Control Sugar Cravings & Metabolism with Science-Based Tools | Huberman Lab Essentials
In a Nutshell
Sugar cravings stem from two neural pathways: one driven by sweet taste perception releasing dopamine via the mesolimbic pathway, and another from post-ingestive gut signals (neuropod cells via vagus nerve) triggered by glucose spikes, amplified by high-GI foods and fructose (especially from high-fructose corn syrup). Fructose disrupts hunger hormones like ghrelin, increasing appetite beyond calories consumed. Key tools to curb cravings: glutamine (3-5g/day), lemon/lime juice or cinnamon with carbs to blunt glucose rises, quality sleep, and potent regulators like berberine (use cautiously with doctor, alongside food to avoid hypoglycemia); pair sweets with fiber/fats to lower glycemic impact.
These notes were generated by AI and may contain inaccuracies.
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. Andrew Huberman is a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today we discuss sugar in particular, how our nervous system regulates our sugar intake and seeking of sugar, and place sugar into its proper context.
When we eat, ghrelin (spelled g h r e l i n) is a hormone in our brain and body that increases depending on how long it's been since we ate last. The longer since the last meal, ghrelin levels are higher, making us hungry by interacting with particular neurons in the arcuate nucleus of the hypothalamus and other areas like the lateral hypothalamus. When we eat, ghrelin levels typically go down.
When we eat carbohydrates, or even just protein and fats, we experience a slight or large rise in blood glucose (blood sugar). The body and brain, particularly the nervous system, don't function well if blood sugar is too high or too low. Insulin, released from the pancreas, regulates glucose in the bloodstream.
The brain's chief organs for glucose utilization are neurons, which are tremendously metabolically active and prefer glucose metabolism. This is also true for neurons in the body. Motor neurons send electrical potentials to muscle fibers for movement and exercise, demanding high glucose, especially during demanding physical work.
Deliberate thought, controlling brain and body movement, skill learning, reading and thinking, or intense listening requires more glucose uptake by neurons in the brain and body. This explains tiredness after long exercise, skill learning, reading, or intense conversations.
Glucose is the preferred fuel for the nervous system. Now concentrating on other sugars like fructose, found in fruit and high fructose corn syrup. Concentrations of fructose in fruit are 1% to about 10%, quite low compared to high fructose corn syrup.
Too much fructose impacts neural circuits that process sugar, not just glucose but fructose. Fructose most likely cannot directly access the brain; it needs conversion to glucose in the liver. This conversion feeds back to hormones and neural pathways related to appetite.
Fructose reduces certain hormones and peptides that suppress ghrelin. Although calories in/calories out is the fundamental principle of weight loss, maintenance, or gain, ingesting fructose shifts our hormone system and hypothalamic neural pathways to make us hungrier regardless of calories eaten.
Recommendations: Eat more fruits and vegetables, but for controlling hunger, ingesting a lot of fructose is not a good idea, especially from high fructose corn syrup (50% or more fructose).
Fructose bridges sugar, hormone function (ghrelin), and the hypothalamus. What makes sugar attractive? Not just taste. Rewarding properties of sugar (sucrose, fructose, or foods increasing glucose highly) are not solely taste-related.
Foods break down into components; glucose shuttles to brain, spinal cord neurons, muscles for function. Many cells, organs, tissues require glucose, leading to dedicated neural machinery in the brain devoted to seeking sugars or sugar-containing foods, knowing their location, and ingesting more.
Two main parallel neural circuits for sugar consumption:
- One related to taste and perception of sweet tastes, leading all animals to seek more sweet-containing foods.
- The other related to the nutritive component (degree to which a food raises blood glucose).
Sweet-tasting foods that raise blood glucose coincide, but this differs from pathways for savory, salty, spicy, or bitter foods. The sweet pathway is hardwired in every mammal.
Getting sweet stuff relates to both taste and nutritive components, as nervous system cells run on glucose (fructose converts to glucose in liver).
Craving chocolate or cake involves both taste craving and neurons craving nutritive components.
One pathway involves conscious perception: Sweet ingestion sends signals from mouth neurons to brain areas causing seeking or attention to sweet sources, changing perception.
Not saying never ingest sweet things; decide appropriate sugar intake. Remarkable when people say they need a "sugar fix" or chocolate. It shifts perception of other foods via dopamine, a neuromodulator from the mesolimbic reward pathway for motivation, craving, pursuit, linked to movement areas.
Sweet taste perception increases dopamine in mesolimbic pathways, conveyed to motor behavior pathways, creating focused action for more sweets.
Dopamine creates wanting more, not satiety. Longer since indulgence, greater dopamine upon engaging.
Dopamine pathways are not bad; understanding them allows leveraging to your advantage.
Second pathway: post-ingestive reinforcing properties of sugar—subconscious gut events driving seeking of sweets or glucose-increasing foods independent of taste.
Gut has neuropod cells (discovered by Prof. Dr. Diego Bohórquez at Duke University) responding to sugar in gut. These send electrical signals via vagus nerve to nodose ganglion (cluster of neurons), then to nucleus of the solitary tract (NTS), important for sugar preference.
Hidden sugars in savory foods trigger neuropod cells, dopamine, craving more food generally.
Two major accelerators for sweet food pursuit, like a car with two accelerators.
Glycemic index (GI) measures how high/fast blood sugar rises post-food:
- Low GI: <55
- Medium GI: 55-69
- High GI: >70
Nuance includes glycemic load. GI measured by ingesting foods in isolation. Ingesting fiber and/or fat (lipids) with food reduces GI (absolute blood glucose level or rise rate).
Paradoxes: Ice cream (with fat) has lower GI than mangoes or table sugar.
GI not wholly reliable as people don't eat foods isolated.
Sharp/high blood glucose rise is more potent signal for dopamine/neural circuits than moderate/slow rise.
To reduce sugar intake, short-circuit dopamine by choosing sweet foods with lower GI or combining with foods reducing GI/load (e.g., fiber with sweets) to blunt dopamine release.
Reduce dopamine via parallel pathways: prevent sweet taste and post-ingestive effects.
Most should ingest fewer refined sugars.
Gut neurons (neuropod cells, others) respond robustly to amino acids.
Glutamine supplementing (several grams/day, e.g., 5g distributed 3-4 times) blunts sugar cravings and treats leaky gut.
No large-scale trials yet, but logic fits: Gut neurons responding to sugar/fatty acids/amino acids mean amino acids like glutamine (few/no calories) trigger dopamine instead of sugar.
Some mix glutamine with full-fat cream.
Increase glutamine gradually to avoid gastric distress. Caution: Potential hazards if pre-existing cancer; discourage if cancer-prone. Talk to doctor.
Lemon juice or lime juice (couple tablespoons before/during/after sugary/high-carb foods) blunts blood glucose response (confirmed via continuous glucose monitor experiments).
Mechanisms: Post-ingestive gut effects (gastric emptying, neuropod firing); sour taste perception on tongue/palate adjusts sweet neural circuits (work of Charles Zuker at Columbia Medical School).
Sour adjusts sweet brain output.
Cinnamon adjusts glucose entry into bloodstream, possibly slowing gastric emptying, reducing GI.
Caution: Cinnamon contains coumarin, toxic at high levels. Limit to ~1-1.5 tsp/day.
So, we've talked about lemon juice and lime juice and cinnamon. These are kind of
Berberine is a serious step for adjusting sugar intake; talk to your doctor before using it. Ingesting berberine causes blood glucose to plummet. Personal experience: taking it caused brutal headaches, dizziness, and inability to see straight due to hypoglycemia from taking it on an empty stomach. Taking berberine with a very large meal including a lot of carbohydrates allowed feeling perfectly fine even at 750 milligrams or a gram. Berberine, metformin, and glibenclamide are heavy-hitting potent tools for regulating blood glucose. Substances like sodium caprate augment berberine's effects via AMPK pathways, increasing its glucose-lowering actions. These are sharp blade tools for controlling blood glucose.
Anytime dealing with blood glucose, the brain's preferred source of fuel, be especially cautious about depriving the brain of what it needs. These substances are very potent and must be taken seriously.
Sleep controls sugar cravings and neural circuits regulating sugar craving and its downstream consequences. Extensive episodes on sleep available, including "Master Your Sleep" at hubermanlab.com in all formats (YouTube, Apple, Spotify); social media provides additional tools.
Study published last year in Cell Reports (Cell Press journal): measured metabolites from breath every 10 seconds throughout the night in humans sleeping in the laboratory. Each stage of sleep associated with particular signature pattern of metabolism; particular phases linked to sugar metabolism, fat metabolism, or other aspects.
Disrupted sleep increases appetite for sugary foods. Quality sleep each night helps regulate appetite and specific forms of metabolism driving specific appetites. Get regular sufficient amount of high quality sleep at least 80% of the time for immune function, clear thinking, and properly regulating metabolism including sugar metabolism.
Thank you for joining this discussion about sugar and the nervous system and how they regulate each other in brain and body. Thank you for your interest in science.
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