Ketosis - key to human babies’ big brains?

Prof Noakes is on trial for ‘advising’ a mom to wean her baby onto low carb, high fat foods. Could babies’ innate ketosis – a state more often associated with low-carb, high-fat diets - be an arrow in Prof Noakes’ defence’s quiver?

By Tamzyn Murphy Campbell

BSc, BSc Med(Hons) Human Nutrition and Dietetics, RD

Did you know that human newborns and exclusively breastfed babies are in ketosis? 1 I am a dietitian, with two years of intensive postgraduate training in nutrition, and I didn’t realise this until just over a month ago. The fact that human babies are naturally in ketosis is an inconvenient truth because it implies that ketosis (which also occurs when fasting or eating a low-carbohydrate, high-fat diet) is not only a natural metabolic state for human infants, but that it’s probably beneficial too. Nature seldom does something without a reason, so it’s likely that ketosis may confer some kind of evolutionary advantage to human infants. Research suggests that it may be one of the main factors behind the development of the large human brain. 2

"Nature seldom does something without a reason, so it’s likely that ketosis may confer some kind of evolutionary advantage to human infants. Research suggests that it may be one of the main factors behind the development of the large human brain. "

A word on ketones and ketosis

Ketosis is a metabolic state where your body uses fat as fuel in preference to carbohydrates – as occurs when fasting or eating a low-carbohydrate, high-fat diet. The body makes ketones from fat, when dietary glucose (from carbohydrates and sugar) is low. Ketones can be used as fuel to produce the energy your body and brain needs to function. The human brain only has two options for fuel: glucose or ketones. The other body organs can also utilise fats as fuel.

Conventional scientific wisdom sees ketones as toxic metabolic by-products of metabolism, which are used as back-up fuel during emergencies only. Ketones are certainly not seen as a preferable fuel to glucose. In fact, many experts are concerned about their potentially adverse effects. Most experts caution against Banting during pregnancy and breastfeeding due to ‘insufficient evidence of ketones’ effect on the foetus and newborn’.

It is important to note that nutritional ketosis is different from the ketoacidosis that diabetics sometimes experience. Nutritional ketosis is when the ketones in the blood are at healthy levels of 1-3mmol/L. Diabetic ketoacidosis is when ketones in the blood reach unhealthy, toxic levels of 10 mmol/L or above.

Ketogenic babies

In the second half of pregnancy ketones supply as much as 30% of the energy required by the foetal brain, implying that ketones are essential for foetal brain development.3 During the third trimester of pregnancy and at birth, both mom and foetus are naturally in a state of mild ketosis.4 Within the first few days after birth, babies adapt to using their fat stores as their primary fuel-source, and begin to produce more ketones.5 Babies convert the fat from their stores and their diet (ideally breastmilk) into ketones.6 These ketones provide them with the energy they need between feeds and act as key building blocks for essential brain structures.7 Human babies are thought to be fatter than other mammals so that they have a reserve to support their higher demands for energy and brain-structure development.8

Breast is best

Breastmilk is high in fat (55%), moderate in carbohydrate (39%) and low in protein (6%). Exclusively breastfed babies are in a state of mild ketosis. Despite this, experts agree breastmilk is the best food for babies and has been associated with various health benefits. Breastfed babies experience better cognitive performance, less frequent and severe infectious diseases, as well as lower rates of sudden infant death syndrome (SIDS), certain cancers, food allergies, asthma, types 1 and 2 diabetes, overweight and obesity, and high cholesterol.9 World authorities including the World Health Organisation agree that infants should be given nothing but breastmilk for the first 6 months, that breastmilk should be the main source of nutrition for the first year of life, and that breastfeeding should continue for at least one year whenever possible, and preferably for up to two years or beyond.10

Complementary feeding: Low carb or high carb?

Human brain-development during gestation and the first few years of life is greater than at any other time. This is also the period during which the brain is best at processing and utilising ketones.11 The human brain continues to be efficient at metabolising ketones well after weaning, which begins with the introduction of complementary food at around 6 months of age.12 So it is likely that the benefits of ketones for young humans’ brain development continue into toddlerhood and possibly beyond.

This begs the question: would babies benefit more from being weaned onto low carb, high-fat foods that support a continuing state of mild ketosis from 6 months of age (such as meat, organ meats, poultry, fish, eggs, butter, coconut oil, olive oil, together with vegetables), as Prof Noakes suggests? Or would a diet high in high carbohydrate, low fat foods (such as infant cereal, grains, fruit and starchy vegetables) be preferable? We will have to wait and see what the HPCSA rules in November.

References:
  • 1 Cunnane SC, Crawford MA. Survival of the fattest: Fat babies were the key to evolution of the large human brain. Comp Bioch Phys. 2003;Part A 136:17-26
  • 2 Cunnane, 2003
  • 3 Cunnane, 2003
  • 4 Wu PY, Edmond J, Auestad N, et al. Medium-chain triglycerides in infant formulas and their relation to plasma ketone body concentrations. Pediatr Res. 1986 Apr;20(4):338-41 http://www.ncbi.nlm.nih.gov/pubmed/3703623
  • 5 Ward Platt M, Deshpande S. Metabolic adaptation at birth. Semin Fetal Neonatal Med. 2005 Aug;10(4):341-50. http://www.ncbi.nlm.nih.gov/pubmed/15916931
  • 6 Cunnane, 2003
  • 7 Cunnane, 2003
  • 8 Cunnane, 2003
  • 9 Mahan LK, Escott-Stump S. Krause’s Food & Nutrition Therapy. International 12th Edition. Saunders Elsevier. 2008
  • 10 World Health Organisation. Breastfeeding. 2015 http://www.who.int/topics/breastfeeding/en/
  • 11 Prins ML. Cerebral metabolic adaptation and ketone metabolism after brain injury. J Cereb Blood Flow Metab. 2008 Jan;28(1):1-16. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2857668/
  • 12 Prins, 2008.
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