Do runners need to add salt to their diet or take salt tablets before a race?

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Salt continues to be a hot topic in endurance sports. Should runners add or avoid salt in their diets? As with most things, the answer is: it depends.

The Scoop on Sodium

Sodium is a key electrolyte that the body needs to function properly; having either too much or too little in the system can lead to problems. Sodium helps maintain fluid balance in your body’s cells and impacts the function of nerves and muscles, including the heart.

Our individual sodium concentration level is partly genetic and these levels are tightly monitored by aldosterone, a hormone produced in the adrenal gland. Excess sodium is excreted through urine and sweat.

In the world of endurance sports, many people take salt to prevent or fix cramps, even though there is little to no research to support this practice. We need to approach the sodium/salt question from a different perspective, and it all starts with fluid balance. The kidneys control the body’s water balance and salt levels, which can be affected in the following ways:

  • If you consume a lot of fluid (water) this will dilute your blood plasma levels and the body will hold on to less water (i.e. excrete more through urine).
  • If you don’t consume a lot of fluids, the kidneys will reabsorb more water back and your blood plasma levels will be more concentrated (i.e. less water is excreted).
  • Exercise raises the core body temperature, so you sweat to cool down. This results in more concentrated blood plasma.
  • Hot temperatures also cause you to sweat more, which concentrates the blood plasma.
  • Salt intake also can make blood plasma more concentrated.
  • New research found that tattooed skin generated less sweat but more sodium concentration than non-tattooed skin, meaning you’ll sweat less but lose more sodium where you have ink. If you have a tattoo on a large area such as your back or arms or covering sweat glands, this could also affect your body’s ability to cool off.

Recommendations

If you are training for an hour or less and consuming under one litre of water, then you probably don’t need salt. Under these conditions, it is unlikely that you will disrupt your blood sodium levels sufficiently through exercise under normal environmental conditions.

If you are training for two to four hours and consuming approximately 500 to 1000 mL of water per hour, then you should take in some salt. A general recommendation of 500 mg of sodium per litre of water consumed is a good starting point to maintain sodium balance over longer training efforts. Salt can be added to your water, taken in pill format or from your fuel (such as sports drinks and gels). Check the labels, as all products are different.

With extreme heat and humidity or high intensity, your needs may change. It is important to get a good handle on your sweat volume during different training conditions to help determine how your fluid intake needs to change. Additionally, women in the second half of their menstrual cycle (high hormone phase) are more at risk for needing extra sodium during exercise as a result of increased loss of sodium due to a decrease in plasma volume at this time.

In your daily diet, make sure you consume some salt, but avoid overdoing it. If you eat out frequently or you eat a lot of packaged or processed foods, you might be consuming more sodium than you think. It’s important to ask about the nutrient content or check the labels. If you drink a lot of water, cook most of your meals at home and tend to shy away from the salt shaker, you might need to evaluate if you need to add a bit of sodium to your daily meals. Keep in mind that little salt goes a long way: one teaspoon of salt has roughly 3000 mg of sodium.

A final important note: If you are on medications to control blood pressure or other medications that may affect fluid balance, or if you are on a specific salt-reduced diet, your needs may be different.

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