Salt consumption is said to raise blood pressure, cause hypertension and increase the risk of premature death. This is why the Department of Agriculture's dietary guidelines still consider salt Public Enemy No. 1, coming before fats, sugars and alcohol. It's why the director of the Centers for Disease Control and Prevention has suggested that reducing salt consumption is as critical to long-term health as quitting cigarettes.And yet, this eat-less-salt argument has been surprisingly controversial -- and difficult to defend. Not because the food industry opposes it, but because the actual evidence to support it has always been so weak.