What do we know already?
Eating less salt can help lower your blood pressure. By itself, high blood pressure isn’t necessarily a big deal, but over time, and combined with other factors such as a high cholesterol level or being overweight, it can increase your risk of heart attack or stroke.

It would be useful to know whether a low-salt diet could cut your risk of these serious health problems, rather than just lowering your blood pressure. Now, researchers have looked at lots of smaller studies on salt intake to get a better picture of the health effects. They combined the results of 13 studies, which looked at more than 1,77,000 people from six countries, including the United States, Scotland and Japan.

What does the new study say?
People who ate more salt had a higher chance of having a stroke. On average, an extra 5 grams of salt a day was linked to a 23 per cent higher risk of stroke.
This might sound like a big increase, but the impact will depend on how likely you are to have a stroke in the first place. Increasing a 1 in 1,000 risk by 23 per cent still only gives you a risk of 1.23 in 1,000. The impact of salt on cardiovascular disease overall (both stroke and heart disease) was less clear. There seemed to be a 14 per cent increase in risk, but statistically the researchers couldn’t be sure that this wasn’t a chance result.

How reliable are the findings?
One problem with the research is that it’s hard to accurately gauge someone’s salt intake. Most of the studies used questionnaires to look at the foods people ate, which relies on accurate (and honest) answers from the participants. Only 4 studies out of 13 measured the amount of salt in people’s urine, which is much more precise. Even these studies only looked at salt levels for one day, so don’t account for any changes in people’s diets over time.

What does this mean for me?
Assuming too much salt is as harmful as the study suggests, a worldwide reduction to recommended levels could prevent (or, rather, delay) 1.25 million deaths a year, by cutting the number of strokes caused by high blood pressure.
The effects of salt on cardiovascular disease, which includes heart problems as well as strokes, are less clear. However, an optimistic interpretation of the results suggests that nearly 3 million deaths from cardiovascular disease could be prevented each year (including the lives saved by preventing strokes).

Whether that’s achievable is another matter. A typical person in the UK eats 9 or 10 grams of salt a day, and in many eastern European and Asian countries the average intake is higher than 12 grams. The Food Standards Agency says people should eat no more than 6 grams of salt a day, so we’re talking about whole populations halving the amount of salt they eat. The World Health Organization says the daily recommended salt intake should be even lower, at 5 grams.

Staples of a modern diet, such as processed, tinned, and fast foods, all tend to be high in salt. Even innocuous-seeming foods like bread and breakfast cereals can contain large amounts of salt. The researchers say that achieving big changes in people’s diet would probably mean action at a national level, rather than just encouraging people to cut their intake.

What should I do now?
If you think you might have high blood pressure, talk to your doctor. There are lots of ways of controlling your blood pressure, including exercise, cutting back on alcohol, and taking medicines.

If you want to cut down on salt, you may wish to:

*Watch out for large amounts of salt in foods like bread, breakfast cereals, and ready meals.
*Replace tinned soups or vegetables with home-made or fresh equivalents, or choose low-salt varieties.
*Avoid adding salt automatically when you’re cooking or at the table.
*Use herbs, spices, black pepper, lime, lemon, wine, tomatoes, or garlic to add flavour to cooking, rather than salt.