How Foods and Nutrients Control Our Moods
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- ~6 min
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- 15 Mar 2021
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- 1:44:07
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KEYPOINTS
- 01
The vagus nerve is a two-way highway, not a 'calm-down' button
Huberman describes the vagus (cranial nerve X) as carrying sensory information from the stomach, intestines, heart, lungs and immune system up to the brain, plus motor commands back down. He calls generic 'vagus stimulation' a terrible concept: the same nerve signals infection and helps trigger fever, so you want to engage specific pathways rather than the whole nerve.
- 02
Polyvagal theory got the branching right but is often stretched too far
He credits Stephen Porges for stressing that the vagus has many branches, but says the dorsal/ventral split does not fully match modern anatomy. His bigger complaint is popular use: diagnosing personality, freeze states or joint hypermobility from 'dorsal vagal tone' goes beyond any known physiology.
- 03
Gut neurons detect sugar without any taste and drive craving via dopamine
Cells in the stomach sense sugar and signal up the vagus to trigger dopamine release. In experiments where people's mouths were numbed and they were blindfolded, they still craved the food that contained sugar. That is why he sees hidden sugars as a problem for the dopamine system, not only for blood glucose.
- 04
A little anxiety before eating is built into the circuitry
As you approach food, the locus coeruleus releases noradrenaline, which acts on the lateral hypothalamus to inhibit feeding. Calming and fullness signals are meant to take over as you eat. He thinks this explains why some people feel stressed at mealtimes, and he suggests using how well you digest as a guide rather than strict rules about never eating while stressed.
- 05
People tend to eat until the brain registers enough amino acids, not until the stomach is full
Gut sensors track both how much protein you have eaten and which amino acids it contains. Amino acids matter beyond building muscle because they are the raw material for neuromodulators. L-tyrosine (found in meats, nuts and some plant foods) is the precursor for L-DOPA and dopamine, although the dopamine neurons that drive motivation live in the brain, not the gut.
- 06
Dopamine is about wanting, and reward prediction error shapes whether you go back for more
Expecting something releases dopamine, and so does getting it. If the actual experience doesn't at least match the build-up, you get less dopamine and are less likely to pursue it again. He uses his own 'affliction' for croissants: hyped croissants tend to disappoint, while one tried at random can satisfy more.
- 07
Most mood-relevant serotonin is made in the brain, even though the gut makes plenty
He pushes back on the popular claim that '90% of serotonin is in the gut, so mood lives in the gut'. Mood and satiety serotonin come mainly from the raphe nucleus. SSRIs such as Prozac, Zoloft and Paxil help many people, he says, but can blunt emotions, appetite and libido.
- 08
Changing the omega-3 to omega-6 ratio can affect depression
In a rodent learned-helplessness swim test, raising omega-3s relative to omega-6s made the animals keep swimming longer. In a human study of 60 people with major depression, 1,000 mg/day of EPA worked as well as 20 mg of fluoxetine over 8 weeks, and the combination worked better than either. He says PubMed now holds many studies pointing the same way.
- 09
EPA may work partly through inflammation and heart rate variability
He cites a 2009 study in which a high omega-6 to omega-3 ratio went along with raised IL-6 and TNF-alpha and poor response to antidepressants. Raising EPA lowered those markers, let low-dose antidepressants work and increased heart rate variability, which he links to the vagal sensing of the heart.
- 10
Gut microbes support mood, but more probiotics is not better
A healthy microbiome supports mood, digestion and immunity. He cites studies, which he calls somewhat controversial, linking very high probiotic intake (e.g. lactobacillus) to brain fog. Citing published work from Justin Sonnenburg's lab, he favors fermented foods such as sauerkraut, kimchi, pickles and natto, at around two servings a day.
- 11
Belief changes how the body responds to food
Alia Crum's work shows that what people believe about a food or activity changes measurable physiology, beyond a simple placebo effect. He stresses that this only works when people don't already know the expected outcome. You cannot talk yourself into a poison being healthy or into twelve croissants causing weight loss.
EXAMPLES
- 01
Milkshake study: same shake, different ghrelin response
Two groups drank an identical milkshake, but one was told it was a low-calorie 'healthy' shake and the other a decadent, high-calorie one. The 'indulgent' group showed a much larger drop in the hunger hormone ghrelin, showing that beliefs about food reach hormones released in the body.
- 02
Hotel housekeepers told their work was exercise
In another Crum study, hotel workers who were told their daily cleaning was good for their health had lower blood pressure, lost significant body fat and enjoyed their work more 8 weeks later, compared with a group that got a different message. Their actual work stayed the same.
- 03
Saccharin and the gut microbiome
A Nature study showed saccharin shifted the microbiome toward bacteria linked to inflammation, and antibiotics blocked the effect. Huberman stresses that saccharin shifts the microbiome rather than killing it. He says the negative findings, as far as he knows, were specific to saccharin. Stevia and monk fruit are chemically distinct, though they still need testing.
- 04
Acetyl-L-carnitine trials
L-carnitine (richest in beef) is converted to acetyl-L-carnitine, which crosses the blood-brain barrier. Studies collected on Examine.com report reduced depressive symptoms, better sperm motility, benefits in PCOS, and reductions in some autism and fibromyalgia symptoms. In a migraine RCT of 133 people, 500 mg for 12 weeks cut monthly attacks, although he notes the control condition was weak.
- 05
Mucuna pruriens, the 'dopamine bean'
This velvet bean is itchy because of serotonin on its surface and contains L-DOPA inside. Reported effects include better sperm quality, eased Parkinson's symptoms, greater well-being, higher testosterone and lower prolactin. He describes these as a window into what an acute dopamine increase does, not as a recommendation.
OTHER RELEVANT
- 01
Time macronutrients to your mental state
Huberman's own pattern: fast and exercise early, eat a high-protein, moderate-fat, low-carb lunch to support dopamine and alertness, then eat starchy carbs and tryptophan-rich foods in the evening to raise serotonin before sleep.
- 02
Be cautious with tyrosine and 5-HTP
He takes L-tyrosine occasionally. He warns it can cause a crash and brain fog the next day, that chronic use may disrupt dopamine pathways, and that people prone to mania should avoid it. 5-HTP knocks him out but wakes him 2–3 hours later, because natural serotonin release peaks late at night. It may also suppress appetite and raise cortisol. Check with a doctor first.
- 03
Aim for about 1,000 mg EPA per day from a clean source
Sources include fish oil, krill (which gave him itchy skin), chia, flax and grass-fed meat. Pick decontaminated brands and bite a capsule to check it isn't rancid. People with bleeding disorders such as factor V Leiden, or women on birth control, should ask their doctor first. In his words, 'better living through chemistry still requires better living'.
- 04
Find the diet that suits your microbiome
Keto, vegan and meat-heavy diets each shift the microbiome, and some people feel better while others feel worse. Highly processed foods, animal or plant, drive overeating, as a Cell Press paper showed. Fasting for a day or more depletes gut microbes, which may explain why the first meal back can feel rough, so return to eating gradually.