"If our findings are confirmed by larger studies, women who receive oral contraceptives may be considered for coenzyme Q10 and/or alpha-tocpherol supplementation," wrote lead author Prabhudas Palan from the Albert Einstein College of Medicine in New York.
Coenzyme Q10 and alpha-tocopherol (a form of vitamin E) are both lipid-soluble antioxidants found in cell membranes. They are capable of mopping up free radicals that can lead to oxidative stress, linked to a variety of disease including Alzheimer's, cardiovascular disease and cancer.
The new study, published in the American Journal of Obstetrics and Gynecology (Vol. 194, e35-e38), recruited 55 pre-menopausal women (average age 33) with regular menstrual cycles. 15 women were taking an oral contraceptive (OC) (norgestimate/ethinylestradiol) while the other 40 were not taking any (OC). Women taking multivitamins or Co-Q10 supplements were excluded.
Non-fasting blood samples were taken randomly during the menstrual cycle and serum levels of a variety of antioxidants measured.
Gamma-tocopherol, alpha- and beta-carotene, and lycopene levels were similar between the groups. However, serum levels of Co-Q10 were 37 per cent lower in the OC group, and alpha-tocopherol levels were 24 per cent lower.
"The results clearly show that the use of OC significantly lowered the serum levels of coenzyme Q10 and alpha-tocopherol, compared with levels in non-OC users," wrote the researchers.
There are several limitations with the study, most notably the small sample size, blood samples were non-fasting and were taken randomly during the menstrual cycle.
In answer to the last limitation, the researchers point out that lipid-soluble antioxidants are related directly to lipid stores and not affected significantly by changes in daily intakes.
"The potential value, if any, for coenzyme Q10 and alpha-tocopherol supplementation in OC users and the effect of menstrual cycle phase on oxidative stress deserve further investigation," they concluded.
A study published in 2004 in the American Journal of Clinical Nutrition (Vol. 80, pp 649-655) reported that Co-Q10 together with alpha-tocopherol could reduce levels of C-reactive protein (CRP) a pro-inflammatory protein linked to CVD.