Lipoic Acid 
 
Marty gives useful background on sources on lipoic acid.
>I have searched the net and even bought a book on lipoic acid, but still
>nobody can tell me authoritatively whether it is affected by cooking what
>gives?
 
The standard line is that only vitamin C and folic acid are affected by heat
(cooking).  50% or more of these vitamins can be lost from food when cooked
(microwaves and stir-frying destroy much less of these two than any other
cooking method).
 
Lipoic acid is similiar to vitamin C in that there are two forms, dihyrolipoic
acid (reduced lipoic acid) and lipoic acid (oxidized lipoic acid).  Cooking
oxidizes vitamin C and leads to it's destruction (that's why we say that the
best source of vitamin C is fresh fruits and vegetables).
 
The reality of the situation is that anytime food is heated, free radicals are
formed and antioxidants in the food get destroyed. 
The water-soluble antioxidants like vitamin C take the biggest hit (membrane
soluble antioxidants like vitamin E are much more stable during the cooking
process but they can get destroyed too).  All cooking oil has some vitamin E in
it but if that oil is reused, there will be little or no vitamin E left in it.
 
Dihyrolipoic acid is very unstable so all the supplements have lipoic acid.  In
the body, vitamin C is used to reduce it to dihydrolipoic acid (this is the
form that is used as an antioxidant).  Reduced glutathione can also do this
reduction.
 

[Editor's note: Gemini twin antioxidant describes the two forms of alpha lipoic acid. Having lipoic acid and dihydrolipoic acid doubles the spectrum of free radicals neutralised by it. ]

 
Spinach is the best plant source for lipoic acid but you would have to eat 50
cups of spinach to get 50 mg of lipoic aicd.  Diabetics need 400 to 800 mg per
day to have a significant impact on the nerve damage that occurs in diabetes.
 
For animal food, the best source is heart muscle but again, the amount you
would get is so low that it's not really going to help you.
 
The question that I get asked the most is that if lipoic acid is so good, why
can't we get good amounts from our food, why do we have to use a supplement?
 
The reason is that animals use glutathione as their major cytoplasmic
antioxidant (this includes animals that still synthesize large amounts of
vitamin C).  The glutathione is synthesized using cysteine, a quasi-essential
amino acid.
 
Sulfur is an extremely good antioxidant and putting the sulfur in glutathione,
lipoic acid and taurine, generates antioxidants that are extremely good at
handling the peroxynitrite free radical and the hydroxyl free radical, the two
free radicals that we think do most of the damage in animal cells.
 
Humans and cats appear to have a higher taurine requirement than most other
animals.  Cow's milk has very little taurine in it but human milk has the
highest level of taurine in it of any mammal studied to date.  Infant formulas
do not have taurine in them (if you do not give a cat taurine in it's diet, it
will die).  Cats are carnivores and they got their taurine by eating other
animals.  No plant food has taurine in it.  This tells us that glutathione can
handle the sulfur antioxidant requirement in humans (but cat's need help).  If
it couldn't, humans would have to have taurine or lipoic acid in their diet to
survive.
 

Humans will make taurine from cysteine. Humans will also make lipoic acid from alpha-linolenic acid (the essential Omega-3 fatty acid).

[ Editors note: Other references give caprylic acid aka octanoic acid as the lipid component]

The sulfur in both taurine and lipoic acid comes from methionine (it does not come from free sulfur). This very high demand for sulfur antioxidant synthesis makes methionine the essential amino acid in humans with the lowest storage pool (lowest reserve).

 
Anything that we can do to spare methionine will help us, especially if there
is a lot of oxidative damage in our body like what is happening in diabetes.
 
Lipoic acid will spare glutathione (the most effective way of getting
glutathione up in a cell is to provide extra lipoic acid).  Without help,
glutathionine levels will drop very low, very rapidly.  We have tried to use
glutathione supplements, methionine supplements, cysteine supplements and
N-acetylcysteine supplements to increase glutathione levels but nothing works
as well as lipoic acid does.
 
One other benefit of lipoic acid is that it's formed from a fatty acid so it
does have some membrane solubility.  The sulfur means that it also has some
water-solubility.  Lipoic acid is the only antioxidant that we know of that can
work both in membranes as well as the cytoplasm of a cell.
 
In studies on animals where antioxidants are being tried to extend the maximum
life span of the animal, the only class that has had a significant effect were
the sulfhydral antioxidants with 2-mercaptoethanolamine being the best (even
better than lipoic acid).  2-mercaptoethanolamine is also the only chemical
studied to date which can provide significant protection against radiation
sickness (radiation kills by hitting water molecules in cells and generating
large amounts of the hydroxyl free radical by splitting the water molecule).
 
With a good intake of sulfur, your liver will form 2-mercaptoethanolamine to
protect itself from alcohol toxicity.  But the key here is that the liver needs
free sulfur to do this and it also needs ethanol and glutamine. The health
benefit of a low amount of ethanol each day may be linked to this liver
synthesis of 2-mercaptoethanolamine. The liver also uses free sulfur to get rid
of the heavy metals like lead and mercury.
 
Liver can get free sulfur from metabolizing glutathione, lipoic acid, taurine,
methionine or cysteine but in reality it does not really like to do this unless
there is excess methionine or cysteine.  One of the health benefits of soy
protein is that it is higher in cysteine than just about any other protein
(including most animal proteins).  For the sulfur containing antioxidants, the
liver should never be purposely destroying them to get sulfur out of them but
if lead or mercury levels are high, it has no choice.  Again, lipoic acid can
be used to decrease the toxicity of heavy metals and help get them out of the
body which makes it an extremely useful supplement.
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