What other sources can be used?
I came across this article on Medium entitled I Wanted to Know the Truth About Carbs. Here It Is. In that article, the author made a spurious claim that our brain cells could only derive energy from carbohydrates, but not from fats, going so far as to make the unsubstantiated claim about carbohydrates that:
It’s also the only source of energy for the brain which, unlike the rest of the human body, cannot draw on fat to function. We will come back to this later.
And of course, never did get back to it in the article.
Unfortunately, that statement is terribly wrong and has to be called out for non-scientific and non-factual writing.
As it is said in this book, Nutrition and Traumatic Brain Injury: Improving Acute and Subacute Health Outcomes in Military Personnel:
In normal metabolism, carbohydrates contained in food are converted into glucose, which is the body’s preferred substrate for energy production. Under some circumstances, like fasting, glucose is not available because the diet contains insufficient amounts of carbohydrates to meet metabolic needs. Consequently, fatty acid oxidation becomes favored, and the liver converts fat into fatty acids and ketone bodies that serve as an efficient alternative fuel for brain cells. The conversion leads to the synthesis of three ketone bodies in particular: β-hydroxybutyrate, acetoacetate, and acetone. Although fatty acids cannot cross the blood-brain barrier, these three ketone bodies can enter the brain and serve as an energy source.
The body (and the brain) would prefer to metabolise carbohydrates, BUT the brain can also make use of fats that the liver has converted into ketones, because those ketones can cross the blood-brain barrier when the fatty acids cannot.
Ketones can be derived from fats, which can cross the blood brain barrier and serve as an energy source for the brain cells. Carbohydrates are not the only source of energy for brain function, which I also do explain at The Science Of Ketosis.
What is a carbohydrate?
As the name suggests, we’re looking at a chemical compound that contains carbon (carbo) and water (hydrate). Glucose is a simple carbohydrate that contains the chemical formula C6H12O6, where we have six carbon atoms and six water (H2O) molecules mixed together to form one glucose molecule.
There are long chain glucose molecules that polymerise and form cellulose polymers, which are considered to be the dietary fibre that we consume. These polymers cannot be digested by the enzymes in our digestive system, hence they tend to clear out gut relatively untouched.
Herbivorous animals such as cows do have a digestive system that contains Ruminococcus bacterial species. These bacteria are able to express cellulase enzymes that can break down the cellulose polymers. Hence, the “dietary fibre” that we excrete in our stools from the cellulose polymers are actully things that can be digested by those animals down into glucose for energy generation.
Hence, carbohydrates can be digestible or indigestible, but the simplest test that one can do to determine the amount of carbohydrates in a sample is to burn the sample and see how much carbon dioxide is liberated from the sample.
Any such burnt samples would indicate on the nutritional label the total carbohydrate content. Therefore, foods such as oats do contain a high level of total carbohydrate… but not all of it is digestible.
How do our brain cells use glucose or ketones as an energy source, then?
Much like any other cell in our body makes use of them.
In The Science Of Ketosis, I write that
It is a common fact that our cells use the tricarboxylic acid cycle (TCA, also known as the citric acid cycle or the Krebs cycle) to generate energy from this molecule known as acetyl-coenzyme A (acetyl-CoA). Acetyl-CoA is oxidized in the mitochondria to synthesize adenosine triphosphate (ATP), the biochemical energy currency that is used by the cells for energy purposes. Acetyl-CoA can be obtained from glucose (carbohydrates) or ketones (from fatty acids), which we do consume in our diets.
The body preferentially uses glucose as a source of acetyl-CoA, but when there is a scarcity of carbohydrates in the diet, the body shifts its source of energy derivation towards the ketones.
ATP then undergoes oxidative phosphorylation and the breaking of phosphate bonds generates the biochemical energy that our cells can then convert into other useful forms of energy.
So whether we’re looking at carbohydrates or fats as an energy source, they’d all end up being converted down into acetyl-CoA for each individual cell to generate energy via the TCA cycle.
The dangers of overconsuming carbohydrates, though…
We live in a world that is full of aesthetically pleasing foods that are unfortunately also drowning in carbohydrates, as we can see in The Problem With Excess Sugar Consumption In Our Lives.
While carbohydrates are one of the key macronutrients that make up our diet, the saturation of the supermarkets and grocery stores with so many processed foods containing excessive quantities of carbohydrates isn’t that great for health.
Glucose can be present as a reactive aldehyde anomer that forces protein glycation, hence diabetics have a higher level of glycated haemoglobin proteins in their blood, which they will know as the HbA1c marker. Protein glycation can also trigger the synthesis of Advanced Glycation End-products (AGEs), which promote a pro-inflammatory response in the body, as I explore in The Unmentioned Implications Of Excess Sugar In Our Blood.
And the pro-inflammatory can also lead on to the cells in the body resisting the insulin signal during feeding time, which leads to an accumulation of glucose in the blood, or Type 2 diabetes, as we can see in The Rime Of The Ancient Mariner And Its Analogy With Type 2 Diabetes.
Which therefore turns Type 2 diabetes into a symptom of an immune system dysfunction, and hence Type 2 diabetics can be more prone to the severe effects of COVID-19, as outlined in Type 2 Diabetes - A Case Of The Immune System Gone Bad, Too?
So while carbohydrates may be a preferred energy source for the cells in our body, they are by no means the only energy source for the cells in our brains.
An excessive carbohydrate consumption, though, would not bode well for out health at all.
For Dr J's nutritional support recommendations for the immune system, do visit the shop at this page.
For Dr J's recommendations for a well-balanced macronutrient support AKA The Breakfast Of Champions, do visit this page.
This article was originally published in Medium.