By Sheela Sinharoy, Student Blogger
Do you consider sugar to be controversial? From reading the mainstream media, where it is not uncommon to see “sugar” and “toxic” in the same sentence, one might assume that any debates about sugar have been resolved. However, Friday’s session on sugars and health made it clear that questions remain about sugar’s role in body weight, cardiovascular disease, insulin resistance, and dental caries.
In many people’s mind, a clear relationship exists between sugar and body weight. However, as Dr. John Sievenpiper explained, a 2013 systematic review and meta-analyses of dietary sugars and body weight (http://www.bmj.com/content/346/bmj.e7492) found no relationship between sugar and weight in isoenergetic comparisons (i.e., in trials where researchers substituted sugar with other carbohydrates, but held total calories equal). The study did find that an increased sugar intake was associated with increased weight, but Sievenpiper argued that this was simply due to increased calories, not to any unique properties of sugar. As he stated, when addressing weight gain, it is important to focus on overconsumption of all caloric food, including those high in added sugars.
Focusing next on cardiovascular disease, Dr. James Rippe shared evidence from a series of trials investigating the relationship of sugars with LDL, HDL, total cholesterol, triglycerides, blood pressure, total body fat, and abdominal fat. The trials found no relationship between sugars and any of the outcomes except for HDL and triglycerides. For these latter two outcomes, Dr. Rippe, like Dr. Sievenpiper, argued that these findings were due more to the excess calories than to any unique contribution of sugars.
The story with sugar and insulin resistance was, again, similar. Dr. Ian Macdonald explained that in animal models, evidence exists of large doses of fructose and sucrose leading to insulin resistance. However, this does not necessarily translate to human nutrition, and randomized controlled trials in humans have been inconclusive. Some studies have shown an effect of high doses of fructose on insulin resistance and liver fat, while others show no relationship.
The most conclusive evidence of an effect of sugar exists in relation to dental caries, which Dr. Paula Moynihan pointed out is the most prevalent chronic disease worldwide. As part of the World Health Organization (WHO) guideline development process, Dr. Moynihan led a systematic review on the relationship between sugar intake and dental caries. Based on the results, WHO has issued strong recommendations for reduced intake of free sugars throughout the life course and for intake of free sugars to be no more than 10% of total energy.
Throughout the conference, a number of speakers have referenced Americans’ changing dietary patterns and increases in consumption. This session was no different, as the overall message seemed to be that sugars alone cannot explain increases in overweight and obesity, cardiovascular disease, insulin resistance and diabetes. Rather, sugars are part of a larger constellation of factors that include dietary patterns and lifestyle patterns as a whole, which should be researched and addressed together in order to reduce the prevalence of chronic disease.