Saturated fatty acid intake and cardiovascular risk.

Since the 1960s, clinical and animal studies have shown that reduction of dietary saturated fatty acid (SFA) consumption is associated with reduced risk of cardiovascular disease (CVD). Thus, reduction of SFA intake is now one of the central strategies of dietary recommendations to reduce CVD worldwide. For example, the World Health Organization and the US Dietary Guidelines recommend dietary consumption of , 10% of total energy intake from SFAs, while the American Heart Association guidelines recommend even more strict dietary SFA consumption of , 7%. However, it has always been a matter of debate whether SFA consumption is truly associated with CVD risk, particularly with risk of stroke, because of insufficient evidence regarding the disorder. Recently, Siri-Tarino et al. performed a meta-analysis to summarize the evidence related to the association between dietary SFA intake and risk of coronary artery disease (CAD), stroke, and CVD (including stroke) in 21 prospective epidemiological studies, where 11 006 out of 347 747 subjects developed CAD or stroke during 5–23 years of follow-up. Because the pooled relative risk (RR) estimate comparing extreme quantiles of SFA intake for CAD, stroke, and CVD was 1.07 [95% confidence inteval (CI) 0.96–1.19; P 1⁄4 0.22], 0.81 (95% CI 0.62–1.05; P 1⁄4 0.11), and 1.00 (95% CI 0.89–1.11; P 1⁄4 0.95), respectively, they concluded that SFA intake was not significantly associated with increased risk of CAD, stroke, or CVD. However, there seems to be an insignificant but mild trend for the relationship between dietary SFA intake and stroke (RR 0.81, P 1⁄4 0.11), which may warrant further investigations. Yamagishi et al. have reported the results from the Japan Public Health Center-based prospective (JPHC) Study that examined whether dietary SFA intake is associated with risk of stroke and its subtypes as well as that of CAD amongst Japanese, whose average dietary SFA intake is lower than in Western populations. The JPHC Study comprised a total of 38 084 men and 43 847 women from two subcohorts: Cohort I, aged 45–64 in 1995, and followed-up through 2009; and Cohort II, aged 45–74 in 1998, and followed-up through 2007. The major strengths of the JPHC Study include the large sample size, detailed evaluation of endpoints, and accurate diagnosis of stroke subtypes with computed tomography (CT)/magnetic resonance imaging (MRI). Consequently, the JPHC Study examined a larger number of cardiovascular events with more detailed analysis, giving a strengthened power in statistics and more useful clinical messages as compared with previous studies. After adjustment with multiple factors, including age, sex, energy intake, cohort, cigarette smoking status, alcohol intake, body mass index, sports at leisure time, walking and standing time, perceived mental stress, energy-adjusted dietary intakes of carbohydrate, protein, cholesterol, vegetables, fruit, and calcium, the JPHC Study revealed inverse associations of dietary SFA intake with total stroke [n 1⁄4 546; adjusted hazard ratio (HR) (95% CI) for the highest vs. lowest quintiles 1⁄4 0.77 (0.65–0.93), P for trend 1⁄4 0.002], intraparenchymal haemorrhage [n 1⁄4 150; 0.61 (0.43–0.86), P for trend 1⁄4 0.005], and ischaemic stroke [n 1⁄4 319; 0.84 (0.67–1.06), P for trend 1⁄4 0.08], providing additional epidemiological evidence that dietary SFA intake is inversely associated with total stroke in a Japanese population. This inverse relationship between SFA intake and stroke observed in the JPHC Study is consistent with the previous observation obtained in the Japan Collaborative Cohort (JACC) Study for Evaluation of Cancer Risk. The JACC study comprised 58 453 Japanese men and women aged 40–79 years at baseline (1988–1990) with a 14.1-year follow-up and revealed inverse associations of SFA intake with mortality from total stroke [n 1⁄4 976; multivariable HR (95% CI) for highest compared with lowest quintiles: 0.69 (0.53–0.89), P for trend 1⁄4 0.004], intraparenchymal haemorrhage [n 1⁄4 224; 0.48 (0.27–0.85), P for trend 1⁄4 0.03], and ischaemic stroke [n 1⁄4 321; 0.58 (0.37–0.90), P for trend 1⁄4 0.01]. Thus, it may be concluded that there exists an inverse association between dietary SFA intake and both incidence and mortality from stroke at least in a Japanese population, where SFA levels are lower than in Western populations. In contrast, however, the results regarding CAD are inconsistent between the JPHC Study and the JACC Study; the JPHC Study