Numerous guidelines and health agencies provide “acceptable” upper intakes of added sugars, but many of these limits allow an intake of added sugars that have been found to cause insulin resistance, prediabetes, diabetes, and obesity. I and two colleagues published this finding in a recent review article in the Mayo Clinic Proceedings.
While some guidelines (such as the American Heart Association's) recommend no more than 6 and 9 teaspoonfuls of added sugars daily for females and males, respectively, others (such as the Institute of Medicine's) allow for up to 25% of total calories per day to be consumed as added sugars. Additionally, depending on someone’s total caloric intake, the 2010 Dietary Guidelines for Americans may allow up to 19% of total caloric intake coming from added sugars. Fortunately, the 2015 Dietary Guidelines Advisory Committee has recommended that added sugars make up no more than 10% of total caloric intake, which hopefully will translate into the new 2015 Dietary Guidelines for Americans.
The prevailing thinking about obesity is that a a calorie is a calorie and that if we maintain a negative caloric balance we will maintain an ideal weight. However, added sugars are more detrimental at promoting insulin resistance, diabetes, and fat storage even when compared to other forms of carbohydrate (such as glucose and starch). Thus, a calorie's worth of fructose (from sugar or high fructose corn syrup) will lead to greater metabolic harm compared to a calorie's worth of glucose (i.e., a calorie is not a calorie).
Importantly though, most dietary sugar does not come from the sugar bowl. Instead, it comes from processed foods. Reducing consumption of added sugars by limiting the intake of highly processed foods would be a decided step in the right direction. Future dietary guidelines should consider lowering their upper level of intake of added sugars to that recommended by the World Health Organization (less than 5% for ideal health) to reduce the risk of diabetes and obesity.
James DiNicolantonio is a Cardiovascular Research Scientist at the Saint Luke’s Mid America Heart Institute. His research focuses on cardiovascular health and disease—specifically, diabetes, obesity, hypertension, lipids, antithrombotics, anticoagulants, as well as nutrition and nutritional supplements. He is the author or co-author of over 150 medical publications, encompassing opinion pieces, review articles, and systematic reviews and meta-analyses. He also serves as the Associate Editor of British Medical Journal’s (BMJ) Open Heart, which is published in partnership with the British Cardiovascular Society. His publications may be accessed here, or follow James on Twitter.