How do I keep my kidneys healthy as I age?
The two best-supported steps to limit kidney damage as you age are keeping your blood pressure under control and exercising regularly. Moderate salt intake and a healthy weight demonstrably contribute to both.
Your kidneys change quietly over the years. They gradually lose filtering cells, receive less blood flow, and recover more slowly from damage. This makes them more vulnerable to everything that puts extra strain on them: high blood pressure, excess weight, or a high salt intake. This has been demonstrated in multiple studies in humans.
High blood pressure is by far the greatest threat to your kidneys as you age. Large studies and randomised trials show that chronically elevated blood pressure is a direct cause of kidney damage, and that you genuinely reduce that risk by keeping your blood pressure under control. Excess weight makes things worse: it causes your body to retain more sodium when you consume salt, which drives blood pressure up.
Salt also plays a larger role as you get older. Your kidneys process sodium less efficiently with age. As a result, your blood pressure rises more after a salty meal than it used to. Moderate salt intake therefore has a greater effect on blood pressure in older people than in younger people.
Regular exercise helps your kidneys in several ways. A study in healthy men showed that repeated training reduces inflammation and cellular ageing processes. There is also evidence that exercise stimulates the production of betaine, a substance that slows ageing in mice. Whether this works in exactly the same way in humans has not yet been proven. However, the beneficial effect of regular exercise on inflammation and cellular ageing has already been demonstrated in humans.
At the cellular level, some aged cells stop dividing but do not die off either. They keep secreting inflammatory substances, damage the blood vessels in the kidney, and inhibit repair. This is called cellular senescence. It is a likely contributing cause of kidney damage during ageing, not merely a by-product. Targeted treatments for it are being investigated, but do not yet exist. The same applies to proteins such as klotho, which decline with age and are associated with faster deterioration of kidney function. Interesting, but not yet an actionable tool for you.
The claims are based on multiple studies in humans, including cohort studies, randomised trials, and a multi-omics study, supplemented by animal research. The evidence for blood pressure is strong. The evidence for cellular ageing and exercise is moderate: demonstrated in humans, but causality and clinical benefit have not yet been fully established. The evidence for betaine in humans and for klotho as a treatment target is preliminary and largely based on mouse studies or associations without a proven causal relationship.