Researchers from New
Zealand's University of Otago have uncovered evidence that sugar has a direct
effect on risk factors for heart disease, and is likely to impact on blood
pressure, independent of weight gain.
Research Fellow with
Otago's Department of Human Nutrition Dr Lisa Te Morenga, Professor Jim Mann
and colleagues have conducted a review and meta-analysis of all international
studies that compared the effects of higher versus lower added sugar
consumption on blood pressure and lipids (blood fats or cholesterol) – both of
which are important cardiovascular risk-factors.
They located dietary
intervention trials published in English-speaking journals between 1965 and
2013, comparing diets where the only intended differences were the amount of
sugars and non-sugar carbohydrates consumed by the participants, and which
measured the effects of these diets on lipids and blood pressure. They found 37
trials reporting effects on lipids and 12 reporting effects on blood pressure.
The findings from the individual trials were then pooled to determine the
overall effects from all the studies.
"Our analysis
confirmed that sugars contribute to cardiovascular risk, independent of the
effect of sugars on body weight," says Dr 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."
Dr Te Morenga says
previous research showed that there did not appear to be any special metabolic
effect of sugars making people more likely to gain weight on high-sugar diets
compared with low sugar diets when the total amount of carbohydrates and energy
remains the same.
"However 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."
"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. 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."
She adds that the
release of their findings online in the American Journal of Clinical
Nutrition is very timely as
national and international organisations are considering recommendations on
safe dietary sugar intakes.
"Our work provides
further evidence to support these recommendations which have been disputed by
the food industry," she says.
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.
Dr Te Morenga says that
anti-sugar researchers have claimed that eating too much sugar causes numerous
harms, including cardiovascular risk.
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