In 1967, three people who had gone without food for five to six weeks had their blood measured on the way into their brains and on the way out. If the brain runs on sugar, those brains should have been starving. They were not. They were running on fat. Ketones, the fuel the body makes from fat, had taken over from glucose as the brain's main source of energy.
That one finding undoes the first line of most "brain food" lists, the one that tells you to eat oats and brown rice because your brain needs carbohydrate. Your brain is picky, but not in the way the lists claim. It weighs about 2% of you and uses up to a fifth of your energy, and the things it is built from come overwhelmingly from animals.
Here are the seven essential nutrients your brain needs, what each one does, and where to get it.
1. Fuel: glucose and ketones
The brain does use glucose, and a lot of it: in a fasted, resting body it takes about 60% of the glucose in the blood. The mistake is the next step, the assumption that the glucose has to come from bread. The liver makes glucose itself, from the amino acids in protein and from glycerol, the backbone of stored fat. The process is called gluconeogenesis, and it runs whether you had toast this morning or not. Your liver has been baking its own bread for longer than you have been buying it.
When carbohydrate is low, the liver adds a second fuel. It turns fat into ketones, and the 1967 brains show how far the brain will go with them. On a low-carb, keto or carnivore plate, the brain runs on a mix of the two, and it never has to ride the rise and fall that a bowl of cereal brings.
The brain has been fed this way on purpose for a century. 8 Smart Ways to Fight Cognitive Decline with Food, linked below, has where the ketogenic diet began, as a treatment for epilepsy. It faded when anti-seizure drugs arrived and then came back, and when it was put to a randomised test, its benefit matched any of the newer drugs.
Where to get it. Meat, fish and eggs give the liver its raw material. You do not need to eat the glucose.
2. DHA, the brain's own fat
DHA is an omega-3 fat, and it is one of the main fats in the membranes of brain cells, concentrated in the cerebral cortex, the thinking layer, and in the retina of the eye.
The old version of this list sent you to flaxseed, chia and walnuts. Those carry ALA, a shorter omega-3, and the body has to build DHA from it. Why Eating Well Isn't Enough Anymore has how badly that goes: the conversion is limited, and weakest of all for DHA, the one the brain wants.
It matters most before birth. What Your Mother Passed On That Was Never in Your Genes has the 11,875 pregnant women in Bristol: the children of those who ate no seafood had about one and a half times the odds of a low verbal IQ. When 44 publications on 106,237 mothers and children were reviewed, the pattern held. Seafood in pregnancy went with better brain development in the child than none, from the smallest amounts eaten through the highest, with no net harm at the top end despite the mercury. The evidence is rated moderate only because randomised tests in pregnancy cannot be run.
The fish also beats the pill. 7 Natural Remedies to Boost Your Memory—and the Three That Pass the Test has the three tests with 3,536 healthy older adults in which omega-3 capsules made no difference to thinking over up to 40 months; only people whose memory had already slipped did a little better.
Where to get it. Oily fish, ready-made: salmon, sardines, mackerel, herring, anchovies. A tin of is the easiest of them to keep in.
3. Cholesterol
Cholesterol has a bad name and a busy job. It is a building block of every cell membrane, and it is concentrated in the brain and the spinal cord. The brain does not wait for it to arrive from the blood. Its own support cells, the astrocytes, make cholesterol and pass it to the neurons, and the brain keeps its supply separate from the cholesterol in your blood.
That is worth knowing the next time you are told to fear the yolk. The brain treats cholesterol as essential enough to make its own. Few things you are told to avoid are taken that seriously by your own head.
Where to get it. You make most of it yourself. Eggs, butter and meat bring the rest, along with the fats that travel with it.
4. Choline
Choline was first isolated in 1849, by Adolph Strecker, from pig bile, and in 1862 he named it after the Greek word for bile, chole. Not the most appetising origin for a brain nutrient. The body uses it to make acetylcholine, the chemical messenger behind muscle control and much of the nervous system, and it is part of the membranes of every cell. The body makes a little choline itself, not enough, which is why it counts as an essential nutrient. It matters most in pregnancy, because it is involved in the early development of the brain. It is also the one most diets miss. About 90% of Americans fall below the adequate intake for choline, most pregnant and breastfeeding women among them, and the food patterns in the official dietary guidelines cannot reach it.
Where to get it. Egg yolks and liver lead by a long way. Weight for weight, egg yolk carries about seven times the choline of raw soybeans and more than forty times that of broccoli, and cooked beef liver more than three times as much as the soybeans. The soybeans, quinoa and broccoli in the old version are a long way behind.
5. Vitamin B12
B12 keeps nerves insulated and the brain supplied. 8 Smart Ways to Fight Cognitive Decline with Food, linked below, has the 107 older adults scanned every year for five years: those with the least B12 in their blood had about six times the odds of losing brain volume fast. A small group and a rough estimate, but the direction is clear. A moderate shortage brings tiredness and a decreased ability to think. Mood changes follow, depression and irritability, and in severe cases psychosis.
Where to get it. Only from animal foods: liver, shellfish, meat, fish, eggs. A plant diet has to replace it with a pill.
6. Iron
Iron carries oxygen in the blood, and an organ that burns a fifth of your energy needs a steady supply of it. Foods That Lift Your Mood, and the Ones That Drag It Down, linked below, has how low iron feels: flat, tired and irritable, often blamed on stress, and common in women with heavy periods well before anaemia shows.
The form matters. How much iron the body absorbs ranges from about 5% to as much as 35%, depending on the source, and the best-absorbed iron comes from animal foods.
Where to get it. Red meat, liver and shellfish, and a tin of brings iron and B12 together.
7. Iodine
Iodine builds thyroid hormone, and thyroid hormone builds the brain, before birth and through childhood. In 2007, by the World Health Organization's count, nearly 2 billion people were not getting enough, and iodine deficiency is the single most preventable cause of intellectual disability in the world. The Quiet Signals of Mineral Deficiency has how close to home that is: among 1,040 mothers and children, the children of mothers low in iodine in early pregnancy were more likely to land in the bottom quarter for verbal IQ and reading at eight and nine.
The United States found out what fixing it was worth. Salt was iodised across the country from 1924, and when army recruits from the two world wars were compared, IQ had risen by about one standard deviation, roughly 15 points, in the quarter of the population that had been shortest of iodine. From the salt shaker. It came with a cost worth knowing: deaths from thyroid trouble rose for a while among older people in the iodine-poor areas.
Where to get it. Fish and shellfish, eggs and dairy. Unrefined salt carries only traces of iodine, so if your salt is unrefined, as it should be, the fish and eggs have to do the work.
Three more the brain uses
Protein. The brain builds its messengers from amino acids: serotonin from tryptophan, dopamine from tyrosine. Foods That Lift Your Mood has where they come from, and meat, fish and eggs are among the richest sources.
Creatine. Part of how brain cells keep their energy topped up. 7 Natural Remedies to Boost Your Memory has the six tests in which memory and reasoning tended to improve on it, most of all in vegetarians, who get the least from food. In one test, 45 young vegetarians took creatine or a dummy for six weeks each without knowing which, and their working memory and reasoning scores rose on the creatine. Meat and fish supply it.
Water. The same article has the 33 tests in which dehydration hurt attention most of all. Drink water through the day, and let thirst and pale urine guide you.
What the old list got wrong
It gave the brain a bowl of oats for fuel, flaxseed for its fat, a smoothie of spinach and blueberries for "antioxidants", and green tea and dark chocolate to finish. The fuel argument falls to the liver. The flax falls to the conversion. And the antioxidant story ends badly in pill form: What a Liver Detox Cannot Do That Your Liver Already Does has the 68 tests with 232,606 people in which antioxidant supplements did not lower deaths at all. A smoothie is a poor substitute for a sardine.
To be fair to the bowl, the trouble is mostly what goes into it. 8 Smart Ways to Fight Cognitive Decline with Food has the Tsimane and Moseté of the Bolivian Amazon, who hunt, fish and grow their own food: six of 604 people over 60 had dementia, about 1%, and Tsimane brains shrink more slowly with age than ours. They eat a lot of starch. What their plates lack is sugar and factory food. The enemy in the breakfast bowl is the sugar and the factory, more than the grain.
A plate for the brain
The brain has always been an expensive organ to run. Ours is about three times the size of a chimpanzee's, while our gut is smaller than a primate of our size should have. In 1995 Leslie Aiello and P. E. Wheeler proposed that the two are linked: an easy-to-digest diet let the gut shrink, and the energy it saved paid for the brain. It is still a hypothesis, and a 2024 test in 70 women came out consistent with it but not conclusive. Either way, the brain is a costly organ, and it is worth feeding well.
Breakfast is eggs, cooked in butter or tallow. Lunch is oily fish, a tin of sardines or a piece of salmon. Dinner is red meat, and some nights it is liver. If liver on the plate is a step too far, capsules are the fallback. Drink water. Between them, those meals cover every one of the seven, with no pill, no powder and no bowl of oats.
The 1967 brains kept working on fat for six weeks. Yours will manage a day.
This week, put liver on the plate once.
Worried about memory as the years go on? 8 Smart Ways to Fight Cognitive Decline with Food — the plate built against decline, what sugar does to the ageing brain, and the vitamins worth testing for.
Is your mood running low as well as your focus? Foods That Lift Your Mood, and the Ones That Drag It Down — the sugar crash, the fish your brain is built from, and the quiet shortfalls behind a heavy mood.
Know someone who starts the day with a smoothie and calls it brain food? Send them this, and a tin of sardines.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional, especially if you are pregnant, take medicines that lower blood sugar, or are thinking of a big change in diet.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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