By Tamzyn Murphy Campbell
BSc, BSc Med(Hons) Human Nutrition and Dietetics, RD
Many people experience certain common side effects when following low carbohydrate high fat (LCHF). These include:
- Keto “flu”: during the first week of starting LCHF some people experience aches and pains, headaches, lethargy, nausea, brain fog and/or irritability.
- Muscle aches/cramps
- Signs of low blood pressure, including heart palpitations, dizziness and nausea.
The good news is that the root cause of these symptoms is the same and completely rectifiable.
What’s behind the symptoms?
When you are eating a conventional high carbohydrate diet, your body is producing quite a lot of insulin. Insulin is produced by the pancreatic beta cells in response to glucose or “sugar” entering the bloodstream after digestion of a carbohydrate-containing food or beverage. Insulin’s job is to remove “sugar” from the bloodstream and put it into the cells, where it’s turned into energy or stored. One of the side effects of insulin is to reduce the kidneys’ excretion of water and certain electrolytes or minerals (namely, sodium or ‘salt’, magnesium and potassium) [1-3].
Conversely, when you eat a low carbohydrate diet the amount of insulin that your pancreas produces is dramatically reduced, as there’s much less carbohydrate entering the blood stream from your diet. The lower insulin level results in increased excretion of water, sodium, magnesium and potassium from the kidneys. This loss of fluid often lowers blood pressure and can cause dehydration if the fluid is not replaced by drinking more. The resulting symptoms can include headaches and symptoms of low blood pressure, including fatigue/lethargy, heart palpitations, dizziness and nausea. The loss of sodium, potassium and magnesium can cause muscle aches, pains and cramps, as well as irritability. 
How to fix it
- Drink plenty of fluids (to thirst)
- Add salt to your food
- Drink a cup of bone broth every day
- Take a magnesium supplement, which provides 400 mg of elemental magnesium daily. Choose a supplement that contains magnesium in the form of a magnesium chelate (elemental magnesium bound to an amino acid), such as magnesium glycinate, for optimal absorption.
Important note: Should drinking more fluids, consuming more salt, drinking bone broth and taking a magnesium supplement not improve your symptoms, it is important that you see your doctor as soon as possible.
- Volek JS and Phinney SD. The art and science of low carbohydrate living. 2011
- DeFronzo RA. The effect of insulin on renal sodium metabolism. A review with clinical implications. 1981 Sep;21(3):165-71.
- Quiñones-Galvan A, Ferrannini E. Renal effects of insulin in man. J Nephrol. 1997 Jul-Aug;10(4):188-91.