The Carbohydrate Brain Fuel Myth

by David Mendosa Patient Advocate

Children learn from playing the game of telephone that information gets garbled as it gets passed along. It's too bad that all medical writers don't seem to know that basic lesson.

That's why, as a medical writer for diabetes, I don't ask you to just trust me. Unlike almost everyone who prepares medical articles for the Internet, I link the primary sources so you can see that it's not just my opinion or a secondary source that other medical writers often reference.

In the children's game of telephone cumulative errors from mishearing often result in what the last player hears isn't anything like the way it started. This can amuse children. But it can lead us seriously astray. One example is the brain fuel myth which can lead people with diabetes to consume a diet far too high in carbohydrates.

If the people who say that our brains need at least 130 grams of available carbohydrate per day to work properly were correct, then nothing you read here can make any sense. For about half a year I have been getting only about a third of that amount.

You can read -- but don't swallow -- what Edutopia Magazine writes about our carbohydrate requirements. "To achieve and maintain normal brain function, adults and children need 130 grams of carbohydrates a day," freelance medical writer named Abby Christopher writes.

She even quotes Diane Stadler, research assistant professor in the Oregon Health and Science University's health promotion and sports medicine division to that effect. "Restricting carbs like the Atkins Diet is going to have an effect on the brain," Ms. Stadler told her.

Closer to home is a comment by a Certified Diabetes Educator (CDE) to one of my articles here. "Remember that the brain does need 130 grams of carbs per day for healthy function," she writes.

Even more grievous is the American Diabetes Association's (ADA) intermediate oversimplification. While the ADA isn't as ridiculously wrong as the Edutopia Magazine article and that CDE, some people still believe what the largest diabetes charity organization tells us. "The recommended dietary allowance (RDA) for digestible carbohydrate is 130 grams per day," says the ADA'sposition statement on its Nutrition Recommendations and Interventions for Diabetes. Why do we need so much carbohydrates?

The RDA is based, the ADA says, "on providing adequate glucose as the required fuel for the central nervous system without reliance on glucose production from ingested protein or fat."

Ah! So it's at least 130 grams of glucose per day that our brain needs! And glucose is not the same thing as carbohydrate.

Our bodies can convert protein into glucose, "but very slowly and inefficiently," as Dr. Richard K. Bernstein wrote in Dr. Bernstein's Diabetes Solution. The conversion of fat to glucose works much better.

"Fat is the perfect fuel," Dr. Michael Eades wrote on his blog. "Part of it provides energy to the liver so that the liver can convert protein to glucose. The unusable part of the fat then converts to ketones, which reduce the need for glucose."

Dr. Eades continues: "If you're following a low-carb diet...the protein you eat is converted to glucose.... If you keep the carbs low enough so that the liver still has to make some sugar, then you will be in fat-burning mode....How low is low enough? Well, when the ketosis process is humming along nicely and the brain and other tissues have converted to ketones for fuel, the requirement for glucose drops to about 120-130 grams per day. If you keep your carbs below that at, say, 60 grams per day, you're liver will have to produce at least 60-70 grams of glucose to make up the deficit, so you will generate ketones that entire time."

In fact, I give the ADA credit for citing the primary source in its "Nutrition Recommendations." That source is a report by the Institute of Medicine's (IOM) food and nutrition board titled Dietary Reference Intakes: Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. The National Academies Press in 2002 published this book. While the ADA fails to provide a link, fortunately for those of us who like to go to primary sources you can find it online.

What is the IOM and why should we trust it? The IOM and its parent organization, the National Academy of Sciences, are hybrid governmental-private organizations. The U.S. government created these private organizations to advise it on scientific and technological matters. Among their functions they set the official recommended dietary allowances (RDAs) for the macronutrients and micronutrients in our diet.

The Institute of Medicine takes 17 dense pages -- from page 277 to 293 -- to consider the evidence for estimating the average requirement for carbohydrate. I've studied them and encourage you to study the source for yourself. I don't need to copy or summarize its recommendations because Gary Taubes did it so well in his ground-breaking new book, Good Calories, Bad Calories, which I have written about here and in several other articles.

The IOM sets an "estimated average requirement" of 100 grams of carbohydrates a day for adults, Taubes writes, so that the brain can run exclusively on glucose, "without having to rely on a partial replacement of glucose by ketone bodies." It then sets the "recommended dietary allowance" at 130 grams to allow a margin for error. But the IOM report also acknowledges that the brain will be fine without these carbohydrates, because it runs perfectly well on ketone bodies, glycerol, and protein-derived glucose.

Many people don't understand what ketone bodies (or "ketones") are, confusing it with a dangerous condition called ketoacidosis. Dr. Eades, however, provides a clear explanation of why ketones are good.

"The liver requires energy to convert the protein to glucose," he writes on his blog. "The energy comes from fat. As the liver breaks down the fat to release its energy to power gluconeogenesis, the conversion of protein to sugar, it produces ketones as a byproduct. And what a byproduct they are. Ketones are basically water soluble (meaning they dissolve in blood) fats that are a source of energy for many tissues including the muscles, brain and heart. In fact, ketones act as a stand in for sugar in the brain. Although ketones can't totally replace all the sugar required by the brain, they can replace a pretty good chunk of it."

No one should be surprised that it's glucose rather than carbohydrates that our brains run on. For a century we have had evidence that our brains don't need any carbohydrates. The arctic explorer Dr. Vilhjalmur Stefansson in 1935 wrote three articles about how "Eskimos Prove an All Meat Diet Provides Excellent Health" that you can read on my website starting with this article. Dr. Stefansson himself lived on an all-meat diet when he went to the arctic in 1906. Even before he wrote those articles, the Journal of Biological Chemistry reported on the experiments performed on him and a colleague at New York's Bellevue Hospital in the article, "Prolonged Meat Diets with a Study of Kidney Function and Ketosis" by Walter S. McClellan and Eugene F. Du Bois (J. Biol. Chem. 87: 651-668, July 1930).

Just now we even have evidence that some of our brains work much better on a very low carbohydrate diet. British researchers reported on May 2 in The Lancet Neurology that a very low carb diet has proved highly effective in reducing seizures in children whose epilepsy didn't respond to medication.

Does this make sense to you? Since I follow a very low-carb diet, I may be courting a nasty case of what Edutopia Magazine calls "'t remember...what was I going to say?"

But I go to the primary sources, and my brain seems to be working as well as ever, thank you. Hello? Can you hear me now?

David Mendosa
Meet Our Writer
David Mendosa

David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.