Sodium
Needed for fluid balance and nerve function — but most people get too much.
What it does
Sodium is essential, even though most people eat far more of it than they need. As the main positively-charged mineral in the fluid outside cells, it is the primary controller of the body's water balance — where sodium goes, water follows. This makes it central to maintaining blood volume and blood pressure, and to keeping the fluid around cells in the right amount and composition.
Working in partnership with potassium across cell membranes, sodium is essential for generating the electrical signals that nerves use and for triggering muscle contraction, including the heartbeat. The body has finely tuned hormonal systems, run largely by the kidneys, to hold sodium at the right level, conserving it when intake is low and excreting the surplus when intake is high.
The practical issue with sodium is excess, not shortage. It reaches us mainly as salt (sodium chloride), and most of that comes from processed and restaurant foods rather than the salt cellar. Consistently high intakes push blood pressure up, which over time raises the risk of heart disease and stroke, which is why health guidance focuses on cutting salt. Genuine deficiency is uncommon and usually results from heavy, prolonged fluid loss rather than diet.
Recommended intake (RDA)
Adults: limit to under ~2300 mg/day (about 6 g salt).
Key roles at a glance
- Fluid balance
- Nerve and muscle function
Food sources
- Table salt
- Processed and packaged foods
- Bread
- Cured meats
- Sauces
If you go without
- Rare from diet
- low levels cause headache, confusion, cramps (often from illness or over-hydration)
Too much
- High intake raises blood pressure and cardiovascular risk