“We’re all addicted to salt,” De Borst states. And that makes it difficult to avoid salty products. “Producers claim you can’t just take salt out of products. It’s not just about taste—it also affects mouthfeel and preservation. Salt has many properties beyond just flavour.”

Salt Calculator
It’s hard for consumers to estimate how much salt they consume daily. “When we talk about table salt, which contains sodium chloride, we recommend a maximum intake of 2 grams of sodium per day. That equals 5 grams of table salt. Many people consume 8 to 13 grams of salt a day. People think they’re doing well by not using the salt shaker when cooking, but it’s actually the hidden salt—like in bread or seasoning packets—that causes problems. We unknowingly consume much more salt than we think. To raise awareness, the Dutch Kidney Foundation has a salt calculator on its website. You can enter what you eat daily and see how much salt you’re actually consuming. Just eating a pizza in the evening can bring you to your daily limit. Ideally, you shouldn’t eat any more salt for the rest of the day—but in reality, that rarely happens.”

High Blood Pressure
If you’ve eaten too much salt, you may only notice a dry mouth the next morning. So, you don’t really feel it. And symptoms appear only at a late stage. But what actually happens in the body due to excessive salt intake? “It causes the body to retain fluid, which leads to high blood pressure. Chronic high blood pressure can irreversibly damage not only blood vessels but also the kidney’s filters. These filters remove waste products from the blood. If they don’t work properly, the body can poison itself.” Moreover, the kidneys play a key role in regulating blood pressure by managing salt and fluid balance and producing a hormone that affects blood pressure. Once the kidneys are damaged, the risk of hypertension increases further. This negative feedback loop worsens over time—and it’s all influenced by salt intake.

Healthy Lifestyle
Kidney damage often goes unnoticed until the later stages, because the kidneys initially compensate by working harder. This, in turn, accelerates their deterioration. When kidney function drops to fifteen percent, a kidney transplant or dialysis is necessary. That’s why preventing kidney damage through a healthy lifestyle is crucial. Once your kidneys are damaged, you’re a kidney patient. In the Netherlands, 1 in 10 people has chronic kidney disease. At that point, salt becomes dangerous in other ways too.

Protein Loss
Kidney patients often lose protein through their urine because the filters no longer work properly. Salt worsens this protein loss by causing fluid retention, which places extra pressure on the kidney filters. The proteins then cause inflammatory reactions deeper in the kidneys, as the tissue cannot tolerate them. This leads to scar tissue formation, further reducing kidney function.

Campaign
For people with chronic kidney disease, it’s especially important to reduce salt intake—but really, it applies to everyone. “Most kidney patients die from cardiovascular disease. That’s a huge cost burden. In England, a study was conducted on the effects of a salt-reduction campaign. Such a campaign would cost a few million pounds, but save 1.5 billion pounds in medical costs annually!”

Research
De Borst has been conducting research on salt intake and kidney damage for quite some time. Last year, he received 2 million euros in funding to explore how AI can help detect kidney damage earlier. “The kidney’s filters are actually bundles of blood vessels. We are born with about 1 million of these filters and lose around 300,000 over our lifetime. That’s not necessarily a problem, as the remaining filters compensate by working harder. With AI, we may be able to determine how many functioning filters a person still has. That could serve as a warning sign, prompting people to change their behaviour. You can detect kidney damage through various tests, like blood or urine tests, but not everyone shows protein in the urine.”

Bright Spots
For De Borst, it’s clear: major steps are needed to tackle the problem of excessive salt intake. Responsibility doesn’t lie solely with politicians—supermarkets, food producers, and consumers all have a role to play. Despite the work ahead, De Borst sees some bright spots. “Some supermarkets are actively working to reduce the salt content in their products, like Lidl. There’s also an initiative to replace baker’s salt in bread with salt that contains potassium and magnesium chloride. That’s a win-win, as these substances can actually benefit our health.”

Martin de Borst gives a lecture during the IFFI Event ‘Salt, less is more’, on May 15.