Salt and heart health

Salt and the heart

4th August 2022

Salt is one of the most used condiments in the world and is essential to the human body. It’s made up of about 60% chloride and 40% sodium – and it’s the sodium that we need to be concerned about.

Our bodies need a small amount of sodium to conduct nerve impulses, contract and relax muscles, and maintain the proper balance of water and minerals.

Too much can lead to high blood pressure, heart disease, and stroke. But too little can also be dangerous.

How much salt should we be eating?

People only need about one or two grams of salt a day to be healthy and to help the body to function. Most health guidelines recommend no more than five grams a day but in Australia, we are typically eating around twice that amount - which equates to about two teaspoons a day.

How does salt affect the heart?

Eating too much salt regularly can lessen the kidney’s ability to remove excess fluid. The extra water/fluid instead becomes diluted in the bloodstream adding to the blood volume which causes the heart to pump harder. These factors combine to cause blood pressure to rise.

High blood pressure is one of the biggest predictors of developing cardiovascular disease in later life. In fact, according to a UNSW Sydney study, high blood pressure is estimated to cause 8.5 million deaths a year globally.^[1]

Where’s the evidence to show salt is bad for the heart?

The evidence for the effect of salt on blood pressure, and in turn on heath health, is strong. Overviews of more than 30 randomised trials in which people were assigned to consume different amounts of salt showed clear benefits of reducing salt consumption on blood pressure.

A recent study from Sydney based The George Institute for Global Health involving 21,000 people also showed a significant reduction in rates of stroke, heart attack, and death in people who replaced their regular table salt with a reduced-sodium, added-potassium "salt substitute".^[2]

The same study revealed that excess salt consumption (more than five grams per day) is responsible for three million deaths each year around the world.

Even a modest reduction inn salt intake for just four weeks or more significantly reduces blood pressure.^[3]

What foods are high in salt?

You’ll be surprised by how many products are loaded with salt. Breakfast cereals, bread, margarine and butter, savoury snacks, potato crisps, processed meats, sausages, instant noodles, dressings, sauces, and stocks can often contain high levels of added salt.

Even healthy-looking foods – labelled organic, meat-free, or plant-based – can still have high levels of salt.^[4]

Tips to cut back on salt

• Check the food labels before you put them in your shopping basket. Aim to choose foods that contain less than 120mg of sodium per 100g where possible, but according to Unpack the Salt anything under 400mg of sodium per 100g is considered to be a healthier choice.
• Be mindful of salt in your own cooking. Whilst it’s estimated that we consume around 70-75% of the salt in our diet from the foods we buy, you can also cut back on salt whilst cooking. You can add flavour by adding spices, chillies, lemon, and herbs to your food.

Incredibly, your taste buds will adjust after just three weeks of eating less salt.

Is rock salt any healthier?

There is a range of salts on sale in supermarkets and at vastly different prices. But salt is salt, and rock, iodised and sea salts have just as much sodium as your everyday table salt.

What about reduced sodium/potassium enriched salts?

The salt substitute used in The George Institute study was low in sodium but high in potassium – which tastes very similar to salt.

Similar products can be bought in most major supermarkets.

But beware! Products containing high potassium levels can be dangerous for people with kidney problems or for those that are on certain high blood pressure medications. So, speak to your GP if you have any concerns before switching.

Can too little salt be a bad thing?

Whilst it’s advisable to cut back on salt, our bodies do need a small amount of sodium to function as it is essential to regulating and balancing the water in our cells.

If sodium levels are diluted, it can lead to issues such as the swelling of cells in our body, which can then lead to a whole host of problems. These can range from minor ailments like headaches and irritability to vomiting, seizures, and in very rare cases death.

The condition called hyponatremia (low sodium concentration in the blood) generally occurs as a result of being sick, certain medical conditions, or side effects of some medicines.

However, it’s actually very difficult to eat too little sodium because of the sodium in foods we eat on a daily basis.

What about if you have low blood pressure – should you be eating more salt?

If you are diagnosed with hypotension – which normally means you have a low blood pressure reading of under 90/60 mm Hg, in certain cases your doctor may recommend you eat foods high in salt – such as pickled items. But this needs to be discussed with your GP as hypotension is a complex condition that is often experienced during pregnancy.

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1. UNSW, 'High blood pressure rates: 1.2 billion people now living with hypertension' August, 2021
2. George Institute for Global Health, 'First direct evidence to show cost-effectiveness of salt substitutes on cardiovascular outcomes', April, 2022
3. Feng. JH, Jiafu L., Graham, AM, 'Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials', April 2013
4. George Institute for Global Health, 'How your meat-free favourites could be tricking you', September 2022