HAMILTON, Ontario—Results of a new study published in the Journal of the American Medical Association is calling recommended sodium intake guidelines into question after researchers discovered people who consumed a moderate amount of salt had the lowest risk of heart problems, while people who had high-salt diets had an increased risk of stroke, heart attack and other cardiovascular events.
Researchers at McMaster University examined 28,880 people at increased risk of heart disease from clinical trials conducted between 2001 and 2008. They 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 this one of the largest studies examining the relationship between sodium excretion, as well as potassium excretion and cardiovascular events. They analyzed the association of urinary sodium and potassium with cardiovascular events, in particular heart attack, stroke, hospitalization for congestive heart failure and death.
Compared with moderate sodium excretion (between 4 to 5.99 grams per day), sodium excretion of greater than seven grams per day was associated with an increased risk of all cardiovascular events, and sodium excretion of less than three grams per day was associated with an increased risk of cardiovascular death and hospitalization for congestive heart failure.
The findings call into question current Canadian guidelines for salt intake, which recommend less than 2.3 grams (or 2,300 mg) per day. The guidelines are mostly based on previous clinical trials that found blood pressure is lowered modestly when sodium intake is reduced to this level (which was also found in the present study). However, there are no large studies looking at whether such low levels of sodium intake reduce the incidence of heart attacks and stroke.
“Our study confirms the association between high-sodium intake and cardiovascular disease. Our findings highlight the importance of reducing salt intake in those consuming high-salt diets and the need for reducing sodium content in manufactured foods that are high in salt," the researchers said. “However, for those with moderate (average) intake, whether further reduction of salt in the diet will be beneficial is an open question. We believe that large clinical trials are the most reliable way to determine if reducing sodium intake to lower levels is of benefit."
