Effects of smoking and oral contraception on plasma beta-carotene levels in healthy women.

Oral contraceptive use and smoking have been known to affect plasma vitamin levels. Total carotenoids have been studied with spectrophotometry, a relatively insensitive technique. In this study plasma concentrations of beta-carotene and retinol were measured in coded samples by sensitive high-pressure liquid chromatography in a cross-sectional study of 149 normal healthy women attending a family planning clinic. At the time of recruitment in the morning, a general health questionnaire was administered for patient age, methods of contraception, smoking habits, and food intake at breakfast. Of the 149 enrolled volunteers, 88 were oral contraceptive users and 61 were not users. Among users, 21 smoked cigarettes, and there were 18 smokers among nonusers. Oral contraceptive users had significantly lower plasma concentrations of beta-carotene (p less than 0.001) and higher retinol levels (p less than 0.0001). Plasma beta-carotene or retinol levels did not differ among users of intrauterine contraceptive devices or barrier methods of contraception. No association was noted between the plasma levels of these two micronutrients and age greater than or less than 30 years. Cigarette smoking alone was associated with significantly reduced plasma beta-carotene levels in nonusers (p less than 0.001). Combined cigarette smoking and oral contraceptive usage were associated with low plasma beta-carotene levels; the results appear to be additive. These findings suggest a possible synergistic effect on plasma beta-carotene levels from the use of both cigarette smoking and oral contraception.