The ketogenic diet and traumatic brain injury

Traumatic brain injury (TBI) initiates a series of neurological events that cause a change in the way that the brain uses energy. The brain typically uses glucose (the metabolic product of carbohydrates) for energy. However, reduced blood flow to the brain after TBI can impair the brain’s ability to process the available glucose supply. Additionally, the brain needs more energy than usual to repair the damage caused by the injury. This energy crisis – increased demand for and decreased supply of glucose – is a leading factor underlying the recommendation that patients rest for 7 to 10 days after TBI, allowing them to conserve energy while the brain uses all of its resources for repair.

When glucose supply is low, such as in times of starvation, the body uses fat for energy. In fact, the ketogenic (keto) diet, a high fat, low carbohydrate diet plan, has recently gained popularity as a way to improve health and lose weight. The main principle of the keto diet is that, by limiting the intake of carbohydrates (which ultimately break down to glucose), the body is forced to metabolize fat for energy. This can help with weight loss both by causing the body to burn fat, and by lowering blood sugar and insulin levels, both of which rise as a natural result of glucose metabolism.

In addition to weight management, the keto diet has been used to treat some neurological disorders. Epilepsy research provides us with the earliest evidence that a keto diet may improve neurological function. In the 1920s, it was observed that seizure activity was reduced when the body was in a fasting state, using fat for energy rather than glucose.1 This observation prompted doctors to recommend a keto diet to their patients to control seizure activity. Though the mechanism by which ketone bodies (the molecules that are produced as a side product of fat metabolism) reduce seizure activity is unknown, the keto diet was, and still is, a popular way to treat recurrent seizures that were unresponsive to other treatments. The keto diet has also been used to treat such other neurological conditions as Alzheimer’s disease, ALS, autism, and ischemic brain injury.1,2

More recently, researchers have begun to investigate whether a keto diet could mitigate the damage caused by TBI.3 These researchers argue that the energy crisis following TBI mimics the body’s metabolic needs during starvation. As a result, increasing dietary intake of fat and reducing intake of carbohydrates may help the brain adapt to a form of metabolism that is less affected by the reduction in the brain’s ability to use glucose. This promising idea has sparked many research studies exploring the effects of a keto diet on TBI symptoms, and evidence from animal models suggests that a keto diet may help with recovery after a TBI. In one study, researchers induced TBI in rats, and then fed them either a normal diet or a keto diet for a week. The rats that were fed the keto diet performed better on tests of motor and cognitive function than the rats that were fed a normal diet.4 In an attempt to understand the mechanism underlying this improvement, another research group showed that rats with TBI who are fed a keto diet experience less neuronal cell death and have fewer free radicals in their blood, which is a sign of lower oxidative stress and better capacity to repair damage.5 Although the research in humans is limited, one study showed that adults with severe TBI are able to effectively metabolize fats to generate ketone bodies.6

Interestingly, some evidence suggests that after TBI, the body prepares for increased fat metabolism by increasing production of the transporters that carry ketones to the brain to use for energy.7 This finding has prompted some doctors and dieticians to suggest adapting a keto diet after TBI. The evidence is still in its early stages, but it provides encouraging rationale to talk to your doctor about the neuroprotective benefits of a keto diet after TBI.

References:

  1. Barañano, Kristin W., and Adam L. Hartman. "The ketogenic diet: uses in epilepsy and other neurologic illnesses." Current treatment options in neurology 10.6 (2008): 410.
  2. Paoli, A., Bianco, A., Damiani, E., & Bosco, G. (2014). Ketogenic diet in neuromuscular and neurodegenerative diseases. BioMed research international, 2014.
  3. Prins, M. L. (2008). Cerebral metabolic adaptation and ketone metabolism after brain injury. Journal of Cerebral Blood Flow & Metabolism, 28(1), 1-16.
  4. Appelberg, K. S., Hovda, D. A., & Prins, M. L. (2009). The effects of a ketogenic diet on behavioral outcome after controlled cortical impact injury in the juvenile and adult rat. Journal of neurotrauma, 26(4), 497-506.
  5. Greco, T., Glenn, T. C., Hovda, D. A., & Prins, M. L. (2016). Ketogenic diet decreases oxidative stress and improves mitochondrial respiratory complex activity. Journal of Cerebral Blood Flow & Metabolism, 36(9), 1603-1613.
  6. Bernini, A., Masoodi, M., Solari, D., Miroz, J. P., Carteron, L., Christinat, N., ... & Foltzer, F. (2018). Modulation of cerebral ketone metabolism following traumatic brain injury in humans. Journal of Cerebral Blood Flow & Metabolism, 0271678X18808947.
  7. Prins, M. L., and C. C. Giza. "Induction of monocarboxylate transporter 2 expression and ketone transport following traumatic brain injury in juvenile and adult rats." Developmental neuroscience 28.4-5 (2006): 447-456.
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