The role of salt in a ketogenic-diet. ‘Keto-Flu’ explained!

I was keen to understand why all the low-carb diet resources tell you to eat more salt. I therefore decided to look into this in greater detail. The problem I encountered was that nothing actually states the reasoning behind it; sources merely allude to the requirements, then make recommendations on how to achieve them.

What I was keen to understand in particular, is the role of insulin in causing the kidneys to retain salt. The below is what I’ve managed to piece together.

As always, I must state that I have no medical or dietary training; all I can do is try and present the results of my own reading in as clear and jargon-free way as possible. If readers’ comments can help guide my understanding, then all feedback will be gratefully received!

So here goes… Salt!

When you switch over to a ketogenic diet, you’re effectively changing the way your body creates and burns energy.

On a glucose-based metabolism, the energy-form ‘glycogen’ is produced in the liver. This energy is water-soluble and transported around the body in your blood. The blood-stream is therefore our ‘road-network’ for distributing energy to all the cells and muscles that need it. Glycogen is also stored in the muscles, so the blood-motorway serves to ‘top up’ these stores when required.

Because glycogen is transported in liquid & is water-soluble; it’s unsurprising that glycogen itself contains a lot of water. In fact, it’s stored in liquid form; three to four parts water to one part glycogen (sources state 3-4g water to 1g glycogen).

When you restrict carbohydrate, you stop consuming glucose, the raw-material from which glycogen is made (see Fuel versus Energy for more details). Your stores of glycogen therefore deplete as your body burns energy, and because glycogen carries 3-4 parts water; your body loses a heck of a lot of liquid with it! This is the reason why weight-loss is often rapid at the start of a LCHF diet. You’re shipping the water stored alongside glycogen; and water is quite heavy!

What’s this got to do with salt?

We’ve identified that depleting glycogen stores also ships water. How is that water excreted? Predominantly in your urine.

Salt is vital to the body for survival; so important in fact that your tongue has special ‘salt-sensors’ in it, to detect its taste and prompt you to add more if levels are insufficient. If something is especially salty, your body prompts you to drink. This is why many pubs offer salty snacks such as peanuts or crisps – they want you to drink more! A high concentration of electrolytes in the body triggers our thirst mechanism – salt is an electrolyte!

So in entering a state of ketosis, your body is excreting water and salt through the depletion of glycogen. If high salt-levels trigger the thirst mechanism, but salt-levels are going down (as is water); it naturally follows that the thirst-mechanism is not sufficiently triggered to cover this water-loss. Our body’s water-balance gets temporarily thrown out of sync and we become dehydrated. This combination of mineral-deficiency and dehydration can leave you feeling incredibly nauseous, tired, weak and highly prone to headaches.

There is something else to throw into the mix – insulin.

This is a very difficult thing for a lay-person to research. The science is prohibitively complex and the information tends not to deal directly with this subject; rather simply referring to it as an aside.

One of the lesser known functions of insulin is to signal salt-retention in the kidneys. When you eat carbohydrate, your insulin levels rise. The insulin then tells your kidneys to retain salt and not excrete it. By eating carbohydrate, we’re not only getting fatter, but the salt we eat is not being released by the body, which then has adverse effects on blood-pressure. A low-salt diet can also lead to insulin-resistance, the precursor to type-2 diabetes (your body no longer responds to the insulin you produce).

Conversely, when you cut carbs; your insulin-levels decrease, which then tells your kidneys to release salt. The healthy ‘salt-cycle’ is restored and the body slowly adjusts to its normal, natural pattern.

In addition to water-loss through glycogen-depletion; insulin-reduction tells your kidneys to release salt from the body. For these two reasons, it’s important to up your salt in-take when first adopting a ketogenic-diet.

To prevent dehydration and the above symptoms (sometimes termed ‘keto-flu’), remember to drink lots of water and top your sodium levels up by drinking bouillon (stock cubes in water) and adding sufficient salt to your meals to cover the loss.

That way, your changeover to a healthy keto-plan will be a happy and safe one. Enjoy the journey!

I hope this helps and thanks for reading,



11 thoughts on “The role of salt in a ketogenic-diet. ‘Keto-Flu’ explained!

  1. I has a tummy bug this week and could not eat for three days. I was drinking as much as I was able to, but the headache that developed was crippling. I was thinking about you and the keto headaches with a great deal of sympathy!


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  6. You seem to be saying that the salt depletion is temporary? Once established in ketosis should we return to a no-too-salty diet?


  7. Hi Bella, thank you for the comment. I caveat my response with the assertion that I’m in no way a medical professional; my view point comes from extensive reading around the subject, from all perspectives; those who criticise a keto-lifestyle; plus those who are heavyly for it!! To answer your question, “One of the lesser known functions of insulin is to signal salt-retention in the kidneys. When you eat carbohydrate, your insulin levels rise. The insulin then tells your kidneys to retain salt and not excrete it.” This means that as soon as your insulin levels increase [prompted by carbohydrate intake], your kidneys will start RETAINING salt, which is the unhealthy and dangerous thing. If you’re in ketosis, your insulin levels will be low and your kidneys will therefore NOT be receiving that message. Your natural electrolyte balance will kick in, and your kidneys will send the message to excrete the salt rather than retain it. This means that as long as you’re in ketosis, your body will happily regulate its own salt balance and there’s no need to worry about it. The ‘temporary’ part is that in the period of adjustment; your body is switching from one fuel source to another. It finds this HIGHLY confusing and that’s why people can often feel fairly terrible. Your body gets a little messed up when it doesn’t know where its energy is coming from and that ‘messed up feeling’ equally applies to salt. Your body has a temporary adjustment period where electrolyte regulation goes a little off kilter! So yes; the salt depletion is temporary, in the period that your body is adjusting to burning ketones. Once that has happened, you won’t experience salt depletion; nor do you have to worry about salty foods. Your body will regulate itself; taking what salt it needs and then naturally excreting the rest. A win win situation! Hop[e that helps and thanks again for the comment. Adam.


    • Thanks Adam. That sounds good, I like not having to worry about salt, but not sure yet whether to give up( worrying that is)
      I have hyperaldosteronism, too much of a hormone that controls blood pressure by regulating salt and potassium. I’m at risk of too much salt and too little potassium, and thereby high blood pressure. I am prescribed a diuretic that keeps the Potassium on board, but I’ve no idea about salt, except I see others with the condition encouraged to consume as little as possible. I shall ask around more to see whether ketosis would help us so salt monitoring is less of a problem, and I can enjoy pork scratching without fear or guilt! Do t worry I’m not holding you responsible for advice with an abnormality to consider!


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