you're undergoing treatment for any disease.

The research presented is very exciting because of the possibility that we may be able to prevent cancer before it begins. Food supplements are just one of many things that may help reduce your risk of cancer: eating more fruits and vegetables, eating less saturated fat, exercising regularly, quitting smoking, and managing stress better. Your health is in your hands--don't drop the ball.


  1. Shiverick, KT et al. Antiproliferative effects of vitamin E involve induction of p21CIP1 and CCAAT/enhancer-binding protein ? in PC- 3 human prostate cancer cells.
  2. Schwartz, JL, et al. Vitamin E acid succinate suppresses malignant transformation and oral cancer cell growth through changes in DNA repair, methylation, and induction of apoptosis.
  3. Tanmahasamut, P, et al. Conjugated Linoleic Acid Blocks Estrogen Signaling in Human Breast Cancer Cells.
  4. Nam-Cheol K, et al. Selective activity of pure flavonolignans from milk thistle (Silybum marianum) against human prostate carcinoma cell lines.
  5. Driggins, SN. The anti-carcinogenic effect of echinacea purpurea on mammalian breast cancer cells.
  6. Rockwell, S, et al. The herbal medicine black cohosh alters the response of breast cancer cells to some agents used in cancer therapy.
  7. Davis, VL et al. Effects of black cohosh on mammary tumor development and progression in MMTV-neu transgenic mice.
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