High Intake of Sodium and Kidney Function Decline!!!

The kidneys are two vital organs that keep the blood clean and chemically balanced.  Kidney disease can be detected through a spot check for protein or albumin in the urine and a calculation of glomerular filtration rate (GFR) based on a blood test. Diabetes and high blood pressure are the two leading causes of kidney failure. People with reduced kidney function should see their doctor regularly. Chronic kidney disease (CKD) increases the risk of heart attacks and strokes. Kidney disease is any disease or disorder that affects the function of the kidneys.

Estimated glomerular filtration rate (eGFR) is a blood test to measure how much blood the kidneys are filtering.  A rate of 60 or more means kidneys are functioning, 30 to 59 means moderate kidney disease, 15 to 29 means severe kidney damage and below 15 means kidney failure (dialysis or transplant may be needed soon). Automatic laboratory reporting of eGFR calculated from serum creatinine measurements would help to identify asymptomatic kidney dysfunction at an earlier stage. eGFR correlates well with complications of chronic kidney disease (CKD) and an increased risk of adverse outcomes such as cardiovascular morbidity and mortality.

Sodium is one of the body’s three major electrolytes (the other two being potassium and chloride). Electrolytes are involved in intracellular osmosis, which means that they control the flow of body fluids into and out of tissues and cells. Most Americans consume too much sodium, from 10 to 35 times more than the recommended daily intake. Enormous amounts of sodium (and chloride) are used in cooking and food processing. Often times this “hidden salt” contributes more to an individual’s daily diet than does the salt shaker.

A current study sought to determine how diet influences microalbuminuria and eGFR decline in people with well-preserved kidney function. The study included 3,348 women who had data on urinary albumin to creatinine ratio in 2000. Of the women included in the study, 3,296 also had data on eGFR change between 1989 and 2000. Researchers were able to derive the cumulative average intake of nutrients over 14 years by analyzing semi-quantitative food frequency questionnaires answered in 1984, 1986, 1990, 1994 and 1998. It was revealed that microalbuminuria was directly associated with eating higher amounts of animal fat and two or more servings of red meat per week. The researchers also found that higher sodium intake was directly associated with declining eGFR while beta-carotene appeared to have a protective effect on the kidneys. These results suggest that people who eat more animal fats, red meat and have a high sodium diet may be at an increased risk of microalbuminuria. The researchers suggested that lower sodium intake and higher beta-carotene intake may reduce the risk for eGFR decline thereby reducing the risk for declining kidney function.1

1 Lin J, Hu FB, Curhan GC. Associations of Diet with Albuminuria and Kidney Function Decline. Clin J Am Soc Nephrol. Mar2010.