Healthy diet may not offset high salt intake

March 5, 2018, Imperial College London
Credit: CC0 Public Domain

A healthy diet may not offset the effects of a high salt intake on blood pressure, suggests a new study.

The research, from scientists at a number of institutions, including Imperial College London and Northwestern University, analysed the diets of over 4,000 people.

The results, published in the journal Hypertension, showed that people eating higher amounts of salt had higher blood pressure - no matter how healthy a person's overall diet.

The scientists behind the research are now advising people to monitor their - and for food manufacturers to lower the in their products.

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. It's thought to have a number of causes, including age, weight and eating too much salt.

It's thought that vitamins and minerals in fruit and vegetables might in some way affect blood vessels, enabling them to .

Previously, experts believed that eating high amounts of fruit and vegetables might help counteract the effect of high salt on blood pressure.

However while these foods do tend to lower blood pressure, the new research suggests they do not counteract the adverse influence of salt intake.

In the paper, the team studied data from the so-called INTERMAP study. In this study, which was conducted between 1997-1999, scientists tracked the diets of 4,680 people, aged 40-59, from the USA, UK, Japan and China. The volunteers were tracked over four days, and two urine samples were taken during this time. Measurements of height, weight and blood pressure were also taken. The study data has since been used for numerous research projects.

In the latest paper, published today, the team assessed concentrations of sodium and potassium in the . Sodium is the main component of salt, while potassium, which is found in green leafy vegetables, has been linked to lower blood pressure.

The team also used dietary data to assess the volunteers' intake of over 80 nutrients that may be linked to low blood pressure, including vitamin C, fibre, and omega-3 fatty acids. Many of these nutrients are found in fruit, vegetables and whole grains.

The 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. The researchers estimated salt intake by analysing sodium in the urine, as well as analysing dietary data.

The recommended upper limit of adult salt intake in the UK is 6g a day - around one teaspoon.

The study found that average salt intake across the study was 10.7g a day. The average intake for the UK was 8.5g, while the intake for the USA, China and Japan were 9.6g, 13.4g and 11.7g respectively.

Increasing salt intake above this average amount was linked to an increased in blood pressure. An increase of an additional 7g (1.2 teaspoons) of salt above the average intake was associated with an increase in of 3.7 mmHg.

Blood pressure is measured in two numbers - the first, called systolic pressure, measures the force the heart pumps blood around the body. The second number, called diastolic pressure, is the resistance to blood flow in the arteries. Ideally, blood pressure should be between 90/60 and 120/80 mmHg. However, reducing blood pressure by just a small amount can reduce the risk of conditions such as stroke.

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.

"We currently have a global epidemic of high salt intake - and . This research shows there are no cheats when it comes to reducing . Having a low salt diet is key - even if your diet is otherwise healthy and balanced."

She added: "As a large amount of the salt in our diet comes from processed food, we are urging food manufacturers to take steps to reduce in their products."

The team acknowledge that because the data was collected over four days, it provides information from a snapshot of time. They now hope to focus on longer term studies, with a greater number of people.

Explore further: Quinn on Nutrition: Sodium: How low can we go?

More information: Hypertension (2018). dx.doi.org/10.1161/HYPERTENSIONAHA.117.09928

Related Stories

Quinn on Nutrition: Sodium: How low can we go?

March 2, 2018
As with much of this science of nutrition, experts don't always agree on what's best for us. Not that they don't have good information. Sometimes we have lots of valid data. But Mr. Jones' response to a dietary change may ...

Low sodium-DASH diet combination dramatically lowers blood pressure in hypertensive adults

November 13, 2017
A combination of reduced sodium intake and the DASH diet lowers blood pressure in adults with hypertension, according to preliminary research presented at the American Heart Association's Scientific Sessions 2017, a premier ...

Reducing salt and increasing potassium will have major global health benefits

April 4, 2013
Cutting down on salt and, at the same time, increasing levels of potassium in our diet will have major health and cost benefits across the world, according to studies published in BMJ today.

Too much salt may damage blood vessels, lead to high blood pressure

June 18, 2012
Eating a high-salt diet for several years may damage blood vessels — increasing your risk of developing high blood pressure, according to research reported in the American Heart Association journal Circulation. People ...

High salt intake associated with doubled risk of heart failure

August 28, 2017
"High salt (sodium chloride) intake is one of the major causes of high blood pressure and an independent risk factor for coronary heart disease (CHD) and stroke," said Prof Pekka Jousilahti, research professor at the National ...

Recommended for you

Inflammation critical for preventing heart attacks and strokes, study reveals

September 19, 2018
Inflammation, long considered a dangerous contributor to atherosclerosis, actually plays an important role in preventing heart attacks and strokes, new research from the University of Virginia School of Medicine reveals.

Effective drug delivery to heart with tannic acid

September 18, 2018
Typical methods of drug delivery to the heart require surgical procedures involving incisions in the chest wall and bones. To efficiently treat cardiovascular and related vascular diseases without surgery, a KAIST research ...

Daily low-dose aspirin found to have no effect on healthy life span in older people

September 16, 2018
In a large clinical trial to determine the risks and benefits of daily low-dose aspirin in healthy older adults without previous cardiovascular events, aspirin did not prolong healthy, independent living (life free of dementia ...

Financial incentives for cholesterol control may be cost-effective

September 14, 2018
A program that offered financial incentives to both patients and their physicians to control low-density lipoproteins (LDL) cholesterol could be a cost-effective intervention for patients at high risk of cardiovascular disease ...

Apple's smartwatch has a heart monitor now

September 13, 2018
There will soon be another way to monitor your heart—from your wrist.

3-D virtual simulation gets to the 'heart' of irregular heartbeats

September 12, 2018
In a proof of concept study, scientists at Johns Hopkins report they have successfully performed 3-D personalized virtual simulations of the heart to accurately identify where cardiac specialists should electrically destroy ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

dogbert
not rated yet Mar 05, 2018
Not a study. Just a re-examination of a previous study of 4680 people over a 4 day period 18 to 20 years ago. The terrible consequences of increased salt?:

The average salt intake was 10.7 g per day. An increase of 7 g (1.2 teaspoons) above that average increased systolic pressure 3.7 mmHG.

That is to say, if your normal blood pressure is 120/70 (considered a very good bp), an increase intake of 1.2 teaspoons of salt per day might raise your systolic reading to 123.7.

Why do these researchers really really want to lower salt intake? There certainly are medical conditions where people cannot easily excrete salt, making salt consumption a factor in their health, but most people have no trouble at all excreting excess salt and are not affected at all by eating a little more salt.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.