Most of us have heard that a diet high in salt is not healthy. Particularly for people who have high blood pressure (hypertension), physicians recommend reducing salt. Hypertension is a risk factor for stroke, heart attack and kidney failure. There is data showing that reducing salt leads to decreases in rates of hypertension and death from cardiovascular disease. The head of the CDC, Thomas Frieden, wrote in an article published in JAMA last year that decreasing sodium by even 400 milligrams a day could prevent 32,000 heart attacks and 20,000 strokes every year (JAMA. 2016;316(6):579-580). Seems like a no-brainer, right? Cut out salt.
And yet…..Controversy arises because of studies that show that it’s also a risk to have too little sodium in your diet. A 2013 report from the Institute of Medicine concludes that too little sodium can be harmful and that dropping sodium below a certain level actually can lead to heart attacks. An article in the British journal, The Lancet (388:10043, 465-475, July 30, 2016) reported a review study which concluded that for people without hypertension, sodium intake did not increase the risk for disease or death. However, less than 3 grams had a 26% increased risk for death or heart disease and stroke, compared with those who consumed 4-5 grams a day. In people with high blood pressure, consuming 7 grams of salt or more a day increased the risk by 23% BUT consuming less than 3 grams increased the risk by 34%! The authors acknowledge that eating less salt helps to reduce blood pressure but warn that the situation is more complex than simply reducing salt intake. The study concludes: “These data suggest that lowering sodium intake is best targeted at populations with hypertension who consume high sodium diets.” Simply: high sodium intake is associated with increased risk in people with high blood pressure and low sodium intake is associated with increased risk in those people with or without hypertension.
The point here is that most medical issues are rarely straightforward or simple. And although the media may present the case for one point of view, people should be skeptical of a lack of complexity in a subject. Something as simple as the case for lowering salt intake illustrates that the advice may depend on your blood pressure readings, your risk factors, your sodium intake, and other factors not yet exposed. It’s a good idea to examine an issue from all angles and even do some research before you believe the headlines.