The essentiality of PUFA is under doubt

[haidut]

The mainstream science and blogosphere is starting to catch up on the fact that the PUFA are not that "essential" after all. While there is no official statement on the issue as of now, there are several studies that call for rethinking the misnomer and replacing it with something milder. Eventually, even that milder version will probably get dropped as new evidence appears. Here are some "recent" news to consider, but don't hold your breath for a change in dietary guidelines like it happened for cholesterol recently.

http://suppversity.blogspot.com/2015/03 ... acids.html
http://www.ncbi.nlm.nih.gov/pubmed/14559071

"...The term 'essential fatty acid' is ambiguous and inappropriately inclusive or exclusive of many polyunsaturated fatty acids. When applied most rigidly to linoleate and alpha-linolenate, this term excludes the now well accepted but conditional dietary need for two long chain polyunsaturates (arachidonate and docosahexaenoate) during infancy. In addition, because of the concomitant absence of dietary alpha-linolenate, essential fatty acid deficiency is a seriously flawed model that has probably led to significantly overestimating linoleate requirements. Linoleate and alpha-linolenate are more rapidly beta-oxidized and less easily replaced in tissue lipids than the common 'non-essential' fatty acids (palmitate, stearate, oleate). Carbon from linoleate and alpha-linolenate is recycled into palmitate and cholesterol in amounts frequently exceeding that used to make long chain polyunsaturates. These observations represent several problems with the concept of 'essential fatty acid', a term that connotes a more protected and important fatty acid than those which can be made endogenously. The metabolism of essential and non-essential fatty acids is clearly much more interconnected than previously understood. Replacing the term 'essential fatty acid' by existing but less biased terminology, i.e. polyunsaturates, omega3 or omega6 polyunsaturates, or naming the individual fatty acid(s) in question, would improve clarity and would potentially promote broader exploration of the functional and health attributes of polyunsaturated fatty acids."

 

[dd99]

"... this term excludes the now well accepted but conditional dietary need for two long chain polyunsaturates (arachidonate and docosahexaenoate) during infancy.

Is this true? Are some PUFAs essential in infancy?

 

[haidut]

"... this term excludes the now well accepted but conditional dietary need for two long chain polyunsaturates (arachidonate and docosahexaenoate) during infancy.

Is this true? Are some PUFAs essential in infancy?

I don't know of a study that proves this. In fact, since mother's milk depends on the diet of the mother people living in tropical areas and consuming mostly saturated fats and no fish tend to have very little AA and DHA in their bodies/milk. Given that their children grow up in a state of AA/DHA deficiency and reach adulthood just fine I doubt AA and DHA are in any way essential for human development.
But if someone has studies showing the contrary I would be very interested in reading them.

 

[dd99]

Perhaps Tom's comment in this thread is relevant:

My thinking is that DHA´s role is mainly to make the fats more "fluid" in the brain, I believe it´s 25 times more "fluid" than linolic acid for example, so very small quantities can achieve this goal. It is probably the most unsaturated fat used by the human body. If it is missing then the body will likely compensate by unsaturating other fatty acids (monounsaturated out of saturated, mead acid out of oleic acid - as seen in vegans that do not obtain any DHA or arachidonic acid). I also think the body perhaps makes 22:4 n6 out of arachidonic acid as this is much more "fluid", so there´s another possible compensation mechanism if DHA is missing. More often however it seems that the body has too much of these unsaturated fats and gets rid of them via the production of prostaglandins. This at least appears to be Peat´s idea. I´m really no expert on all of this, I just find that Peat´s ideas makes more sense at least than that of all the corrupted experts working for the fish oil industry etc.

 

[Tom]

"Dietary analyses show that vegan diets are devoid of DHA and vegetarian diets that included dairy food and eggs only provide about 0.02gDHA/d. Vegetarian and especially vegan diets supply more linoleic acid (18:2n-6) than omnivore diets. The intake of α-linolenic acid (18:3n-3) also tends to be similar or greater but depends on culinary oils used. The proportions of DHA in plasma, blood cells, breast milk, and tissues are substantially lower in vegans and vegetarians compared with omnivores. The lower proportions of DHA are accompanied by correspondingly higher proportions of the long-chain derivatives of linoleic acid, indicating that the capacity to synthesize long-chain polyunsaturated fatty acids is not limited. Short-term dietary supplementation with α-linolenic acid increases the proportion of eicosapentaenoic acid (20:5n-3) but does not increase the proportion of DHA in blood lipids. Small amounts of preformed DHA (as low as 200mg) result in a large increase in the proportion of DHA in blood lipids in vegetarians and vegans. There is no evidence of adverse effects on health or cognitive function with lower DHA intake in vegetarians."

http://www.plefa.com/article/S0952-3278(09)00086-6/abstract

I wonder if in this example arachidonic acid and other long chain n6 are produced in higher quantities to compensate for the lack of DHA, so to make for example the brain fat properly "fluid". I do not think the brain can function if the fat is just monounsaturated and saturated. It is for the similar reason that cold blooded species living far north (like fish) have such a high concentration of long chain omega-3´s. It needs to have a certain fluidity and the colder the environment the more unsaturated the fats need to be to acheive this goal.

Could a lack then of PUFA mean that the brain would shrink / fail to grow, because the body prefers to have a small brain that works rather than a bigger brain that doesn´t? Or could desaturation of other fats to increase mead acid (quite unsaturated), oleic acid and others, compensate?

Another point is that these vegans despite apparently not making any DHA themselves and only obtaining miniscule amounts, still had some DHA in their bodies, so it suggest to me that the DHA they obtained earlier in life can be preserved for long periods of time and is very slowly depleted. Meaning there´s very little use for it expect for perhaps making the fat in the brain and eyes etc properly fluid.

I don't know of a study that proves this. In fact, since mother's milk depends on the diet of the mother people living in tropical areas and consuming mostly saturated fats and no fish tend to have very little AA and DHA in their bodies/milk. Given that their children grow up in a state of AA/DHA deficiency and reach adulthood just fine I doubt AA and DHA are in any way essential for human development.
But if someone has studies showing the contrary I would be very interested in reading them.

Very little AA and DHA yes, but it is not completely absent. Low requirement does not equate no requirement. I also suspect many of these primitive people ate insects, larvae etc that sometimes can be very high in DHA. http://www.iufost.org/iufostftp/Revd%20 ... r%2016.pdf


Perhaps Peat has failed to realize the effect of starches (and to a much lesser extent sugars), as an indirect source of saturated fat that can balance out the PUFAs. He does mention how increased saturated and monounsaturated fats can function almost like an "antioxidant" like vitamin E in that it stabilizes the PUFAs, and I think he also mentions the importance of the ratio of saturated to unsaturated, and should be at least 2:1. But this is usually easily acheived if fat derived from starch is part of the equation, assuming fat intake is not high. Perhaps the experiments he base his opinion on is the types where the diet was high fat - low starch- high pufa, like feeding animals almost exclusively seeds or seed oils.