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Comment by ek750 | Hacker News Reader

I feel that this sort of simplification is common to our mis-understanding of health and nutrition. I also heard similar myths like: Calories in = Calories out, you are what you eat (meaning if you eat high fat you'll gain fat), etc.

Can you explain why you think salt raises blood pressure?

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It's a very well understood effect -- as your body absorbs salt, it also retains more water to maintain osmotic pressure. This additional fluid in your circulatory system necessarily causes your blood pressure to increase.

That's the very simple chemistry behind salt increasing blood pressure. The biology is more complex and the effect isn't necessarily long lasting or linear, but there is indeed a direct relationship between sodium intake -> blood pressure.

It would seem to make sense, until biology gets in the way. Mammals have several exquisite mechanisms for regulating sodium. Unless you're very sick, they work fine. So there is no 'direct' relationship at all.

It should also be noted this is a study evaluating a reduced sodium diet (standard treatment for those having heart failure) vs. an even further reduced sodium diet. Further reduction yielded little difference in results. That is to say reducing your intake below 1,500 mg per day doesn't present any net benefits. The study should not be interpreted as salt intake has no effect whatsoever on your blood pressure.

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