Omega-3s May Slow Down the Progression of One of the Most Common Childhood Solid Cancers

June 16th, 2010 - by: David Servan-Schreiber, M.D., Ph.D.

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In a new article in the International Journal of Cancer, researchers from Sweden's Karolinska Institute explain that omega 3 fatty acids don't just contribute to preventing cancer; they also help slow down the growth of existing tumors.

Neuroblastoma is one of the most common solid cancers in children. (A solid cancer is one that affects 'solid' organs such the breast or liver, rather than, say, leukemia, which affects the blood). And the study -- of rats -- that was published last month by the Karolinska researchers demonstrates that neuroblastoma cells don't grow as much when the rats are fed large doses of a long chain omega 3 fatty acid called DHA (docosahexaenoic acid).[1]

As you may recall, the three main omega 3 fatty acids are:

- ALA (alpha linolenic acid), which is found in herbs, plants, nuts, flaxseeds and rapeseeds (the seeds of canola oil), and seaweed. It's made up of only 18 atoms of carbon and is therefore called a "short chain" omega 3 fatty acid.

When ALA is ingested by animals (particularly fish, but to a lesser degree this is also true of hens, cows and human beings), it is converted within their bodies into "long chain" omega 3 fatty acids.

These are:

- EPA (eicosapentaenoic acid), which has 20 atoms of carbon and is particularly abundant in fish. EPA has an anti-inflammatory effect within the body, and in addition very probably acts as an antidepressant as well.

- DHA (docosahexaenoic acid), which has 22 atoms of carbon, is particularly useful to the construction of cell membranes (especially in the brain), as well as contributing to the stability of heart membranes.

In the Karolinska study, rats consumed significant quantities of DHA before being grafted with one million cells from a human neuroblastoma. Stunningly, several of these rats developed no tumor at all. Most of them developed tumors that were far smaller than those developed by the control group, whose diet was not rich in DHA.

Similarly, when DHA was administered to rats that had already developed a neuroblastoma, this caused the weight and volume of most of their tumors to decrease.

When researchers examined the biology of the tumors they noted that the tumors that had decreased the most were those which had incorporated DHA into their tissue. Conversely, the few tumors that -- for reasons still poorly understood -- had not incorporated DHA in significant amounts did not experience reduced volume.

There are several possible explanations for these results:
- When DHA is incorporated into tumor tissue, it is rapidly oxydized, and cancer cells are more sensitive to oxydation than ordinary cells ( See my blog posting on the study by Prof Bougnoux in Tours, France, which reached a similar conclusion regarding decreased progression of breast cancer during chemotherapy complemented with DHA)

- Within the body, DHA is converted into biologically active molecules that reduce inflammation, and interfere with the angiogenesis that the tumors require for growth.

- Under normal circumstances, cancer cells are characterized by their escape from natural death. DHA acts on the "transduction signals" at the deepest level of the cell metabolism, particularly on those that control natural cell death ("apoptosis"), re-activating this process in cells that have succeeded in escaping it.

The Karolinska researchers found similarities between their study in rats and the demonstration by a US team working in Alaska that Inuit children who eat a diet rich in fish -- and whose level of omega-3s in general (and DHA in particular) is very high -- have up to ten times fewer cancers than children from the same area whose diet is much more Westernized. [2]

Still, we should note that this was a study in animals, and care should be taken when extrapolating its results to human beings. The doses utilized were extremely high: between 120 mg/Kg/day and 2.1 g/Kg/day. For a child weighing 10 kg, that would translate to between 1.2 g and 21 g of DHA per day. At this high level there's a risk of side-effects, especially digestive problems (including diarrhea) and blood clotting disorders (hypo-coagulability, with the risk of bleeding).

The most frequent source of DHA is 'purified' fish oil. This substance has been purified of, among things, the contaminants that easily fix onto the fat of cold-water fish, and has also been procesed to increase its ratio of DHA to EPA. It's now also possible to find DHA that has been manufactured by seaweed rather than by fish; since this has no animal origin it's more suitable for vegetarians.


Bibliography
1. Gleissman, H., et al., Omega-3 fatty acid supplementation delays the progression of neuroblastoma. International Journal of Cancer, 2010. 9999(999A).
2. Lanier, A.P., et al., Childhood cancer among Alaska Natives. Pediatrics, 2003. 112: p. e396. Share     

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