Sugar and Cardiovascular Disease: Refining the Message on a Complex Topic

The paper by Johnson, Appel et al. [1] does an excellent job of addressing a subject that had previously been under-studied or ignored due to a lack of direct evidence documenting an adverse impact of dietary sugar on cardiovascular disease. Recent popularity of low carbohydrate diets may have helped to generate new awareness of the distinction between refined and complex carbohydrate foods. The former generally refers to sugar-dense foods whereas the latter is found in fruits, vegetables and whole grains, the very foods that are advocated to help control weight and reduce risk for cardiovascular and other chronic diseases.[2] This paper helps place into context the role of sugar in the diet and how it now appears to contribute to risk of developing cardiovascular disease through several potential pathways.

As national recommendations on reducing total and saturated fats were increasingly embraced by the food industry, use of sugar, fructose, and high fructose corn syrup were increasingly substituted instead. Potential consequences of this shift appear to be increased levels of serum triglycerides and reduced levels of high density lipoprotein (HDL) in vulnerable individuals.[3-5] Whether increased sugar intake from all sources further increases inflammatory and oxidative stress responses remains the subject of ongoing investigation, as Johnson, Appel et al. [1] point out. Perhaps the most compelling aspect of this paper is the documented and quantified population-wide increases in various forms of sugar, thereby at least partially explaining the increased energy intake and increasing rate of obesity in this country. As stated by these authors, "Increases in the intake of soft drinks, fruit drinks, desserts, sugars and jellies, candy, and ready-to-eat cereals largely account for the increased energy intake from sugars/added sugars." Soft drinks and other sugar-sweetened beverages are the primary sources of added sugars in Americans' diets, including that of children and adolescents.[6-9] Between 1970 and 2000, per person daily consumption of caloric soft drinks increased 70%, from 7.8 ounces to 13.2 ounces.[9]

Likewise, total calorie intake has increased by approximately 150-300 calories per day, with half of these calories coming from liquid sources, eg. sugar-sweetened beverages.[10-11] Because there has been no concomitant change in physical activity [11,12], the net result is the well known rise in overweight and obesity that currently plague our nation in epidemic proportions.[13]

Positive energy balance with as few as 110-165 calorie surplus daily can yield an excess of ten or more pounds over one year's time.[10,11] "Supersized" portions in the U.S. have maximized energy content of numerous foods and beverages. From 1977 to 1996, "typical" servings for soda and other sugary beverages have increased by 50 and 68 calories, respectively.[4]

Perhaps most disturbing is the impact these environmental changes have had on America's youth.[13-15] Children who consume more calories due to larger portion sizes do not eat less at other times. Sugary beverages contribute up to 10%-15% of total daily energy intake among children.[7] A meta-analysis examining the link between sweetened beverages and weight gain reported that higher intakes of soda and other sugary drinks are positively correlated with weight gain in the pediatric population.[16] Recommendations to reduce added sugars are highly relevant.[17] Whether it is purely the added calories and resulting weight gain that indirectly impact cardiovascular risk, or possible direct influences on blood pressure, blood lipids, insulin or insulin resistance, there is a need to pay attention to excessive sugar intake. Regardless of its form, e.g. fructose, sucrose or high fructose corn syrup, etc, sugar appears to be a potentially serious contributor to cardiovascular risk. In this obeseogenic era when the majority of the population is in positive energy balance, providing effective guidance on the specific impact of sweetened beverages, excessive intake of nutrient-poor discretionary calories, and the special needs of children warrants urgent attention.