You probably already know that too much salt is bad for you. However, you may not know why the sodium in the food we eat causes us problems in the first place. Hopefully, once you've read this article you'll be more aware of your sodium intake and why it matters.
What is sodium?
You probably know it as a constituent of table salt, sodium chloride.
Pure sodium is a soft, shiny metal, which is extremely reactive, combining explosively with water. In the body, however, sodium is present as a much more stable sodium ion.
The human body contains around 70 grams of sodium. Most of it in the extracellular fluids that bathe the cells.
Although sodium is abundant in the seas and oceans, its less abundant on land. As a result, our bodies have evolved efficient sodium uptake and retention mechanisms from the food we eat.
This impacts heavily on sodium nutrition, as we shall see later...
Why do we need sodium?
Sodium is the main mineral you'll find in extracellular fluids. That is to say, all the fluid that isn't inside any particular cell in your body.
Furthermore, it's fundamental for the regulation of the fluid volume inside cells.
Additionally, it also helps to maintain the correct acid/base balance in the body. For many reasons, we need to absorb a certain amount of sodium in our food each day.
Another vital function revolves around the ability of sodium to rapidly permeate into cells and temporarily displace potassium (the main intracellular mineral).
This mechanism is at the heart of electrical signalling in the body and is essential for muscle contraction and nerve transmission. In addition, sodium is known to be involved in transporting amino acids (protein fragments) into cells.
What should my sodium intake be? How much sodium do I need each day?
Current recommendations are that total sodium intake should be curtailed to around 2-2.5 grams per day. In other words, 5-6 grams of salt.
In normal conditions, a daily intake of just 500mgs (i.e. half a gram) is enough to maintain sodium balance.
However, the overuse of salt as a flavouring and preservative agent means that most of us get far more than this, with typical intakes around 2500 — 6000mgs and for those with salty palates, intakes of up to 15000mgs (that's 15 grams) are not unheard of.
The current UK Reference Nutrient Intake (RNI) for sodium is 1600mgs per day, well below average consumption levels.
Where can I find sodium in food?
Any food with added salt (that's virtually all processed foods!) will contain high levels of sodium.
Even bread contains over 500mgs per 100 grams.
Foods that are naturally high in sodium with no added salt (for example seafood) still only contain around 100mgs per 100 grams.
What happens if I don't get enough sodium?
Since so many foods have added sodium, a sodium deficiency is rare.
However, it can arise as a result of profuse sweating, extreme endurance exercise, diarrhoea or a severely restricted sodium diet.
Sodium deficiency can lead to muscle weakness, twitches and cramping. Additionally, it can cause low blood pressure and mental confusion.
In recent years a number of athletes have also developed low blood sodium (which can prove fatal) by ingesting too much water in an attempt to stave off dehydration, thereby diluting sodium excessively.
Exercise physiologists recommend that athletes in events lasting longer than 4 hours drink fluids containing some sodium to prevent this.
Sodium levels in some common foods (per 100g)
Food / Food group
sodium content (mg)
Beef mince (raw)
Oat flakes (raw unprocessed)
Can I get too much sodium and who should take the most care to regulate their intake?
Yes, and most people consume too much sodium in their food.
Excessive sodium intake is known to be a risk factor for high blood pressure, strokes and even coronary heart disease.
It's important to remember that most sodium comes courtesy of hidden added salt in processed foods (see table) — not from the salt shaker.
If your diet is high in processed food and takeaways, you're almost certainly getting too much sodium.
There's also evidence that the potassium/sodium balance may be as important as total sodium intake.
Although the ideal ratio is around 3:1 in favour of potassium, many Western diets have completely reversed ratios. For example, around 1:3 or higher. That is to say, nine times as much sodium in their food as potassium.
Am I getting too much sodium in my food?
You're almost certainly getting enough sodium — in fact, you're probably getting too much. Use the table above to get an idea of sodium levels in some common foods. Note how much is added in the form of salt when foods are processed.