Do you want salt on that?
Nutrition is often described as complicated, confusing, or difficult to understand but within that, there are a small number of ‘known facts’ that are basically truisms at this point.
- Eat your vegetables
- Drink plenty of water
- Don’t drink a lot of alcohol
And to this list is typically added “cut back on salt”, but is that ACTUALLY good advice, or is there some unspoken nuance that’s worth adding in here? In this short blog, I hope to add a little bit more detail to the conversation so that you can better appreciate the role of salt in a healthy diet, and whether or not it’s a good idea to add it when cooking or at the table.
The first thing I want to make really clear is that here I’m talking about people who are generally healthy (meaning “have not been diagnosed with any medical conditions”). If you have been told to reduce your salt intake by your doctor because of a specific health concern, then please ignore the following and go with the advice of your medical professional. If you’ve only ever been told to cut back on salt as a general recommendation, or you’re interested in this topic because you’ve only ever heard about salt being spoken about as a bad thing, however, then read on.
Salt, or sodium chloride, is made up of two essential minerals (sodium and chloride, funnily enough) that your body utilises to properly manage water balance. That means that salt is involved in total hydration, but also in the physiological processes that dictate WHERE your body water is stored. Body water is generally placed into three different places:
- In your cells
- In your blood
- In your lymphatic system, including the water between cells
Very briefly, at any given time your body maintains a relatively high amount of sodium and chloride in your blood and a relatively high amount of potassium in your cells. The balance between these two levels leads to what is known as osmotic pressure (you may remember osmosis from school science lessons – it’s where solutions even themselves out across a permeable membrane) and so it is this balance that makes sure your blood volume, intracellular water hydration, and overall water balance stays where it should be.
If the concentration is higher on one side of a cell’s membrane than it is on the other, then water will pass from one side to the other until everything evens out. The main area in which this happens, which you need to know about, is the kidneys, which sense blood sodium concentration and then either increase or decrease body water retention to bring it back to ideal levels.
In short, if sodium concentration gets too high your kidneys make you pee less and store more water, increasing blood volume to dilute the sodium there. If sodium concentration drops, your kidneys make you pee more, reducing your body water (so blood volume) to increase it again.
Reading this you may already be able to see where recommendations to reduce salt came from – if you eat a lot of salt this increases sodium concentration, which leads your kidneys to retain more water and increase blood volume. This increases blood pressure, and so it increases cardiac health risk! This is supported by studies involving people consuming large doses of salt. Their blood volume and so blood pressure increase significantly, theoretically increasing health risk…
But there’s a problem with that. Here’s how such a study would be run:
- Get a bunch of people
- Have them eat extremely low salt diets for a week to make sure everyone has the same low blood sodium level
- Give them a lot of sodium in a sitting
- See what happens
And of course, this isn’t really how ANYONE eats day to day! This kind of study ignores the dynamic nature of the human body and its adaptive nature. If instead, you take a number of people with a relatively high habitual sodium intake and study them, their blood pressure doesn’t appear to be affected by their intake. This is because over time potassium levels within their cells increase according to the sodium concentration in the blood – balancing everything out and resulting in healthy blood volume!
In practical terms, this means that while an acute high intake of sodium will cause water retention and elevated blood pressure, eating a habitually moderate to high sodium intake will not have the same effect because your body is able to adapt to your typical intake. Of course, this is not to say that you can literally eat as much salt as you want – at some point everything becomes unhealthy – but it IS to say that you don’t have to worry about eating a little more than the recommended 6g limit so long as you’re eating plenty of potassium (read: vegetables!).
This is ESPECIALLY the case for those with an athletic lifestyle. Sodium is one of the primary non-water components of sweat, and if that salt isn’t replaced exercisers are prone to cramp, and far worse – hyponatraemia.
Hyponatraemia (hy-po-na-TREE-me-ah) is a state of excessively low blood sodium, caused by sweating and replacing lost fluid without replacing the salts (easily done by sweating a lot and only drinking plain water). As noted above, low blood sodium causes increased urination and reduced water retention, meaning that – counterintuitively – drinking a lot of water and not consuming salt means that you CANNOT properly get hydrated.
This is even experienced by people who drink a lot of water during the day but don’t exercise – it’s characterised by thirst despite drinking a lot, dry lips, a feeling of brain fog and fatigue, and excessively frequent urination which is completely clear. This can affect productivity, day to day energy, and potentially health if the habit is continued long term.
People that drink a lot of water, or people who exercise a lot, should, therefore, do the exact opposite of what people tend to do when adopting a healthier diet – they should ensure that they do add a little salt to meals, or to recipes when cooking. Indeed, it may be the case that those who start to cook food from scratch instead of buying more processed foods find that they need to add MORE salt to their food than they did before because they’re not naturally getting the amount that they used to simply from their food choices.
In summary: salt is to be respected, yes, but it’s definitely not to be avoided. Indeed avoiding salt is probably worse for you than having a little bit more than the recommended 6g, especially if you exercise!