Does Altering Dietary Salt Intake Aid In The Prevention And Treatment Of Diabetic Kidney Disease?
Dietary restriction of salt has been found to be as effective as single drug therapies for hypertension. An altered dietary salt intake could aid in the prevention and treatment of diabetic kidney disease.
About 75% of cardiovascular disease (CVD) in diabetes may be attributed to hypertension. Raised blood pressure (BP) is known to be the largest direct cause of death due to the strokes, heart attacks and heart failure in diabetic patients. Diabetes makes it more likely to develop high BP. Kidneys contain millions of tiny filters called nephrons. Consistently high values of glucose, as it occurs in diabetes damage these nephrons resulting in Diabetic kidney disease (DKD). DKD is the leading cause of chronic kidney disease (CKD), a condition where there is progressive loss in renal function over a period of months or years.
It is known that our current consumption of salt is a major factor in increasing BP. Salt sensitivity is particularly high in diabetic patients. Public health guidelines recommend reducing dietary salt intake to less than 5-6 g/day. A modest reduction in salt intake lowers BP, irrespective of levels of blood pressure being normal or raised. However the current knowledge of the role of salt in regulating BP and its impact on DKD is limited to small studies. There are no standard criteria for high and low salt diets.
A study was done to evaluate the effects of salt restriction on the prevention and progression of DKD. A meta-analysis of Randomised Control Trials (RCTs) of salt reduction was performed. It included 13 studies including 254 patients with type 1 and type 2 diabetes. The results were published in Cochrane Reviews, a reliable source of evidence-based health care.
It was found that reducing salt intake by 8.5 g/day lowers BP by 7/3 mm Hg in type 1 and type 2 diabetes. This effect is equivalent to that produced by a single drug therapy. Tight control of BP in diabetics slows the progression of diabetic kidney disease. All diabetics should consider reducing salt intake at least to less than 5-6 g/day. The recommendation of 5-6 g/day is actually meant for the general population. Diabetics may consider lowering salt intake to still lower levels.
The number of patients studied are not large but the results have significant implications owing to the fact that it is often difficult in clinical practice to control BP to the levels now recommended by guidelines. If a modest dietary restriction can be as effective as drug therapy - the fact has significant preventive implications to countries such as India and China that have seen rising incidence of both diabetes and hypertension.
Citation: Suckling RJ, He FJ,MacGregor GA. Altered dietary salt intake for preventing and treating diabetic kidney disease.
Database of Systematic Reviews 2010, Issue 12. Art. No.: CD006763. DOI: 10.1002/14651858.CD006763.pub2.