CONSEQUENCES OF IRON OVERLOAD

[Ref 39]

Iron free radicals and diseases (human)

Iron is supposed to play a key role, especially by catalyzing the formation of OH^. radicals* in some
pathologic conditions:

1 Coronary heart disease
2 Ischaemia reperfusion damage
3 Rheumatoid arthritis
4 Certain types of cancer

...where iron possibly may stimulate lipid peroxidation and destruction of proteins and DNA.

Normal conditions

During normal (non-pathologic) conditions the "oxidative stress" is supposed to be limited. This is due to natural mechanisms of protection which remove free radicals.

INTRACELLULAR ANTIOXIDANTS, e.g.:

• Superoxide dismutase
• Glutathione peroxidase
• Catalase
• Vitamin E
• Vitamin C

EXTRACELLULAR ANTIOXIDANTS, e.g.:

• Vitamin E
• Vitamin C
• Ceruloplasmin (copper ions)
• Albumin (copper ions)
• Transferrin (iron ions)
• Haemopexin (haem)
• Haptoglobin (haem proteins)

"EVERYTHING IN MODERATION"

Most of the ferric complexes react more slowly (if at all) with H₂O₂ than the ferrous complexes.

Reducing substances stimulate the Fenton reaction.
This may happen with vitamin C (ascorbic acid):

• Fe(III) + ascorbate --> Fe(II) + semidehydroascorbate,
  
  Fe(II) joins the Fenton reaction.

Mixtures of iron salts, ascorbic acid and H₂O₂ may thus be good
sources for OH^. radicals.

In other words, vitamin C in reasonable amounts acts as an antioxidant; in megadoses (> 500 mg/d) vitamin C may be damaging by acting as a prooxidant, especially in individuals with iron overload.

[Ref 40]