How did our brains get so big?
Seafood made us smarter. An interesting paper was published last week, which discusses how we came to have the awesome brains that differentiate us from our primate cousins. Compared to every other mammal, we are born with brains that are incredibly vulnerable, and use up a much larger proportion of the energy we consume. In a newborn baby, for instance, the brain uses up almost 75% of daily energy intake!
We know that building neurons and synapses (the connections between neurons) in a large brain requires:
- The omega-3 fat DHA
- Ketones. These are made from fats by the liver.
- Various minerals like selenium, iodine, zinc and iron.
In order to feed the hungry monster in our head, we are the only species born with a large layer of fat that can act as a store of DHA and short/medium-chain triglycerides (which are then turned into ketones). Ketones provide energy for the brain, but are also used to make cholesterol. In fact, once you take away the water, DHA and cholesterol make up 40% of the brain.
For many years, evolutionary biologists have argued over whether or not a shore-based diet (sea food and sea vegetables) helped us to develop our large, complex brain structure. On one side, they argue that by eating the brains and bone marrow of other animals (initially by scavenging, and later by hunting), we obtained the calories and fats (especially DHA) required to provide the necessary brain-building blocks. This paper argues, however, that all those brain-building materials above are more easily obtained from eating shellfish and seaweed, so it therefore makes sense that our early hominim ancestors ate a shore-based diet, at least intermittently, which helped the development of our current brain size. This is not my area of expertise, so I won’t choose sides. However, the paper does have some interesting implications for everybody trying to maximise brain health.
Adults: We know that we continue to make new neurons throughout life, particularly in the “memory-centre” of the brain, the hippocampus. To maximise that effect, we should probably make sure we get enough DHA, selenium, zinc, iron and iodine. These are abundant in seafood, particularly shellfish. It also seems sensible to increase ketone levels, at least occasionally. This can be done by minimising carbohydrate intake, or consuming medium chain triglycerides. The latter are particularly abundant in coconut fat.
Brain injury: My area of research surrounds brain injury in babies. Looking at what we needed to make our brains in the first place, it would make sense that DHA, ketones and the correct minerals should be supplied to the injured brain during healing. However, it is very difficult to maintain normal blood sugar levels in sick babies. As such, they are often not fed for many days, and are given something like a glucose (sugar) drip instead. The effect of nutrition after brain injury has not been widely investigated, but if we want to minimise long-term brain damage, changing the way we feed these babies could affect their ability to recover. This is an area ripe for future research.
Thanks to Bill Lagakos from Calories Proper for posting this paper. You can find the full version here.
Speaking of the brain:
A stroke of insight. This is an absolutely brilliant TED talk by neuroanatomist Jill Bolte Taylor. When she had a stroke in her 30’s, she generated some amazing insight into how the two halves of the brain function differently. Her description of her experience is both funny, and deeply moving. Watch it here.
Let's talk about rape:
The topic of rape has come up a lot recently, particularly following the publication of a study saying that at least 1 in 10 women have been victims of rape. This number appears to be fairly standard across Western populations (and certainly could be higher both here and elsewhere). In the UK, a UKIP politician recently stated that he didn’t “believe” rape could exist within a marriage. In the USA, there have also been some rather unenlightened comments about how women are probably overstating the case of rape in order to get a “coveted” victim status. Only by creating an open discussion about this issue can we begin to change this.
Here is a first-hand account that covers why rape is so underreported, and how it really is more prevalent than we think.
It’s not pretty, but it definitely needs to be talked about: