DHA, Fish and Alzheimer’s: Press Misinformation

The general public are reliant on the media for their most recent update on “what to eat and what not to eat” and so it’s terribly important that studies are reported objectively and fairly – and, of course, that we are given the whole picture. It is not a very new concept that eating fish such as salmon, sardines and mackerel may offer an element of protection against developing dementia and indeed the media has reported on a number of studies showing that people who consume a significant amount of oily fish or fish oil are less likely to develop Alzheimer’s disease. This week’s headline, “Fish may not be Alzheimer’s answer” suggests, however, that Alzheimer’s patients may not benefit from eating fish, despite this “brain food” reputation.

Our understanding of the significant health benefits associated with fish oil supplementation has come a long, long way since scientists’ original discovery, back in the 1950s, that cod liver oil was a rich source of fatty acids. Researchers have since then progressed far beyond the basic understanding that fish oil is a promoter of general good health, and moved onto the next phase of innovation – investigating which particular elements within this oil are biologically active and whether a physical deficiency in this bioactive element results in some degree of physical deterioration. Indeed, fish oil contains two major fatty acids EPA and DHA and it is only really in recent years that these important fatty acids have been investigated individually rather than dumping them in the same boat with the generic label of omega-3.

DHA is the most abundant omega-3 fatty acid in cell membranes, present in all organs and most abundant in the brain and retina. In contrast, EPA is present in minute quantities. It could be easily assumed that DHA is the more dominant of the two fatty acids and put all of our focus here. However whilst DHA has a primarily structural role, EPA plays an important functional role. In actual fact whist EPA and DHA are both considered to be important regulators of immunity, platelet aggregation and inflammation, their influencing bi-products arise from very different pathways and it is therefore not surprising that their mechanism of action will differ.

So what is my problem with the latest headline? Well what’s very misleading with this is the loose use of the word “fish”. The study didn’t even have a vague whiff of fish about it but was conducted using a DHA supplement and a dummy placebo. The importance of this is that the information put forward to eager ears gives the impression that all that mackerel eating is a waste of time. But hear me out. This study took but one of the major fatty acids associated with fish oil, showed no benefit, but happily used the word fish to summarise the findings. If we recall, fish oil contains two important fatty acids, DHA and EPA. It is becoming increasingly clear that the marked differences between the effects of EPA and DHA mean that we can no longer generalise the effects of ‘fish oil’ as a reservoir of omega-3. EPA not only plays a major role in cell signalling but also contributes to the compaction and stabilisation of neurones. Indeed previous studies have shown that high plasma EPA concentration may decrease the risk of dementia and that EPA can actually reduce the atrophy associated with the shrinking brain. I’m not objecting to their findings that DHA is not the fatty acid which plays a role in dementia, rather it’s the fact that the message implies that it we should now question or even rule out the protective role of fish altogether. But when we dig deeper and unravel the scientific evidence and put that on our plates to eat, we see that things are a little more convoluted than we initially thought – well, if you read the recent headlines, that is. Just because the bigwigs are now telling us that DHA won’t save our brains (this week at least) it doesn’t mean that we should now disregard our efforts to include fish as part of our diets in our bid to prevent age-related mental decline. I, for one, shall be continuing to get my twice weekly portions in and I hope you will too. Do remember that once again, it’s not black or white, to fish or not to fish.

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