Alpha-lipoic acid (ALA) is a sulfur-containing
fatty acid that performs vitamin-like roles in the body. Also known as "lipoic
acid" or "thioctic acid," ALA functions, in a similar way to B complex
vitamins, as a co-enzyme in the metabolism of carbohydrates that produces
energy inside cells for the body’s metabolic needs. ALA is required for
synthesis of "acetyl CoA," a key metabolite in the cellular process that
turns glucose (blood sugar) into energy. Because the body produces ALA on
its own, it is not classified as a true vitamin. As with other so-called
"non-essential" nutrients, however, internal ALA production may not always
be optimal. Alpha-lipoic acid functions as both a water-soluble and
fat-soluble antioxidant. (Antioxidants neutralize free-radicals, normal
by-products of metabolism that, while necessary at normal levels, may damage
tissues over time if not properly kept in check by antioxidants.) ALA’s
ability to act upon free radicals in both a watery and fatty environment
makes it a highly versatile antioxidant. In the body, alpha-lipoic acid can
be converted (reduced) to DHLA, or dihydrolipoic acid. Together, these two
forms of ALA make up a "redox couple," which means that each form can
chemically change into the other and back again. DHLA also functions as an
antioxidant.
How “about R-Lipoic” Acid ?
Alpha Lipoic Acid occurs in two forms, designated "R" and "S". Studies
suggest that R-alpha lipoic acid, the natural form, is more biologically
active than the S form. Like ALA, RLA recycles antioxidant nutrients, such
as vitamin C and E, and helps maintain healthy blood sugar levels when used
as part of the diet.
Supports the Body’s Defense Against
Free Radicals*
Recycles Antioxidant Nutrients such as Vitamin C and Vitamin E*
Helps Maintain a Healthy Blood Sugar Level when used as part of the diet*
Alpha-lipoic Acid––the "Ideal
Antioxidant"
The antioxidant potential of a
substance is based on a number of criteria, including:
1) Ability to quench specific free-radicals.
2) Ability to bind or "chelate" metal ions that can generate free radicals.
3) Supports function of other antioxidants.
4) Absorption/bioavailability.
5) Concentration in tissues, cells and extra cellular fluids.
6) Ability to function as an antioxidant in fatty and watery environments.
The "ideal antioxidant" would meet all
the above criteria. Very few antioxidants do, yet a particular antioxidant
with but a few of the characteristics is still valuable and effective.
Vitamin E, for example, is one of the most important dietary antioxidants,
yet it only works in fatty environments such as cell membranes.
As a team, ALA and DHLA come close to
the ideal, for the following reasons:1,2,3
1) ALA is easily absorbed when consumed orally.
2) ALA is readily converted to DHLA in various tissues.
3) As a pair, ALA and DHLA neutralize superoxide, hydroxyl, peroxyl, and
hypochlorus radicals.
4) ALA and DHLA form stable complexes with metal ions such as iron,
manganese, copper and zinc ions.
5) ALA and DHLA scavenge free radicals in fatty environments and watery
environments.
6) DHLA recycles other important antioxidants.
DHLA-regenerates vitamin C, vitamin E
and glutathione
Within the cell, antioxidants work as
a team to keep free radicals from damaging cell structures. In order to
neutralize a free radical, an antioxidant such as vitamin C must give up an
electron, which mean it becomes oxidized. Before it can function as an
antioxidant once again, it must be regenerated back to its "reduced" form,
by gaining an electron to replace the donated electron. For this, it needs
the help of other antioxidants. Vitamin C, vitamin E and glutathione are key
antioxidants that can be generated by cycling between their oxidized and
reduce forms. This is necessary to maintain the balance between oxidation
and its reverse––the neutralization of free radicals by antioxidants.
DHLA is an essential component in the
interaction between these antioxidants.4 Studies show
that addition of alpha-lipoic acid to liver tissues results in increased
vitamin C levels. It has been found that DHLA is responsible for
regenerating vitamin C, which in turn regenerates vitamin E.3 DHLA also
converts glutathione from its oxidized form back into its free radical
scavenging reduced form.3,5 The ALA/DHLA pair is thus
vital for prevention of "oxidative stress," which occurs which the balance
is tipped in favor of oxidation in cells.4 DHLA helps
preserve antioxidants in both the watery cell interior and the fatty
structure of cell membranes.6 Evidence from animal
studies suggests that DHLA protects the brain against free radical damage.7
Alpha-lipoic Acid and Blood Sugar
Alpha-lipoic acid is a key factor in
the cellular process that metabolizes glucose to produce energy for cellular
functions. The importance of ALA’s role in blood sugar metabolism is
evidenced in studies on ALA and type-2 diabetes. In a small pilot study, 13
people with type-2 diabetes showed improved utilization of glucose in muscle
tissue in response to intravenous administration of ALA.8
In a four week controlled multicenter trial, 74 people with type-2
diabetes took ALA in oral doses of 600, 1200 or 1800 mg per day. After 4
weeks, the normal lowering of blood sugar levels in response to insulin
improved.9 In vitro studies have shown that ALA has a
positive effect on insulin-stimulated uptake of glucose by muscle cells.10
1. Packer, L.. Witt, E., Tritschler, H. Alpha-lipoic acid as a
biological antioxidant. Free Radical Biology and Medicine 1995;19(2):227-50.
2. Suzuki, Y., et al. Thioctic acid and dihydrolipoic acid are novel
antioxidants which interact with reactive oxygen species. Free Rad. Res.
Comms. 15(5):255-63.
3. Biewenga, G., Haenen, G., Bast, A. The pharmacology of lipoic acid. Gen.
Pharmac. 29(3):315-31.
4. Serbinova, E. Maitra, I., Packer, L. The synergy between vitamin E and
alpha-lipoic acid--–possible relationship against oxidative stress in vivo.
Life Chemistry Reports 1994;12:17-21.
5. Bast, A. Haenen, G. Interplay between lipoic acid and glutathione in the
protection against microsomal lipid peroxidation. Biochimica et Biophysica
Acta 1988; 963:558-561.
6. Kagan, V. et al. Dihydrolipoic acid––a universal antioxidant both in the
membrane and in the aqueous phase. Reduction of peroxyl, ascorbyl and
chromanoxyl radicals. Biochem Pharmacol 1992;44(8):1637.
7. Prehn, J. et al. Dihydrolipoate reduces neuronal injury after cerebral
ischemia. J Cereb Blood Flow Metab 1992;12(1):78-87.
8. Jacob, S. et al. Enhancement of glucose disposal in patients with type-2
diabetes by alpha-lipoic acid. Arzneimittelforschung 1995;45(8):872-4.
9. Jacob, S et al. Oral administration of RAC-alpha-lipoic acid modulates
insulin sensitivity in patients with type-2 diabetes mellitus: a
placebo-controlled pilot trial. Free Radical Biology & Medicine
1999;27(3/4):309-14.
10. Estrada, D. et al. Stimulation of glucose uptake by the natural coenzyme
alpha-lipoic acid/thioctic acid: participation of elements of the insulin
signaling pathway. Diabetes 1996;45(12):1798-804.
*Above statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.
