• Glenn Wilson

    Dr. Greger: Blood sugar, also known as blood glucose, is the universal go-to fuel for the cells throughout our bodies. Our brain burns through a quarter-pound of sugar a day, its “preferred metabolic fuel.” Our body can break down proteins and make glucose from scratch, but most comes from our diet in the form of sugars and starches. If we stop eating carbohydrates, or stop eating altogether, most of our cells switch over to burning fat. But fat has difficulty getting through the blood-brain barrier. But our brain has a constant massive need for fuel, one organ accounting for up to half of our energy needs. Without it, the lights go out…permanently.

    To make that much sugar from scratch, our body would need to break down about a half-pound of protein a day. That means we’d cannibalize ourselves to death within two weeks. But people can fast for months. The answer to the puzzle was discovered in 1967. Harvard researchers famously stuck catheters into the brains of obese subjects who had been fasting for over a month, and discovered that ketones had replaced glucose as the preferred fuel for the brain. Your liver can turn fat into ketones, which can then breach the blood-brain barrier and sustain your brain if you’re not getting enough carbohydrates. Switching fuels has such an effect on brain activity that it has been used to treat epilepsy since antiquity.

    The prescription of fasting for the treatment of epileptic seizures dates back to Hippocrates. In the Bible, Jesus seems to have concurred. To this day, it’s unclear why switching from blood sugar to ketones as a primary fuel source has such a dampening effect on brain overactivity. How long can you fast, though? To prolong the fasting therapy, in 1921 a distinguished physician scientist at the Mayo Clinic suggested trying what he called a “ketogenic diet,” a high-fat diet designed to be so deficient in carbohydrates it could effectively mimic the fasting state. “[R]emarkable improvement” was noted the first time it was put to the test—efficacy that was later confirmed in randomized, controlled trials. Ketogenic diets started to fall out of favor in 1938 with the discovery of the anti-seizure drug that would become known as Dilantin, but ketogenic diets are still in use today as a third- or fourth-line treatment for drug-refractory epilepsy in children.

    More at NutritionFacts: Is Keto an Effective Cancer-Fighting Diet?

    To see the full transcript or links to cited sources go to the link above, then scroll below the video and click on View Transcript or Sources Cited.

    This is the first in a seven-video series on Ketogenic Diets.

    More in the category Health and Medical.

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