The Ketogenic Diet's Side-Effects
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The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet. It forces the body to burn fats rather than carbohydrates. Normally, carbohydrates in food get converted to glucose, which is important in fuelling the brain. However, when carbohydrates in one's diet are low, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain, possibly acting as a "backup" energy source.
The ketogenic diet is not a benign, holistic or natural treatment; it is a medical therapy that provides neuroprotective and disease-modifying benefits for a number of adult neurodegenerative disorders.[1][2]
As with any serious medical therapy, there may be complications. These are generally less severe and less frequent than with medication or surgery.[3]
Common but easily treatable short-term side effects include constipation, low-grade acidosis, and hypoglycaemia if there is an initial fast. Raised levels of lipids in the blood affect up to 60% of people on the diet[4] and cholesterol levels may increase by around 30%.[3] This can be treated by changes to the fat content of the diet, such as from saturated fats towards polyunsaturated fats, and, if persistent, by lowering the ketogenic ratio.[4] Supplements are necessary to counter the dietary deficiency of many micronutrients.[5]
Long-term use of the ketogenic diet increases the risk of retarded growth, bone fractures, and kidney stones.[5] Though the stones are treatable,[6] Johns Hopkins Hospital now gives oral potassium citrate supplements to all ketogenic diet patients, resulting in a sevenfold decrease in the incidence of kidney stones.[7] However, this empiric usage has not been tested in a prospective controlled trial.[8] Kidney stone formation (nephrolithiasis) is associated with the diet for four reasons:[6]
- Excess calcium in the urine (hypercalciuria) occurs due to increased bone demineralisation with acidosis. Bones are mainly composed of calcium phosphate. The phosphate reacts with the acid, and the calcium is excreted by the kidneys.[6]
- Hypocitraturia: the urine has an abnormally low concentration of citrate, which normally helps to dissolve free calcium.[6]
- The urine has a low pH, which stops uric acid from dissolving, leading to crystals that act as a nidus for calcium stone formation.[6]
- Many institutions traditionally restricted the water intake of patients on the diet to 80% of normal daily needs;[6] this practice is no longer encouraged.[5]
The ketogenic diet also has an adverse affect on bone health. Many factors may be involved, such as acidosis and suppressed growth hormone.[4]
In adults, common side effects include weight loss, constipation, raised cholesterol levels and, in women, menstrual irregularities including amenorrhoea.[9]
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- Gasior M, Rogawski MA, Hartman AL. Neuroprotective and disease-modifying effects of the ketogenic diet. Behav Pharmacol. 2006;17(5–6):431–9. PMID 16940764
- Maalouf M, Rho JM, Mattson MP. The neuroprotective properties of calorie restriction, the ketogenic diet, and ketone bodies. Brain Res Rev. 2009 Mar;59(2):293–315. doi:10.1016/j.brainresrev.2008.09.002. PMID 18845187
- Turner Z, Kossoff EH. The ketogenic and Atkins diets: recipes for seizure control (PDF). Pract Gastroenterol. 2006 Jun;29(6):53, 56, 58, 61–2, 64.
- Bergqvist AG. Long-term monitoring of the ketogenic diet: Do's and Don'ts. Epilepsy Res. 2011 Aug 18. doi:10.1016/j.eplepsyres.2011.05.020. PMID 21855296.
- Kossoff EH, Zupec-Kania BA, Rho JM. Ketogenic diets: an update for child neurologists. J Child Neurol. 2009 Aug;24(8):979–88. doi:10.1177/0883073809337162. PMID 19535814
- Sampath A, Kossoff EH, Furth SL, Pyzik PL, Vining EP. Kidney stones and the ketogenic diet: risk factors and prevention (PDF). J Child Neurol. 2007 Apr;22(4):375–8. doi:10.1177/0883073807301926. PMID 17621514
- McNally MA, Pyzik PL, Rubenstein JE, Hamdy RF, Kossoff EH. Empiric use of potassium citrate reduces kidney-stone incidence with the ketogenic diet. Pediatrics. 2009 Aug;124(2):e300–4. doi:10.1542/peds.2009-0217. PMID 19596731
- Kossoff EH, Zupec-Kania BA, Amark PE, Ballaban-Gil KR, Bergqvist AG, Blackford R, et al. Optimal clinical management of children receiving the ketogenic diet: recommendations of the International Ketogenic Diet Study Group. Epilepsia. 2009 Feb;50(2):304–17. doi:10.1111/j.1528-1167.2008.01765.x. PMID 18823325
- Kossoff E. Is there a role for the ketogenic diet beyond childhood? In: Freeman J, Veggiotti P, Lanzi G, Tagliabue A, Perucca E. The ketogenic diet: from molecular mechanisms to clinical effects. Epilepsy Res. 2006 Feb;68(2):145–80. doi:10.1016/j.eplepsyres.2005.10.003. PMID 16523530
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