Salt makes your body hold more water, which increases blood volume and raises blood pressure through simple physics.

“Sodium is osmotically active, which means wherever sodium goes, water follows. When you eat a meal high in salt, sodium gets absorbed into your bloodstream. And because your body wants to keep the concentration of sodium in your blood tightly controlled, it pulls water in from the surrounding tissues to dilute it. That increases your plasma volume temporarily. And more fluid in a closed circulatory system means higher pressure. It's basic fluid mechanics, not some complex hormonal cascade.”