HAMILTON, ONT. — A high intake of salt was associated with an increased risk of stroke, heart attack and other cardiovascular events while a low intake of sodium was also associated with an increased risk of cardiovascular death and hospitalization for congestive heart failure, according to a study recently published in the Journal of the American Medical Association. The study showed that a moderate level of salt intake was associated with the lowest risk of cardiovascular events.
Conducted by researchers at McMaster University, the observational study examined 28,880 people who were at increased risk of heart disease from clinical trials conducted between 2001 and 2008. The researchers estimated 24-hour urinary sodium and potassium excretion from a morning fasting urine sample. Follow-up found more than 4,500 cardiovascular events occurred, making the study one of the largest to examine the relationship between sodium excretion, potassium excretion and cardiovascular events.
Compared with moderate sodium excretion, which was defined as being between 4 grams to 5.99 grams per day, the researchers found that sodium excretion of greater than 7 grams per day was associated with an increased risk of all cardiovascular events, and sodium excretion of less than 3 grams per day was associated with an increased risk of cardiovascular death and hospitalization for congestive heart failure.
The findings call into question current guidelines for salt intake, which recommend less than 2.3 grams (2,300 mg) per day, according to the researchers. Those guidelines, they said, are mostly based on previous clinical trials that found blood pressure is lowered modestly when sodium intake is reduced to the 2.3 gram level.
“This research addresses an important population health issue — the association between salt intake and cardiovascular disease,” said Martin O’Donnell, an associate clinical professor in the department of medicine at McMaster University. “In general, previous observational studies have either reported a positive association, no association or an inverse association between sodium intake and heart disease and stroke. This has resulted in a lot of controversy. Our study is the first to report a J-shaped association between sodium intake and cardiovascular disease, which may explain why previous studies have found different results.”