It’s been suggested that a high-intake of dietary sugars is a cause of obesity, several chronic diseases, and a range of cardiometabolic risk factors, two such risk factors including high blood pressure and poor lipid profile. To date, we have a good amount of experimental data looking at the effect of high sugar intake on blood pressure and lipids, but there hasn’t been a recent systematic review looking at what all this research says combined. Thus, Dr. Lisa A Te Morenga and colleagues recently performed a systematic review and meta-analysis to examine the effect of high sugar intake on cardiometabolic risk factors.(Te Morenga LA et al, 2014) They wanted to know, compared to a control diet, does high sugar intake affect lipids and blood pressure? They published their results in the most recent volume of the American Journal of Clinical Nutrition.
Two independent investigators searched electronic databases for randomized trials related to effects of dietary sugars on blood lipids and blood pressure in humans according to Cochrane Collaboration guidelines. They searched OVID Medline, Embase, Scopus, Web of Science, and the Cumulative Index to Nursing and Allied Health Literature for English-language trials published between 1960 and August 2013. The investigators searched for studies that compared dietary interventions that altered intake of sugar in one group compared with another group of the study. Sugars studied included both (1) sucrose and (2) free sugars, free sugars including all monosaccharaides and disaccharides added to foods by the manufacturer, cook, or consumer, plus sugars naturally present in honey, syrups, and fruit juices. Comparison groups could include a control diet or an intervention in which sugar intake was quantifiably different from sugar intake of the experimental group. To be included in this systematic review, studies were required to report differences between treatment groups in intake of free sugars or intake of a component of total sugars and at least one measure of blood pressure:
- systolic blood pressure (SBP), or
- diastolic blood pressure (DBP), or
- average blood pressure
Or one measure of blood lipids:
- triglycerides, or
- total, LDL, or HDL cholesterol
Literature search results
The researchers found 40 randomized trials that met inclusion criteria involving a total of 1,699 people. Of these, 39 trials reported lipid outcomes and 12 trials reported blood pressure outcomes.
For effect of sugars on blood pressure, the researchers found:
- Overall, there was no significant effect of higher sugar intakes on SBP.
- A higher sugar intake was associated with significantly greater DBP of 1.4 mm Hg (95% CI: 0.3, 2.5 mm Hg; P = 0.02) overall.
In sub analysis, length of the trial affected results. For example, trials less than 8 weeks showed no effect of higher sugar intake on SBP, whereas trials over 8 weeks did show sugars to increase SBP. Also in further analysis, the exclusion of 5 studies that received funding from sugar industries strengthened associations between high intake of sugars and SBP and DBP. For effect of sugars on blood lipids, the researchers found:
- A higher sugar intake was associated with a 0.11 mmol/L (95% CI: 0.07, 0.15 mmol/L; P = 0.0001) increase for triglycerides.
- A higher sugar intake was associated with a 0.16 mmol/L (95% CI: 0.09, 0.24 mmol/L; P = 0.0001) increase for total cholesterol.
- A higher sugar intake was associated with a 0.12 mmol/L (95% CI: 0.05, 0.19 mmol/L; P = 0.001) increase for LDL cholesterol.
- A higher sugar intake was associated with a 0.02 mmol/L (95% CI: 0.00, 0.03 mmol/L; P = 0.02) increase for HDL cholesterol.
The authors conclude:
This systematic review and meta-analyses of randomized controlled trials provides evidence that higher compared with lower intakes of sugars are associated with increased concentrations of triglycerides, total and LDL cholesterol, and blood pressure, although for SBP, this effect was only significant in studies of a longer duration.
Past research has shown a strong association between obesity and high blood pressure and poor lipid profiles. Because of this association, it might be assumed that increase in sugar intake leads to obesity, thus explaining the results in this systematic review. However, in a subgroup analysis, researchers found that studies that had no weight change between interventions or worked to control caloric intake had the most consistent associations between higher intakes of sugars and higher concentrations of triglycerides and total cholesterol. This suggests that sugar may have an effect on blood pressure and lipids independent of change in weight. Although the effects of sugars on lipids and blood pressure are relatively modest in this systematic review and meta-analysis, a population-wide reduction in sugar intake could have significant public health relevance. In a meta-analysis of prospective studies (Hokanson and Austin, 1996), the risk of cardiovascular disease was increased by 6% in men and 12% in women for each 0.2-mmol/L increase in triglyceride concentrations. As a population, decreasing our sugar intake could be an effective measure in reducing our risk of cardiovascular disease.
Te Morenga LA, Howatson AJ, Jones RM, Mann J. Dietary sugars and cardiometabolic risk: systematic review and meta-analyses of randomized controlled trials of the effects on blood pressure and lipids. Am J Clin Nutr 2014;100(1):65-79. [PubMed abstract]
Hokanson JE, Austin MA. Plasma triglyceride level is a risk factor for cardiovascular disease independent of high-density lipoprotein cholesterol level: a meta-analysis of population-based prospective studies. J Cardiovasc Risk 1996;3:213–9. [PubMed abstract]