Guidelines advocate changes in fatty acid consumption to promote cardiovascular health. To summarize evidence about associations between fatty acids and coronary disease. MEDLINE, Science Citation Index, and Cochrane Central Register of Controlled Trials through July 2013. Prospective, observational studies and randomized, controlled trials. Investigators extracted data about study characteristics and assessed study biases. There were 32 observational studies (512 420 participants) of fatty acids from dietary intake; 17 observational studies (25 721 participants) of fatty acid biomarkers; and 27 randomized, controlled trials (105 085 participants) of fatty acid supplementation. In observational studies, relative risks for coronary disease were 1.03 (95% CI, 0.98 to 1.07) for saturated, 1.00 (CI, 0.91 to 1.10) for monounsaturated, 0.87 (CI, 0.78 to 0.97) for long-chain ω-3 polyunsaturated, 0.98 (CI, 0.90 to 1.06) for ω-6 polyunsaturated, and 1.16 (CI, 1.06 to 1.27) for trans fatty acids when the top and bottom thirds of baseline dietary fatty acid intake were compared. Corresponding estimates for circulating fatty acids were 1.06 (CI, 0.86 to 1.30), 1.06 (CI, 0.97 to 1.17), 0.84 (CI, 0.63 to 1.11), 0.94 (CI, 0.84 to 1.06), and 1.05 (CI, 0.76 to 1.44), respectively. There was heterogeneity of the associations among individual circulating fatty acids and coronary disease. In randomized, controlled trials, relative risks for coronary disease were 0.97 (CI, 0.69 to 1.36) for α-linolenic, 0.94 (CI, 0.86 to 1.03) for long-chain ω-3 polyunsaturated, and 0.86 (CI, 0.69 to 1.07) for ω-6 polyunsaturated fatty acid supplementations. Potential biases from preferential publication and selective reporting. Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats. British Heart Foundation, Medical Research Council, Cambridge National Institute for Health Research Biomedical Research Centre, and Gates Cambridge.

Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with mortality from cardiovascular, cancer, or other conditions, under various circumstances. Design Systematic review and meta-analysis of observational studies and randomised controlled trials. Data sources Medline, Embase, Cochrane Library, and reference lists of relevant studies to August 2013; correspondance with investigators. Study selection Observational cohort studies and randomised controlled trials in adults, which reported associations between vitamin D (measured as circulating 25-hydroxyvitamin D concentration or vitamin D supplement given singly) and cause specific mortality outcomes. Data extraction Data were extracted by two independent investigators, and a consensus was reached with involvement of a third. Study specific relative risks from 73 cohort studies (849 412 participants) and 22 randomised controlled trials (vitamin D given alone versus placebo or no treatment; 30 716 participants) were meta-analysed using random effects models and were grouped by study and population characteristics. Results In the primary prevention observational studies, comparing bottom versus top thirds of baseline circulating 25-hydroxyvitamin D distribution, pooled relative risks were 1.35 (95% confidence interval 1.13 to 1.61) for death from cardiovascular disease, 1.14 (1.01 to 1.29) for death from cancer, 1.30 (1.07 to 1.59) for non-vascular, non-cancer death, and 1.35 (1.22 to 1.49) for all cause mortality. Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements_. In randomised controlled trials, relative risks for all cause mortality were 0.89 (0.80 to 0.99) for vitamin D₃ supplementation and 1.04 (0.97 to 1.11) for vitamin D₂ supplementation_. The effects observed for vitamin D₃ supplementation remained unchanged when grouped by various characteristics. However, for vitamin D₂ supplementation, increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods. Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease, cancer, and other causes. Supplementation with vitamin D₃ significantly reduces overall mortality among older adults; however, before any widespread supplementation, further investigations will be required to establish the optimal dose and duration and whether vitamin D₃ and D₂ have different effects on mortality risk.

It remains largely unclear whether consumption of total and individual polyunsaturated fatty acids (PUFAs) is associated with chronic systemic inflammation in healthy, free-living individuals. While available evidence (stemming principally from mechanistic studies) has indicated that greater intake of n-6 PUFAs may lead to increased levels of inflammation—for instance, by their acting as precursors to proinflammatory eicosanoids and increasing levels of oxidized linoleic acid metabolites—n-3 PUFAs are precursors to some antiinflammatory eicosanoids. New human data from a Dutch prospective study, the Rotterdam Study—as presented by Muka et al. (Am J Epidemiol. 2015;181(11):846–856) in this issue of the Journal—now make an important contribution to the relatively scarce literature on the association of dietary n-3 and n-6 PUFAs with serum levels of C-reactive protein (CRP), a key marker of inflammation, in a general population. The study by Muka et al. benefitted from repeated CRP measurements, comprehensive correction for potential confounding, and wide-ranging sensitivity analyses. The findings show no significant trend regarding n-3 PUFAs but indicate an important inverse association between n-6 PUFAs and chronic systemic inflammation. This study provides support for existing dietary guidelines, which encourage consumption of a combination of n-3 and n-6 PUFAs in the diet.