A bout of indigestion could be a sign of more than just digestive woes. New research increasingly shows the trillions of microbes in your gut—collectively called the gut microbiota—could impact organs beyond the intestines, right down to your kidneys.
Our kidneys remove waste products, toxins, and excess water from our body in the form of urine. They also maintain the salt and mineral balance in the blood. Naturally, good kidney health is important for optimal functioning of our body. In certain health conditions, kidney functions are reduced, leading to accumulation of waste products and toxins in our body. These toxins then damage various organs, affecting our overall health.
Kidney health has a very close link to gut microbiota. Mumbai-based clinical nutritionist Shreya Shah says, “The gut microbiota plays a very crucial role in maintaining our overall health. When the balance of the gut microbiota is disrupted (gut dysbiosis), plenty of health issues, including kidney diseases, are seen in a person.” These could be chronic kidney disease (CKD), acute kidney injury (AKI), kidney stone formation, immunoglobulin A (IgA) nephropathy and end stage renal disease (ESRD), elaborates the founder of Healthfuel.
This pathogenic interconnection between kidney and gut microbiota is known as the gut-kidney axis. The interaction between them is bidirectional, in which changes in gut microbiota have an impact on kidney health and vice versa, Shah explains.
Gut matters
The gut microbiota actively maintains gut health by preserving the intestinal barrier, boosting immunity, and tamping down inflammation. The gut microbes also generate antimicrobial substances that fend off invading pathogens.
In dysbiosis, the balance tips towards more harmful bacteria thriving at the expense of beneficial species, Shah points out. The harmful microbes release chemicals that damage the protective mucous layer, attack intestinal cells, and trigger inflammation. The cumulative effect is the breakdown of critical gut barrier. The disrupted barrier and rise in inflammation, in turn, impair kidney function.
According to Shah, injury to intestinal barrier permits toxins and bacteria to escape the gut into bloodstream enroute to kidney. Once there, these microbes and toxins stimulate immune cells to infiltrate and attack the organ. This provokes inflammation and plunging kidney performance.
The gut and the kidney
When we eat our food, the digestion of proteins releases amino acids in the intestine which are further absorbed there. “Certain gut bacteria produce many uremic solutes and toxins by the metabolism of amino acids that are harmful to the kidney. These toxins are generally cleared by the kidney. But when there is gut dysbiosis, the population of bacteria producing uremic toxins increases, leading to an increase in the toxins,” says Shah.
Poor kidney health damages the gut
These uremic toxins are harmful to the renal tubular cells. They induce fibrosis in the kidney and cause inflammation. Naturally, the kidney health falls. As kidney function declines, waste products like urea accumulate in the body and get secreted in high concentrations into the intestine. There, gut bacteria’s urease enzyme breaks down the urea into ammonia and other toxic substances that damage the intestinal lining and increase gut permeability, explains Shah.
Additionally, kidneys with reduced function cannot completely filter out uremic toxins from the bloodstream. This sparks a vicious cycle where blood levels of harmful uremic solutes escalate over time, further impairing kidney functions in a self-perpetuating downward spiral.
“Thus, the link between gut dysbiosis and kidney function is bidirectional. Kidney function and its health are important to maintain gut health. The gut health would also play a very important role in maintaining kidney health,” says Shah.
Restoring gut health
Restoring gut microbiota to normalcy helps deal with kidney diseases. The trick lies in increasing beneficial bacteria to repair the gut barrier and decreasing harmful bacteria that produce uremic toxins. This will reduce the inflammation of the gut as well as kidneys, making them function more normally once again. And how can we do this? “By consuming a diet rich in fibre and avoiding foods rich in saturated fat, salt and sugar. Gut-friendly probiotics also improve kidney health,” says Shah.
