| Summary: | The effects of cigarette smoking on n-3 essential FA metabolism were studied in male and female subjects by fitting the concentration-time curves of the d5-labeled plasma fatty acids (FAs) originating from a dose of d5-18:3n-3 to a compartmental model of n-3 FA metabolism. For 3 weeks, female (smokers, n = 5; nonsmokers, n = 5) and male (smokers, n = 5; nonsmokers, n = 5) subjects subsisted on a beef-based diet. Beginning in the third week, subjects received a dose of d5-18:3n-3 ethyl ester (1 g). Plasma FAs were analyzed using gas chromatography (GC) and GC-mass spectrometry, and the kinetic rate parameters were determined from the concentration-time curves for d5-18:3n-3, d5-20:5n-3, d5-22:5n-3, and d5-22:6n-3. Women smokers had a 2-fold greater percent of dose in plasma (5.8% vs. 2.9%; P < 0.01) and a higher fractional rate constant coefficient for formation of d5-22:6n-3 from d5-22:5n-3 (0.03 h−1 vs. 0.01 h−1; P < 0.01), compared with nonsmokers. Male smokers had elevated total plasma n-3 FAs, more-rapid turnover of 18:3n-3 (13.3 mg/day−1 vs. 4.3 mg/day−1; P < 0.001), a disappearance rate of d5-20:5n-3 that was both delayed and slower (0.001 h−1 vs. 0.012 h−1; P < 0.05), and a percentage of d5-20:5n-3 directed into formation of d5-22:5n-3 (99% vs. 61%; P < 0.03) that was greater compared with nonsmokers. Smoking increased the bioavailability of n-3 FAs from plasma, accelerated the fractional synthetic rates, and heightened the percent formation of some long-chain n-3 PUFAs in men and women.
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