A healthy diet will not protect you from heart attacks and stroke if you still eat too much salt, a study has found.
Consuming too much salt will raise your blood pressure even if you eat plenty of fruit and vegetables, researchers say.
High blood pressure affects more than one in four adults in the UK and increases the risk of a number of conditions including heart attacks and stroke.
Previously, experts believed that eating lots of fruit and vegetables might help to counteract the effect of high salt on blood pressure. But the latest findings, which looked at the diets of more than 4,500 people, suggest the only way to lower the risk is not to exceed the recommended daily amount of 6g equivalent to one teaspoon. Scientists from Imperial College London are also calling on food manufacturers to lower the salt content in their products.
The international study tracked participants from the UK, US, Japan and China, aged from 40 to 59, over four days.
Using urine samples, the scientists assessed concentrations of sodium the main component of salt and potassium, found in leafy green vegetables and linked to lower blood pressure.
They also assessed their intake of 80 nutrients that may be linked to low blood pressure, including vitamin C, fibre, and omega-3 fatty acids, often found in fruit, vegetables and whole grains.
Although salt intake has dropped in recent years, the average British adult still consumes 8.5g a day, according to the study.
Researchers found a correlation between high blood pressure and higher salt intake, even in people who were eating a high amount of potassium and other nutrients.
Blood pressure is measured in two numbers the first, systolic pressure, measures the force the heart pumps blood around the body. The second, diastolic pressure, is the resistance to blood flow in the arteries.
People should have a blood pressure below 120 over 80 (120/80). An increase of an additional 7g of salt above the average intake, across the study, of 10.7g a day was associated with an increase in systolic blood pressure of 3.7mmHg, according to the results published in the journal Hypertension.
Experts estimate 80 % of salt intake comes from processed food, suggesting more needs to be done by manufacturers to reduce salt levels.
Dr Queenie Chan, joint lead author of the research from the School of Public Health at Imperial, said the research shows the importance of cutting salt intake.
Co-author Jeremiah Stamler, of Northwestern University in the US, said: The salt content in the food supply must be reduced significantly.'