Editor, Nephrology Dialysis Transplantation
RE: Microvascular disease and its role in the brain and cardiovascular system: a potential role for uric acid as a cardiorenal toxin.
To the Editor:
Along with a review of the role of microvascular disease in hypertension and related diseases, a recent paper by Kanbay et al.1 also proposes that sugars rich in fructose may be a root cause via the formation of intracellular uric acid. Their premise is flawed in two important aspects.
First, the association suggested by the authors between dietary fructose and hypertension is unproven for typical patterns and amounts consumed. The study cited in support of the association (author reference 45) monitored uric acid and other metabolites in test subjects receiving fructose supplements of 200 g/d. The authors calculated that fructose provided one-third of the total daily energy intake for these subjects, nearly four-times the mean fructose intake in the US and twice the estimated intake for the 95th population percentile.2
And second, while fructose from added sugars did increase generally over the past century, its prevalence in the diet has been in decline since 1999, the peak year for high fructose corn syrup use.3 Because a positive association cannot exist between declining fructose use and recent increases in uric acid and incidence of hypertension, it is highly unlikely that fructose plays a unique and significant role.
Though Kanbay et al. may wish for fructose to play a central role in their uric acid-mediated view of microvascular disease, their basic premise is seriously flawed.
References
1. Kanbay M, Sanchez-Lozada L-G, Franco M, Madeero M, Solak Y, Rodriguez-Iturbe B, Covic A, Johnson RJ. Microvascular disease and its role in the brain and cardiovascular system: a potential role for uric acid as a cardiorenal toxin. Nephrol Dial Transplant 2011. 26:430.
2. Marriott B, Cole N, Lee E. National estimates of dietary fructose intake increased from 1977-2004 in the U.S. J Nutr2009. 139:1228S.
3. Buzby J, Wells HF. Loss-adjusted per capita availability: Average daily added sugar and sweeteners from the U.S. food supply, adjusted for spoilage and other waste. In: USDA Economic Research Service, ed.: http://www.ers.usda.gov/Data, Updated 1 February, 2010.