While it’s quite likely few have heard of docosahexaenoic acid (much less pronounce it), the term “Omega-3” has been splattered over the health and wellness headlines for years. I bring it up because of a May meeting of the Royal Society of Medicine (UK) that discussed the wonders of docosahexaenoic acid, fortunately abbreviated to DHA. Wonders is an appropriate word, even in the context of this meeting, as covered by an article in the Economist Fish and no chips DHA is considered the alpha dietary chemical from the class of omega-3 fatty acids.

By ‘alpha’ I mean among the several omega-3 fatty acids, it is the one with the most interesting and arguably important effects. DHA is prevalent in two locations for most animals: The eye, where it makes up 60% of the fatty acid molecules, and the brain where it registers about 40%. That it is found in the eyes is an artifact of evolution. According to some scientists, DHA’s first role was converting light into electricity in early single-cell organisms. From there it also became involved with a way of controlling the electric potential (the gradient of electric charge between locations in a cell), which among other things is the basis of the nervous system. At the molecular level, biologists and neuroscientists have been at work for some time, attempting to unravel the behavior of the complex DHA molecule.

A tantalizing aspect of DHA is its relationship to problems of the central nervous system. Where DHA is in deficiency, there is an association with cognitive decline – or put another way, people with abnormally low levels of DHA often have symptoms of severe depression, Alzheimer’s disease, and other brain disorders. There are numerous studies showing the correlations. However, definitive description of the molecular processes that link DHA to the diseases are usually lacking. Likewise there are studies linking DHA and omega-3 deficiencies to violent behavior. Other studies have shown that babies with weak DHA production of their own, when fed with formula milk low in DHA have on average significantly lower IQs.

Often prompted (loosely) by such findings, nutritional scientists have produced many studies about the natural (and unnatural) occurrence of DHA, on the premise that there may be benefits to a diet rich in DHA (or rich in omega-3 fatty acids in general). Fish, especially certain fatty fish such as salmon, are known to have considerable DHA, and therefore are usually high on the recommendation list.

Of course, not everyone likes to eat fish, or these days can afford to. So the health food and nutritional supplement industries have gladly stepped in to provide DHA in both natural and man-made forms. The catalogs and shelves of most health food outlets have many “Omega-3” or DHA products on offer, often without much pharmaceutical pedigree.

The various perspectives on DHA come from an uneasy relationship between molecular biology, neuroscience, nutritional science, the health food industry, and the nutritional supplement industry. It’s a mix with a variety of agendas. Unfortunately the status of the scientific research is mostly at the level of ‘interesting correlation’ rather than ‘explained causation.’ It’s a kind of scientific limbo, which makes it difficult to separate the kernel of truth from the chaff of profit seeking.

By now most people who have an interest in nutrition have noticed that the supposed benefits of most vitamins, minerals, proteins, and yes – fatty acids like omega-3s tend to fade in and out of favor over periods of time like a decade or two. That has at least two big contributing factors: New studies are conducted, often with different methodologies or working from a different perspective and therefore produce different and sometimes contradictory results. Secondly, the progress in understanding the effects of omega-3s and DHA at the molecular level sometimes calls into question or changes the interpretation of the studies.

For the consumer – the person trying to decide if increasing intake of DHA and omega-3s is a good thing – the article in the Economist has a closing phrase:

Eating fish is all very well, but the oceans are under enough pressure as it is. Biotechnology might be brought to bear—creating genetically modified crops such as soyabeans with higher levels of DHA. Until that day, though, the best advice is probably that which was posted over the oracle at Delphi: “Nothing in excess”.

[Source: The Economist]