ScienceDaily -- Individuals who consume a diet high in sodium or artificially sweetened drinks are more likely to experience a decline in kidney function, according to two papers being presented at the American Society of Nephrology's annual meeting in San Diego, California.
Julie Lin MD, MPH, FASN and Gary Curhan, MD, ScD, FASN of Brigham and Women's Hospital studied more than 3,000 women participating in the Nurses' Health Study to identify the impact of sodium and sweetened drinks on kidney function.
"There are currently limited data on the role of diet in kidney disease," said Dr. Lin. "While more study is needed, our research suggests that higher sodium and artificially sweetened soda intake are associated with greater rate of decline in kidney function."
The first study, "Associations of Diet with Kidney Function Decline," examined the influence of individual dietary nutrients on kidney function decline over 11 years in more than 3,000 women participants of the Nurses' Health Study. The authors found that "in women with well-preserved kidney function, higher dietary sodium intake was associated with greater kidney function decline, which is consistent with experimental animal data that high sodium intake promotes progressive kidney decline."
The second study, also conducted by Dr. Lin and Dr. Curhan, "Associations of Sweetened Beverages with Kidney Function Decline," examined the influence of sugar-sweetened and artificially sweetened beverages on kidney function decline in the same group of Nurses' Health Study participants.
An analysis of the nationally representative NHANES III participants had previously reported an association between sugar-sweetened soda and urinary protein, but data on kidney function change was not available. This investigation reported "a significant two-fold increased odds, between two or more servings per day of artificially sweetened soda and faster kidney function decline; no relation between sugar-sweetened beverages and kidney function decline was noted" said Dr. Lin.
This association persisted even after the study authors accounted for age, caloric intake, obesity, high blood pressure, diabetes, cigarette smoking, physical activity, and cardiovascular disease. The mechanisms for kidney decline in the setting of high intake of artificial sweetenters have not been previously studied and deserve further investigation.
The study participants were older Caucasian women and the authors note that the findings may not be directly applicable to men or people of other ethnicities.
More bad news for salt cravers!
High Salt Intake Directly Linked to Stroke and Cardiovascular Disease
As reported in ScienceDaily, high salt intake is associated with significantly greater risk of both stroke and cardiovascular disease, concludes a study published on the British Medical Journal website.
The link between high salt intake and high blood pressure is well established, and it has been suggested that a population-wide reduction in dietary salt intake has the potential to substantially reduce the levels of cardiovascular disease.
The World Health Organization recommended level of salt consumption is 5 g (about one teaspoon) per day at the population level, yet dietary salt intake in most Western countries is close to 10g per day (and much higher in many Eastern European countries).
Collaborative research conducted by Professor Pasquale Strazzullo at the University of Naples, Italy and Professor Francesco Cappuccio at the University of Warwick, UK analysed the results of 13 published studies involving over 170,000 people that directly assessed the relationship between levels of habitual salt intake and rates of stroke and cardiovascular disease.
Differences in study design and quality were taken into account to minimise bias.
Their analysis shows unequivocally that a difference of 5 g a day in habitual salt intake is associated with a 23% difference in the rate of stroke and a 17% difference in the rate of total cardiovascular disease.
Based on these results, the authors estimate that reducing daily salt intake by 5 g at the population level could avert one and a quarter million deaths from stroke and almost three million deaths from cardiovascular disease each year. Furthermore, because of imprecision in measurement of salt intake, these effect sizes are likely to be underestimated, say the authors.
These results support the role of a substantial population reduction in salt intake for the prevention of cardiovascular disease, they conclude.
This study is a useful and welcome addition to the medical literature, and strengthens the case for population-wide salt reduction, says Professor Lawrence Appel from Johns Hopkins University, in an accompanying editorial.
* Cardiovascular disease is the first cause of death and disability in the world among people aged over 60 years and the second one among those 15 to 59 years old.
* According to the World Health Organization, 62% of all strokes and 49% of coronary heart disease events are attributable to high blood pressure.
* There is a direct causal relationship between levels of dietary salt intake and levels of blood pressure.
* Most of the salt we eat comes from that added to food in the manufacturing process by industry, caterers and food producers.
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