Abstract
Introduction: Sugar intake is increasing and has been linked to non-communicable diseases including obesity, diabetes and cardiovascular disease. Blood pressure is a known risk factor for cardiovascular disease. High dietary sugar intake is theorised to increase blood pressure by several mechanisms, including by increasing the synthesis of serum uric acid and subsequently impairing the synthesis of nitrous oxide which mediates vasodilation. The aim of this research was to investigate the effects of a higher sugar diet on measures of blood pressure compared to a lower sugar diet.
Design and Methods: A systematic review and meta-analysis of randomised control trials was conducted following the guidelines of the Cochrane Collaboration. Medline, Scopus, Embase, CINAHL and Web of Science electronic article databases were searched for human trials conducted between 1960 and April 2012, where dietary sugars intake was increased in one arm of the study in comparison to another arm of the study, and where the effect of sugar could be isolated from the effect of any other intervention. Trials of less than two weeks duration and those involving participants affected by a metabolism-altering or acute disease were excluded. Outcome measures were systolic, diastolic and mean arterial blood pressures. Eligibility was established and data extracted by two independent researchers. Review Manager 5.0 computer software was used to analyse results, assess bias and generate forest plots of effect measures. Data were pooled using inverse variance models with random effects to account for heterogeneity.
Results: From the 11824 studies identified through electronic searching, eleven met the inclusion criteria for the meta-analysis for systolic blood pressure, ten for diastolic blood pressure and none for mean arterial blood pressure. In parallel trials, a higher sugar diet was significantly associated with increased systolic blood pressure (mean effect 3.81 mmHg (95% CI: 0.27, 7.35) p = 0.04). In all trials, a higher sugar diet was significantly associated with an increase in diastolic blood pressure of 1.42 mmHg (95% CI: 0.07, 2.76) p = 0.04. Subgroup analyses showed a significantly stronger association between higher sugars intakes and both systolic and diastolic pressures in studies of greater than eight weeks duration (mean differences 6.78 mmHg, p < 0.0001 and 5.65 mmHg, p = 0.0005 respectively). There was also a significantly stronger association between higher sugars intakes and both systolic and diastolic blood pressures in trials where a higher sugars intake resulted in a higher body weight at the end of the study compared to lower sugars intake (mean differences 5.86 mmHg, p = 0.006 and 4.89 mmHg, p = 0.01, respectively). Sensitivity analysis showed that the associations remained for systolic blood pressure following exclusion of data from potentially biased trials, but were attenuated for diastolic blood pressure.
Conclusions: The findings of this research suggest that there is a relationship between dietary sugar intake and systolic and diastolic blood pressure; especially in trials of longer duration and in trials in which there was increased weight in the higher sugars group compared with the lower sugars group after intervention. The findings of this meta-analysis provide evidence for the development of dietary recommendations regarding dietary sugar intakes for the prevention of non-communicable diseases.