Oxidation of plasma proteins is not increased after supplementation with eicosapentaenoic and docosahexaenoic acids.
BACKGROUND
It is generally thought that as the intake of dietary polyunsaturated fatty acids increases, so should that of alpha-tocopherol, to protect the polyunsaturated fatty acids from increased in vivo peroxidation. However, there are little quantitative data about the concentration of alpha-tocopherol that is necessary when eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are consumed.


OBJECTIVE
The purpose of this study was to measure changes produced in 2 indexes of lipid oxidation after supplementation with EPA and DHA from fish oil and 3 doses of RRR-alpha-tocopheryl acetate in postmenopausal women.


METHODS
Daily supplements of fish oil providing 2.5 g EPA and 1.8 g DHA and 0, 100, 200, or 400 mg alpha-tocopheryl acetate were given to 46 postmenopausal women in a 4-treatment, 4-period crossover design.


RESULTS
The supplements increased plasma concentrations of EPA, DHA, and alpha-tocopherol. The fish-oil supplement increased the plasma concentration of thiobarbituric acid-reactive substances (TBARS) (P: = 0.0001) but not that of oxidatively modified protein, as indicated by the carbonyl content. The alpha-tocopheryl acetate and fish-oil supplements had no significant effect on plasma concentrations of TBARS or oxidized protein.


CONCLUSIONS
Although these data show a small but statistically significant increase in oxidative stress on the basis of plasma TBARS concentrations after the consumption of EPA and DHA, the clinical relevance of this change is questionable. In addition, as supplements of alpha-tocopheryl acetate were added to the diet, neither the plasma TBARS concentration nor the protein oxidation changed. Consequently, the results of this study indicate that there is no basis for vitamin E supplementation after consumption of EPA and DHA.
Wander
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RC
Department of Nutrition and Food Management, Oregon State University, Corvallis, USA. rcwander@uncg.edu
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SH
D000368:Aged; D000975:Antioxidants / Q000494:pharmacology; D001798:Blood Proteins / Q000378:metabolism*; D018592:Cross-Over Studies; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004311:Double-Blind Method; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010084:Oxidation-Reduction / Q000187:drug effects; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D024505:Tocopherols; D014810:Vitamin E / Q000031:analogs & derivatives / Q000494:pharmacology; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D000975:Antioxidants; D001798:Blood Proteins; D017392:Thiobarbituric Acid Reactive Substances; D014810:Vitamin E; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D024502:alpha-Tocopherol; D024505:Tocopherols