Fructose‐Containing Sugars Do Not Raise Blood Pressure or Uric Acid at Normal Levels of Human Consumption

The article by Angelopoulos and colleagues published in this month’s issue of The Journal of Clinical Hypertension brings to the forefront the continued debate regarding the role of dietary sweeteners in health and disease, specifically that of fructose and its relationship with hypertension. The study consisted of 268 weight-stable, normotensive individuals (blood pressure [BP] <140/90 mm Hg) whose BP and uric acid measurements were followed before and after 10 weeks of consuming one of four sugar-sweetened milk beverages, each containing a single sweetener (high-fructose corn syrup, fructose, glucose, and sucrose) at a particular percentage of calories for weight maintenance. At the end of the 10 weeks there was a significant reduction in both systolic and diastolic BP with no change in uric acid levels despite an average 2-pound weight gain. However, the BP was not measured using 24-hour ambulatory BP monitoring. Energy intake increased by 12.1%, with increased protein intake but decreased fat intake. Dietary sweeteners are logical research targets as a cause of chronic disease considering that rates of hypertension, obesity, and overall metabolic disturbances have escalated over the past decades, an effect that parallels increased added sugar consumption. Of all the sweeteners, fructose is touted to be most detrimental since it is metabolized differently than other monosaccharides: (1) it is poorly absorbed in the intestine; (2) it does not stimulate insulin secretion; (3) it provides a rapid substrate for synthesis of lipids in the liver; (4) it can elevate uric acid levels; and (5) it may stimulate the endogenous production of inflammatory, glycated products. Based on existing published literature, the results from this study are not entirely unexpected: the participants were normotensive at recruitment and were asked to consume a sweetened milk beverage. Milk peptides have been shown to reduce BP in some clinical trials and meta-analyses. The authors suggested that the amount of sweetener was reflective of a “normal level of consumption. ” This is a significant point, as the level of dietary fructose has been shown to be deterministic in its metabolic effects. As Livesey stated, “Fructose is proving to have bidirectional effects. At moderate or high doses, an effect on any one marker may be absent or even the opposite of that observed at very high or excessive doses. ” Research indicates that higher-than-normal daily intake (≥100–200 g/d) of fructose intake may lead to a host of metabolic changes, including hyperuricemia. Most recently, Jayalath and colleagues reported no association of fructose consumption with the incidence of hypertension in a systematic review and metaanalysis of three prospective cohort studies (n=37,375 men and 185,855 women). While they found no effect of fructose at average levels of consumption over time, a positive association was identified with high intakes of fructose. In the 9% fructose group in the Angelopoulos study, participants received about 50 g of fructose, which has been classified by Livesey and Taylor as “moderate” intake. One pear contains about 11 g of fructose. Thus, if we consider that general nutritional guidelines advocate 2 to 3 servings of fruit per day, and the amount of 11 g is used as an average, 22 g to 33 g of fructose might be what could be considered acceptable, a number that comes in less than what Angelopoulos and colleagues studied. In contrast to fruit, a 12-ounce soft drink has between 16.3 g (cola) and 22.4 g (lemonlime) fructose. Le and associates demonstrated that acute consumption of 24 ounces of high-fructose corn syrup–sweetened beverages (an estimated average of 40 g of fructose per day) led to significant changes in metabolic biomarkers in healthy men and women, such as systolic BP and serum uric acid compared with a sucrose-sweetened beverage. Although not tested headto-head, it would seem that the overall nutritional composition of the fructose-containing food might be extremely relevant, considering that 24 ounces of a soft drink may not differ much in fructose content from the overall amount ingested from daily fruit intake, yet different metabolic results may be seen. High-fructose corn syrup intake is thought to be particularly concerning because of the potential for its relatively excessive intake from soft drinks and sugarsweetened beverages. Brown and colleagues demonstrated that consumption of sugar-sweetened beverages, even at one serving per day, led to significantly greater BP levels. In the study by Angelopoulos and associates, all sweeteners were consumed within a milk beverage rather than in a soft drink. The fact that participants were given milk may have been significant as dairy products contain naturally occurring angiotensinAddress for correspondence: Mark Houston, MD, MS, MSc, Associate Clinical Professor of Medicine, Vanderbilt University School of Medicine, Director, Hypertension Institute and Division of Human Nutrition, Saint Thomas Hospital, Nashville, TN 37069 E-mail: boohouston@comcast.net