Brain Food: How To Eat Smart
MORE It's common to resolve to lose weight, but any sane person dreads a diet's dulling effect on the brain. In fact, many studies have shown that counting calories, carbs or fat grams, is truly distracting — to the point that it taxes short-term memory. But how we eat can affect our minds at more fundamental levels, too. Whether you are seeking brain food for exams or just want to be at your sharpest ever day, here are five things you should know about feeding your brain: 1. Fuel it up The brain, which accounts for 2 percent of our body weight, sucks down roughly 20 percent of our daily calories. A picky eater, it demands a constant supply of glucose — primarily obtained from recently eaten carbohydrates (fruits, vegetables, grains etc.). Only in extreme instances of deprivation will the brain use other substances for fuel. More recently evolved areas of the brain, such as the frontal cortex (it's like the CEO of the brain), are particularly sensitive to falling glucose levels, while brain areas regulating vital functions are more hardy, said Leigh Gibson of Roehampton University in England. "When your glucose level drops, the symptom is confused thinking, not a change in breathing pattern," he said. This is not to suggest that we should constantly slurp soda to keep our brains functioning optimally. On the contrary, high glucose levels slowly but surely damage cells everywhere in the body, including those in the brain, said Marc Montminy of the Salk Institute for Biological Studies in California. And according to a recent study published in the Oct. 3 issue of the journal Cell, by Dongsheng Cai and colleagues at the University of Wisconsin, the brain may react to excess food as if it were a pathogen. The resulting immune response, which occurs irrespective of weig Continue reading >>
Myth Busting: Your Brain And That "required" 130 Grams Of Carbohydrate
My email has been filed this past week with emails from people with diabetes whose doctors or nutritionists have told them that it is dangerous to eat less than 130 grams of carbohydrates a day. It isn't true. In fact, for most people with diabetes the opposite is true: eating more than 130 grams of carbs a day guarantees blood sugars that are so high they raise your risk of blindness, amputation, kidney failure and heart attack. The old wives tale that you must eat 130 grams of carbohydrate a day has no basis in science. Is is one of those factoids that has been passed from teacher to student in the health profession for generations--long after anyone remembers where it originally came from. As it turns out, it came from two sources, one was ignorance of how the body works and the other a problem common 25 years ago that has been solved by medical progress. Let's look at the origins of the damaging myth that you have to eat 130 grams of carbohydrate every day: 1. Though the brain requires carbs, you don't need to eat carbs to provide your brain with carbs. The brain is unique among organs in its need for glucose. All your other organs can run on ketones or free fatty acids, both the byproducts of the metabolizing fat--but your brain does does require a certain amount of glucose to keep functioning--somewhere around 120 grams. But before you rush off to eat a bagel for breakfast, you need to know while your brain needs glucose, you do not need to EAT glucose to provide your brain with the glucose that it needs. That is because your liver has the remarkable ability to transform the protein that you eat into glucose. This process is called "gluconeogenesis." You liver can transform 58% of every gram of protein you eat into glucose, so any deficit created by eating less th Continue reading >>
Cognition - Food For Thought
Featuring: Captex® 8000 (high C8 content MCT) ABITEC's Captex medium-chain triglycerides come in a variety of grades, each with unique characteristics for different formulations. Our Captex 8000 MCT contains ≥ 90% C8 acyl groups. Medium-chain triglycerides (MCT) are fats typically containing 8-12 carbons. Each MCT can vary in C8-C12 content. Captex 8000, with its high content of C8 acyl groups, has fewer carbons than fats (triglycerides) with longer acyl groups. This is noteworthy because studies have shown that ingestion of MCTs with high C8 significantly increases the ketone production compared to longer-carbon MCTs [11,12]. A recent study from Cunnane et al, showed C8 fatty acids derived from such MCTs increases blood ketones 3 times more than C10 over an 8-hour period [13]. ABITEC's Captex 8000 can be taken alone or incorporated into a wide range of different formulations such as: Ready-to-drink (RTD) Beverages Bars Gelpaks Energy Shots Coffee Creamers References 1. Cahill, G.F., Jr., Fuel metabolism in starvation. Ann Rev Nutr, 2006. 26: p. 1-22. 2. Dahlquist, G. and B. Persson, The rate of cerebral utilization of glucose, ketone bodies, and oxygen: a comparative in vivo study of infant and adult rats. Pediatr Res, 1976. 10(11): p. 910-7. 3. Owen, O.E., et al., Brain metabolism during fasting. J Clin Invest, 1967. 46(10): p. 1589-95. 4. Blennow, K., M.J. de Leon, and H. Zetterberg, Alzheimer’s disease. Lancet, 2006. 368(9533): p. 387-403. 5. Mosconi, L., et al., Hypometabolism exceeds atrophy in presymptomatic early-onset familial Alzheimer’s disease. J Nuclear Med, 2006. 47(11): p. 1778-86. 6. Ogawa, M., et al., Altered energy metabolism in Alzheimer’s disease. J Neurol Sci, 1996. 139(1): p. 78-82. 7. Cunnane, S., et al., Brain fuel metabolism, aging, and Continue reading >>
Is The Brain Fueled By Fat, Protein, Or Carbs?
The human brain consumes up to 20% of the energy used by the entire human body which is more than any other single organ. The brain represents only 2% of body weight yet it receives 15% of the cardiac output and 20% of the total body oxygen consumption. (source) Our brains create major nutrition demands on our bodies in order to function optimally. So is it best to fuel the brain with fat, protein, or carbohydrates? The answer is none of these. Even though the brain is composed of 60% fat, it is designed to be fueled by glucose. The brain accounts for 25% of the total body glucose utilization. 1. Glucose is the human body’s key source of energy. The breakdown of carbohydrates (eg: starch) yields mono- and disaccharides, most of which is glucose. (source) If glucose is available, the body will use it first since it is easiest and quickest to metabolize. Whole simple carbohydrates like raw fruit and whole complex carbohydrates like grains, legumes, and tubers are excellent sources of glucose for the brain. Refined carbohydrates can deprive the brain of glucose.1 Click: Know Your Complex, Simple, and Refined Carbs Glucose is virtually the sole fuel for the human brain, except during prolonged starvation. In starvation, ketone bodies generated by the liver partly replace glucose as fuel for the brain. (source) 2. If insufficient carbohydrates are consumed to meet our fuel needs, then fats and proteins can be converted into sugars. The human body has little capacity to store excess carbohydrates or protein, but can convert both to fat stores for later use as fuel when converted to glucose via gluconeogenesis. When fats are converted to sugar in the absence of carbohydrates, ketones are produced. These molecules are very similar to acetone in their structure. They affect br Continue reading >>
The Carbohydrate Brain Fuel Myth
We distort knowledge faster than things. Some things are so easy to assemble that “even a child can do it” in outer space. But even children know that information disassembles all too readily. Children learn by playing the game of telephone that information gets garbled as it gets passed along. Too bad that medical writers don’t know that basic lesson. That’s why that although I am also a medical writer about diabetes, I don’t ask you to 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 at secondary sources like Reuters Health write. 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. The brain fuel myth can lead those of us who have diabetes to 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,” some freelance medical writer named Abby Christopher writes there. 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 effe Continue reading >>
Review Brain Energy Metabolism: Focus On Astrocyte-neuron Metabolic Cooperation
Main Text Introduction Glucose is the obligatory energy substrate of the adult brain. Nevertheless, under particular circumstances the brain has the capacity to use other blood-derived energy substrates, such as ketone bodies during development and starvation (Nehlig, 2004; Magistretti, 2008) or lactate during periods of intense physical activity (van Hall et al., 2009). Glucose enters cells trough specific glucose transporters (GLUTs) and is phosphorylated by hexokinase (HK) to produce glucose-6-phosphate. As in other organs, glucose 6-phosphate can be processed via different metabolic pathways (Figure 1A), the main ones being (1) glycolysis (leading to lactate production or mitochondrial metabolism), (2) the pentose phosphate pathway (PPP), and (3) glycogenesis (in astrocytes only, see below). Overall, glucose is almost entirely oxidized to CO2 and water in the brain (Clarke and Sokoloff, 1999). Nevertheless, as evidenced by the different metabolic routes that glucose can follow, each individual brain cell does not necessarily metabolize glucose to CO2 and water. Indeed, a wide range of metabolic intermediates formed from glucose in the brain can subsequently be oxidized for energy production (e.g., lactate, pyruvate, glutamate, or acetate) (Zielke et al., 2009). Figure 1. Brain Glucose Utilization (A) Schematic representation of glucose metabolism. Glucose enters cells trough glucose transporters (GLUTs) and is phosphorylated by HK to produce glucose-6-phosphate (glucose-6P). Glucose-6P can be processed into three main metabolic pathways. First, it can be metabolized through glycolysis (i), giving rise to two molecules of pyruvate and producing ATP and NADH. Pyruvate can then enter mitochondria, where it is metabolized through the tricarboxylic acid (T Continue reading >>
Scaling Of Brain Metabolism With A Fixed Energy Budget Per Neuron: Implications For Neuronal Activity, Plasticity And Evolution
Abstract It is usually considered that larger brains have larger neurons, which consume more energy individually, and are therefore accompanied by a larger number of glial cells per neuron. These notions, however, have never been tested. Based on glucose and oxygen metabolic rates in awake animals and their recently determined numbers of neurons, here I show that, contrary to the expected, the estimated glucose use per neuron is remarkably constant, varying only by 40% across the six species of rodents and primates (including humans). The estimated average glucose use per neuron does not correlate with neuronal density in any structure. This suggests that the energy budget of the whole brain per neuron is fixed across species and brain sizes, such that total glucose use by the brain as a whole, by the cerebral cortex and also by the cerebellum alone are linear functions of the number of neurons in the structures across the species (although the average glucose consumption per neuron is at least 10× higher in the cerebral cortex than in the cerebellum). These results indicate that the apparently remarkable use in humans of 20% of the whole body energy budget by a brain that represents only 2% of body mass is explained simply by its large number of neurons. Because synaptic activity is considered the major determinant of metabolic cost, a conserved energy budget per neuron has several profound implications for synaptic homeostasis and the regulation of firing rates, synaptic plasticity, brain imaging, pathologies, and for brain scaling in evolution. Figures Citation: Herculano-Houzel S (2011) Scaling of Brain Metabolism with a Fixed Energy Budget per Neuron: Implications for Neuronal Activity, Plasticity and Evolution. PLoS ONE 6(3): e17514. Editor: Matjaz Perc, Universi Continue reading >>
Each Organ Has A Unique Metabolic Profile
The metabolic patterns of the brain, muscle, adipose tissue, kidney, and liver are strikingly different. Let us consider how these organs differ in their use of fuels to meet their energy needs: 1. Brain. Glucose is virtually the sole fuel for the human brain, except during prolonged starvation. The brain lacks fuel stores and hence requires a continuous supply of glucose. It consumes about 120 g daily, which corresponds to an energy input of about 420 kcal (1760 kJ), accounting for some 60% of the utilization of glucose by the whole body in the resting state. Much of the energy, estimates suggest from 60% to 70%, is used to power transport mechanisms that maintain the Na+-K+ membrane potential required for the transmission of the nerve impulses. The brain must also synthesize neurotransmitters and their receptors to propagate nerve impulses. Overall, glucose metabolism remains unchanged during mental activity, although local increases are detected when a subject performs certain tasks. Glucose is transported into brain cells by the glucose transporter GLUT3. This transporter has a low value of KM for glucose (1.6 mM), which means that it is saturated under most conditions. Thus, the brain is usually provided with a constant supply of glucose. Noninvasive 13C nuclear magnetic resonance measurements have shown that the concentration of glucose in the brain is about 1 mM when the plasma level is 4.7 mM (84.7 mg/dl), a normal value. Glycolysis slows down when the glucose level approaches the KM value of hexokinase (~50 μM), the enzyme that traps glucose in the cell (Section 16.1.1). This danger point is reached when the plasma-glucose level drops below about 2.2 mM (39.6 mg/dl) and thus approaches the KM value of GLUT3. Fatty acids do not serve as fuel for the brain, beca Continue reading >>
The Carbohydrate Brain Fuel Myth
We distort knowledge faster than things. Some things are so easy to assemble that “even a child can do it” in outer space. But even children know that information disassembles all too readily. Children learn by playing the game of telephone that information gets garbled as it gets passed along. Too bad that medical writers don’t know that basic lesson. That’s why that although I am also a medical writer about diabetes, I don’t ask you to 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 at secondary sources like Reuters Health write. 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. The brain fuel myth can lead those of us who have diabetes to 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,” some freelance medical writer named Abby Christopher writes there. 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 effe Continue reading >>
The Role Of Insulin In Human Brain Glucose Metabolism
An 18Fluoro-Deoxyglucose Positron Emission Tomography Study The effect of basal insulin on global and regional brain glucose uptake and metabolism in humans was studied using 18-fluorodeoxyglucose and positron emission tomography (FDG-PET). Eight healthy male volunteers aged 49.3 ± 5.1 years were studied twice in random order. On each occasion, they received an infusion of 0.1 mg · kg−1 · min−1 somatostatin to suppress endogenous insulin production. In one study 0.3 mU · kg−1 · min−1 insulin was infused to replace basal circulating insulin levels, and in the other study a saline infusion was used as control. We sought stimulatory effects of basal insulin on brain glucose metabolism particularly in regions with deficiencies in the blood-brain barrier and high density of insulin receptors. Insulin levels were 27.07 ± 1.3 mU/l with insulin replacement and 3.51 ± 0.4 mU/l without (P = 0.001). Mean global rate of brain glucose utilization was 0.215 ± 0.030 mmol · kg−1 · min−1 without insulin and 0.245 ± 0.021 mmol · kg−1 · min−1 with insulin (P = 0.008, an average difference of 15.3 ± 12.5%). Regional analysis using statistical parametric mapping showed that the effect of basal insulin was significantly less in the cerebellum (Z = 5.53, corrected P = 0.031). We conclude that basal insulin has a role in regulating global brain glucose uptake in humans, mostly marked in cortical areas. The effect of insulin in peripheral tissues is the stimulation of glucose uptake, oxidation, and storage. The effect of insulin on the brain is less well defined. Elevations of circulating insulin can alter brain function, augmenting the counterregulatory response to hypoglycemia (1,2), altering feeding behavior (3,4), and modulating auditory evoked potentials (5). Continue reading >>
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Normal Cerebral Glucose Metabolism
The brain relies on glucose for energy1 The brain is one of the most metabolically active organs in the body. Together with the heart, liver, and kidneys, it consumes about 60% of the body’s energy requirements.1 The heart and kidneys are more metabolically active than the brain, but as the brain is larger, it takes a higher proportion of the body’s energy needs. At rest, it uses approximately 20% to 23% of the body’s total energy requirements, despite accounting for only 2% of the body’s mass. Almost all of that oxygen is used to oxidize glucose to carbon dioxide and water.1 The brain stores little energy as glycogen and relies almost entirely on circulating glucose for fuel. Once inside neurons, glucose is metabolized by mitochondria in a number of steps to produce cellular energy, or adenosine triphosphate.2 Most of the glucose consumed by the brain is used to maintain synaptic function and resting potential of neurons.1 The energy requirements of different types of neurons varies. Large-projection neurons with relatively long axons are most affected by Alzheimer’s disease and these neurons generally have high energy requirements. Without sufficient energy supply, these neurons cannot function efficiently.3 Metabolism of glucose in neuronal mitochondria2 Continue reading >>
Dear Mark: How Much Glucose Does Your Brain Really Need?
116 Comments We now know that the oft-repeated “your brain only runs on glucose!” is wrong. I’ve mentioned it before, and anyone who’s taken the time to get fat-adapted on a low-carb Primal eating plan intuitively knows that your brain doesn’t need piles of glucose to work, because, well, they’re using their brain to read this sentence. Obviously, you eventually adapt and find you have sufficient (if not much improved) cognition without all those carbs. That said, some glucose is required, and that’s where people get tripped up. “Glucose is required” sounds an awful lot like “your brain only uses glucose” which usually leads to “you need lots of carbs to provide that glucose.” And that’s the question today’s edition of “Dear Mark” finds itself attempting to answer: how much glucose is required? Let’s get to it. Hi Mark, I have a little problem. Even though I’m able to function at work, maintain conversations, and go about my daily life without having segments of my brain suddenly stop working while eating Primal, my friends are worried about my brain. All they know is that the brain needs glucose. What can I tell them? How much glucose does my brain actually require to keep working? Thanks, Frank I wouldn’t be too hard on your friends. They mean well and it’s a common misconception. Instead of chiding them, rubbing their faces in the knowledge that you can function quite adequately on a high-fat diet, educate them. How much glucose the brain requires depends on the context. There’s not one single answer. If you’re on a very high fat, very low carb diet – like a traditional Inuit diet – your brain will eventually be able to use fat-derived ketones for about 50-75% of its energy requirements. Most ketones are produced in t Continue reading >>
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Effects Of Blood Glucose Changes And Physostigmine On Anesthetic Requirements Of Halothane In Rats
Changes in blood and brain glucose concentration induce neurophysiologic and neurochemical changes in the brain. [1–3 ] During hypoglycemia, these changes are clinically shown as somnolence and lethargy, slow waves on the electroencephalogram (EEG), and eventual unconsciousness. [4,5 ] Thus hypoglycemia could affect anesthetic requirements. Hyperglycemia by itself [3 ] and diabetes-induced hyperglycemia [6,7 ] have also been reported to affect brain function. The anesthetic requirement of inhaled anesthetics was reported to decrease in streptozotocin-induced diabetic rats. [8 ] However, neither the effect of hypoglycemia nor hyperglycemia on the minimum alveolar concentration (MAC) have been investigated. Under hypoglycemia of 30–45 mg/dl blood glucose, in which slow waves in EEG are observed, acetylcholine in the brain has been reported to be significantly reduced, probably due to impaired incorporation from choline to acetylcholine. [1,2,9 ] At this level of moderate hypoglycemia, decreases in amino acid neurotransmitters or failure of ion transport have not developed. [1,2 ] Those events are appreciable when energy failure ensues with blood glucose levels less than 20 mg/dl. [1,2,10 ] Acetylcholine thus might play an important role in changes in the brain function during hypoglycemia, particularly mild to moderate hypoglycemia. The present studies were designed to determine (1) whether hyperglycemia and hypoglycemia affect MAC and (2) whether physostigmine, which has been confirmed to increase brain acetylcholine in experimental animals, [11–13 ] alters the effects of hypoglycemia on MAC if hypoglycemia changes MAC. The experiments were performed in rats anesthetized with halothane. Anesthesia was induced by inhalation of halothane in a transparent container. A Continue reading >>
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Myth - Requiring 130 Grams Of Carbohydrate For The Brain To Function.
The MYTH of requiring 130 grams of carbohydrate in the diet for the brain to function. This is an outdated concept. We require far less carbohydrate in our diet because the liver will convert protein into glucose to adequately ‘run’ the brain. That’s how we survive in starvation. I am told over and over that the brain is dependent on glucose and its dangerous to run low carb. This is the primary concern of doctors, medical students, dietitians, midwives and most people, but not biochemists. Let’s explore some religion to break a myth. Would God (in whatever form that is) make our most important organ, the brain, dependent on only one fuel source of glucose? Surely not. On a foreign aid trip to Vanuatu I was looking through a 1996 textbook of physiology. There it all was on page 22 of a 1148 page textbook – in the Introduction to Physiology chapter. We are not even in the ‘fine print’ area! Here’s some basic biochemistry. The mitochondria is the engine of the cell. It will process a variety of fuel sources into Acetyl-CoA which then enters the Krebs cycle and converts into ATP – Adenosine Tri phosphate. ATP is found in all living tissue and provides energy for virtually all physiological processes. We are completely dependent on that ATP – it is life itself. That mitochondria is like a teenager looking for food. It doesn’t care where the Acetyl CoA comes from, as long as it’s there. Acetyl-CoA can be made from glucose, carbohydrate, ketone bodies (fatty acids) from fat, and amino acids from protein. The mitochondria is a hybrid engine and it will run efficiently on these different fuel sources. Any cell that has mitochondrion will need Acetyl-CoA. Every cell in the brain has mitochondria. As a result every brain cell can run along on ketones and l Continue reading >>
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Does The Brain Consume Additional Glucose During Self-control Tasks?
A currently popular model of self-control posits that the exertion of self-control relies on a resource, which is expended by acts of self-control, resulting in less of this resource being available for subsequent acts of self-control (Baumeister, Vohs, and Tice, 2007; Muraven and Baumeister, 2000; Schmeichel and Baumeister, 2004; Vohs et al., 2008). The nature of this resource was previously left unspecified, referred to using metaphorical terms such as “willpower,” or with the notion that self-control was “like a muscle” (Muraven and Baumeister, 2000). Recently, Gailliot et al. (2007) reported the results of nine studies designed to make this model more concrete, specifying glucose as the resource necessary for, and depleted by, acts of self-control (see also Gailliot and Baumeister, 2007). Like much research in this literature, the studies in question used methods along the following lines. First, a “self-control” task was performed by subjects, after which a second “self-control” task was performed. In this literature, it is frequently reported that compared to relevant controls, performance on the second task tends to be lower (see Hagger, Wood, Stiff, and Chatzisarantis, in press, for a recent meta-analysis); the “resource” explanation of such effects is that a resource was depleted by the first task, causing a reduction in performance on the second. For the glucose account to be able to explain such results, both of the following propositions must be true. Proposition 1. Performing a self-control task reduces glucose levels relative to a control task. Proposition 2. Performing a self-control task reduces glucose levels relative to glucose levels before the task. If Proposition 1 is not true, then the difference in performance observed in these Continue reading >>
