What your kidneys actually do, what threatens them, and what the latest science says about keeping them working for the long haul.
First, Understand What They Do
Your kidneys filter your entire blood supply roughly thirty times every day – around 150 litres in total. They regulate blood pressure, manage fluid balance, produce hormones that keep your bones strong and your red blood cells plentiful, and maintain the precise acid-base balance your cells require to function. They are not merely a waste-disposal system. They are a biochemical control centre, and when they begin to fail, the effects ripple through virtually every other system in the body.
Which is why the number that tracks how well they’re working deserves to be as familiar to you as your cholesterol count.
The Number to Know: Your GFR
GFR – glomerular filtration rate – is your kidney’s report card. It is calculated from a simple blood test and tells your doctor how efficiently your kidneys are clearing waste. A GFR above 90 is considered normal. Below 60, sustained over three months, qualifies as chronic kidney disease. Below 15, you are approaching kidney failure.
For years patients were told that a declining GFR was irreversible – that once the kidneys began to lose function, the only direction was downward. That view is shifting. Diet, blood pressure control, and blood sugar management can slow the decline significantly, and in some cases stabilise it. The important word is early. The earlier you know, the more you can do.
Ask your GP for a kidney function test – it is a standard blood panel – and ask them what your GFR number actually is. Do not wait to be told.
“Ask your GP what your GFR number is. Do not wait to be told.”
The Drug in Your Medicine Cabinet That’s a Risk
If you use ibuprofen or naproxen regularly – for back pain, joint pain, headaches, the ordinary physical complaints that accumulate with age – pay attention to this. Both drugs interfere with kidney function. Used occasionally at recommended doses by people with healthy kidneys, the risk is low. Used regularly, or by anyone whose kidney function is already compromised, they can cause serious and lasting damage.
This is not a minor footnote. NSAIDs are among the most common causes of drug-induced kidney injury. If you are in any doubt about your kidney health, discuss alternatives with your doctor before reaching for the ibuprofen.
How to Eat for Your Kidneys
There is no supplement that will protect a kidney and no superfood that will regenerate one. What works is sustained, consistent dietary discipline – and it overlaps considerably with what works for your heart, your weight, and your longevity more broadly.
- Reduce animal protein. The kidneys work harder to process animal protein than plant protein. Reducing meat – particularly red meat – reduces that burden.
- Cut your sodium. Salt raises blood pressure, and high blood pressure is one of the two leading causes of kidney disease. The target is under 2,300mg a day – roughly one teaspoon. Processed food is the biggest culprit.
- Manage your blood sugar. Diabetes is the other leading cause of kidney disease. If you are pre-diabetic or managing type 2 diabetes, your kidneys are on the front line.
- Eat more plants. Fruit and vegetables reduce blood pressure, support healthy body weight, and help maintain the acid-base balance that kidneys regulate. Aim for variety and volume.
- Drink water, not sugar. Sugary drinks drive the diabetes and obesity that drive kidney disease. Swap them out. Hydration itself matters too – mild chronic dehydration is more common than most people realise and puts unnecessary strain on the kidneys.
The Science That’s Changing Everything
For most of the twentieth century, kidney damage was considered irreversible. Nephrons – the tiny filtering units inside the kidney – were thought to be gone once lost, like neurons. A 2023 discovery at the University of California San Francisco changed that picture significantly. Researchers identified what they called “hybrid cells”: cells capable of repairing damaged kidney tissue. The mechanism they use is called the Wnt pathway – the body’s own cellular repair signalling system.
Think of it as an emergency broadcast. When kidney cells are damaged, certain proteins send a signal that wakes up specialised repair cells lying dormant in the tissue. Those cells mobilise, migrate to the damage, and begin rebuilding. The complexity is calibration: the signal must be strong enough to trigger meaningful repair, but not so strong that the repair cells go into overdrive and attack healthy tissue. Too weak, the damage continues unchecked. Too strong, the result is fibrosis – scar tissue where functioning cells should be.
Researchers are now working on ways to modulate the Wnt signal therapeutically – to give the kidneys, in effect, a nudge toward repair that they may be capable of but not currently performing. It is early-stage science. But it represents a fundamental shift in how medicine thinks about kidney disease: not as a one-way street toward dialysis, but as a condition that may, under the right conditions, be partially reversible.
“A 2023 discovery changed how medicine thinks about kidneys: not a one-way street toward dialysis, but a condition that may, under the right conditions, be partially reversible.”
What Other Traditions Have Long Known
Western medicine, for all its precision, tends to treat the kidney in isolation. Other traditions take a more integrated view – and some of what they have observed for centuries is beginning to find support in clinical research.
Traditional Chinese Medicine: Goji Berries
Used for centuries to strengthen kidney function and support vitality, goji berries have attracted modern research interest for their anti-inflammatory properties. Clinical evidence is still limited, but for general kidney support – and as a replacement for more damaging snacks – they are a low-risk addition.
Ayurvedic Medicine: Punarnavadi Kashayam
A study in the Journal of Ayurveda and Integrative Medicine found this traditional herbal decoction – built around ingredients including Punarnava (known as “the rejuvenator”), turmeric, Giloy, and dried ginger – improved kidney function and reduced blood pressure in patients with chronic kidney disease. Sourcing the complete preparation in the West is difficult, but individual ingredients are increasingly available, and anti-inflammatory diets incorporating turmeric in particular have significant mainstream research support.
The Teas Worth Trying
Hibiscus tea has clinical evidence behind it for reducing blood pressure – one of the two primary drivers of kidney disease – and may help prevent kidney stones. Green tea, rich in antioxidants, has shown protective effects on kidney tissue in several studies. Neither is a treatment. Both are sensible additions to a kidney-conscious routine.
The Bottom Line
Willem Kolff built the first dialysis machine from butcher’s sausage casing in an occupied country during a war, motivated by the death of a twenty-two year old and the face of his mother. It took him seven years and seventeen patients before he had a working proof of concept. The treatment that machine made possible now keeps three million people alive.
Medicine has come a long way since 1943. But the underlying truth Kolff was working toward has not changed: the kidneys matter enormously, they are vulnerable in ways most of us don’t anticipate, and catching a problem early – before it announces itself – is the difference between managing it and being managed by it.
Know your GFR. Watch your blood pressure. Eat less salt, less sugar, less meat. Swap the ibuprofen. And the next time someone asks which organ you’d most like to protect as you get older, consider giving an answer that might surprise them.
