The FDA is renewing it’s attack on salt consumption and it’s a big mistake.
The attack is based on the supposed effects salt has on blood pressure. Most studies that link salt intake to increased blood pressure are observational studies, NOT experimental studies. Observational studies are very poor at testing cause and effect since they unintentionally examine thousands (or even millions) of variables, not one isolated variable.
In an observational study, researchers observe what is happening, or what has happened in the past, and they then draw conclusions based on these observations. There is no human intervention. Observational studies try to link things (such as salt intake and high blood pressure) by observing a large population to determine if there is a correlation. While sometimes useful, observational studies often find correlations between two variables even when the one thing (salt) does not cause the other (high blood pressure). Think of an observational study this way – if you eat a pizza and there’s an earthquake, that doesn’t mean that eating a pizza causes earthquakes.
In an experimental study on the other hand, the researcher manipulates a single variable to determine how the manipulation influences other variables.There is human intervention. An experimental study allows you to be pretty certain that the variable that was manipulated actually caused the change (if there was one). There are reasons to not do an experimental study – ethical issues, lack of resources or influence, or impracticality – but in the case of salts influence on blood pressure, an experimental study is needed and completely practical. How do you know what caused the high blood pressure if you are not testing just that variable?
People that eat a lot of salt tend to eat a lot of processed foods (carbs). Those proceed carbs are the true cause of high blood pressure, not salt. As we learned in PART 1 of our Salt Articles, carbs hold significantly more water than salt. In some experiments higher salt intake actually lowered blood pressure. If you are eating a lower carb diet, salt has almost no effect on blood pressure. If you are eating a higher carb diet, it’s the carbs that are causing the water retention (and hence increased blood pressure). In one study, switching to a low carbohydrate diet resulted in the dropping of blood pressure in high BMI (39.3) subjects. Another study, a systematic review of randomized controlled trials, found “There were significant differences between the groups (low-carbohydrate & low-fat/low-calorie diets) for weight, high-density lipoprotein cholesterol, triacylglycerols and systolic blood pressure, favouring the low-carbohydrate diet.”.
You don’t have to take my word. Do the Tim Ferris method and test it for yourself:
Eat a low carb diet for a week or two while eating a lot of salt. Measure your blood pressure.
Then add a lot of carbs. Measure again.
Then drop your salt. Measure again.
You’ll see that blood pressure will track very closely with your carb intake and not much at all with the salt intake (If you are eating very little salt and then intake a large amount the next day this will alter the result, although any increased blood pressure seen won’t last but a few hours to a day).
Focusing people salt reduction is misleading and ineffective. If you are eating well, your food is fairly bland. Salt is one of few things that gives pleasure with no calories. If you have high blood pressure and are consuming a lot of sodium, you almost surely are eating a lot of proceed food, thus the high blood pressure. The FDAs misguided focus is steering people in a dangerous direction, allowing them to justify their poor food choices. The FDA needs to focus on the true cause – processed carbohydrates. Until THAT is attacked, blood pressure will continue to rise alongside obesity.