Women who consume cod-liver oil every day have 25% lower mortality from all cancers.

This summer, a sizeable Norwegian study of over 68,000 women observed that women who consumed cod-liver oil every day (either as a liquid or in the form of capsules), and who, despite this, developed cancer, survived far better than women who did not. The reduction of mortality was about 25% for all cancers, and it reached 45% for lung cancer in particular. (1)
Cod-liver oil is very rich in vitamin D -- a nutritional element that is very important to slowing the growth of tumors and supporting the immune system -- and also in long-chain omega-3 fatty acids that are commonly found in oily fish. Omega-3s contribute to reducing inflammation in the body, and thus reduces the growth of tumors and the new blood vessels that they need in order to spread (angiogenesis).

The researchers in this study wanted to analyze the benefits of consuming cod-liver oil for at least a year before the diagnosis of cancer. Thus although many women started taking cod-liver oil once they had learned they were ill, for the purposes of this study such women were counted as if they had not taken it. In other words, if the omega-3s and vitamin D in cod-liver oil do indeed help slow cancer, then this study is likely to strongly underestimate their benefits.

Final remark: the kind of people who take this kind of nutritional supplement usually pay more attention to their health than the average person (better nutrition in general, more physical activity, more attention to stress management, less exposure to toxic substances in their environment). So it's difficult to conclude that their supplemental nutrition is the sole factor behind this highly significant improvement in survival after cancer has developed. However, the study does, once again, confirm that lifestyle factors -- nutritional and others -- have a considerable impact on the course of the disease and the benefits that can be obtained from conventional treatment.

My recommendations, as outlined in Anticancer, A New Way of Life:
- eat oily fish (sardine, mackerel, salmon, whole anchovies) at least twice a week
- check that your blood level of vitamin D3 is above 30 ng/ml if you're healthy, and closer to 50 ng/ml if you have cancer (do this under medical supervision)
- continue all other practices for good health: 30 minutes of physical activity, such as a brisk walk, five times a week; cardiac coherence or other form of stress management to avoid the helplessness that arises from chronic stress; avoidance of common contaminants which may contribute to the appearance or growth of cancer.

1. Skeie G, Braaten T, Hjarta A, Brustad M, Lund E. Cod liver oil, other dietary supplements and survival among cancer patients with solid tumors. Int J Cancer 2009;125:1155-60.