Omega-3 fatty acids likely NOT associated with prostate cancer

A weakly constructed study was reported recently that purportedly associated higher levels of omega-3 fatty acid blood levels and prostate cancer. See this CBS News report, for instance.

Lipid and omega-3 fat expert, Dr. William Harris, posted this concise critique of the study, exposing some fundamental problems:

First, the reported EPA+DHA level in the plasma phospholipids in this study was 3.62% in the no-cancer control group, 3.66% in the total cancer group, 3.67% in the low grade cancer group, and 3.74% in the high-grade group. These differences between cases and controls are very small and would have no meaning clinically as they are within the normal variation. Based on experiments in our lab, the lowest quartile would correspond to an HS-Omega-3 Index of <3.16% and the highest to an Index of >4.77%). These values are obviously low, and virtually none of the subjects was in “danger” of having an HS-Omega-3 Index of >8%. So to conclude that regular consumption of 2 oily fish meals a week or taking fish oil supplements (both of which would result in an Index above the observed range) would increase risk for prostate cancer is extrapolating beyond the data.

This study did not test the question of whether giving fish oil supplements (or eating more oily fish) increased PC risk; it looked only a blood levels of omega-3 which are determined by intake, other dietary factors, metabolism and genetics.

The authors also failed to present the fuller story taught by the literature. The same team reported in 2010 that the use of fish oil supplements was not associated with any increased risk for prostate cancer. A 2010 meta-analysis of fish consumption and prostate cancer reported a reduction in late stage or fatal cancer among cohort studies, but no overall relationship between prostate cancer and fish intake. Terry et al. in 2001 reported higher fish intake was associated with lower risk for prostate cancer incidence and death, and Leitzmann et al. in 2004 reported similar findings. Higher intakes of canned, preserved fish were reported to be associated with reduced risk for prostate cancer. Epstein et al found that a higher omega-3 fatty acid intake predicted better survival for men who already had prostate cancer, and increased fish intake was associated with a 63% reduction in risk for aggressive prostate cancer in a case-control study by Fradet et al). So there is considerable evidence actually FAVORING an increase in fish intake for prostate cancer risk reduction.

Another piece of the picture is to compare prostate cancer rates in Japan vs the US. Here is a quote from the World Foundation of Urology:

"[Prostate cancer] incidence is really high in North America and Northern Europe (e.g., 63 X 100,000 white men and 102 X 100,000 Afro-Americans in the United States), but very low in Asia (e.g., 10 X 100,000 men in Japan).”

Since the Japanese typically eat about 8x more omega-3 fatty acids than Americans do and their
blood levels are twice as high, you’d think their prostate cancer risk would be much higher...
but the opposite is the case.

Omega-3 fatty acids are physiologically necessary, normalizing multiple metabolic phenomena including augmentation of parasympathetic tone, reductions of postprandial (after-meal) lipoprotein excursions, and endothelial function. It would indeed make no sense that nutrients that are necessary for life and health exert an adverse effect such as prostate cancer at such low blood levels. (Recall that an omega-3 RBC index of 6.0% or greater is associated with reduced potential for sudden cardiac death.)

I personally take 3600 mg per day of EPA + DHA in highly-purified, non-oxidized triglyceride form (Ascenta Nutrasea liquid) that yields an RBC omega-3 index of just over 10%, the level that I believe the overwhelming bulk of data suggest is the ideal level for humans.

Comments (6) -

  • Jeff

    7/23/2013 10:56:11 PM |

    Can you advise where you get the Nutrasea Liquid that you mention you personally use above?.  I'm not finding any in the 3600mg range.  I couldn't find any where 2 doses equals that amount either.  Looking for high quality Omega 3's that are not sourced from Krill due to shell fish allergy.  Currently taking fish oil gel caplets of dubious quality.  Thanks in advance.

  • pickinthefive

    7/29/2013 5:58:45 PM |

    Hi Dr. Davis,
    A question I would have.  If you are at a known risk for prostate cancer, i.e. father or uncle's already have it, or in my case a reletively high PSA and symptoms of BPH, would it be wise to avoid the Omega 3's ?
    Thank you,

  • Edwin

    8/14/2013 9:27:43 AM |

    So my eating a canned salmon sandwich for lunch most days which has about 1g of Omega3 (I take no supplements) should be safe?

  • Stephen in Anaheim

    8/15/2013 5:29:38 AM |

    I have to say that this is a great thing to read! In most dietary articles that I stumble across nowadays, I can find at least a paragraph or more on why people should be adding more Omega-3 fatty acids to your diet. In fact, I have read that Omega-3 can be quite beneficial for a number of medical conditions ranging from childhood asthma to fibromyalgia. It is scary to think that it could associated with a higher risk of prostate cancer, even though the underlying study was not well constructed.

  • Edward

    8/16/2013 3:08:29 AM |

    Dr. Davis,
    I take fish oil from a brand called "Carlson fish oil" it contains omega 3 fish oil 1,600. What would be the highest safest amount a person can take in Omega 3 in your experience from your patients and practice? What are your thoughts on the Linus Pauling Heart therapy which calls for a person taking at least 10 grams of vitamin C and 3-5 grams of Lysine in order to reverse plaque and heart disease? I have read the two time Nobel prize winner's books and his writings on heart disease are compelling. I would love the insight from an actual cardiologist with a practice to confirm what works and doesn't work.

  • Edward

    8/16/2013 1:19:06 PM |

    Dr. Davis,
    How much fish oil would you consider the highest and safest dosage for a person to take for heart disease and would the dosage a person who is healthy or heart problems differ?

Sleep: A to Zzzzzzzzzz

Sleep: A to Zzzzzzzzzz

Take a look at the results from the Heart Scan Blog's most recent reader poll (399 respondents):

How many hours do you sleep per night (on average)?

9 or more hours per night
15 (3.7%)

8-9 hours per night
72 (18%)

7-8 hours per night
152 (38.1%)

6-7 hours per night
111 (27.8%)

5-6 hours per night
38 (9.5%)

Less than 5 hours per night
11 (2.8%)

Like many issues in health, too much or too little of a good thing can present undesirable consequences.

Too much sleep: While psychologists and sleep researchers advise us that at least 9 hours are required to fully eliminate sleep "debt" and achieve optimal vigilance and mental performance, epidemiologic studies have shown increased mortality with this quantity of sleep.

Too little sleep: Getting less than 7 hours habituallly increases blood sugar, appetite, inflammatory measures, and encourages weight gain. Mortality is also increased, just as with sleeping too much. It is also associated with increased likelihood of a positive heart scan score.

7-8 hours per night from a health viewpoint is that Goldlilocks "just right" value: just enough to not erode mental performance substantially, but not so little that inflammatory, insulin-disrupting, and appetite-increasing effects develop.

Of our 399 respondents in the poll, 56.1% (38% + 18%) slept what appears to be an optimal amount for health. While only 3.7% slept too much (9 hours or more), the remaining 40.1% slept too little.

Our informal poll confirms what most of us observe in everyday life: The majority of people shortchange sleep in order to meet the demands of their high-pressure, squeeze-as-much-as-possible-into-every-day lives. But not paying off your sleep "debt" is like not paying the mortgage for a couple of months. You wouldn't expect your friendly neighborhood bank to say, "Oh, you forgot to pay your mortgage? Forget about it. Just pay next month's." Sure, fat chance. But if you don't pay off your sleep "debt," you will pay it back with health.

Comments (5) -

  • Anonymous

    6/23/2009 7:30:43 PM |

    Some thoughts I have about the causality vs. correlation. Those studies that show correlation with increased mortality /disease with sleep times longer than 9 hours per day could suggest that people with deseases sleep longer because of the disease?  Not that longer sleep periods them selfs are the cause of the disease and early death but a sign of troubles in health which need more time for the body to trying to recuperate?

    I personally sleep between  7 - 9 hour per day if I can rest up to my taste, but if I'm stressed I sleep less and if I'm sick I sleep more.

    (Sorry for possible spelling mistakes, I'm not native english speaker.)


  • Dr. William Davis

    6/23/2009 7:40:51 PM |


    Excellent point.

    In fact, I wonder if greater sleep need is, for many, a red flag for hypothyroidism, in addition to other conditions.

  • kris

    6/24/2009 2:04:35 PM |

    Brain study shows differences in night owls, early risers
    Last Updated: Tuesday, June 23, 2009 | 5:36 PM MT  
    CBC News  

    Scientists at the University of Alberta have found there are significant differences in the way our brains function, depending on whether we are early risers or night owls.

    Using magnetic resonance imaging-guided brain stimulation, neuroscientists tested muscle torque and the excitability of pathways through the spinal cord and brain.

    "We found that the brains of morning people are more excitable in the morning and evening people are completely opposite," neurophysiology researcher David Collins said Tuesday.

    "The evening people ... it's almost a perfect storm of excitability in the central nervous system, where the brain is maximal in the evening and the spinal cord is maximal in the evening.... They generate the most force in the evenings," he said.

    David Collins, neurophysiology researcher at the University of Alberta (CBC) "Morning people ... their brains are most excitable in the morning, but their spinal cords are most excitable in the evening," Collins said.  

    The results may suggest that morning people are performing below their maximum possible level at all times of the day because of this, he said.
    Morning person may be steadier

    If you could change morning people into evening people, maybe their performance would be best in the evening, he suggested. This doesn't mean it's necessarily better to be an evening person, he said.

    "A morning person may be a more consistent, steady plodder over the course of the day," Collins said.

    Kaitlin Cleveley, a sports performance researcher at the U of A, likes to begin work around 10 p.m. and go until 3 a.m.

    "Anything that starts in the morning is absolutely brutal for me to try and get up and try and function," she said. This study brings new perspective to training, she said.

    "It's about trying to peak the athlete.... It can help to set up a sleep program, and it can help to reduce jet lag and sort of help you to determine you know 'When should I book the flight?, When should I get there?'" Cleveley said.

    The research has lots of applications, including understanding mental and physical peaks and how people can maximize performance, she said.

    Initially the research was to determine if brain function changes over the day, Collins said.

    The study evolved with some early findings around two subjects in the study. One proved to be an extreme morning person, the other an extreme evening person, he said.

  • Anonymous

    6/27/2009 12:15:28 AM |

    How does napping fit into this?  Does napping count in the "hours per night" or is it separate?  Any statistics on mortality and napping?

    A lot of cultures have an afternoon siesta but Americans tend to frown on napping.

  • Anna

    6/29/2009 6:43:05 PM |

    A close family member just underwent double bypass surgery in the past few weeks (doing well now, though it took a blood transfusion to get over a 2 day slump while in the hospital), after more than a year of symptoms with exertion,  poor stress test results, a lot of career stress recently, etc.  None of us were told though until just before the recent angiogram.   I always viewed this situation as a "when", not an "if", because I had a different view than the AHA's, but it's always "too soon", even if expected.

    The angiogram revealed multiple sites of stenosis in locations not suitable for stents, so double bypass was performed.

    Aside from family history (her father died of CVD at age 50), there were other risk factors, so she faithfully followed most of the AHA guidelines since at least the 80s - regular chol panels (high results), statins, HRT, low fat/high chol, reduced saturated fat, reduced fat dairy, lean meats, lots o' carbs (even lots of whole grains), etc.  

    But obviously, this didn't work (I think it's a recipe for a bypass), because  CVD happened anyway despite all this adherence to  "prevention" (I use that word loosely in this context).  

    Other risk factors include tendency toward "apple" shape, "strong explosive" personality (sort of Type A), and as I suspected, diabetes (though that was concealed from the family until just before the surgery).  On top of that ...(drum roll)...

    and pertinent to this post - 25+ years of working the third shift as a nurse in L & D.  She was *chronically* and noticeably sleep-deficient (very often apparent, even over the phone), not to mention also Vitamin D deficient (her calcium supplement only added a tiny amount).  The coronary calcium scan wasn't done until last year, when there was marked plaque and shortness of breath & fatigue symptoms.  Of course no program such as Track Your Plaque was suggested or undertaken.  It was fate, right? - the family history - nothing could be done to override that, right? Note: if you are reading this with a sarcastic tone, that's about right Wink.

    Talk about an AHA failure to prevent. Everything I've  I shared about about the AHA's misguided approach to prevention, low carb and grain restriction to manage BG and diabetes, and all the other ways to prevent CVD fell on deaf ears.  Still does.  Still keeping my fingers crossed that the bypass arteries don't clog up.