This post is a letter written by Dr. Bruce Davidson to the editor of The Bonaire Reporter. This letter was written in response to two recent articles published by nutritionist Stephanie Bennett and was published in the edition of The Bonaire Reporter dated March 30-April 13.
Having read both of the two columns relating to omega fatty acids (Omega 3 & 6 - Revisited, March 2-16; The Hidden Dangers of Polyunsaturated Fatty Acids, March 16-30) I feel I must write to address the glaring errors in both articles. I can say errors as I have been involved in research in the field of polyunsaturate biochemistry for more than forty years, and taught the subject to medical students for the last twenty eight.
The assertion that polyunsaturates are the root cause of all the pathologies that were mentioned in Body Talk is totally absurd, and flies in the face of all the proven scientific facts. Indeed, at least three health related Nobel prizes have gone to scientists involved in characterizing the roles and importance of both polyunsaturates and the eicosanoids, so they can't be all bad can they?
Back in 1930 Burr and Burr proved that both linoleic and alpha-linolenic acids were essential components of the dietary intake of all vertebrates, including humans. Uncountable studies since then have reconfirmed this and further expanded on the vital roles played by polyunsaturates in health.
As correctly indicated by column author Stephanie Bennett, the polyunsaturates we need have double bonds in the molecule, with the first one from the 'methyl' end being either in the n6 (omega 6) or n3 (omega 3) position. Now, double bonds in these positions cannot be either put in or taken out by animals, but are required for survival and so have to ultimately be got from the plants that make them, so they are essential fatty acids (EFAs). To get these EFAs we have to eat the plants that make them, or eat the animals that have eaten the plants.
Why do we need them? Well, at a very basic level, all of the membranes of every single cell of our bodies are dependent on a mixture of fatty acids, saturates, monounsaturates and polyunsaturates, as part of their structure, along with cholesterol and proteins. So any deficiency can be a serious threat to the stability of our cells, especially the highly sensitive ones that make up our nerves and brain. Apart from this, they have specialized functions within our bodies other than in membranes, eg. as part of the waterproofing layer in our skin, which prevents us from losing too much water and becoming dehydrated. In fact EFA deficiency is a well characterized condition, with a progressively worsening set of symptoms, that may even be fatal if untreated.
However, it is not just the plant EFAs we need. They also get converted into longer chain polyunsaturates with more double bonds from the EFAs, so there are two families of polyunsaturates, the omega 6 (n-6) and omega 3 (n-3). Of these, arachidonic acid (AA, an omega 6) has been shown to crucial in the brain for memory, while docosahexaenoic acid (DHA, an omega 3) has also been shown to be important in memory as well as in the actual transmission of signals between brain nerves. Its precursor, eicosapentaenoic acid (EPA, another omega 3), is one of the more common marine fatty acids, hence both of them are the 'omega 3' you see in fish oils. And all three of them are crucial for normal brain development in children.
It's true to point the finger at AA as being a precursor for prostaglandins, etc. and that these AA derivatives are implicated in many pathologies, but they also are vital for normal health, as inflammatory processes, to mention one of many, are a critically important part of our bodies ability to fight toxins and infections. Indeed, it's a balance between two AA products, that stops your blood from clotting on its own. In parallel, both EPA and another n6, dihomogammalinolenic acid (DGLA), are made into other prostaglandins that usually have the opposite effect to those from AA, ensuring a balance in a normal, healthy person.
Getting around to vitamin E, its primary function is to be oxidized to mop up any excess reactive oxygen. That's why it's called an antioxidant because it stops damage to the polyunsaturates in your cell membranes by being oxidized instead!
As to serum cholesterol, if it was so damaging why would our liver produce grams of the stuff every day? The crucial thing is the balance between high density lipoprotein cholesterol (HDL) and low density lipoprotein cholesterol (LDL). LDL takes cholesterol from the liver to be used in the rest of the body, while HDL takes excess cholesterol back to the liver for clearance.
This is completely normal; it's only when there is a pathology, like atherosclerosis, that the difference becomes significant. And dietary cholesterol is not important as we only take in tiny amounts per day compared to what our liver is making. In contrast, dietary saturates do matter. Too much of them and our liver is stimulated to make more cholesterol, so if we have an artery problem they can make it worse. But guess what? Our liver doesn't use polyunsaturates for making cholesterol, only saturates, so the higher the polyunsaturates in our diet the less saturates, and therefore the lower the cholesterol from our liver.
There is even one group of humans, the Inuit, (Eskimos) who have extremely high omega 3 intakes, because their diet consists of fish and seals that have eaten the fish. Before the 'West' stuck its nose in the Inuit had lived for thousands of years on a diet almost devoid of plant materials, and they had no more health problems than anyone else, in fact probably fewer. It was only when they were settled into formal townships and became exposed to 'Western' foods that their health profile deteriorated to its generally poor state now.
In contrast, I agree entirely with the position of Body Talk that the industry has pushed and pushed and pushed, but that is true of all vested interests throughout the health and nutrition business, indeed any business, and doesn't detract from the importance of the EFAs and their derivatives, both omega 6 and omega 3, in human health.
Professor Bruce Davidson. Dean of Students at Saint James School of Medicine, Bonaire.
