When your body doesn't respond to insulin, your kidneys hold salt and your blood vessels stiffen, making blood pressure stay high no matter how little salt you eat.

“But in someone with insulin resistance, which describes the majority of adults in the UK and the US, insulin doesn't fall. It stays elevated throughout the day because cells aren't responding to it properly anymore. So, the pancreas has to keep producing more just to maintain normal blood sugar. When insulin is chronically high, the kidneys never get the signal to release sodium. They're locked into retention mode. This is why so many patients reduce their salt intake to see almost no change in their blood pressure. They're treating the volume side of the equation while the hormonal control system is still holding on to sodium regardless of how much they're eating. The kidneys aren't passive filters. They're hormonally controlled pressure valves. And if the hormones are wrong, the valve stays closed. What makes this worse is that insulin resistance also damages the endothelium. High insulin levels over time reduce nitric oxide production, which means vessels lose their ability to relax. So you end up with a system where blood volume is being artificially expanded through sodium retention and simultaneously vascular resistance is climbing because the arteries can't dilate properly. Both arms of the blood pressure equation are being driven up at once and cutting salt alone doesn't address either one of them.”