Salt and Blood Pressure: What the Evidence Actually Shows and How Much Salt Is Too Much

Reviewed by GPhC Pharmacist at Halton Pharmacy Clinical Team, Leeds

The link between salt and blood pressure is one of the most thoroughly studied relationships in nutrition science. It’s also one of the most commonly misunderstood.

At Halton Pharmacy in Leeds, we regularly hear from patients who feel their diet “isn’t particularly salty,” or who’ve heard conflicting claims that the salt and blood pressure link is overstated. This article explains the evidence, how it actually works in your body, how big the effect really is, and what it means practically if you’re managing your blood pressure.

How Salt Raises Blood Pressure

Salt (sodium) helps control the fluid balance in your body, working through your kidneys and a hormone system called RAAS.

Here’s the chain of events:

1. When you eat more salt, your kidneys hold onto more water to keep your blood’s sodium level balanced.
2. This increases the total volume of blood circulating in your body.
3. A higher blood volume puts more pressure on your artery walls.
4. This raises both your systolic and diastolic blood pressure readings.
   
   

Some people are more affected than others. This is called “salt sensitivity,” and it’s more common in older adults, Black individuals, and people with chronic kidney disease. People who are salt sensitive see a bigger blood pressure drop when they cut back on salt, compared with people who are less sensitive to it.

There’s currently no simple way to test for salt sensitivity in routine clinical practice. This is why general advice to reduce salt intake is based on the average benefit across the whole population, which remains genuinely meaningful, even though individual results can vary.

How Big Is the Effect, Really?

A major 2020 review of over 100 clinical trials found:

• Reducing salt intake by around 130 mmol a day lowered systolic blood pressure by an average of 4.26 mmHg in people with high blood pressure
• The same reduction lowered it by an average of 1.98 mmHg in people with normal blood pressure
  
  

A follow up 2021 review of over 133 trials confirmed a clear pattern: the more you cut your salt intake, the more your blood pressure drops, with the biggest improvements seen in people who started with the highest salt intake and highest blood pressure.

How Much Salt Should You Actually Have?

• NICE guidance: no more than 6 grams of salt a day (equivalent to 2.4 grams of sodium)
• WHO and the British Heart Foundation: a slightly lower target of 5 grams a day

The average UK adult currently eats around 8 to 9 grams of salt a day, noticeably more than either recommendation.

Bringing this down to the recommended level is a realistic, achievable step, and one with real evidence behind it for lowering blood pressure, especially alongside other healthy lifestyle changes.

Where Your Salt Actually Comes From

Here’s the part that surprises most people: about 75% of the salt UK adults eat doesn’t come from the salt shaker. It comes from processed and ultra processed food.

The biggest sources of hidden salt in a typical UK diet:

• Bread and bakery products (often high in salt despite not tasting salty at all)
• Processed meats: bacon, ham, sausages
• Ready meals and soups
• Canned foods
• Hard cheese
• Sauces

What this means in practice: cutting back on the salt you add while cooking or at the table helps, but it has a much smaller effect than cutting back on processed and ultra processed foods, since that’s where most of your salt intake is actually coming from.

Why This Matters for Your Heart Health

If your blood pressure has come back elevated at Halton Pharmacy, or anywhere else, reducing salt is one of the lifestyle changes with the strongest, most consistent evidence behind it.

A 5 mmHg drop in systolic blood pressure might not sound like much on its own. But at a population level, a change of this size translates into a genuinely meaningful reduction in heart attacks and strokes.

Combining salt reduction with the DASH diet (rich in fruit, vegetables, potassium, and low fat dairy) has an additive effect on blood pressure. In some patients, this combination can produce blood pressure improvements that rival what a blood pressure medication would achieve on its own.

This article is for general information only. It’s not personal medical advice. To discuss your blood pressure and get personalised lifestyle advice, please book a Heart and Metabolic Health assessment at Halton Pharmacy, Leeds.