How effective are current dietary guidelines for cardiovascular disease prevention in healthy middle-aged and older men and women? A randomized controlled trial23
Background: Controversy surrounds the effectiveness of dietary guidelines for cardiovascular disease (CVD) prevention in healthy middle-aged and older men and women.
Objective: The objective was to compare effects on vascular and lipid CVD risk factors of following the United Kingdom dietary guidelines with a traditional British diet (control).
Design: With the use of a parallel-designed randomized controlled trial in 165 healthy nonsmoking men and women (aged 40–70 y), we measured ambulatory blood pressure (BP) on 5 occasions, vascular function, and CVD risk factors at baseline and during 12 wk after random assignment to treatment. The primary outcomes were differences between treatments in daytime ambulatory systolic BP, flow-mediated dilation, and total cholesterol/HDL cholesterol. Secondary outcomes were differences between treatment in carotid-to-femoral pulse wave velocity, high-sensitivity C-reactive protein, and a measure of insulin sensitivity (Revised Quantitative Insulin Sensitivity Check Index).
Results: Data were available on 162 participants, and adherence to the dietary advice was confirmed from dietary records and biomarkers of compliance. In the dietary guidelines group (n = 80) compared with control (n = 82), daytime systolic BP was 4.2 mm Hg (95% CI: 1.7, 6.6 mm Hg; P < 0.001) lower, the treatment effect on flow-mediated dilation [−0.62% (95% CI: −1.48%, 0.24%)] was not significant, the total cholesterol:HDL cholesterol ratio was 0.13 (95% CI: 0, 0.26; P = 0.044) lower, pulse wave velocity was 0.29 m/s (95% CI: 0.07, 0.52 m/s; P = 0.011) lower, high-sensitivity C-reactive protein was 36% (95% CI: 7%, 48%; P = 0.017) lower, the treatment effect on the Revised Quantitative Insulin Sensitivity Check Index [2% (95% CI: −2%, 5%)] was not significant, and body weight was 1.9 kg (95% CI: 1.3, 2.5 kg; P < 0.001) lower. Causal mediated effects analysis based on urinary sodium excretion indicated that sodium reduction explained 2.4 mm Hg (95% CI: 1.0, 3.9 mm Hg) of the fall in blood pressure.
Conclusion: Selecting a diet consistent with current dietary guidelines lowers BP and lipids, which would be expected to reduce the risk of CVD by one-third in healthy middle-aged and older men and women. This study is registered at www.isrctn.com as 92382106.
Supported by funding from the UK Food Standards Agency and Department of Health and by the National Institute for Health Research (NIHR) Clinical Research Facility at Guy’s and St Thomas’ NHS Foundation Trust and NIHR Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London. Archer Daniel Mills PLC, Veetee Rice, Heinz PLC, Almond Board of California, and the Southern African Macadamia Growers Association supplied some foods for the study. Donor companies were not involved in the trial design, data collection, data analysis, or reporting of the results.