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Ketogenic diet (KD)

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Ketogenic diet (KD)

  • developed in the 1920s by a faith healer to help children with epilepsy, this diet induces a state that mimics carbohydrate starvation (1)
    • ketogenic diet primarily consists of high-fats, moderate-proteins, and very-low-carbohydrate
      • dietary macronutrients are divided into approximately 55% to 60% fat, 30% to 35% protein and 5% to 10% carbohydrates
      • specifically, in a 2000 kcal per day diet, carbohydrates amount up to 20 to 50 g per day (2)

  • KD is a high-fat, low-carbohydrate diet induces ketone body production in the liver through fat metabolism
    • the goal is to mimic a starvation state without depriving the body of necessary calories to sustain growth and development
    • very high-fat diet almost eliminates carbohydrates from the patient's food selection - result is the substitution of ketone bodies as a source of energy
      • ketone bodies replace glucose as a primary source of energy
        • during ketogenesis due to low blood glucose feedback, stimulus for insulin secretion is also low, which sharply reduces the stimulus for fat and glucose storage
        • other hormonal changes may contribute to the increased breakdown of fats that result in fatty acids
        • fatty acids are metabolized to acetoacetate which is later converted to beta-hydroxybutyrate and acetone
          • are the basic ketone bodies that accumulate in the body as a ketogenic diet is sustained
          • metabolic state is referred to as "nutritional ketosis"
          • if the body continues to be deprived of carbohydrates, metabolism remains in the ketotic state
          • ketone bodies acetoacetate and -hydroxybutyrate then enter the bloodstream and are taken up by organs including the brain where they are further metabolized in mitochondria to generate energy for cells within the nervous system
          • ketone body acetone, produced by spontaneous decarboxylation of acetoacetate, is rapidly eliminated through the lungs and urine
          • nutritional ketosis state is considered quite safe, as ketone bodies are produced in small concentrations without any alterations in blood pH
          • greatly differs from ketoacidosis, a life-threatening condition where ketone bodies are produced in extremely larger concentrations, altering blood ph to acidotic a state
  • classic KD is typically composed of a macronutrient ratio of 4:1 (4 g of fat to every 1 g of protein plus carbohydrates combined) - so shifting the predominant caloric source from carbohydrate to fat

    • lower ratios of 3:1, 2:1, or 1:1 (referred to as a modified ketogenic diet)
      • can be used depending on age, individual tolerability, level of ketosis and protein requirements

    • more 'relaxed' variants have been developed, including the modified Atkins diet (MAD), the low glycemic index treatment (LGIT) and the ketogenic diet combined with medium chain triglyceride oil (MCT)
      • MAD
        • typically net 10-20 g/day carbohydrate limit
          • roughly equivalent to a ratio of 1-2:1 of fat to protein plus carbohydrates
      • LGIT
        • 40-60 g daily of carbohydrates with the selection of foods with glycemic indices <50
        • approximately 60% of dietary energy derived from fat and 20-30% from protein
      • MCT variant KD
        • uses medium-chain fatty acids provided in coconut and/or palm kernel oil as a diet supplement and allows for greater carbohydrate and protein intake than even a lower-ratio classic KD, which can improve compliance

  • adverse effects:
    • short-term effects (up to 2 years) of the ketogenic diet are well reported and established - however, the long-term health implications are not well known due to limited literature
    • most common and relatively minor short-term side effects of ketogenic diet include a collection of symptoms like nausea, vomiting, headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance, and constipation, sometimes referred to as keto flu
      • symptoms resolve in a few days to few weeks (2)
      • adequate fluid and electrolyte intake can alleviate some of these symptoms
    • long-term adverse effects include:
      • hepatic steatosis, hypoproteinemia, kidney stones, and vitamin and mineral deficiencies

  • cautions and contraindications
    • with respect to diabetic patients
      • appropriate adjustment of insulin or oral hypoglycemic agents is required to avoid severe hypoglycaemia if the medications are not appropriately adjusted before initiating this diet
      • ketogenic diet is contraindicated in patients with pancreatitis, liver failure, disorders of fat metabolism, porphyrias, primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency, or pyruvate kinase deficiency
      • false positive breath alcohol test
        • if on a KD then this can rarely cause a false positive breath alcohol test
          • secondary to ketonemia, acetone in the body can sometimes be reduced to isopropanol by hepatic alcohol dehydrogenase which can give a false positive alcohol breath test result

Reference:


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