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BioCeuticals Article

Inconclusive: Omega-3 Link to Prostate Cancer



Inconclusive: Omega-3 Link to Prostate Cancer
Date: 2013-07-15
Author: - Editor
Access: Public


BioCeuticals joins the Complementary Health Council (CHC) and other industry representatives in contesting recent inconclusive research linking omega-3 and prostate cancer.

The study, published in the Journal of the National Cancer Institute, found an increased risk of prostate cancer among men with high blood concentrations of long chain omega-3 polyunsaturated fatty acids.1

However, this study was not specifically designed to look at the exact relationship between omega-3 fatty acid intake and prostate cancer. The men in the study were all part of a larger study on the effects of vitamin E and selenium on prostate cancer.  

The men had normal levels of prostate-specific antigen (PSA) – raised levels of which may be a risk factor for developing prostate cancer. They were assumed to be cancer-free at the beginning of the study, but this had not been confirmed by biopsy so there is no way to rule out any pre-existing cancer. In addition it has been shown that some men with normal PSA levels do have prostate cancer and that many men with higher levels do not have prostate cancer. 

Discussing the study results, Research Fellow at the Cardiothoracic Surgical Research Unit at Monash University (Alfred Hospital) Dr Lesley Braun, PhD  BPharm DipAppSciNat GradDipPhyto, said the results were inconclusive.

“It was not an intervention study and use of supplements is not reported so we have no way of knowing whether supplementation was implicated. It is also not known how long people had high intakes of omega-3s for: five years or 20 years? This was not reported,” said Dr Braun.

 “The authors state they were surprised by the results – I am too as there are preclinical models showing potential benefits for prostate cancer with omega-3 EFAs. There might have been other confounding factors that are not clear yet, however it’s hard to determine from the paper. We clearly need to understand the results better and require further research."

The study showed that:

  • High blood concentrations of the omega-3 fatty acid docosahexaenoic acid (DHA) were linked to a higher risk of high-grade prostate cancer.
  • The omega-3 component eicosapentaenoic acid (EPA) was not associated with risk of high-grade prostate cancer, and associations were similar when there were both high levels of EPA and DHA.
  • There were no significant associations between omega-3 alpha-linolenic acid (ALA) and high- or low-grade prostate cancer.
  • For omega-6 linoleic acid (LA), there was no association with high-grade disease, but there was an association with risk of low-grade disease in men with a family history; there was no association among men without a family history.
  • Lower blood levels of certain transfats were linked to a lower risk of high-grade prostate cancer.

According to the CHC, flaws in the study include:

  • No documentation was provided in the paper regarding intake of fish or fish oil in the study group.
  • The difference in mean blood plasma phospholipid fatty acid blood level for omega-3s was 4.66% in the combined cancer group versus 4.48% in the control. Results are based on just 0.2% difference in omega-3 levels.
  • Plasma phospholipid fatty acids, as measured in this study, are not considered a good index of long term intake and are influenced dramatically by a single meal or timing of a fish oil dose. Therefore, looking at plasma levels in healthy or sick people may only provide insight into the recent intake habits of these individuals.
  • Absolute serum levels of EPA, DHA and docosapentaenoic acid (DPA) were not reported.
  • The association between individual omega-3 fatty acids, EPA, DHA and DPA and prostate cancer was NOT statistically significant within the CPH (Cox proportional hazards) model.
  • The CPH model is considered more suitable to a pharmaceutical medicine that is taken at the same time every day, at the same level. It is not considered suited for something like fish or fish oil intake where the levels in blood serum will vary considerably depending on food and complementary medicine consumption patterns.
  • The study was not designed to look at omega-3 and confounded with selenium and vitamin E used in the treatment arms.
  • The so called ‘meta-analysis’ of earlier studies (carried out at the end of the paper) only included three previous studies. One of which was the lead authors own (Brasky 2011). Another by Park et al. 2009 used the same nested case control design, while the remaining study by Chavarro et al 2007 showed a strong benefit for marine omega-3 fatty acids reducing the risk of prostate cancer.

The evidence: omega-3s and prostate cancer

In a study from Iceland it was observed in a group of elderly men that while salted or smoked fish may have increased the risk of advanced prostate cancer, fish oil consumption on the other hand could be protective against progression of prostate cancer.2  It was concluded that “In a setting with very high fish consumption, no association was found between overall fish consumption in early or midlife and prostate cancer risk”.

In a meta-analysis published in 2010 looking at fish consumption and prostate cancer risk it was concluded that “Our analyses provide no strong evidence of a protective association of fish consumption with prostate cancer incidence but showed a significant 63% reduction in prostate cancer-specific mortality."3

In a recently published Australian study, researchers looking at data from the Melbourne Collaborative Cohort Study found no positive association between omega-3 fatty acids from blood or diet and prostate cancer. In fact, they did not observe any clear associations between %plasma phospholipids or dietary EPA or DHA and prostate cancer, all HRs (hazard ratios) were below unity for EPA and DHA intakes, meaning a reduced risk though these were not statistically or clinically significant.4

Daily omega-3 requirements

Dr Braun said as with all things, consideration should be made concerning risk versus benefit. 

“The authors state that high levels of omega-3 intake were associated with increased risk – this supports the view that moderation is required. In reality, the dose of fish oils required to have beneficial cardiovascular effects in people with established disease is actually quite low – about 500-800mg daily.”

At BioCeuticals, we believe it is important for healthcare practitioners to be aware of the recommended dietary intake for omega-3s, and educate their patients on selecting an essential fatty acid for their needs. Further still, we recommend choosing a high-strength fish oil with the highest mark of quality such as the BioCeuticals UltraClean range, which surpasses the international standards of the Global Organisation for EPA and DHA Omega-3s (GOED).

BioCeuticals fish oils are currently under clinical trial at the Alfred Hospital, Melbourne where patients presenting for cardiac surgery, as part of the hospital’s Cardiac Wellness Program, are supplemented with BioCeuticals UltraClean EPA/DHA Plus®. The fish oil was also trialled at the Alfred Hospital on patients aged 60 years and older who were undergoing total knee replacement surgery. Those who received the active treatment were able to leave hospital sooner after surgery than those in the placebo group.

The Prostate Foundation of Australia recommends men over 50 years to speak to their healthcare practitioner about being tested for prostate cancer every year. If there is a family history of the disease, men should speak with their healthcare practitioner annually from the age of 40 onwards. 

 

References

  1. Brasky TM,  Darek AK, Song X, et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. JNCI J 2013. First published online: 10 July 2013, 10.1093/jnci/djt174
  2. Torfadottir JE, Valdimarsdottir UA, Mucci LA, et al. Consumption of fish products across the lifespan and prostate cancer risk. PLoS ONE 2013;8(4):e59799. 
  3. Szymanski KM, Wheeler DC, and Mucci LA. Fish consumption and prostate cancer risk: a review and meta-analysis. Am J Clin Nutr 2010;92:1223-1233. 
  4. Bassett JK, Severi G, Hodge AM, et al. Plasma phospholipid fatty acids, dietary fatty acids and prostate cancer risk. Int J Cancer 2013, doi: 10.1002/ijc.28203 [Epub ahead of print]

 


Tags: fish oil, prostate cancer, omega-3,

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