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A1CR
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Joined: 18 Jan 2006
Posts: 559
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 Posted: Mon Feb 13, 2006 5:25 am Post subject: FAT is "Cleanest-Burning" Energy source |
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This article was posted on behalf of MR:
Someone wrote:
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Generally burning carbohydrates is the cleanest energy source for the cells, so burning ALL fat will increase free radical production over burning ALL glucose.
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MR responds:
This assertion has been made repeatedly. I've never been clear where the idea came from, and I keep expecting someone to chirp in to remind all that this isn't so, as was noted in the Alb*tr*ss. In fact, under normal circumstances the production of energy from fat produces 1/6 fewer opportunities for fumbled e- than a similar number of ATP generated from carbohydrates.
From The Mitochondrial Free Radical Theory of Aging by the hallowed Dr. Aubrey DNJ De Grey:
"[C]oenzyme Q10 does not harbor a transition metal atom to carry the electrons: it carries them itself, like NAD and FAD. It has one very striking difference from NAD and FAD, though: ... it exists not in two alternative states but in three. The first and third states, ubiquinone and ubiquinol, differ in content by two electrons just like the two states of NAD and FAD.
... The intermediate form, ubisemiquinone, exists only fleetingly while CoQ is interacting with Complexes I [for which it is the e- acceptor] or III [to which it is a donor], and is fairly tightly bound to them during this time. However, its existence is ... the weak link in the respiratory chain, because it can spontaneously revert to uviquinone, and the electron it releases in doing so can, in due course, do immense harm." (pg. 17)
To wit: this "fumbling" of an e- is THE source of ROS production in the mitochondrial respiratory chain, the largest source of ROS production in the body & also (it is widely accepted) the most deleterious. "Interestingly, the other enzymes which donate electrons to ubiquinone -- complex II, faty acyl CoA dehydrogenase, and s,n-glycerophosphate dehydrogenase -- appear not to contribute to [ros] production. This is probably because they do not form [ubisemiquinone] at any stage, but instead transfer two electrons in unison from FADH2 to ubiquinone." (p. 140).
The point: under normal circumstances, 5/6 of the electrons stripped out of carbohydrates are transferred into the electron transport chain thru' NADH into Complex I; the remainder comes in via FADH2, & is thus "safe." By contrast, for every six e- stripped out of fat, only 4 come into ETS via Complex I: one goes via from FADH2 via fatty acyl CoA dehydrogenase & one from JComplex II. See de Grey's book, many first-year biology books, and most "Molecular Biology of the Cell" type ones.
I.e., there are 1/6 fewer opportunities to "fumble" an electron, forming superoxide, for every unit of ATP produced from fat vs. carbohydrates.
Since very few e- are ACTUALLY fumbled in the exchange, this doesn't mean that you're actually cutting down on 1/6 of your mt ROS production by substituting 6 units of energy from 6 units of CHO [Ed.: a molecule of carbohydrate is composed of Carbon-Hydrogen-Oxygen] with 6 units of fat. It does, however, make FAT, and not carbohydrates, the "cleanest energy source for the cells, so burning ALL fat will decrease free radical production over burning ALL glucose" -- i.e. carbohydrates and (usually) protein.
Since, further, fat may actually slow down metabolic rate in primates, & especially in CRONies, the above analysis may actually underestimate the reduction in mt ROS from replacing CHO w/fat.
-MR
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