That which sets us apart from our animal cousins, the thing that most differentiates us as humans, as Homo sapiens sapiens, is our outsized brain — a brain that’s capable of abstraction and higher-order learning and philosophizing, a metabolically white-hot, energy-devouring machine. And it’s mostly made of fat. The human brain is nearly 60% fat by total weight, and that big, powerful brain needs to be provided with certain types of fats (both saturated and unsaturated) throughout life to provide a balance of structural integrity and fluidity to its cells.
By and large, we get these fats from our diets, and what we eat gets incorporated directly into the membranes of the cells that make up the brain and nervous system. The neuronal membranes and insulating sheaths are especially dependent on the long-chain fatty acids docosahexaenoic acid (DHA) and arachidonic acid (AA), which comprise over 50% of the neuron cell membrane and over 70% of the myelin sheath. We can also build these essential fats from plant-based precursor molecules to a small degree, but this process is inefficient and does not produce sufficient quantities to fuel the brain. For optimal health and function, we’re far better off consuming these essential molecules ready-made from what we eat. The best sources are fatty fish — salmon, mackerel, anchovies — and eggs, organ meats, dairy, and muscle meats (especially from wild game), as well as such plant sources as sea algae.
The need for quality fat intake begins before birth, when the fetal brain (both the gray and white matter) is forming de novo. The essential fatty acid DHA is especially crucial for the development of the visual cortex, retina, and frontal cortex. The developing brain demands these essential nutrients, which it extracts from the mother via the placenta. If the mother is deficient in DHA, the infant’s brain will suffer. And even if she begins with normal levels, if she doesn’t replace them in adequate amounts through what she eats, she can become depleted. M. W. Markhus et al. suggest such a deficiency may contribute to the development of postpartum depression (1).
In an ideal world, nutrition for the developing young brain after birth would come from the mother’s breast milk, a protein-rich, fat-rich, DHA-replete, perfect meal. It isn’t possible for some mothers to breastfeed their infants successfully, and for others, it’s logistically difficult. Fortunately, today almost all infant formulas produced commercially are now fortified with both DHA and AA, making better fatty acid nutrition possible for those infants without access to breast milk.
Before contemporary mores shifted to render prolonged breastfeeding less of the norm, a mother’s milk kept feeding infant brains for perhaps the first several years of life or was at least supplemental to solid foods. Today, once weaning is complete from bottle or breast, there’s an essential fat nutrition gap for the still-growing young brain, unless it’s met by DHA- and AA-rich solid foods in the diet, such as eggs, meat, and fatty fish.
Once a brain’s formation is complete (or at least mostly so) at about the time we’re entering kindergarten or first grade, what then? Does it matter which fats we eat at that point? Does dietary fat impact the function of the formed brain? Some research suggests so.
We know the organization and maturation of the brain’s executive functions is ongoing between the ages of 5 and 25, and that the centers controlling judgment and decision-making aren’t fully formed in the frontal cortex until a person is in their 20s (2). This is the region of the brain where DHA is most abundant (3). Thus, during these years of actively building networks of connectivity throughout the brain (but especially in the frontal cortex), there’s still a dietary need for essential fats. During these formative years, current nutritional advice enjoining us to restrict fat (especially saturated fat and cholesterol), curb meat and egg intake, and eschew natural fatty foods can prove quite insidious.
Too many young brains today are being fed a diet that is chiefly composed of processed wheat, corn, or rice, plus sugar or high-fructose corn syrup, plus industrially processed vegetable oils (all of which are omega-6 heavy with scant to no omega-3 or stable saturated fat). Though the package it arrives in may vary — it could be boxed cereal, toaster pastries, crackers, chips, pasta with processed cheese sauce, or any of another hundred similar offerings, and the grain it’s made of could be organic, the sugar could be honey or coconut sugar, and the seed oils organic and cold-pressed — it wouldn’t matter. At its core, it’s all just junk made of one, two, or all of those three basic things: processed grain, sugar, and vegetable oil, none of which offers the necessary nutrition for the growing, developing brain.
What happens when a brain’s fed poorly? It functions poorly.
The diet of ancient humans is arguably a good model for what an appropriate nutritional paradigm might be for us today, since it is, after all, the diet that many millennia of natural selection molded the human brain and metabolic machinery to thrive upon. Paleolithic research suggests the diet of early humans contained about equal amounts of omega-6 and omega-3 fats, a ratio of 1:1 or at most 2:1. Today’s fear of saturated fat and cholesterol and the heavy reliance on so-called “heart-healthy” vegetable oils — soybean, canola, safflower, sunflower, and other seed oils — has crowded out more beneficial fats and oils we once regularly consumed in fatty fish, eggs, dairy, organ meats, etc. This shift has tipped that natural omega balance to something on the order of 17:1 or more, and the consequences may have an impact on a panoply of disorders, including depression, ADHD, cognitive dysfunction, major affective disorders, and dementia (4).
The traditional/cultural diet in some countries (the Japanese and Scandinavian reliance on fatty fish and the French fondness for paté, omelets, and pungent cheeses, for instance) naturally encourages greater consumption of sources of EPA and DHA from a young age. But the diet favored by the youth of America and many Western countries is of the grain-sugar-vegetable-fat sort, containing little if any DHA or even the precursors from which we could inefficiently make a bit of them. Kids (and even adults) today eat fewer eggs and little (if any) fish other than the fast-food variety, which comes battered and fried in omega-6-heavy vegetable oils — not a recipe for feeding a brain properly or bringing the essential fatty acid ratio back into balance.
The brain’s need for AA and DHA from conception to death is indisputable. In addition to these essential fats, another critical nutritional component is cholesterol. Cholesterol, like essential fats, is required as a raw material for the manufacture of the cell membrane of every new cell being built, including neurons. It’s required to build new cells and new synapses between neurons. This means it is essential to connectivity, which supports all learning and memory and executive functionality.
Fortunately, virtually every cell in the body, including neurons, can manufacture this vitally important molecule, and the body’s ability to do so usually means that levels are adequate for growth and maintenance of body and brain, at least during early life. (Granted, later in life that may not be the case, as people of all ages are now routinely exhorted to limit their intake of dietary cholesterol and dozens of millions have been put on statin drugs to lower blood cholesterol levels in a misguided push to halt cardiovascular disease.)
Young brains need to be fed properly from conception onward to function optimally. They need essential fats. They need cholesterol. They don’t need industrial seed oils. Feed them eggs, meat, and full-fat dairy for dietary cholesterol, AA, and DHA; fatty fish for EPA and DHA; and fresh whole fruits, vegetables, and other foods that don’t come in cellophane and cardboard. Perhaps we ought to feed all brains, regardless of age, that way.