Does Cod Liver Oil Cause Malignant Melanoma?

There has been some interest of late about data from 1997 Norwegian study that showed that women who consumed cod liver oil (CLO) had increased rates of cutaneous malignant melanoma (malignant skin cancer). The study was a pretty good study, and as is common, those people with an alternative to real cod liver oil used the data to condemn CLO and promote their own products.

The findings were interesting –seeming to isolate the increased rates of cutaneous malignant melanoma (CMM) in women to cod liver oil consumption – even when other similar studies have showed the opposite findings. The Norwegian study showed increased rates of CMM in women who consumed CLO and reduced rates in women who drank coffee.

Yet even the study researchers – who had no financial interest in the study – suggested that the relationship between CMM and CLO might be inconclusive. They said, “The lack of consistency in the findings make it difficult to draw any conclusions regarding coffee and CLO. (Both) coffee and CLO consumption are probably closely related to mode of living, and confounding from habits not corrected for in the present analyses cannot be ruled out. A simple and plausible explanation is that these habits are related to outdoor exposure patterns, e.g., coffee drinking being related to spending time indoors, whereas taking CLO is related to a healthy lifestyle including much outdoor physical activity.” In other words, CLO users get much more sun exposure than coffee drinkers.

The researchers sum up the study by saying that there are two possible conclusions:

  1. “There is a female-specific association between the incidence of CMM and intake of CLO and coffee.” This means that women somehow react differently to the biochemistry of CLO and coffee…and
  2. “The results are due to chance or there is residual confounding due to length of education and county of residence being imprecise measurements of social class and sun exposure, respectively.” This means that the results may have had nothing to do with CLO or coffee, but rather to education, where the subjects live, and poor measurements of their lifestyle habits and sun exposure.


Scientific Studies Can Be So Confusing
It is easy to see how one might automatically relate CLO intake to CMM – even though increased rates of CMM may simply be due to social class, where you live, poor measurements, lifestyle habits, education, and more. Nonetheless, it does appear that intake of highly processed cod liver oil may be related, at least in women, with increased rates of CMM.

And here is the rub. There is no mention in this study (or any other study) of any relationship between cod livers and CMM. During the industrialization of fish oils and CLO, the heat damages the polyunsaturated fats. These damaged fats can create problems with our health. And all the fish oil mills know this and are trying to figure out how to process fish oils without the damaging industrialization process. They are doing this for a reason. They know that their fish oils are on the radar of the Food and Drug Administration (FDA) and other medical groups.

Even still, just about all fish oils are industrially processed, and by definition, potentially damaged. The oils are heated to over 400 degrees under high pressure, which is necessary to clean up free radicals in the oil. However, in so doing, the fats are further damaged, molecular bonds are broken, and the nutrients in the oils are degraded. For these reasons, lots of manufacturers strip out all the natural fat-soluble vitamins A and D and replace them with synthetics in the end product.

These processed fats and oils, including all store bought CLO, are not the same as raw fats – as in raw cod livers.  The cod liver oil that I use is more expensive because it is derived from raw, fermented cod livers.  And any free radicals in the oil are naturally cleaned up by the expensive and time-consuming fermentation process. Naturally, this oil is not damaged by heat or other manufacturing processes. It is simply not even the same product as just about every other CLO.

When I am asked about one nutritional product or another, my answers are always pretty much the same. It is all about the source of the raw materials and how they are processed into nutritional supplements, concentrates, or extracts. If you start with poor raw materials (like degraded cod) and then industrially process the oil with heat and other methods, you end up with a refined, highly processed, pure, biochemically-altered oil that may cause health problems.

Does the highly processed CLO cause increased rates of CMM in women? Neither the scientists performing the study nor I know for sure. But the conclusion should be the same as all conclusions regarding nutritional supplements…it is just one more not to consume highly processed fish oils, cod liver oils, or nutritional supplements. And that is why I only use oil from fermented cod liver oil. – Blue Ice Fermented Cod Liver Oil.