Too many antioxidants become pro-oxidants?

[chillin408]

Is it true? or is just because when there all used up they are no longer antioxidants and the more taken invariably leads to this?

I was gonna start taking Quercetin, Lypocene, and a high polyphenolic green tea extract. Could this do more harm than good? I already take 2 multivitamins a day and extra vitamin E.

This is kinda a stupid a question..I have a feeling I'm gonna get flamed.

 

[anthrax]

that's not a stupid question

I have also had this ? and I have found that extra amounts of antioxidants might be turning into pro-oxidants.

Here is an extract of Mercola's article about it:

(BTW it is lycopene not Lypocene)

Extra amounts of antioxidants might be turning into pro-oxidants (which promote the removal of electrons from atoms), fueling free-radical production and its damage.

Supplements might do nothing at all because they can't get to where they are needed.

Or antioxidants might not be the magic beneficial chemical in the food we eat after all.

Can antioxidants turn on you? Several studies have shown that people who did not get the daily recommended allowance of vitamin C had an increase in free-radical damage to their DNA. But, paradoxically, people who took megadoses of C also had an increase in DNA damage. The second scenario might happen, Halliwell says, because vitamin C can worsen cell damage once it has already started.

Within a cell, certain metal compounds are released as a result of free-radical damage. These metals themselves can act as a catalyst for further free-radical damage when they are in a "reduced" state, with a missing oxygen or extra hydrogen atom. Antioxidants place metals in this reduced state. Thus, in this environment, antioxidants become pro-oxidants, Halliwell says.

This was demonstrated in laboratory animals exposed to the pesticide paraquat, a known carcinogen. Animals that received vitamin C before exposure were largely protected from cancer. Animals that received vitamin C after exposure didn't fare so well: The antioxidant aggravated the damage caused by the herbicide and led to more cancers.

The American Cancer Society (ACS) advises cancer patients not to prescribe themselves antioxidants because of this potential effect, although it has never been demonstrated convincingly in human studies.

 

[anthrax]

another one, a bit more technical:

Free Radic Biol Med 1999 Dec;27(11-12):1313-23 Related Articles, Books, LinkOut

Anti- and pro-oxidative effects of flavonoids on metal-induced lipid hydroperoxide-dependent lipid peroxidation in cultured hepatocytes loaded with alpha-linolenic acid.

Sugihara N, Arakawa T, Ohnishi M, Furuno K Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Hiroshima, Japan.

Lipid hydroperoxide (LOOH)-dependent lipid peroxidation was induced in alpha-linolenic acid (LNA)-loaded hepatocytes by adding Fe, Cu, V, or Cd ions at concentrations from 20 to 500 microM. The effects of structurally related flavonoids at concentrations from 10 to 500 microM on the lipid peroxidation were examined.
The results with regard to each flavonoid subclass are as follows:
Flavonols such as myricetin, quercetin, fisetin, and kaempferol, but not morin, showed dose-dependent antioxidative activity against metal-induced lipid peroxidation at all metal concentrations. Myricetin, quercetin, and fisetin were the most effective antioxidants, although their efficacies depended on the metal ion. Kaempferol and morin had antioxidative activity equal to the other flavonols in the presence of Cu ions, but were much less effective for the other three metal ions.
Flavones, luteolin, apigenin, and chrysin were antioxidative at low Fe concentrations, but were pro-oxidative at high Fe concentrations. Luteolin exhibited antioxidative activity similar to that of catechol-containing flavonols in the presence of the other three metal ions. Apigenin and chrysin also acted as pro-oxidants with V or with all metal ions, respectively.
Taxifolin, a flavanone, also showed both anti- and prooxidative activity, depending on Fe concentrations, but with other metal showed only antioxidative activity ions.
Epigallocatechin, a flavanol, was antioxidative with all metal ions, and its activity was similar to that of catechol-containing flavonols. The various effects of flavonoids on metal-induced lipid peroxidation in LNA-loaded hepatocytes is discussed with regard to the change in redox potential of flavonoid-metal complexes.

 

[dnoel]

Is it true? or is just because when there all used up they are no longer antioxidants and the more taken invariably leads to this?

I was gonna start taking Quercetin, Lypocene, and a high polyphenolic green tea extract. Could this do more harm than good? I already take 2 multivitamins a day and extra vitamin E.

This is kinda a stupid a question..I have a feeling I'm gonna get flamed.

good question bro... --no one's going to flame you for asking intelligent questions