SALT IN HEALTH AND PERFORMANCE
THE QUESTION OF how much salt you need is both confusing and contentious. Salt is a prominent ingredient in many sports nutrition products and is considered to be an important factor in nutrition guidelines when it comes to hydration and cramps. Adding to the confusion on what is appropriate when it comes to salt intake – and somewhat at odds – is the decades-old message that salt is a prime culprit when it comes to high blood pressure and heart disease. We’re often told that we should put the shaker down. So what do we know about salt? And how much salt does an endurance athlete really need?
The shake down on salt
Salt is comprised of 40 per cent sodium and 60 per cent chloride. Sodium is a vital nutrient: as a key component of extracellular fluid, the electrolyte, along with potassium, magnesium and calcium, helps balance cell fluid levels and maintain blood plasma volume necessary for cellular metabolism and absorption. Sodium also helps regulate heart contraction and function. Both components of salt – sodium and chloride – are also important when it comes to nerve signalling and muscle contraction. The general thinking went that if sodium intake was high, blood pressure would soar, putting extra strain on the cardiovascular system. But over recent years, research has emerged quashing this accepted wisdom and revealing that, in fact, the link between salt intake and hypertension (high blood pressure) is overstated.
Recommendations still generally advise an intake of below 1,500 mg of sodium per day, well below the average 3,400 mg intake for most of us. But the truth is that, in healthy individuals the kidneys do a good job of regulating levels of water and sodium (and other electrolytes) across a broad range of dietary sodium intakes. A sudden increase in salt will cause a shift of fluid from intra- to extracellular fluid – helping to explain that fluid retention and swollen limbs we experience after a Friday night feast of pizza and chips. But, over time, the kidney compensates and starts excreting extra sodium to match dietary intake. This is an important concept to consider when talking about athletes and so-called “salty sweaters” – the ones whose race suits and run clothes end up crusted with white salt.