Salt is a vital part of life. The levels of salt in the blood are carefully monitored and defended by many body systems. Humans and all animals will go to extremes to obtain salt if they are deprived. That's just like thirst and hunger.
The cheap abundance of salt in our diets has become a liability though. Everyone knows that people with high blood pressure should reduce their salt intake. However, it seems like salt has little or no effect on the blood pressures of people without hypertension.
The New England Journal of Medicine this month had a report of a study showing that everybody's blood pressure will go down if they eat less salt. Yes, I guess if you never ate any salt at all your blood pressure would eventually be zero - you'd be dead. But there's salt in almost everything, especially in the typical U.S., diet so it would be almost impossible to eat no salt.
The report was titled "Effects on blood pressure of reduced dietary sodium and the dietary approaches to stop hypertension (DASH) diet." The DASH diet consists of fruits, vegetables, and low-fat dairy products and whole grains, poultry, fish and nuts and only small amounts of red meat, sweets and sugar-containing beverages. All the sorts of things that you've heard are good. This study, by a consortium of medical centers, also found that the DASH diet lowered blood pressure independently of salt and weight loss. It is impossible to say at this time what aspects of that diet are most important.
The relationship of salt to blood pressure parallels that of total calories to weight. But hypertension does not carry the stigma that obesity does in our society. Just like the resistance you meet when you try to lose weight by eating less, the effects of decreasing salt intake are resisted more and more strongly by the body. At any reduced level of salt intake there is a leveling off of blood pressure and to lower it more requires a much more drastic reduction in salt intake. That is to say that your body resists change and that resistance gets stronger the harder you try to beat it. An interesting question would be, "How much can we reduce our salt intake before we begin to crave it and lose control?" Is that craving different in people with high blood pressure?