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One of the standard dietary recommendations seems to be that we should curb our salt intake. We are advised not to add salt to our food - at the table or when cooking - and to avoid salty food like potato chips, salted nuts and processed food. We were told that too much salt in our diet leads to high blood pressure with associated risk of heart disease and strokes.
Restrictions on salt intake
Current recommendations from the American Heart Association, the US Department of Agriculture and the US Department of Health and Human Services, advise restricting daily salt intake to 2,300mg per day in the general population. And for particular groups - anyone over 50, African Americans, people with high blood pressure, diabetes or chronic kidney disease, the level is set at 1,500mg per day. This amounts to little more than half a teaspoon a day.
Despite the recommendations, the average salt intake in America and other parts of the world is 3,400mg per day and many people are concerned about salt consumption.
What does the new report say?
The institute of Medicine was commissioned by the Centers for Disease Control and Prevention to assess the validity of the data on which these recommendations were based. (Ironically it was the Institute’s evaluation of the data in 2005 which led to the current recommendations on salt intake).
In their latest review the Institute were unable to support the current recommendations as they found that the evidence on which they are based fails to prove that consuming more than 1500mg of salt a day will have harmful effects on health.
Why the change of opinion?
The Institute discovered a number of issues which made them question the validity of the current recommendations. One was that the original advice was based on the assumption that high blood pressure as a result of excessive salt causes heart attacks and strokes. This is termed using high blood pressure as a ‘marker’ for these adverse events.
But reanalysis of the data failed to support this assumption.
For example in some of the studies the risk of heart disease continued to fall with reduced salt intake, even when blood pressure stayed the same. This may indicate that the positive effects were being brought about by some other change in diet and was not due to lowering of blood pressure.
Worryingly there was also some evidence of low salt intake being associated with higher risk of heart attack and death.
Also, it is very difficult to accurately measure a person’s salt intake as much of it is invisible ie not just what we sprinkle on our food. Many of the studies relied on participants reporting their salt intake.