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Fish and fish oils - Brasky: Risky for prostate cancer


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Fish and fish oils - Brasky: Risky for prostate cancer


Jim Marshall (not a doctor) said ...

Our bodies need at least a dozen different fatty acids to function. They come from food, or are made within our body, or both.


In seems from a number of studies that the balance of different fatty acids in our bodies is important for our health. We use some of all types in our bodies.


In general, research seems to say:

  • a goodly amount of the omega-3 (ω-3) fatty acids found in fish and some other seafoods seems good for prostate cancer;
  • the same is not true for omega-3 (ω-3) fatty acids found in plants (like flax) which is not good for prostate cancer; 
  • too much of the omega-6 (ω-6) fatty acids found in animal meat seems bad for prostate cancer.


So the surprising thing about the study by Brasky reported below is that it seems to turn earlier research upside down.


When they compared men with the most omega 3 fatty acids in a blood sample with men with the least omega 3 fatty acids in a blood sample, they report:

  • a 44% greater risk for low-grade prostate cancer;
  • a 71% greater risk for high-grade prostate cancer; and
  • a 43% greater risk for any type of prostate cancer.


In contrast, men with relatively elevated levels of omega-6 fatty acids they report had:

  • a 75% lower risk for low-grade prostate cancer; and
  • a 75% lower risk for any type of prostate cancer.


So, should men stop eating fish and taking fish-oil tablets, and start tucking into animal fats and hydrogenated oils?


My advice is:

  • Wait until an expert on prostate cancer and diet gives their opinion on whether the evidence in this one study is so strong that it over-rides earlier studies.
  • Then ask your doctor.
  • Experts on prostate cancer and diet I trust are Dr Charles "Snuffy" Myers and Professor Mark Moyad.


Snuffy Myers has indicated he will produce a video on the subject on his website Ask Dr Myers  about 26 July 2013. As he announced this he told us his next meal would be salmon.


Mark Moyad has already given a largely dismissive advice on an earlier paper by the same group here: Omega 3 and Prostate Cancer


In the meantime, a few amateur thoughts of my own:

  • This was not a study designed to study fish or fish-oil.
  • There was a different study designed to find out whether the supplements Vitamin E and Selenium protected against prostate cancer. (They did not.) Brasky and colleagues just used the blood samples taken from that supplement study. They did not find out about whether the men ate fish, or took fish oil supplements at all, or anything about what they ate.
  • The men in the supplement study had no sign of prostate cancer. They just volunteered.
  • It occurs to me that men volunteering for a supplement study may not be a random sample.
  • I think men who take supplements already might be more inclined to join.
  • I think men who are worried about prostate cancer, perhaps because they know it is in their family might be more inclined to join.
  • I think the men worried about prostate cancer might be more inclined to be eating more salmon and other oily fish, or be taking fish oil capsules.
  • Men with close relatives with prostate cancer are more likely to develop prostate cancer themselves.
  • So, I would expect that when you look at this non-random sample, men who developed prostate cancer would be more likely to have signs of fish or fish oil in their blood - which is what this study shows.


When I look at the Brasky study, I see from Table 1 (Baseline demographic and health-related characteristics and cancer outcomes of SELECT participants, by prostate cancer grade), I see that of the men that developed prostate cancer:

  • 45.5% had one first-degree relative with prostate cancer; and
  • 11.9% had two first-degree relatives with prostate cancer.


Other studies on fish and prostate cancer on our site:


Fish and fish oils - the Swedish study - no fish: more prostate cancer


Fish and fish oils - drop chances of metastases and dying of prostate cancer


Fish and fish oils - lower risk of prostate cancer death


Fish and fish oils - deep frying increases prostate cancer risk, especially advanced prostate cancer


Fish and fish oils - protective, especially metastatic prostate cancer. Fish yes. Supplement not necessarily.


Fish and fish oils - reduced risk of prostate cancer using better blood test


Fish and fish oils - reduced risk of prostate cancer. Plant sources not. Fish better than supplements.



An abstract of the Brasky study can be found here:

Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial


The full paper can be purchased from that site for $32 US.

... end Jim

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Good overview, Jim.

I'm in general agreement with you. However, there are more useful distinctions that can be made among the fatty acids, which might be worth sharing.for the benefit of our members,
There are three variations among fatty acids, viz 
1. The length of the 'backbone'  chain of carbon atoms (C12-C22)
2. The absence or presence of C-C links with hydrogen 'gaps'  (unsaturated)
3. The number of such unsaturated C-C links ('mono-unsaturated, polyunsaturated) 
4. The position off the unsaturated C-C links along the C-chain relative to the terminal ('acid') C (w3, w6, w9)
5. The effect on the geometric directions of the unsaturated C-C links and the terminal 'acid' C (cis- or trans-, meaning 'same side', 'opposite sides') 
The percentage of saturated, mono-unsaturated, poly-unsaturated and trans acids, and sometimes of w3,and w6 fatty acids are given on the labels of retailed foods.  
Shorter-chain C12-C16 (typically dairy-sourced) fats in excess, and trans-acids (in margarines and commercially fried and baked foods) are associated with poorer outcomes in both heart disease and prostate cancer, as are saturated fats. Medium chain oleic acid (the C18 mono-unsaturated fat in olive oil) and linoleic acid (a C18 polyunsaturated w6) are two of the essential fats, whereas linolenic acid (the C18 w3 fat in flaxseed oil) is not, and  arichidonic acid (a C18 unsaturated fat in red meat and egg yolks) seems to be associated with cellular inflammation and prostate cancer. The long-chain C20 and C22 w3 fatty acids from deep-sea fish are essential fats, which the body has difficulty making from the shorter-chain C18 w3 fats like flaxseed oil. 
The RATIO of  w6 to w3 fatty acids (blood test available) also seems to be at least as important as the individual levels of blood lipids, with a desirable target being 1.5. This can be achieved by a deliberant reduction in oils from (white) meat, cooking oils, nuts, seeds and grains, and an equally deliberate increase in deep-sea fish and fish oil.
I hope this will help.  
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Thanks for expanding that for us.

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