Why does eating too much salt cause edema?

Eating too much salty food can cause edema mainly due to excessive intake of sodium ions, which increases the concentration of sodium in the body and leads to water retention and accumulation, resulting in edema.

Sodium ions are one of the key electrolytes responsible for maintaining fluid balance inside and outside the body's cells. However, when excessive sodium is consumed, the kidneys may fail to promptly excrete the surplus, causing elevated sodium levels in the body. To maintain sodium balance, the body adjusts water distribution, leading to water retention and accumulation, thereby forming edema.

In addition, salty foods can stimulate the kidneys to excrete large amounts of urine, potentially causing dehydration, which may further worsen edema. Therefore, to prevent edema, it's important to control the intake of salty foods—especially for individuals prone to edema, such as those with hypertension, kidney disease, or heart conditions, who should be particularly cautious about salt consumption.

In daily life, drinking plenty of water and consuming more potassium-rich foods such as vegetables and fruits can help promote sodium excretion and alleviate symptoms of edema.