Why is salt bad for our health?
Salt puts up our blood pressure. Raised blood pressure (hypertension) is the major factor which causes strokes, heart failure and heart attacks, the leading causes of death and disability in the UK. There is also increasing evidence of a link between high salt intake and stomach cancer, osteoporosis, obesity, kidney stones, kidney disease and vascular dementia and water retention. Salt can also exacerbate the symptoms of Ménière's disease and diabetes.
Small amounts of salt are essential for our health. Adults need less than 1 gram per day and children need even less. As a nation we are all eating approximately 8.1g of salt per day, far more than we need and more than the recommended maximum of 6g per day, putting us at risk of all of these health problems. The good news is that reducing your salt intake can lower your blood pressure and the risk of disease. In fact right down to 3g per day, the lower the salt intake, the lower the blood pressure.
Blood pressure is the amount of pressure that blood puts on your blood vessel walls as it is pumped around the body. Certain factors such as being overweight, lack of exercise and, in particular, a high salt diet can raise your blood pressure, leading to heart attacks and strokes. A third of adults have high blood pressure, defined as 140/90 mmHg, and many don’t even know they have it as it has no symptoms; your GP will be able to check your blood pressure for you. The risk of disease starts within the normal range of blood pressure, well below 140/90 mmHg, so most people will benefit from lowering theirs. It’s a myth that developing high blood pressure is inevitable as you grow older, keeping your salt intake down, watching what you eat and taking exercise will keep it under control.
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A stroke usually occurs when the blood supply to part of the brain is cut off, reducing the flow of oxygen to the brain, causing cells to die. There are two main types of stroke; ischemic strokes, when a blood vessel becomes blocked, and haemorrhagic strokes, when a blood vessel bursts and bleeds into the brain. Stroke is the third biggest killer in the UK and a leading cause of severe adult disability. High blood pressure is the single most important risk factor for stroke and salt is the major factor that raises blood pressure, salt is therefore responsible for many of these strokes. Stroke is not an inevitable part of aging and many can be prevented by keeping blood pressure under control, through salt reduction, exercise and healthy eating.
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Coronary Heart Disease
Coronary heart disease (CHD) is the term used to describe what happens when the heart’s blood supply is reduced or blocked leading to heart failure and heart attacks. CHD is the UK's biggest killer, with one in every four men and one in every six women dying from the disease. Approximately 300,000 people have a heart attack each year.
Raised blood pressure is a major risk factor for CHD. It causes the walls of blood vessels to become thick so that the blood vessels become too narrow and can’t carry enough blood to the heart. Over time this can lead to a thickening of the heart muscle, reducing the heart’s ability to pump blood around the body, leading to heart failure - where not enough blood is carried around the body. The thickened blood vessel walls can also lead to clots forming; these clots can block the blood supply to the heart and cause a heart attack.
As raised blood pressure is a major risk factor for CHD and salt raises blood pressure, lowering salt intake, losing weight and making other lifestyle changes can dramatically reduce your risk.
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A high salt diet increases the risk of stomach cancer. A quarter of the 7000 new cases each year can be attributed to salt. The bacterium Helicobacter pylori (H. pylori) is the major risk factor for stomach cancer as it can lead to inflammation of the stomach which can in turn lead to stomach ulcers and stomach cancer. H. Pylori in the stomach will not necessarily cause damage, however salt can damage the lining of the stomach, making it more vulnerable to the effects of H.pylori, and salt may also increase the growth and action of the bacterium making it more likely to cause damage. Men are at a higher risk than women and there are other important risk factors for stomach cancer explained in the fact sheet.
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Osteoporosis is a condition which causes thinning of bones, making them brittle and prone to breaking. In the UK an estimated 3 million people are suffering from osteoporosis; 1 in 2 women and 1 in 5 men will break a bone after the age of 50, mainly due to poor bone health.
Most calcium in the body is stored in bones. A high salt diet can cause calcium to be lost from bones and excreted in the urine, making bones weak and easily broken. High blood pressure caused by a high salt diet can speed up the loss of calcium from bones, worsening the problem. Older people are most at risk of osteoporosis because bones naturally become thinner as we get older. Postmenopausal women are particularly at risk of bone thinning due to the drop in the hormone oestrogen which normally protects bone health. However, men, women and children of all ages need to look after their bone health to avoid osteoporosis later on.
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A quarter of British adults are obese and two thirds are either obese or overweight. Obesity is linked with numerous health conditions such as high blood pressure, diabetes, CHD and sleep apnea. Salt does not cause weight gain itself but it does make you thirsty, this leads you to drink more fluids, if the fluids are sugary drinks they can cause weight gain because they contain a lot of energy. This is a major problem for children and teenagers as a third of the fluids they drink are sugary soft drinks.
Kidney stones are a common problem, caused by a build up of calcium in the kidneys. Both a high salt intake and high blood pressure can cause too much calcium to be excreted by the kidneys into the urine, leading to a build up of calcium and therefore kidney stones. They can be very painful and in some cases can lead to kidney disease.
The kidneys control fluid balance and blood pressure by controlling the amount of fluid lost from the blood into urine. A high salt diet can disrupt the function of the kidneys and cause high blood pressure, this in turn puts a strain on the kidneys leading to kidney disease. A high salt diet can also cause existing kidney disease to progress faster. People with kidney disease, or at risk due to persistent urinary tract infections or Chrohn’s disease, should reduce their salt intake to avoid exacerbating the condition.
Dementia is a loss of brain function that affects memory, thinking, language, judgment, and behaviour. Vascular dementia is a common form of dementia. It is caused by a blocked blood vessel in the brain which occurs after a stroke or a series of mini strokes; around one in three people who have a stroke develop vascular dementia. A high salt intake raises blood pressure, increasing the risk of stroke and therefore the risk of dementia. Good blood pressure control is hugely important in preventing strokes so keeping salt intake down in younger life, along with leading a healthy lifestyle, can be recommended as part of a preventative diet.
A high salt intake causes us to retain water, up to 1.5 litres(!) of it. Women who find they suffer from bloating may see a benefit from salt reduction and, more seriously, patients already with heart failure, nephrotic syndrome and cirrhosis of the liver, will particularly benefit in a cut in salt intake
Ménière’s is a rare disease which damages the ear and causes giddiness with nausea and vomiting, tinnitus and hearing loss. A high salt diet can worsen the symptoms of Ménière’s because it causes fluid retention, this can increase the pressure in the inner ear which causes and worsens the symptoms of Ménière’s. A lower salt diet is thought to be extremely effective in treating Ménière’s.
There are currently over 2.5 million people with diabetes in the UK. Salt can raise the risk of developing diabetes by raising blood pressure. People who already have diabetes can also benefit from eating less salt because keeping blood pressure in the healthy range helps to reduce the risk of the long term complications of diabetes.