Salt

Aim for under 2 g of sodium a day (about 5 g of salt). In US data most of it comes from packaged and restaurant food, so eating fewer of those meals is the lever that works; favour potassium-rich whole foods alongside.

How much, and where it comes from

The World Health Organization target is under 2 g of sodium a day, which is about 5 g of salt. The average US adult eats around 3.4 g of sodium a day.

Very little of that is shaken on at the table. In a study of 450 adults in three US regions, about 70% of sodium came from salt added during commercial processing and restaurant cooking, not from the salt shaker or home cooking.^[1] That was one US sample, not proof for every diet, but it explains why cutting at the shaker is the smallest lever and eating fewer processed and restaurant meals is the real one. Processed meat is a concentrated source: it carries about four times the sodium of fresh red meat per serving, and sodium alone is estimated to explain about two-thirds of the gap in coronary heart disease risk between the two (a modelled estimate).^[2]

Blood pressure: the randomised evidence

The firmest evidence is a controlled feeding trial. The DASH-Sodium trial assigned 412 adults to three sodium levels, on either a typical US diet or the DASH diet (Dietary Approaches to Stop Hypertension, rich in fruit, vegetables and low-fat dairy). On the typical US diet, going from high to low sodium lowered systolic blood pressure (the top number) by about 7 mm Hg — a substantial fraction of what a single first-line blood-pressure drug delivers. Combining the low-sodium level with the DASH diet reached 11.5 mm Hg in people with hypertension, compared with the high-sodium typical diet. The two levers overlap: doing both beats either alone, but by less than the sum of the two.^[3]

The effect is larger in salt-sensitive people, who are more common with age, in people of African ancestry, and among people with hypertension or chronic kidney disease; it is smaller in salt-resistant people.^[4] Population advice leans towards the salt-sensitive side because the harm runs that way. How common salt sensitivity really is, along with targets, monitoring and drug treatment, is covered under Blood pressure.

Potassium is the other half

The ratio of sodium to potassium may predict cardiovascular outcomes better than sodium alone. That finding came from a trial follow-up that measured both with repeated full 24-hour urine collections, so it does not suffer from the measurement problem described below.^[5] It is a reason to favour potassium-rich whole foods as much as to cut salt. Potassium-enriched salt substitutes, and who should not use them, have their own page.

Why "too little salt is dangerous" doesn't hold up

The best-known support for the idea is a 17-country study of about 102,000 people. It reported a J-shaped curve: excess risk of death and major cardiovascular events above about 7 g of sodium a day (6 g in people with hypertension), and again below about 3 g a day.^[6]

The low end is the problem. The study estimated each person's daily sodium from a single fasting morning urine sample, using a formula that itself includes age, weight and creatinine — most of which predict death on their own. That method is known to produce a spurious J-shape. Studies that use repeated full 24-hour urine collections find risk rising steadily with intake, and much of the apparent harm of low salt is reverse causation: people who are already ill eat less.^[7] The very-low-intake harm signal is largely a measurement artefact, not a reason to stop cutting salt.

Salt and stomach cancer

Salt is also linked to stomach cancer, through a separate route. Across prospective cohort studies, each extra 5 g of salt a day tracked with about 12% higher risk of gastric cancer.^[8] An earlier pooling found the same direction: about 68% higher risk in the highest salt-intake group compared with the lowest.^[9] The proposed mechanisms are damage to the stomach lining, the formation of N-nitroso compounds in the gut, and an interaction with Helicobacter pylori. This is observational evidence of moderate strength, not a trial result.

What to do

1. Aim for under 2 g of sodium a day (about 5 g of salt), the WHO target.
2. Cut the packaged and restaurant food first. In US data that is where about 70% of the sodium comes from, and processed meat is a concentrated source.
3. Favour potassium-rich whole foods.
4. Don't be put off by "low salt is dangerous" headlines. They rest largely on a measurement method known to create the effect, and on ill people eating less.
5. If you have high blood pressure or kidney disease, salt matters more for you; see Blood pressure before reaching for a potassium salt substitute.

Further reading

• Sacks FM et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med 2001.^[10]
• Harnack LJ et al. Sources of Sodium in US Adults From 3 Geographic Regions. Circulation 2017.^[11]
• O'Donnell M et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med 2014.^[12]
• Cappuccio FP et al. Sodium and Health: Old Myths and a Controversy Based on Denial. Curr Nutr Rep 2022.^[13]
• Fang X et al. Landscape of dietary factors associated with risk of gastric cancer: A systematic review and dose-response meta-analysis of prospective cohort studies. Eur J Cancer 2015.^[14]
• D'Elia L et al. Habitual salt intake and risk of gastric cancer: a meta-analysis of prospective studies. Clin Nutr 2012.^[15]