Sugar has a direct effect on risk factors for heart disease, and is likely to impact on blood pressure, independent of weight gain, according to new analysis of 39 clinical trials.
An international review and meta-analysis of all English language studies comparing the effects of higher versus lower added sugar consumption on blood pressure and lipids has found that dietary sugars have significant influence on blood pressure and serum lipids that is independent of effects of sugars on body weight.
Led by Dr Lisa Te Morenga and Professor Jim Mann at New Zealand's University of Otago, the team analysed data from clinical trials that compared sugar and non-sugar carbohydrate consumption for their effects on blood lipids and blood pressure after noting that while sugars have been suggested as a cause of obesity, chronic diseases, and a range of cardiometabolic risk factors, “there is no convincing evidence of a causal relation between sugars and risk factors other than body weight.”
"Our analysis confirmed that sugars contribute to cardiovascular risk, independent of the effect of sugars on body weight," said Te Morenga.
"Although the effects of sugars on blood pressure and lipids are relatively modest, our findings support public health recommendations to reduce added sugar in our diets as one of the measures which might be expected to reduce the global burden of cardiovascular diseases."
"Our work provides further evidence to support these recommendations which have been disputed by the food industry," she commented - adding that while there is still a need for further longer term well-powered studies looking at the effects of sugars on various health outcomes, it is becoming increasingly difficult for the food industry to continue to claim that liberal sugar consumption is risk free.
Commenting on the research, Dr Glenys Jones nutritionist and nutrition communications manager at Sugar Nutrition UK noted that the review looks at an important area of health and nutrition - adding that the mixed results, particularly in regards to cholesterol, "highlight the complex nature of interpreting nutrition research."
"As the authors note, there are a number of inherent limitations to the studies reviewed. More research is needed of longer duration and larger sample sizes, using reliable dietary intake data," she said.
From a total of 11,517 trials initially identified, Te Morenga and her colleagues included 37 trials reporting effects on lipids and 12 reporting effects on blood pressure – with the findings from individual trials then pooled to determine the overall effects from all the studies.
"Our latest study did find significant effects of sugars on lipids and blood pressure among these types of energy-controlled studies. This suggests that our bodies handle sugar differently to other types of carbohydrates,” said the lead researcher.
"We were also relatively surprised that there was a positive association between sugars and cardiometabolic risk factors given that a large body of the research which met our inclusion criteria is funded by the food industry,” she added. “This is because such trials are less likely to find a significant association between sugars and health outcomes.”
"In subgroup analyses we showed that by excluding the trials funded by the food/sugar industry, we found larger effects of sugar on lipids and blood pressure,” said Te Morenga.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.113.081521
“Dietary sugars and cardiometabolic risk: systematic review and meta-analyses of randomized controlled trials of the effects on blood pressure and lipids”
Authors: Lisa A Te Morenga, Alex J Howatson, Rhiannon M Jones, Jim Mann