of the salt we eat is already in our food
Before we cook. Before we add anything. It comes from processed food, ready meals, bread, cheese, and meat products — not from the shaker on the table. The shaker accounts for only about 25% of total intake.
1
What is it?
Salt is something most of us barely think about. It arrives in our food invisibly — in bread, breakfast cereals, soups, sauces, ready meals, and restaurant food — long before we ever reach for the shaker.
The relationship between salt and blood pressure is one of the most studied, most replicated, and most clinically important findings in all of nutritional science. The evidence is not disputed. Eating less salt lowers blood pressure. And lower blood pressure means lower risk of heart attack, stroke, and premature death.
Salt is made up of sodium and chloride. It is the sodium component that affects blood pressure. When there is too much sodium in the blood, the body retains water to dilute it — increasing the volume of blood in circulation, and with it, the pressure on artery walls.
Most people in the UK consume around 8–9 grams of salt per day — well above the NICE and NHS recommended maximum of 6 grams (roughly one teaspoon, including all salt already present in food). For many people, simply reducing intake to the recommended level would have a meaningful and measurable effect on their blood pressure.
75%
This is the most important and least understood fact about salt. Most efforts to reduce intake focus on what we add ourselves — but the biggest gains come from choosing less processed food more often.
Key Terms
Sodium
The component of salt (sodium chloride) that affects blood pressure. Measured in milligrams (mg) on food labels. To convert sodium to salt: multiply by 2.5. So 1g of sodium = 2.5g of salt.
Systolic blood pressure
The upper number in a blood pressure reading — the pressure in the arteries when the heart beats. Reducing it is one of the most powerful ways to lower cardiovascular risk.
Diastolic blood pressure
The lower number in a blood pressure reading — the pressure in the arteries between heartbeats.
mmHg (millimetres of mercury)
The unit used to measure blood pressure. A reading of 120/80 mmHg means 120 systolic, 80 diastolic.
DASH diet
Dietary Approaches to Stop Hypertension — a well-researched dietary pattern combining low sodium with high potassium, calcium, and magnesium, specifically designed and tested to lower blood pressure.
Potassium
A mineral found in fruit, vegetables, beans, and dairy. Works in opposition to sodium — helps the kidneys excrete sodium and relaxes blood vessel walls, lowering blood pressure.
Renin-angiotensin system
A hormone system that regulates blood pressure and fluid balance. High sodium intake can dysregulate this system, contributing to sustained high blood pressure.
Hidden salt
Salt already present in processed and packaged foods before cooking or seasoning. Accounts for approximately 75% of total UK salt consumption.
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Why does it matter?
High blood pressure is the single largest contributor to cardiovascular disease globally — and salt is one of the most significant dietary drivers of high blood pressure. The relationship is causal, dose-dependent, and consistent across populations.
8–14
mmHg reduction in systolic blood pressure from a low-sodium DASH diet — comparable to the effect of a single antihypertensive drug3
DASH-Sodium Trial, NEJM 2001
24%
lower stroke risk associated with higher potassium intake — fruit, vegetables, beans, and dairy are the main sources5
Aburto et al, BMJ 2013
−42%
fall in stroke mortality during the UK salt reduction programme (2003–2011), when average salt intake fell by approximately 15%4
He et al, BMJ Open 2014
~35,000
stroke and coronary heart disease deaths potentially preventable each year in the UK from reducing average salt intake to 6g/day2
He FJ & MacGregor GA, Hypertension 2003
Salt reduction is also cost-free, has no side effects, and works alongside — and often enhances the effect of — blood pressure medication. The INTERSALT study, pooling data from 52 countries and over 10,000 people, showed that populations with the lowest sodium intakes had far less of the age-related rise in blood pressure that most people in Western countries experience as normal.1
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What your doctor might do
High blood pressure rarely causes symptoms — most people don't know they have it. GPs check blood pressure at routine appointments, and where it is elevated will typically ask about diet — including salt intake — alongside alcohol, physical activity, and weight.
Reading food labels
Many food labels show sodium rather than salt. To convert: multiply the sodium figure by 2.5. So a product showing 0.6g sodium per 100g actually contains 1.5g of salt.
| Label reading | What it means |
|---|---|
| High salt — more than 1.5g per 100g | A less frequent or smaller-portion choice |
| Medium salt — 0.3g to 1.5g per 100g | Reasonable choice |
| Low salt — 0.3g or less per 100g | Good lower-salt option |
Practical strategies in UK clinical practice
| Strategy | Why it helps |
|---|---|
| Reducing processed and packaged food | The main source of hidden salt — the biggest single lever |
| Checking labels before buying | Wide variation between brands of the same product |
| Using herbs, spices, lemon, and pepper | Effective flavour alternatives that don't raise blood pressure |
| Including potassium-rich foods | Fruit, vegetables, beans, dairy — counteract sodium's effect on blood pressure |
| Tasting food before adding salt | Salt preference adjusts downward over 2–4 weeks of lower intake |
When lifestyle change alone is not enough. For people with established hypertension, salt reduction is recommended alongside — not instead of — medication. NICE guideline NG136 recommends salt reduction as a first-line lifestyle intervention for everyone with high blood pressure, regardless of whether they are on medication.
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What the research shows
Global
dose-response between sodium intake and blood pressure confirmed across 52 populations — populations with lowest sodium had the least age-related BP rise
INTERSALT · BMJ 1988
The worldwide picture on salt and blood pressure
The INTERSALT study1 remains one of the most important pieces of evidence in this area. Comparing sodium intake and blood pressure across 52 populations worldwide, it found that populations with the lowest sodium intakes had significantly lower blood pressure — and crucially, showed far less of the age-related rise in blood pressure that most people in Western countries experience as normal. Sodium excretion ranged from near zero in the Yanomamo people of Brazil to 242 mmol per 24 hours in north China — with blood pressure tracking closely alongside intake across the full range.
8–14 mmHg
reduction in systolic blood pressure from a low-sodium DASH diet — comparable to the effect of a single antihypertensive medication
Sacks et al · NEJM 2001
The strongest controlled trial evidence — DASH-Sodium
The DASH-Sodium trial3 was a randomised controlled trial that tested two dietary patterns at three different sodium levels in 412 adults. Reducing sodium intake produced significant reductions in blood pressure — and the effect was additive with the DASH dietary pattern itself. The trial also demonstrated that even people without hypertension benefited meaningfully from sodium reduction.
Lower = lower
the more sodium reduced within the 3–12g/day range, the greater the blood pressure reduction — sustained over 4 or more weeks
He et al · Cochrane 2013
Long-term salt reduction — what the meta-analysis confirms
A Cochrane systematic review and meta-analysis by He FJ, Li J, and MacGregor GA3b of randomised trials of salt reduction found that modest, sustained reductions in salt intake over four or more weeks produced consistent, significant reductions in blood pressure in both hypertensive and normotensive individuals. The effect was larger in those with higher blood pressure at baseline.
−42%
fall in stroke mortality during the UK salt reduction programme (2003–2011), alongside a 15% reduction in average salt intake
He et al · BMJ Open 2014
Real-world population change — what happened in the UK
Between 2003 and 2011, the UK ran a voluntary salt reduction programme with the food industry, targeting salt levels across a wide range of processed foods.4 Average salt intake fell by approximately 15% (1.4g per day). Stroke mortality fell by 42% and ischaemic heart disease mortality by 40% over the same period. The timing and magnitude of the cardiovascular improvements are consistent with the known effects of population-level blood pressure reduction.
24%
lower stroke risk associated with higher potassium intake — with no adverse effect on blood lipids or kidney function
Aburto et al · BMJ 2013
Potassium — the other side of the equation
A systematic review and meta-analysis published in the BMJ (2013), commissioned by the World Health Organization5, found that higher potassium intake was associated with a 24% lower risk of stroke (risk ratio 0.76, 95% CI 0.66 to 0.89). Potassium directly counteracts sodium's pressure-raising effect. Foods rich in potassium include bananas, sweet potatoes, spinach, beans, lentils, and dairy products.
Putting it all together
The evidence on salt and blood pressure is among the most consistent in nutritional science. Reducing salt intake lowers blood pressure. Lower blood pressure reduces the risk of heart attack and stroke. And most of the salt consumed is already in food — meaning the biggest gains come not from putting the shaker away, but from choosing less processed food more often.
What that looks like in practice — and how it fits alongside any medication or treatment — is a conversation for you to have with your GP or healthcare professional.
References
1
INTERSALT Cooperative Research Group. INTERSALT: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. BMJ. 1988;297(6644):319–328.
2
He FJ, MacGregor GA. How far should salt intake be reduced? Hypertension. 2003;42(6):1093–1099.
3
Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. NEJM. 2001;344(1):3–10.
3b
He FJ, Li J, MacGregor GA. Effect of longer-term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013;346:f1325.
4
He FJ, Pombo-Rodrigues S, MacGregor GA. Salt reduction in England from 2003 to 2011: its relationship to blood pressure, stroke and ischaemic heart disease mortality. BMJ Open. 2014;4(4):e004549.
5
Aburto NJ, Hanson S, Gutierrez H, et al. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013;346:f1378.
6
NICE Guideline NG136. Hypertension in adults: diagnosis and management. National Institute for Health and Care Excellence. 2019 (updated 2023).
This article is for health education only. It is not a substitute for medical advice, diagnosis, or treatment. Anything personally relevant is a conversation for you to have with your GP or healthcare professional.