How Essential Are the Essential Fatty Acids?

[NU_nutrition_TS]

The PUFA Report Part 1: A Critical Review of the Requirement for Polyunsaturated Fatty Acids

By Chris Masterjohn. Cholesterol-And-Health.Com Special Reports Volume 1 Issue 2. 25 pages, 3 figures, 114 references.

Abstract

Current reviews and textbooks call the omega-6 linoleic acid and the omega-3 alpha-linolenic acid "essential fatty acids" (EFA) and cite the EFA requirement as one to four percent of calories. Research suggests, however, that the omega-6 arachidonic acid (AA) and the omega-3 docosahexaenoic acid (DHA) are the only fatty acids that are truly essential. Eicosapentaenoic acid (EPA) occurs in fish products but is probably not a normal constituent of the mammalian body and in excess it interferes with essential AA metabolism. The EFA requirement cited in the scientific literature is inflated by several factors: the use of diets composed mostly of sucrose, glucose, or corn syrup; the use of diets deficient in vitamin B6; the use of purified fatty acids instead of whole foods; the use of questionable biochemical markers rather than verifiable symptoms as an index for EFA deficiency; and the generalization from studies using young, growing animals to adults. The true requirement for EFA during growth and development is less than 0.5 percent of calories when supplied by most animal fats and less than 0.12 percent of calories when supplied by liver. On diets low in heated vegetable oils and sugar and rich in essential minerals, biotin, and vitamin B6, the requirement is likely to be much lower than this. Adults recovering from injury, suffering from degenerative diseases involving oxidative stress, or seeking to build muscle mass mass may have a similar requirement. For women who are seeking to conceive, pregnant, or lactating, the EFA requirement may be as high as one percent of calories. In other healthy adults, however, the requirement is infinitesimal if it exists at all. The best sources of EFAs are liver, butter, and egg yolks, especially from animals raised on pasture. During pregnancy, lactation, and childhood, small amounts of cod liver oil may be useful to provide extra DHA, but otherwise this supplement should be used only when needed to obtain fat-soluble vitamins. Vegetarians or others who eat a diet low in animal fat should consider symptoms such as scaly skin, hair loss or infertility to be signs of EFA deficiency and add B6 or animal fats to their diets. An excess of linoleate from vegetable oil will interfere with the production of DHA while an excess of EPA from fish oil will interfere with the production and utilization of AA. EFA are polyunsaturated fatty acids (PUFA) that contribute to oxidative stress. Vitamin E and other antioxidant nutrients cannot fully protect against oxidative stress induced by dietary PUFA. Therefore, the consumption of EFA should be kept as close to the minimum requirement as is practical while still maintaining an appetizing and nutritious diet.

[Luffers]

EFA are polyunsaturated fatty acids (PUFA) that contribute to oxidative stress.

I did not realise that!

Is this the reason why taking krill oil is a better option than regular fish oil?

[NU_nutrition_TS]

In essence, all anti-oxidants can become pro-oxidant under the right set of circumstances. This is especially true of those ingested as a natural part of some foods like vitamins C and E, minerals such as zinc and the polyphenols in various plant foods.

Some of the best antioxidants are the ones we make naturally ourselves inside our own bodies; like glutathione and uric acid (which may have been a human evolutionary substitute for ascobate).

Uric acid is thought to provide half of the antioxidant ability of plasma.

Glutathione is released and acts close to the source of free radical (or rare oxygen species - ROS) production: the mitochondria of each individual cell.

The more antioxidants we consume in certain foods or supplements the more 'ammunition' we provide for a free radical cascade: the antioxidants neutralise the free radicals but, in so doing often become free radicals themselves and so on:

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The problem with thinking about antioxidants as "good guys" is that every antioxidant can become a prooxidant, i.e., it can reverse its role in our metabolism. In chemical terms, when a substance functions as an antioxidant, what it does it give away an electron. Electron-give-away is what antioxidants do. (This potential power for giving away electrons is called reduction potential).

What's so good about a compound that gives away electrons is that it can donate it to a "reactive" substance that is in need of one since substances in our body can become far too reactive when they are left with an uneven number of electrons. (Electrons like to exist in pairs, and don't like being "unpaired"). One leftover electron is enough to cause trouble.

When a substance has a leftover electron and becomes too reactive, it can damage anything nearby, including the wall of a blood vessel or the membrane of a cell. (Highly reactive substances that cause damage to body parts include a group of substances you may already be familiar with, called free radicals). If these highly reactive substances can just get hold of one additional electron, they can be quieted and potential damage can be avoided. That's what's so good about antioxidants that give away electrons.

However, when an antioxidant gives away an electron, another problem occurs. The antioxidant itself becomes a radical, because it now has a leftover electron. When vitamin C (ascorbic acid) acts as an antioxidant and gives away an electron, it becomes vitamin C radical (ascorbyl radical). It's no longer helpful to us as an antioxidant (or a vitamin) in this form. Like all radicals, we don't want excessive amounts of ascorbyl radical in our body.

WHFoods: Can you get too many antioxidants?

Krill oil is also a PUFA but it is in phospholipid form, which is better absorbed, and more stable, and comes with its own natural antioxidant - astaxanthin.

[daffy]

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Some of the best antioxidants are the ones we make naturally ourselves inside our own bodies; like glutathione and uric acid (which may have been a human evolutionary substitute for ascobate).

Wasn't sure whether to answer this here, or back in the uric acid thread I made ages ago. Feel free to move if a mod thinks it is more appropriate elsewhere.

I've recently been seduced by the argument that our inability to metabolize to uric acid, is down to it having been genetically advantageous, rather than as a substitute for ascorbic acid. Uric acid metabolism is expensive in terms of water loss. Evolutionary studies suggest that we lost the ability in a period where water was in short supply, and thus it was essential to our survival. Our inability to synthesize vitamin C is most likely down to us being omnivores and getting sufficient quantities from diet.

Unfortunately I'm not able to go into much detail as my sources are in London, and I'm somewhere else, and I'm going off memory, but you should get the gist of what I'm suggesting.

[daffy]

I can't say I've ever looked at the EPA/DHA ratios of food sources, since I've always just relied on getting some salmon or necking some fish oils.

Is the EPA/DHA ratio very different in other sources? I think I did see a paper stating brain has a different ratio compared to the rest of the body, or that might have been something else.

[hailtotheking]

I've posted a peer-reviewed study before in the Advanced Discussion section to show that fish oil has a net overall anti-oxidant effect, so the whole argument for fish oil causing free-radicals doesnt wash with me.

[NU_nutrition_TS]

That study doesn't actually say that and the study I quoted in the OP agrees with it:

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EFA are polyunsaturated fatty acids (PUFA) that contribute to oxidative stress.

Agrees with:

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PUFA are susceptible to oxidation.

However...

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...these results suggest that dietary n-3 PUFA do not have adverse effects on plasma TAC or the plasma concentration of most antioxidant vitamins.

Does not necessarily contradict:

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Vitamin E and other antioxidant nutrients cannot fully protect against oxidative stress induced by dietary PUFA.

Because to say it does is rather like saying:

If I put out 100 mouse traps (antioxidants) in a mouse-infested (oxidising PUFAs) cellar (body) and I discover, after some time, that I have 50 traps still set with no mouse (still have antioxidants in my body) I must have killed all the mice (neutralised all the free radicals produced by the PUFAs)! Clearly that is not necessarily the case.

Besides all that, it is not really the central issue of the original post but rather what fatty acids in particular are truly essential and in what quantity.

The antioxidant issue was just ancillary and was touched upon in response to Luffers' question. The answer to which was that antioxidants, by their very nature, can be pro-oxidant - which is self-evident, really, if you consider they are just 'electron donors' and 'free radicals' are oxygen atoms missing an electron. Once the anti-oxidant has donated its electron to the free radical (neutralising it) it must, itself, be an electron short and therefore a free radical. Hence the 'cascade' effect!

[NU_nutrition_TS]

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Is the EPA/DHA ratio very different in other sources? I think I did see a paper stating brain has a different ratio compared to the rest of the body, or that might have been something else.

This is an excellent - easy to read and understand - web site about EFAs and the brain:

The Human Brain - Fats

The section that particularly corroborates the information in the study quoted in the OP says:

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DHA (docosahexaenoic acid) and AA (arachidonic acid) are both crucial to the optimal development of the brain and eyes. During pregnancy the mother supplies the developing fetus with these fatty acids, and she continues to provide this important brain food to her infant through breast milk.

Specific deficits of essential fatty acids in fetal umbilical cords at birth correlate to low birth weight, small head circumference, and low placental size.5 This is significant, because birth weight and head size are associated with growth factors that influence later development of the central nervous system and cognitive ability.6


When the formula of 10-month old infants was supplemented with DHA and AA, it was found that "an infant's three-step problem solving ability is significantly improved" – and persisted beyond the period of supplementation.4

The importance of DHA and AA in infant nutrition has been demonstrated many times, and both substances are routinely added to infant formula throughout Europe and Asia.

No mention of EPA.

Also:

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DHA and arachidonic acid are the predominant essential fatty acids in the human brain. Fatty acids in human gray matter phosphatidylethanolamine is roughly 25% DHA, 25% stearic acid, 14% arachidonic and 12% oleic acid. In the outer segments of retina photo-receptors of the eye, DHA accounts for more than 50% of the fatty acid content, probably because of the high membrane fluidity required for sensitivity to light.

http://www.benbest.com/health/essfat.html#brain

Notice the 25% stearic acid - a long-chain saturated fatty acid!