Chronic Kidney Disease (CKD) is defined as either kidney damage or a decline in renal function as determined by decreased glomerular filtration rate (GFR) for three or more months . It is estimated that 1 in 9 adults in the United States meet this criteria, while an additional 1 in 9 adults are at increased risk for CKD . In the general population, a decline in renal function is considered an independent risk factor for both cardiovascular disease and all-cause mortality . However, the extent to which a mild diminution in renal function influences this risk is not known .
According to the National Kidney Foundation guidelines, CKD is classified into five stages, each of which directly correlates with the severity of the disease . As one progresses from stage 1 to 5 there is a concomitant decline in GFR and thus renal function. The final stage, known as end stage renal disease, represents the most severe manifestation of CKD . This classification system provides a universal standard for application of clinical treatment guidelines.
Hypertension is the second leading cause of CKD and accounts for approximately 30% of all cases in the U.S. [30, 31]. In one study, hypertension was associated with a premature decline in renal function in men with normal kidney function . Although, initial estimates of CKD prevalence in hypertensive individuals were about 2%, recent evidence suggests that prevalence rates may be significantly higher . Blood pressure control is of particular importance in hypertensive individuals with CKD. This point has been demonstrated in several trials in which antihypertensive therapy slowed the progression of CKD [34–36].
Race, gender, age and family history are four risk factors for CKD [37–40]. Recent findings suggest that modifiable lifestyle risk factors (i.e., physical inactivity, smoking, obesity) are also associated with CKD. Limited data exist regarding the role of dietary protein intake as an independent risk factor for either the initiation or progression of renal disease but population studies have consistently demonstrated an inverse relationship between dietary protein intake and systemic blood pressure [41, 42]. In a randomized control trial , dietary protein and fiber had additive effects in lowering 24-hour and awake systolic blood pressure in a group of 36 hypertensives. While these findings suggest that high protein diets may be beneficial to hypertensive individuals, additional research is warranted since increased protein intakes often result in increased consumption of certain micronutrients known to impact blood pressure (e.g., potassium, magnesium, calcium) .