Good diet 'doesn’t offset high salt'
5th March 2018 – Eating a healthy diet may not offset the effects of a high salt intake in raising blood pressure, a study has found.
Scientists say the discovery should encourage policy makers and food manufacturers to lower the salt content in their products.
It is estimated that more than 1 in 4 adults in the UK have high blood pressure, also known as hypertension, although many have not been formally diagnosed.
The condition is a major risk factor for strokes and heart disease.
Blood pressure and diet
Experts have previously recommended a healthy diet to lower blood pressure. This includes the Dietary Approaches to Stop Hypertension – the DASH diet. This encourages people to eat more nutrient-dense fruit and vegetables, choose fat-free and low-fat dairy products, wholegrains, fish, unsalted nuts, and unsaturated vegetable oils.
The latest research, from scientists at a number of institutions, including Northwestern University in the US and Imperial College London, say most of the available data on salt and blood pressure are from studies that did not take other dietary factors into account.
The team turned to the International Study on Macro/Micronutrients and Blood Pressure (INTERMAP) which included 4,680 men and women aged 40 to 59 from the US, Japan, China, and the UK.
Information on their height, weight, and blood pressure was recorded, and over the course of 4 days, 2 urine samples were taken.
The scientists assessed concentrations of sodium and potassium in these urine samples. Sodium is the main component of salt, while potassium is found in leafy green vegetables – one of the dietary ingredients that has been linked to lower blood pressure.
The team also analysed participants' intake of 80 nutrients that may have links to lower blood pressure, including vitamin C, fibre, and omega-3 fatty acids.
The findings confirmed a link between higher blood pressure and eating high levels of salt, even among those people who were eating large amounts of potassium and other nutrients.
Salt and processed foods
The authors of the study, published in the journal Hypertension, conclude that "sizable reduction in the salt content of commercially prepared foods (e.g. breads), is a key strategy for prevention and control of the cardiovascular diseases epidemic".
In the UK, adults are advised to eat no more than 6g of salt a day – around 1 teaspoon.
Commenting in an emailed statement, Mhairi Brown, assistant nutritionist at Consensus Action on Salt and Health (CASH) says: "This robust and extremely well conducted study demonstrates once again the overwhelming importance of reducing our salt intake to stop the devastating effects that high blood pressure has on our health, causing strokes and heart disease – the biggest cause of death in the UK.
"By reducing our reliance on processed food, we can lower the amount of salt we eat, as well as increasing our intake of healthier nutrients.
"We shouldn’t overlook the importance of increasing the amount of potassium we eat, from fruits and vegetables, to protect our general health."