Salt and hypertension

People with high blood pressure, diabetics and smokers are all at increased risk of having a stroke or heart attack.

A stroke occurs when part of the blood flow to the brain is cut off. This causes a break in the oxygen supply, causing cells to die. Stroke is the third most common cause of death in England and Wales, with an estimated 150,000 strokes and mini strokes and 67,000 deaths from strokes every year.

Stroke has a greater disability impact compared to any other chronic disease. The outcomes of strokes are wide ranging, but sufferers can experience paralysis, speech impediment and memory problems which can be highly frustrating and difficult for both the individual and the family. 

Raised blood pressure is a major cause of cardiovascular disease, responsible for 62% of stroke and 49% of coronary heart disease. Salt is the major factor that increases blood pressure and is therefore responsible for many strokes and heart attacks every year. From the blood pressure reduction seen in a meta-analysis, it was estimated that a reduction of 6 g of salt per day would reduce stroke by 24% and coronary heart disease by 18%. This would prevent approximately 2.5 million deaths worldwide.

Salt intake can directly and independently lead to enlargement of the heart. Reducing salt intake has been shown to reduce left ventricular hypertrophy, which is a major risk factor for cardiovascular disease.

A number of cross-sectional studies have shown a positive correlation between 24-h urinary sodium and left ventricular mass. A reduction in salt intake has been shown to decrease left ventricular mass in hypertensive individuals.

Almost everyone of the Western world eats too much salt. The daily recommended amount is no more than 6 grams a day; the current average salt intake is 8.6g salt a day although many people are eating more than this.

It has been shown that a high salt intake, a low consumption of fruit and vegetables (which corresponds to a low potassium intake), obesity, excess alcohol intake and lack of physical exercise all contribute to the development of high blood pressure. However, the diversity and strength of the evidence is much greater for salt than for other factors. People with, or considered at risk, of stroke or heart disease should take extra care to ensure that they keep their salt intake below the recommended maximum of 6g.