An estimated one in seven cases of stomach cancer in the UK could be avoided by reducing salt intake, experts have claimed. Campaigners discuss the wider health problems linked to excess salt, and how much it is healthy to consume.
By Lisa Salmon
As you liberally sprinkle salt on your chip buttie, before splodging on some ketchup, bear in mind that it's not just the fat contents of your snack that could be harmful.
As well as the salt on your chips, just two slices of certain types of bread can provide nearly half a person's daily recommended salt intake of 6g, and some ketchups and sauces could add another half a gram.
Consuming so much salt regularly can lead to numerous health problems - including cancer and heart disease.
The World Cancer Research Fund (WCRF) has just revealed that one in seven cases of stomach cancer in the UK could be prevented, if everyone cut their daily salt intake to 6g - a level teaspoon's worth.
Salt is made up of 40% sodium, which is an essential mineral, and 60% chloride. While a small amount is essential for the body to function normally, adults need just 1g a day (a large pinch) and children need even less.
However, the average daily salt consumption in the UK is now 8.1g - 2.1g above the recommended amount - and the campaign group Consensus Action on Salt and Health (CASH) warns that almost everyone eats too much.
High consumption isn't just because people add extra salt to meals, but because many are unaware of how much salt food contains already. It's believed that around 75% of total intake is consumed this way, and people may have no idea that they're eating unhealthy levels.
According to CASH, bread is responsible for a fifth of our daily salt intake, and one in four loaves contains as much salt per slice as a packet of crisps.
"One loaf of bread can have half as much salt as another," says CASH's campaign director Katharine Jenner, a public health nutritionist. "But it's difficult to know that without looking at the label and understanding it."
Other culprits include some types of ketchup and other sauces, processed meats, smoked fish, convenience foods like pizza, pasties and ready meals, and salty snacks like crisps and salted nuts.
The WCRF is calling for a standardised 'traffic light' system on the front of food and drink packaging, to clearly flag up sat, fat and sugar levels.
In the meantime, it's important for people to read food labels before they buy, says Jenner.
"The easiest thing to happen would be for manufacturers not to put so much salt in food," she says.
"But people can take control of their own salt intake by adding less when cooking, using fresh foods, and looking at the labels on food and choosing the lowest salt option."
Stomach cancer was the cause of 4,966 deaths in the UK in 2010, according to Kate Mendoza, head of health information at the World Cancer Research Fund.
Of these, 14% could have been prevented by cutting salt intake, as a high-salt diet can cause changes to the stomach lining, making it more vulnerable to cancer-causing substances.
The bacterium helicobacter pylori (H.pylori) is a known risk factor in stomach cancer, and salt increases the bacterium's action.
"Stomach cancer is difficult to treat successfully because most cases aren't caught until the disease is well-established," says Mendoza.
"This places even greater emphasis on making lifestyle choices to prevent the disease occurring in the first place - such as cutting down on salt and eating more fruit and vegetables."
Excess salt is also linked to high blood pressure, the main cause of stroke and a major cause of heart disease, the biggest killers in the UK.
Too much salt disrupts the body's natural sodium balance, causing fluid retention, which raises blood pressure.
Around one in three adults in the UK (16 million people) have high blood pressure, with five million not even aware of it.
CASH says that reducing the UK adult's average daily salt intake to the recommended 6g could prevent about 12,500 heart attacks and strokes a year, half of which would be fatal.
Dr Wayne Sunman, a consultant stroke physician, agrees. "Consuming salt puts blood pressure up a small but important amount: the more you take, the greater the effect," he says.
"Conversely, by reducing the amount of salt we take, we could all reduce our blood pressure."
High salt consumption is also linked to osteoporosis, a condition which causes bones to become weak and fragile and prone to fracture. An estimated three million people in the UK are affected.
Calcium is a major part of bone mass, and CASH says studies show a high salt intake increases calcium losses in the urine (calciuria), some of which will be directly from bones.
"Sodium and calcium work in similar ways, and the sodium displaces the calcium, leading to weakening of bones in the long-term," says Jenner.
"There are lots of reasons for developing osteoporosis, but it's known that if you reduce salt, you lower your risk."
In turn, this could mean bad news for kidneys, too. The calcium lost through this process will have to pass through the organs, and can lead to painful kidney stones.
A high-salt diet is also linked to kidney failure, as a good sodium balance is needed for the kidneys to draw excess water out of the blood. In addition, too much salt has been shown to increase protein in the urine, a major risk factor in reduced kidney function.
Jenner says: "Excess sodium puts a lot of pressure on the kidneys to try and excrete it. They have to work extra-hard, which can cause problems in the long term."
Too much salt can also make you bloated and very thirsty, and there is thought to be an indirect link between excess levels and obesity.
While salt does not in itself cause weight gain, the increased thirst it causes is believed to be linked to consumption levels of sugar-filled soft drinks, particularly among children.
According to CASH, 31% of the fluid drunk by 4-18 year olds is sugary soft drinks, which can contribute to obesity.