Dietary and Lifestyle Considerations to Promote Kidney Health
Avoidance of Nonsteroidal Anti-inflammatory Drugs
Use of nonsteroidal anti-inflammatory drugs (NSAIDs) for the treatment of pain and inflammation can increase the risk of NSAID-induced kidney damage. The lowest effective dose should be used; shorter durations of use may also be protective. Regular follow-up with a clinician, including testing for kidney function, and discontinuation of the drug if signs of toxicity develop are advised (Curiel 2013).
Evidence for the impact of aspirin on kidney health is mixed. One study showed that regular use of aspirin actually slowed the progression of CKD in individuals over a 5–7 year period (Evans 2009). Also, an earlier study, published in the New England Journal of Medicine, showed that acetaminophen and NSAID use was associated with risk of end-stage kidney disease, but aspirin use was not (Perneger 1994). Conversely, 150 mg of aspirin daily was associated with deterioration of creatinine clearance, compared with clopidogrel (Plavix), in a study of preventive anti-platelet therapy in individuals with type 2 diabetes and CKD (Dash 2013). In addition, a study in 1884 CKD patients receiving 100 mg aspirin daily for cardiovascular prevention found that usage doubled serum creatinine levels and incidence of renal death (Kim, Lim 2014). Similarly mixed results have come from studies on the use of low-dose aspirin in elderly patients (Akinwusi 2013; Segal 2006). On the basis of currently available evidence, those with existing kidney disease should consult their healthcare provider before initiating a low-dose aspirin regimen. Such individuals on low-dose aspirin therapy should have regular testing for kidney function (Curiel 2013; Akinwusi 2013).
“Western-style” vs. Mediterranean-style Diets
Compared with a standard “Western-style” diet, a Mediterranean-style diet is lower in animal protein and high-glycemic carbohydrates, and higher in vegetables, fruits, unsaturated fats, and fiber—thus, it contains less of the dietary factors that contribute to kidney disease. A “Western-style” diet rich in high-glycemic carbohydrates and excess salt increases the risk of hypertension and metabolic syndrome, which increase CKD risk (Odermatt 2011).
A study examined the degree of adherence to a Mediterranean diet among 597 men, 42% of whom had a GFR < 60 and were thus considered to have CKD. Study participants were divided into three degrees of adherence to Mediterranean diet: low, medium, and high. Subjects with medium and high adherence were 23% and 42% less likely, respectively, to have CKD compared with those with low adherence. Compared with those with low Mediterranean diet adherence, medium and high adherence were associated with a 25% and 23% lower mortality risk, respectively (Huang, Jimenez-Moleon 2013). Another study found that creatinine clearance score, a measure of healthy kidney function, was positively correlated with fruit and moderate alcohol consumption (moderate alcohol consumption is an aspect of Mediterranean-style diet). The same study also found that higher consumption of potatoes, red meat, and poultry decreased creatinine clearance scores, and thus was correlated with diminished kidney function (Chrysohoou 2010).
A Mediterranean-style diet has been shown to decrease cardiovascular risk in chronic renal failure patients (Mekki 2010). One group of authors proposed a novel mechanism for the beneficial effects of a Mediterranean-style diet on kidney function, suggesting it promotes a healthy gut microenvironment, which prevents the accumulation of uremic toxins (Montemurno 2014).
The DASH Diet
The DASH (Dietary Approaches to Stop Hypertension) diet decreases blood pressure, improves blood lipid levels, and reduces the risk for cardiovascular disease. The DASH diet is based on studies supported by the US National Institutes of Health. Two important characteristics of the DASH diet are that it does not require special types of food and the recipes are easy to follow (PubMed Health 2014).
The DASH diet places emphasis on vegetables, fruits, and low-fat or fat-free dairy products; it includes fish, poultry, whole grains, and nuts; and it limits sodium, sweets, sweet drinks, and red meat. It can be implemented together with medical therapies and other lifestyle interventions in most patient populations (Tyson 2012).
The DASH diet was shown to lower blood pressure in individuals with prehypertension and stage I hypertension (Tyson 2012). A subgroup analysis from the Nurses’ Health Study revealed that the DASH-style diet was associated with an almost 50% decreased risk of rapid eGFR decline (Lin 2011). A prospective cohort study that enrolled over 88 000 nurses and followed them for 24 years reported a 27% decrease in total coronary heart disease and a 34% decrease in fatal heart disease (Fung 2008; McCarron 2008).
Potassium Salts/Sodium Chloride Balance
Both low and high blood concentrations of potassium are associated with increased risk of dying in chronic kidney disease and end-stage renal disease patients (Kovesdy 2013). Sodium chloride (table salt and the salt in processed foods) is a known risk factor for high blood pressure, which is a risk factor for CKD. Sodium chloride appears to affect some people more than others, but in the general population only amounts over 2300 mg per day are conclusively linked with hypertension (Jin 2014; AHA 2014b).
Restriction of sodium in patients with CKD, to 6 g/day, also enhances the activity of angiotensin-converting enzyme (ACE) inhibitor medications, one of the standard therapies for CKD (Bellizzi 2013). Lowering dietary sodium chloride and increasing dietary potassium salts may also decrease chronic low-level acidosis, which may be associated with bone loss and muscle loss, and progression of nephropathy (Frassetto 2007; Frassetto 2001; Goraya, Simoni 2012; Scialla 2013; Goraya 2013).
Sugar consumption, particularly from sweetened beverages, has been postulated to contribute to the incidence of CKD in the United States (Karalius 2013). One study demonstrated a statistically significant link between consumption of sugar-sweetened soda and CKD (Cheungpasitporn 2014). In another study, higher levels of dietary fructose consumption were significantly associated with CKD (Yuzbashian 2014). Fructose, a sugar present in sucrose (table sugar) and high-fructose corn syrup, may increase uric acid levels, which may contribute to hypertension and kidney disease (Karalius 2013).
See Life Extension’s Gout and Hyperuricemia protocol for more information on associations between uric acid and these diseases.
Saturated vs. Unsaturated Fats
Diets high in polyunsaturated fats were shown to significantly decrease risk of CKD in two observational studies (Yuzbashian 2014; Gopinath 2011). On the other hand, a large population study showed that those who ate the most saturated fat had significantly higher protein loss from their kidneys compared with those who ate the least saturated fat (Odermatt 2011; Lin 2010).
Diets rich in monounsaturated fats may reduce many risk factors associated with CKD; these fats promote healthy blood lipid profiles, improve hypertension, and may improve glycemic control and reduce obesity risk (Kumar 2013).
High blood phosphate levels have been associated with reduced kidney function and progression to renal failure in CKD patients. Even in healthy individuals, elevated blood phosphate (> 4 mg/dL) is an independent predictor of future CKD. Phosphorus from meat is more easily absorbed than phosphorus from plant-based foods; therefore, animal protein is a larger contributor to dietary phosphorus than vegetable protein. Dietary calcium may mitigate negative consequences of phosphorus, as a lower ratio of calcium to phosphorus intake appears to increase the chance of negative outcomes, regardless of the level of dietary phosphorus (Uribarri 2013).
Animal proteins generally, and high-sulfur protein sources specifically, yield acidic metabolites that must be excreted by the kidneys (Scialla 2013; Goraya, Wesson 2012; Frassetto 2001). Thus, protein restriction, if undertaken judiciously, may be an effective strategy for slowing CKD and preserving kidney function (Eyre 2008; Mandayam 2006).
At the same time, patients who restrict protein may tend to eat more alkaline vegetables and fruits, thus further relieving systemic acidity (Frassetto 2001). The success of adherence to the plant-based Mediterranean diet for preserving kidney function may derive from this mechanism (Chrysohoou 2010).
Protein restriction may slow progression of CKD (Kovesdy 2013; Bellizzi 2013), and it also appears that increased consumption of animal protein and low consumption of vegetables and fruit contribute to acidosis in renal transplant recipients (van den Berg 2012). A protein-restricted diet may enhance the blood pressure-lowering and antiproteinuric effect of angiotensin-receptor blockers (ARBs), a standard therapy for hypertension and kidney diseases that cause proteinuria (Bellizzi 2013). In one study, healthy individuals who consumed plant-based rather than animal protein had less risk of developing CKD (Yuzbashian 2014).
Adequate protein intake for individuals with CKD has been estimated at 0.55 g/kg/day, provided caloric requirements are met (Bellizzi 2013).
Kidney disease is associated with poor vitamin status. This is especially well documented in the case of vitamin D (which is activated in the kidneys), so individuals with kidney disease should test their blood level of 25-hydroxyvitamin D. Kidney disease has also been associated with vitamin B6 and B12 deficiency (Mariani 2014; Lacour 1983; Saifan 2013).