Sodium

The FDA Daily Value (DV) for sodium is 2,300 mg/day — equivalent to about 1 teaspoon of table salt. The American Heart Association recommends ideally no more than 1,500 mg/day for adults with high blood pressure or cardiovascular disease risk. The National Academies set an Adequate Intake (AI) of 1,500 mg/day for adults (the minimum for physiological function) and a Chronic Disease Risk Reduction Intake (CDRR) of 2,300 mg/day, meaning reductions below 2,300 mg/day reduce chronic disease risk. Average intake in the US is approximately 3,400 mg/day — nearly 50% above the DV. There is no established Tolerable Upper Intake Level because the dose-response between sodium and blood pressure is continuous, without a clear threshold below which there is no effect.

Yes — the evidence is strong and consistent across population studies, metabolic feeding trials, and randomised controlled trials. The DASH-Sodium trial (Sacks et al. 2001, NEJM) showed that reducing sodium from 3,500 mg to 1,500 mg/day lowered systolic blood pressure by 8.9 mmHg in hypertensive individuals eating a typical American diet. The mechanism is direct: excess sodium expands plasma volume, which increases cardiac output and activates the renin-angiotensin system to maintain pressure. However, "salt sensitivity" varies substantially between individuals — roughly 50–60% of people with hypertension are salt-sensitive, while the effect in normotensive individuals is more modest. Genetic factors, race (Black populations tend to be more salt-sensitive), age, and kidney health all modulate response.

Salt (sodium chloride, NaCl) is approximately 40% sodium by weight. So 1 teaspoon of table salt (~5.8 g) contains about 2,300 mg of sodium — exactly the FDA Daily Value. When nutrition labels show "sodium," they report only the sodium portion, not the full weight of salt. Other sodium-containing compounds in food include sodium bicarbonate (baking soda), sodium nitrate/nitrite (curing agents in deli meats), sodium benzoate (preservative), monosodium glutamate (MSG), and disodium phosphate (emulsifier in processed cheese). All of these contribute to total sodium intake and appear in the "sodium" line on Nutrition Facts panels.

Table salt is essentially pure sodium (2,300 mg per 1 tsp). Processed food sodium leaders per 100 g include: soy sauce (5,493 mg), fish sauce (5,175 mg), bouillon cubes (~15,000 mg), beef jerky (1,800 mg), canned anchovies (3,668 mg), pickles (1,208 mg), processed deli meats (prosciutto: 2,585 mg; salami: 1,900 mg), olives in brine (1,556 mg), hard cheeses (Parmesan: 1,184 mg), canned soups (300–500 mg per 100 mL), and bread (400–600 mg per 100 g). Fresh whole foods — unprocessed fruit, vegetables, meat, fish, eggs, legumes, and grains — contain very little sodium naturally; the majority of intake comes from processing and preparation.

In healthy adults eating typical diets, "too little dietary sodium" is virtually impossible to achieve by food choice alone — minimum physiological needs are around 500 mg/day, and almost all diets provide far more. However, clinical hyponatraemia (low blood sodium concentration) is a serious medical condition caused most often by water retention (syndrome of inappropriate ADH secretion, SIADH), not by insufficient salt intake. In specific situations, genuine sodium depletion can be harmful: endurance athletes replacing sweat only with plain water may develop exercise-associated hyponatraemia; people with salt-wasting kidney disease, adrenal insufficiency, or prolonged gastrointestinal illness are at risk. Some observational research has found J-shaped relationships between sodium intake and cardiovascular mortality (with very low intakes also associated with risk), but this finding is controversial and may reflect reverse causation. Major health organisations universally recommend that the priority in most populations is reducing intake, not increasing it.