Dietary changes are considered first line non pharmacological options for chronic disease prevention and management in patients with diabetes and hypertension. Concerns have been growing in regards to foods high in digestible starch as they may contribute to an increasing risk of chronic diseases (1). These types of diets may result in dysbiosis or changes in the gut microbiota and this may play a large role in progressively worsening kidney disease (1).
Chronic kidney disease (CKD) can be defined as a reduction in kidney function as shown via a glomerular filtration rate (GFR) less than 60 mL/min per 1.73 m2, or identification of any markers related to kidney damage, or both, of a minimum of 3 months, regardless of the precipitating cause (2). Hemodialysis (HD) is a treatment reserved for patients with kidney failure (KF), or in select cases of acute kidney injury, providing lifesaving renal replacement therapy. Prior studies in patients on HD have shown reduced amounts of beneficial bacteria and higher fecal concentrations of uremic toxins (3).
Dysbiosis is a source of inflammation which can increase the likelihood of renal disease progression (4). Chronic low-grade intrarenal inflammation can negatively affect microcirculation and blood perfusion ultimately inducing kidney damage (4). The inflammatory response is also related to oxidative stress and the production of reactive oxygen species (ROS) which can lead to further renal tubular injury (4). Dietary strategies have been designed to help combat the concerns with inflammation and oxidative stress that occur due to changes in gut microbiota. Resistant starch (RS) is a carbohydrate that cannot be broken down in the small intestine by digestive α-amylases, as opposed to soluble fibre for example (1)(3). RS instead passes to the colon whereby it begins to ferment and act as a digestible substrate for beneficial colonic bacteria (1)(3). RS can be divided into 4 different types and are characterized as either type I, type 2, type 3, or type 4 (5). Types 1–4 are differentiated based on their physical properties as well as which food sources they originate from (5). Important effects of RS through gut bacteria modulation include a reduction of harmful metabolite build up and the production of short chain fatty acids (SCFA), which are vital for their positive effects on immunity and inflammation (1)(3).
RS may also have an important role in reducing the amounts of toxic nitrogenous waste buildup which are known to accumulate in patients with CKD (3). Some of the main culprit toxins include urea, p-cresol sulfate, and indoxyl sulfate (3). Both p-cresol sulfate and indoxyl sulfate have been associated with an increased risk of mortality and cardiovascular events in patients with CKD as well as tubular and kidney damage, which would be linked with further progression of renal disease (6).
Due to the ease of administration and relatively low cost of RS it can become an important part of the treatment regimen of patients with CKD. Thus, the main objective of this systematic review is to assess the efficacy and tolerability of RS versus placebo in reducing the progression of renal disease in adult patients with CKD. This information will hopefully provide a basis and foundation for further clinical studies for resistant starch use in patients with CKD.
Does the consumption of resistant starch vs. placebo reduce the progression of renal disease in adult patients with chronic kidney disease?