There is an understanding that we shouldn’t have too much salt. But what is the problem with salt and how much is too much? Did you know that there isn’t one single study that actually demonstrates health benefits of the lower sodium intake? But does it mean we shouldn’t worry about it? Let’s find out.
First, let’s try to understand what happens in your body when you have too much salt. The cells in our body must maintain a very delicate balance of ion concentration between inside and outside of each cell. 65% of all the water in your body is inside the cells, which have a very very low sodium concentration. The rest of the water is a part of blood and tissue fluid and that’s where all the sodium goes to. When you consume salt, the level of sodium in your blood and tissue fluid increases and in order to maintain the same concentration our bodies are forced to take the water from inside the cells and move it into the blood and tissues. This adds to the blood volume so blood pressure increases (think about opening the water tap too much). The tissues swell up as well – that’s what people refer to as “retaining water”. This also, ironically, makes you thirsty as the inside of the cells is now dehydrated. Thankfully, in an otherwise healthy person, kidneys will be busy eliminating all the extra sodium before any negative effects kick in.
There is also another way to help our bodies restore the balance – increasing the concentration of the ions inside the cells. These ions are mainly potassium and they pretty much counterbalance the effects of sodium. The more I read about the whole “salt problem” the more it became clear that it’s actually about keeping your sodium and your potassium intake in balance. The problem is, most people tend to eat a lot of sodium and not enough potassium. Why does that happen? Only a small part of all sodium consumption comes from the salt that we manually add in food during cooking. Majority of it is hidden in other foods, such as sauces, dressings, smoked meats and fish, hams and deli meats, crisps, tinned products like soups, frozen ready meals and even cereal. And it’s not limited to savoury foods, lots of packaged cakes and doughnuts contain sodium too. Potassium, on the other hand, is mostly present in “healthier” foods, such as dark leafy greens, beans, fish, avocadoes, sweet potatoes, and bananas. No wonder many people don’t get enough of it to level out the sodium intake.
After looking at the studies, I found some unexpected results. Several studies have indicated that whilst higher intake of sodium (>6g per day) is associated with higher risk of cardiovascular disease, lower intake (<3g per day) is also associated with higher risk despite lower blood pressure levels! Which is ironic since the recommended daily amount is currently 2.4g (which is about 6g of salt).
In 2011, a large review analysed the relevant studies from 1950 to 2011 and confirmed a reduction of blood pressure but admitted that the magnitude of the effect doesn’t warrant a general recommendation for reduced sodium intake (1% for people with normal blood pressure and 3.5% for individuals with hypertention).
I was very surprised that, despite the sodium / potassium balance being a very well known biological fact, many studies didn’t take potassium intake into account and looked at sodium only. As we have seen before, level of potassium in your body directly influences the effects of sodium so the studies that didn’t take it into consideration have missed out a very important variable. There is a possibility that the outcome of the study would have been different had they adjusted for that.
Incidentally, there was a review article from 2015 that actually concluded that, looking at current evidence, reduction of sodium shouldn’t be an isolated recommendation and that an alternative approach of high quality, potassium rich diet might achieve greater health benefits.
Interestingly, there was a large study that followed over 2500 individuals for 10 years and found no correlation between sodium intake and mortality, cardiovascular disease or heart failure. After diving into the details, I could see that they did find the “U” shape, i.e. higher risk at both too low and too high levels of sodium consumption but the effect was not strong enough to be considered scientifically significant. The main limitations of the study were that the age of the participants was between 71 and 80 years old so we cannot be sure if there would be a stronger effect in a different age group, and they used a questionnaire to determine sodium intake which, arguably, is not the most reliable method.
Is sea salt better than table salt? It’s important to know that they both contain the same amount of sodium (about 40%). Sea salt is obtained directly through evaporation of water so it retains trace levels of some minerals whereas table salt is processed to give it fine texture and is stripped from these minerals. But before you switch to sea salt, consider this – the amount of minerals in it are so minute that they don’t have any significant impact on your diet, whereas table salt usually contains added iodine which is a very important mineral. Adding iodine to salt is the most widely used strategy to control iodine deficiency and if you are not using iodised salt you might be at risk.
A moderate intake of sodium is optimum for a healthy diet and it should be complemented by potassium rich food to counteract any possible negative effects of salt. Iodised table salt is preferable to use at home and we must watch for “hidden” salt in pre-packaged food.
Disclaimer: please note that the above applies to healthy adults. Individuals with kidney and heart problems should be more careful when it comes to salt. It is also a widely accepted recommendation that younger children’s sodium intake should be limited.