A team of researchers from Ireland and Canada suggested that both high and low levels of salt intake may put people with heart disease or diabetes at increased risk of cardiovascular complications, according to a press release from NUI Galway.
The study, published in the Journal of the American Medical Association, found that moderate salt intake is associated with the lowest risk of cardiovascular events, whereas higher intake of sodium was associated with an increased risk of stroke, heart attack and other cardiovascular events while low intake was associated with an increased risk of cardiovascular death and hospitalisation for congestive heart failure.
The research was co-led by Professor Martin O’Donnell of NUI Galway, Ireland, and Dr Salim Yusuf of McMaster University, Canada. “This research addresses an important population health issue – the association between sodium (salt) intake and cardiovascular disease,” said Professor O’Donnell. “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.”
Compared with moderate sodium excretion between 4 to 5.99 grams per day, the researchers found that sodium excretion of greater than 6-7 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 hospitalisation for congestive heart failure.
The findings call into question current guidelines for salt intake, which recommend less than 2.3 grams per day.
The guidelines are mostly based on previous clinical trials that found blood pressure is lowered modestly when sodium intake is reduced to these levels, which was also found in the present study, but there are no large studies looking at whether such low levels of sodium intake reduce the incidence of heart attacks and stroke. Clarifying the optimal daily intake of sodium is particularly important in patients with established heart disease, as they may be especially vulnerable to the cardiovascular effects of very high- and low-salt intake and are most likely to receive recommendations on restricting sodium in their diets, the authors concluded.
“Our research confirms the association between high sodium intake and increased risk of cardiovascular disease, which emphasizes the importance of salt reduction in those consuming high-sodium diets (over 6-7g per day) and the importance of efforts to reduce sodium content of many high-salt manufactured foods. However, our study, together with other recent studies, raises uncertainty about whether those with moderate/average sodium intake should reduce their intake further. The only way to resolve this uncertainty is with a large randomized controlled trial that determines whether reducing moderate sodium intake to lower levels results in lower rates of heart disease and stroke. While we accept there are challenges to conducting such trials, they are required urgently given their public health implications’ said Professor O’Donnell.