— and are born on the ketogenic diet.

Maria Cross MSc
Jul 11 · 9 min read
Source

There’s nothing as cute as a chubby baby. Each fat little finger and toe is adorable. But that fat isn’t there just to make you go weak and gooey. While the rest of us strive to restrict body fat to within certain limits, a baby’s biology is geared towards high fat storage.

It’s all about growing a healthy baby brain, and ultimately a healthy adult brain. Plants need soil, brains need fat.

The right kind of soil and the right kind of fat.

Born ketogenic

“It is entirely normal for healthy infants to be constantly in mild ketosis; it is not due to them being sick, underfed or diabetic.” (Cunnane 2018).

You’ve probably heard of the ketogenic diet. It has a global army of devotees who swear by its effectiveness as a weight loss tool and as a dietary strategy to combat diabetes and heart disease. Others — mostly the establishment of the nutrition world — consider it a dangerous, fad diet.

You can call it what you like, but you cannot call it new. We’ve being doing the ketogenic diet since we’ve been humans. You did it in the womb and after you were born.

When you are on the ketogenic diet — essentially a low carbohydrate, high fat diet — you are in a state of ketosis. That means that your body is burning fatty acids for fuel. Some of that fat is converted in the liver into ketones, which provide fuel for the brain.

Babies burn ketones for brain fuel before and after birth, and even when weaning begins body fat continues to supply ketones.

Fat on arrival

Baby steps

Humans are unique in that they are the only land mammals born fat. The human brain — which is 60% fat — is so highly evolved that it must come equipped with a large fuel reserve, else risk severe damage. A baby lands in this world with around 500g of fat packed away, mostly under the skin. Its brain burns an astonishing 70%-80% of all available fuel, so needs this back-up.

Even our nearest relative, the chimpanzee, is born with a virtual absence of body fat. The chimp is, alas, small-brained. That’s the compromise: whereas humans are born big-brained but feeble, other animals with their little brains are able to stand up and stagger about shortly after birth.

Rapid accumulation of fat begins during the third trimester of pregnancy, as brain growth goes into overdrive, expanding much faster than the rest of the body. This phenomenon continues after birth and throughout the first five years of life.


The link between dietary fat and its role in brain function is nowhere more evident than in epilepsy. Epilepsy is a brain disorder, and the ketogenic diet is a well-established treatment for the condition.

Studies have found that half of affected children experience at least 50% reduction in seizures after 6 months on the ketogenic diet, and one third achieve over 90% reduction. Indeed, research has found that it is a form of therapy that can, in some cases, completely remove the need for medication.

The ketogenic diet used to be the treatment of choice (if not the only treatment) for severe childhood epilepsy in the 1920s. Then, with the introduction of anticonvulsant medications in the 1930s, the use of the diet all but disappeared. It re-emerged in the 1990s with the publication of new scientific research.

If the ketogenic diet works for epilepsy, why not for other brain disorders? Preliminary studies suggest that what’s good for the goose, is good for the gander.

“The ketogenic diet (KD) is now a proven therapy for drug-resistant epilepsy supporting its use in multiple neurological disease states.” (Stafstrom & Rho 2012).

As well as needing fat for fuel, a baby’s brain requires specific fat for normal cognitive development and intellectual skills. Without that specific fat, there is the serious risk of developing brain dysfunction.

There are two fats that are essential for optimal brain function in the developing foetus and the newborn baby: the omega-3 fatty acid DHA (docosahexaenoic acid) and the omega-6 fatty acid ARA (arachidonic acid).

Both these fats form part of each cell membrane, and control what passes in and out of each nerve cell. They help develop the central nervous system. They are involved in communication between nerve cells, the firing of neurons, the regulation of neurotransmitters and the development of cognitive skills.

Surf and turf

DHA and ARA are polyunsaturated fats that are found pre-formed in animal-source foods only. The main dietary source of DHA is fish and seafood, and the main dietary source of ARA is meat.

DHA is found abundantly in seafood and oily fish, including salmon, mackerel, trout, herring and anchovy. Meat contains only small amounts of DHA, though offal — especially brain — is a great source, albeit not a terribly popular one.

ARA is found largely in meat, but some can be obtained from sea and fresh water foods. The best sources of ARA are beef, poultry, seafood and eggs.

Nuts and seeds and other plant foods are often suggested as a suitable vegetarian source of omega-3 fats. That is not the case. Although it is true that the body can make some limited DHA (and EPA, its precursor) from plant sources, its ability to do so is poor, and effectively meaningless. The liver converts less than 0.5% of the omega-3 fat in plant sources to DHA. That’s on a good day: in many studies, that conversion rate has been shown to be less than 0.1%, making it “negligible”.

“Thus, the developing human brain unequivocally needs to be provided with pre-formed DHA or it will not be able to optimally accumulate DHA.” (Cunnane & Crawford 2014)

The same goes for ARA, which too is abundant in the brain. ARA is structurally similar to DHA, and is a significant component of the cell membrane, though they are metabolically and functionally distinct. One cannot replace the other.

Like DHA, pre-formed ARA is unique to animal-source foods, and conversion of omega-6 fats in plant foods to ARA is very low and unreliable.

“The synthesis of DHA and ARA is limited in infants and both DHA and ARA must be obtained from dietary sources.” (Hadley et al 2016)

What happens without enough of these two fatty acids?

Only two mammalian species have disproportionately large brains and advanced cognition — humans and bottlenose dolphins. Both depend on DHA for that cognition.

Smart

Children who lack DHA are more likely to have increased rates of neurological disorders, in particular attention deficit hyperactivity disorder (ADHD), and autism.

“It is our contention that the movement in the 19th to 21st centuries away from traditional use of sea foods and increased emphasis on land based food supply is a likely cause in the rise in brain disorders including mental ill-health, stress, and other psychiatric disorders.”(Crawford et al 2014).

Today, ADHD is the most frequently diagnosed neuro-behavioural disorder of childhood, and it is becoming increasingly prevalent. In 2014, the Centers for Disease Control and Prevention confirmed that there had been a 42% increase in the number of children diagnosed with the condition since 2006. In America today, 11% of children aged 4 to 17 live with ADHD.

There is a growing body of evidence to suggest that ADHD may be preceded by low DHA in the womb.

The link between dietary fat and autism is also strong, and low levels of both DHA and ARA have been found in children on the autistic spectrum. In a study published in 2015 in International Journal of Molecular Sciences, the fatty acid profile of 121 autistic children, aged 3–7, was analysed and compared with children without the condition. The autistic children were found to have levels of ARA and DHA that were “particularly decreased”, compared to the non-autistic controls.


A healthy baby is born with a limited store of DHA and ARA. Human milk provides both these fats, but how much depends on the mother’s diet, and this can vary enormously.

DHA has been subjected to much more research than ARA, and what is known about DHA is that people who do not eat oily fish or seafood are at greatest risk of deficiency. Intake of DHA and EPA (the precursor to DHA) is low in vegetarians and virtually absent in vegans.

“..intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are low in vegetarians and virtually absent in vegans.” (Saunders et al 2013)

Deficiency of DHA is certainly not unique to vegetarians and vegans: anyone who does not eat fish is at risk. One study of the omega-3 status of vegans found that although low, it was no worse than that of omnivores who ate no fish.

“We conclude that vegans have low baseline omega-3 levels, but not lower than omnivores who also consume very little docosahexaenoic and eicosapentaenoic acids.” (Sarter et al)

What about baby milk formulas?

There is widespread consensus that, before weaning, breast is best, but not always possible.

In the US, The American Academy of Pediatrics (AAP) states that iron-fortified cow’s milk formula is the most appropriate feed for infants aged 0–12 months who are not breast-fed. Iron is important because deficiency in infants is associated with poor cognitive performance.

Not all babies can tolerate cow’s milk, and not all parents, including vegetarians and vegans, want to feed it to their babies.

The problem for these parents is that there are no vegan formula feeds, the main obstacle being vitamin D3. This vitamin — which like iron is essential for brain function — is found only in animal-source foods. Currently, vegetarian formulas contain D3 from sheep’s wool — lanolin.

There is no legal obligation to add DHA and ARA to formula milk, and in the US, the AAP has no official position on the subject. Fortunately, most manufacturers of formula feed voluntarily offer products containing added DHA and ARA and have done so since 2001.

In Europe, the inclusion of DHA and ARA is also still optional for manufacturers. That is set to change, at least partially. In February 2020, an EU Directive setting minimum requirements for DHA, but not ARA, comes into force. It’s a start, but only a half measure, because:

“Without the provision of preformed ARA in human milk or infant formula the growing infant cannot maintain ARA levels from synthetic pathways alone that are sufficient to meet metabolic demand.” (Hadley et al 2016)

Production of the only vegan formula I have come across — the French, rice-based Premiriz — stopped earlier this year, ahead of the new EU Directive which would make it illegal. You can still find US websites advising vegan parents that they can order Premiriz directly from France.

Which begs the question: why on earth would parents deliberately seek out a formula feed that lacks nutrients that are crucial to the developing brain?

The answer is simply that they don’t know, because nobody is telling them and the information is hard to come by.

So why are we told to avoid fat when it is so essential?

Good question.

Since the 1960s we’ve been drip-fed the official mantra that fat is bad, and we should cut down on dietary fat. A huge and highly profitable processed food industry has been built around the low-fat dogma, which persists to this day.

In her book “The Big Fat Surprise”, science journalist Nina Teicholz tells us that:

“By 1995, a survey of about a thousand mothers found that 88 percent of them believed that a low-fat diet was “important” or “very important” for their infants, and 83 percent responded that they sometimes or always avoided giving fatty foods to their children.”

The only fats that we were advised to eat were those used by the processed food industry. Surprise surprise. The 1960s saw the start of a massive rise in the use of these oils (mainly corn and soya) in both home cooking and in processed foods. These came to replace traditional butter, beef dripping and lard, and were sold to us on a health ticket. These omega-6 oils turned out to be anything but healthy, for numerous reasons, including the fact that in high amounts they block the absorption of omega-3 fats, including DHA.


It takes around 20 years to grow a fully developed human brain, from chubby baby to mature adult. It took 2.5 million years to hone that level of biochemical engineering. It takes no time at all to dismantle it.

For more information on the role of fat in the prevention of dementia in adults, see my article How eating more fat can improve your memory.

Feed Your Brain

Exploring the link between diet and mental health

Maria Cross MSc

Written by

I’m a nutrition science writer, specialising in diet and mental health. Subscribe to AllYouCanEat.org.uk for free brain food guide. @MariaXCross

Feed Your Brain

Exploring the link between diet and mental health

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