We need more salt!
Thoughts on salt consumption in cystic fibrosis

How much table salt should we eat when we sweat? This question concerns all cystic fibrosis (CF) patients who exercise a lot or travel to hot countries. How much sodium chloride (NaCl), as table salt is chemically known, does the body need? We looked into the matter. (Foto: Bruno auf Pixabay)

The body of a healthy adult contains about 150 to 300 g of table salt and needs one to three grams daily to compensate for the loss through sweat and excretion. Since it used to be difficult for humans to obtain sufficient amounts of table salt, salt intake is rewarded with a release of dopamine: salt in the right amount tastes good.

How much extra salt should a cystic fibrosis patient eat?

It is difficult to find exact figures, as the amount needed depends on how much you sweat. The guidelines issued by the German Sports Working Group recommend adding “a pinch of salt” to your drink when exercising. In the expert council ECORN-CF, Prof. Rainald Fischer recommends “an additional 2-3 g depending on the level of exertion” – that would be about a level teaspoon. However, even a healthy athlete can easily sweat a liter per hour, which contains approx. 3 g of salt. Because the salt content in the sweat of CF patients without CFTR-Modulators is at least 2-3 times higher than in healthy people (1), this can amount to 10 g per hour or more, which is a level tablespoon! (During CFTR-modulator therapy like Trikafta, based on the sweat test, the necessary amount of salt might be much lower!).

During longer jogs or in hot temperatures, daily salt loss can exceed 20 g. The recommendation for adults with CF therefore varies between two grams of salt per day in hot weather and up to 20 g depending on exertion and the amount of sweating (1). Indicators include white marks on clothing or white salt crusts on the skin. At the latest when you have headaches or cramps, you should consider salt deficiency.

Isn't it dangerous to eat so much extra salt?

The German Nutrition Society recommends that healthy people eat a maximum of 6 g of salt per day. That is one heaped teaspoon – we usually already consume that much in ready-made foods. However, the frequently cited risk of cardiovascular diseases such as high blood pressure only increases with a long-term consumption of 15 g or more. Long-term overdose is impossible: the body simply excretes excess salt in the urine.

Why don't I get thirsty like other runners?

This is an important detail: when a healthy person sweats, they lose a lot of water and little salt, which means that the salt concentration in their blood increases and they become thirsty. Because salt is also excreted in CF patients, the salt content in the blood does not rise, they do not get thirsty and drink much less than would be necessary due to water loss (so-called “voluntary dehydration,” see 2).

Drinking plenty of fluids is therefore even more important than eating salt. You should drink enough (e.g., one liter per hour of physical activity, see 3) that you need to urinate again soon (your urine should not be concentrated). Drinking can of course be combined with the intake of table salt.

How can I eat 10 g of salt without feeling sick?

It is possible to consume it with food, e.g., 100 g of salt flakes already contain 4 g of salt. With normal salt tablets, which contain 1/4 g of salt, you won't get very far and it will be very expensive. Fortunately, there are also larger salt tablets in a dose of 1 g/tablet (e.g., Fagron). With isotonic electrolyte drinks, you should check the ingredients, because “isotonic” does not say anything about the NaCl content of the drink – they should contain 3 g/liter, while most isotonic drinks only contain 1 g/liter. Hardliners simply pour a heaped teaspoon of salt (approx. 5 g) into a glass of apple spritzer, but you have to like that. Parents had the idea of giving their children 4 ml NaCl ampoules (e.g., 6% – actually intended for inhalation) to drink at school – however, the child would have to open 12 of these ampoules, costing a total of approx. €2.50, to obtain 3 g of salt – so this is expensive and time-consuming compared to salt tablets.

Stephan Kruip, CF patient and marathon runner

(this text was published in the German CF Magazine MUKOinfo in 2016)

1 T.O. Hirche et.al.: Travelling with cystic brosis: Recommendations for patients and care team members – Journal of Cystic Fibrosis 9 (2010) 385–399

2 Webb AK, Dodd ME. Exercise and sport in cystic fibrosis: benefits and risks. Br J SportsMed1999;33(2):77–8.

3 Kriemler S, Wilk B, Schurer W, Wilson WM, Bar-Or O. Preventing dehydration in children with cystic brosis who exercise in the heat. Med Sci Sports Exerc 1999;31(6):774–9.

4 Leaflet of the Canadian CF association on the issue of dehydration and salt