Objective: To study seasonal variation in intake and plasma concentrations of fatty acids (FAs) in Japanese female dietitians.
Subjects and methods: We assessed consumption of FAs based on four season 7 consecutive day weighed diet records from 71 Japanese female dietitians in 1996-1997. Using overnight fasting venous blood, plasma concentrations of FAs were analyzed by gas chromatography. Seasonal variation in consumption and plasma concentrations was examined by ANOVA for repeated values, followed by Tukey's multiple t-test. We calculated Spearman's partial rank correlation coefficients (CCs) between intake and plasma concentrations of FAs. Furthermore, we computed inter-seasonal Spearman's partial rank CCs for consumption and plasma concentrations of FAs.
Results: Statistically significant seasonal differences were observed in consumption for most FAs, except for myristic acid, monounsaturated FAs, oleic acid, n-6 polyunsaturated FAs (PUFAs), linoleic acid, gamma-linolenic acid, alpha-linolenic acid, PUFAs/saturated FAs, and n-6 PUFAs/n-3 PUFAs, and for most plasma concentrations, except for stearic acid, gamma-linolenic acid, n-3 PUFAs, alpha-linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and n-3 highly unsaturated FAs (HUFAs). However, statistically significant Spearman's partial rank CCs between intake and plasma concentrations were observed for EPA, DHA, n-3 HUFAs, n-6 PUFAs/n-3 PUFAs and n-6 PUFAs/n-3 HUFAs for almost all seasons.
Conclusions: Seasonal variation exists in consumption and plasma concentrations of FAs, so that this should be taken into account in epidemiological analyses, including case-control and cohort studies.