A Fishy Tale?

Readers of this column will know that this reviewer is extremely interested in the beneficial effects of omega-3 fatty acids and the importance of the correct fatty acid ratios in the diet.

Monday March 27^th was when the rosy glow surrounding all the good and emerging news about omega-3 fatty acids was dulled somewhat by that most scientific of media channels - The New Zealand Herald. This our favourite daily paper, trumpeted the following headline, “Heart benefits of omega-3 a medical myth, study finds.”

Another journalist then added to the fire a few days later by calmly announcing “beware fishy claims of white coat brigade”.

This sort of reporting belittles and derides all the good science that has been done in this area for the last 25 years by many eminent researchers.

Many scientists, researchers and nutritionists were galvanised into replying to the original article which was published in the British Medical Journal.

The Original Article

This was entitled “Risks and benefits of omega-3 fats for mortality, cardiovascular disease and cancer: systematic review” (Hooper at al) BMJ online.doi

Their actual conclusion in the paper read “This systematic review assessed the health effects of long and short chain omega-3(mainly as capsules/supplements) and found no evidence of a clear benefit of omeg-3 fats on health. To understand the effects of omega-3 on health, we need more high quality clinical trials of long duration.”

These actual conclusions bear no resemblance to the original article nor to the follow up piece that was intended to be droll and amusing.

The rapid response

Concerned and irritated readers were quick to respond to the article and these can be found by anyone interested by logging into BMJ online.

Response by Dr William Lands

Dr Lands has been involved in the research into the biochemistry of omega 3 oils for 25 years and more, below is his letter to the BMJ

A very limited view of “evidence for an effect of long chain and shorter chain omega-3 fatty acids” produced an incorrect conclusion that “long chain and shorter chain omega-3 fats do not have a clear effect on total mortality, combined cardiovascular events or cancer” (1). The bias came from evaluating only randomized clinical trials (RCTs), omitting large amounts of published evidence (2) on how dietary omega-3 fats compete with omega-6 fats as they maintain healthy tissues and prevent disease processes.

The biased view failed to interpret the reported estimates of omega-3 fat intakes in relation to existing levels of competing omega-6 fat intakes, a balance readily seen with gas chromatographic analyses of blood lipids (3). Such analytical biomarker information would show whether the reported efforts of the various RCT interventions had actually succeeded in sufficiently shifting tissue proportions of omega-3 and omega-6 fatty acids to the extent intended (and whether all subjects complied with the intended dietary intervention).

An RCT in which tissue proportions of long chain omega-3 and omega-6 fats changed very little has little merit in forming a useful conclusion. The authors shed little light on such evidence, which is needed for a truly sound interpretation.

1 Hooper L, Thompson RL, Harrison RA, Summerbell CD, Ness AR, Moore HJ, et al. Risks and benefits of omega3 fats for mortality, cardiovascular disease and cancer: a systematic review. BMJ 2006. [Epub ahead of print; doi = 10.1136/ bmj.38755.366331.2F].

2 Lands WE. Fish, Omega-3 and Human Health 2005 AOCS Press, Champaign

3 Lands WE. Dietary fat and health: the evidence and the politics of prevention: careful use of dietary fats can improve life and prevent disease. Ann N Y Acad Sci. 2005 Dec; 1055: 179-92.

This reviewer sought the opinion of DSM Nutritional (previously Roche nutrition) a long term supplier of quality omega-3 oil from reputable sources

The following is their logical and scientific response

POSITION PAPER       

BMJ, doi:10.1136/bmj.38755.366331.2F (published 24 March 2006)

Objective. To review systematically the evidence for an effect of long chain and shorter chain omega 3 fatty acids on total mortality, cardiovascular events, and cancer.

• If w-3 PUFAs have an impact on cardiovascular health, they should lower the mortality from cardiovascular disease. Since most of the studies are too small to see a significant effect, it is attemptable to use the statistical tool of a meta-analysis. This has been done successfully by H. Bucher et al[1] who reported a positive effect of w-3 PUFAS.
• The authors conclude that long chain and shorter chain omega-3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer. But they do not rule out an important effect of omega 3 fats on total mortality. The advice to eat more oily fish should continue.
• However, if they removed the study DART 2 by Burr et al.[2], they received the same positive result as Bucher et al. [i] in his meta-analysis who did not include the Burr trial: risk of death RR = 0.83, 95% CI = 0.75 to 0.91 that means a clear, significant benefit.
  • Burr recruited for his randomized, controlled factorial trial 3114 men under 70y of age with angina. Mortality was ascertained after 3-9y.The subjects were randomly allocated to 4 groups:
    • advised to eat 2 portions of oily fish each week, or to take 3 fish oil capsules daily (Maxepa, 540 mg EPA plus 360 mg DHA)
    • advised to eat more fruit, vegetables and oats
    • advised to combine 1 and 2
    • no specific dietary advice
  • All cause mortality was not reduced by either form of advice. Men advised to eat oily fish, particularly those using fish oil supplements, had a higher risk of cardiac death. These results remained unexplained.
• The present evaluation combined more studies; among others also DART 2 with the unexpected finding of an increased risk for consumers of fish or fish oil supplements. Since there is no valid explanation except some speculations for this result, each attempt to combine it with other studies must cause confusions about the usefulness of omega 3 PUFAs. Due to the high number of participants and the long duration it weights heavily in all analysis.
• Removing this one particular study, the results change in favour of the w-3 PUFAs and reveal the expected lowering of the cardiovascular risk.
• Therefore, we should stick to the official, still valid recommendation to increase the intake of long-chain omega 3 PUFAs. The golden rule is the ISSFAL (International Society for the Study of Fatty Acids and Lipids) recommendation of 500 mg EPA/DHA per day[3].

National Heart foundation position

Input was sought from various technical and nutritional advisors to the Foundation which resulted in the following letter to the editor ;

The Editor, NZ Herald

“I read with interest the article published on Monday 27^th March entitled “Heart benefits of omega 3 a medical myth, study finds”.

The particular review study highlighted in the article actually drew no firm conclusions on the omega 3 issue, instead suggesting the need for more definitive research.  Systematic reviews such as this one can be helpful but have limitations, especially when large numbers of very different sets of information are combined.

Accordingly, the article headline may have caused confusion for readers with an interest in dietary matters and the health benefits of omega 3 fats, especially from fish.  The review does not rule out the possibility that omega 3 fats may have an important effect in overall health and well-being.

In New Zealand, omega 3 fats are available from a variety of food sources including flaxseed oil, canola oil, walnuts, linseeds, oily fish and some fortified food products.  Most of the research to date has investigated the relationship between consumption of omega 3 fats from whole fish or fish oils and the occurrence of heart and blood vessel disease.

The National Heart Foundation of New Zealand advises healthy people, as well as those living with heart disease, to include some fish as part of a normal, varied eating pattern.  Fish remains a highly nutritious food, as an excellent source of iodine and a good protein source for all people.  It is low in saturated fats, and high in the ‘good’ unsaturated fat and omega 3 oils.  Supplements of omega 3 fish oils are not generally recommended but may benefit people during the year following a heart attack.

While this study stimulates discussion and debate on nutrition and health matters, there is no reason for people to start overlooking or removing omega-3 rich foods from a balanced healthy eating pattern.”

David Roberts

National Dietitian, The National Heart Foundation of New Zealan

Conclusions

This reviewer firmly believes in the beneficial properties of consuming quality fish and of managing the correct fatty acid ratios in the diet.

Care must be taken when studying the effects on people of taking uncharacterised supplements. Many fish oil capsules from around the world have been shown to be either rancid, full of dioxin, PCB’s and pesticides.

Oil used for supplements or encapsulation must be from oil that is free from contaminants and has extremely low levels of oxidised species.

In an age where consumers receive a daily dose of “science” with their morning news, scientific people will have to be on the look out for misleading or incorrect summation of peer reviewed journals for the non-scientific public.

Shakespeare should have the last word about the disservice done to credible research in this important area.

He would apply the words of Macbeth-“it is a tale told by an idiot, full of sound and fury, signifying nothing”.