Latest / Common Sense Health / Human Brains Are Shrinking—Here's Why
Transcript
- Stephen Thomas BSc. Hons: Hello. I want to talk about something today that sounds almost unbelievable at first, but once you hear the argument it starts to make a lot of sense. It is the idea that human brains may have been shrinking and that one of the missing pieces in the modern diet could be DHA or decosa hexanoic acid, pronounced dicosa hexanoic acid. Now that is a mouthful. It sounds like someone dropped a scrabble board into a biochemistry textbook, but it it has a very simple meaning. Decoosa means twenty two, hexa means six, and inoic acid tells us that we're talking about a fatty acid with double bonds. So decosa hexanoic acid simply means twenty two carbon fatty acid with six double bonds. That is DHA, and DHA is one of the most important fats in the human brain. This whole topic comes from a Brilliant interview with Dr. Michael Crawford, who has spent decades studying the relationship between fats, seafood, human evolution, and the brain. Now his argument is not that just omega-3 is good for you in the vague way that people often say it. His argument is much stronger than that. He's saying that DHA is a structural brain fat. In other words, it's not just fuel, it is part of the actual hardware. And that matters because we often talk about nutrition as if the whole body has the same requirements. We talk about protein, calories, growth, body weight, muscle mass and energy. All of that matters, of course, but Crawford makes a very simple point that I think cuts right through the noise. The body is largely built from protein, but the brain is largely built from fat. So if we design a food system around feeding the body, but forget the specific fats needed by the brain. We may end up with exactly what we're seeing now. People are fed, but not necessarily nourished. Maybe taller, definitely heavier, perhaps even overfed in some ways, but mentally, neurologically, and developmentally under-supported. And this is where the brain size data becomes very interesting. Because Crawford talks about early human ancestors from roughly two million years ago having brain sizes around 400 to 450 cubic centimetres. Our cubic centimeter is is is simply a measure of volume. So we're talking about the physical size of the brain cavity. Then as human evolution progresses, brain size rises dramatically. By the time we get to early Homo sapiens, such as Hurto people from around 160 to 200,000 years ago, brain capacity is being discussed at around 1450 cubic centimeters. Then we get to Cro Magnon humans. from roughly twenty-eight thousand to thirty-two thousand years ago. Crawford talks about brain sizes around one thousand five hundred to a peak of one thousand seven hundred cubic centimetres, the upper figure, like I say, being one thousand seven hundred cubic centimetres. Now that is enormous. Then comes the uncomfortable bit, because Crawford says that when he was Working on this subject in the nineteen seventies, modern human brain size was often given as around one thousand four hundred and fifty C C, but today he gives the average as about one thousand three hundred and thirty six C. Now we do have to be careful here because brain size research is debated. Not everyone agrees on the exact timeline and not everyone agrees on the causes, but the broad claim that human brain size rose dramatically during evolution and may have decreased. Declined from its upper Paleolithic peak is a serious point, not just some sort of pub trivia. And even if we argue about the exact numbers, the bigger question remains: what built the human brain in the first place? Crawford's answer is clear. Access to the ripe fats and nutrients, especially from marine and animal foods. And this is where DHA comes in. DHA is an omega-3 fatty acid. Now, omega-3 sounds complicated, but it is actually just a description. of the structure of the fat. Fatty acids are chains of carbon atoms. Some of those chains have double bonds. An omega three fat has its first double bond three carbons in from one end of the structure. That structure makes omega three fats more flexible. The DHA is especially flexible because it has twenty two carbon atoms and six double bonds. So that flexibility is one of the reasons DHA is so important in the brain and the retina. The retina is the light sensitive part at the back of the eye. So when we talk about DHA, we are not just talking about some optional supplement. We're talking about a fat involved in the structure of the brain, the nervous system, and vision. There are several omega-3 fats, and this is where people often get confused. The plant omega-3 is called ALA or alpha linoleic acid, ALA. Is found in things like flaxseed, chai seeds and walnuts. Then there is EPA EPA has twenty carbons and five double bonds. Then there is DPA or decosa pentanoic acid, DPA has twenty two carbons and five double bonds. And then there's DHA or decosa hexanoic acid. So DOA. That's again D cosa. Hexanoic acid DHA has 22 carbons and six double bonds. So if we put that very simply, ALA is a plant parent omega-3. EPA is important for signaling and information pathways. DPA is like a longer omega-3 that sits between EPA and DHA in some ways, but DHA is the big one for the brain. And this is crucial. Plant omega-3 is not the same as DHA. The body can convert some ALA into EPA and DHA, but the conversion to DHA is generally very poor. So when someone says I get my omega 3 from flaxseed, that does not necessarily mean they're getting meaningful DHA. That is like saying I have bricks in the garden, therefore I have a finished house. No, you have some starting material, but the brain wants the finished product, and the finished product is DHA. This is why seafood is so important. Fish, shellfish, roe, mussels, oysters, crabs, sardines, mackerel, herring, salmon, and anchovies can provide this pre-formed DHA. That means the DHA is already made. The body does not have to convert it from a plant precursor. And this fits very neatly with an animal food view of nutrition. Human beings did not evolve eating modern ultra-processed foods or seed oils or even breakfast cereals. and low fat yogurts actually, with cartoon characters on the packet. We evolved eating real food, including animal foods. But Crawford's argument adds an important detail. It is not enough to say eat meat and leave it there. Meat is important, protein is important, but red meat is nutrient dense. But the brain story seems to point s especially towards marine animal foods. In other words, steak is wonderful, but the brain may still be asking, Well, where are the sardines? This does not mean everyone has to live on oysters and seafood, but it does suggest that a purely animal based diet, especially one mainly based on muscle meat, may miss part of the ancestral brain building picture. Crawford talks about the marine food web because seafood gives us not only DHA, but it also gives us minerals such as iodine, selenium, zinc, copper and manganese. iodine, is essential for thyroid hormones, and thyroid hormones are crucial for brain development. Selenium is involved in antioxidant production and also interacts with mercury biology. And this matters when people talk about fish and pregnancy, by the way. For years, many pregnant women have been frightened away from fish because of mercury warnings. Now, of course, there are sensible cautions around large predatory fish, such as sharks, swordfish, and Some large tuner, nobody sensible is saying pregnant women should eat high mercury fish every day, but Crawford's concern is that the message became too blunt. Instead of saying choose low mercury high DHAC food, many women heard avoid fish. And that may be exactly the wrong message during pregnancy because pregnancy is when the baby's brain is being built. Crawford discusses research from the ALSPAC study, that is the large Avon study from Bristol. Following thousands of pregnancies and children, the finding he highlights is that mothers who ate more seafood during pregnancy tended to have better developmental outcomes in their children. That is very important. The brain is not built from good intentions, it is built from nutrients, and if we remove the foods that supply DHA, iodine, selenium and other marine nutrients, we should not be surprised if there are some consequences. This also brings us to modern animal farming. Crawford is not simply saying all animal fat is automatically the same. He makes a distinction between wild or naturally raised animals and modern livestock that may be pushed towards rapid fattening. He criticises the obsession with marbling and excessive fattening because that is not necessarily the same as producing the best food for human brains. So this is where joined up thinking matters. Animal foods are not just protein blocks. Different animal foods produce Bring different nutrient profiles. Beef gives us superb protein with iron and zinc and B vitamins and creatine and carnitine and many other nutrients. Eggs give us choline and fat-soluble nutrients and some DHA, by the way, depending on the hen's diet. And shellfish give minerals in extraordinary amounts. Oily fish give preformed DHA and EPA, and Rho gives us DHA in a very concentrated form. So the most brain aware animal based diet is probably not just endless chicken breast and steak. It is more nose to tail, sea to land approach, meat, eggs, fish, sh shellfish organs where they're tolerated, and ideally some oily fish or roe. In practical terms, the simplest advice is this eat seafood at least twice a week and probably more if you enjoy it and tolerate it. Small, oily fish are excellent. Sardines, herring, Anchuvies and mackerel are often better choices than large predatory fish because they are lower down in the food chain and usually lower in mercury. Shellfish are also superb. Mussels, oysters, crab, and prawns are nutrient dense and bring minerals that are harder to get elsewhere. And if someone truly cannot eat seafood, then a DH, a rich supplement may be worth considering. But the food first answer is obvious. Eat the foods that contain the nutrient already formed. This is especially important for pregnancy, breastfeeding babies and children, older people, and anyone concerned about brain health. But really it matters for all of us because Crawford's broader warning is not just about individual nutrition, it is about civilization. I mean he points to the enormous cost of brain disorders and mental health conditions, developmental disorders and neurodegenerative diseases. We spend fortunes dealing with the consequences, but perhaps We have not asked enough about the nutritional foundations. We talk endlessly about obesity and heart disease and calories and and cholesterol, but the brain is the organ that allows us to think, to plan, to speak, to love, to learn, remember and behave properly in the in the queue at the supermarket, and frankly some of the behaviour in supermarket cues suggests we may need a bit more DHA. Now the key message from Crawford's interview is that the human brain did not appear by accident. It required specific building materials. It required energy. Yes, that's true. It required protein. Yes, that's also true. But above all, it required the right fats and minerals. DHA is not just another omega 3. It is a dominant omega 3 structural fat of the brain and retina. EPA definitely matters. DPA matters. And I suppose ALA has its place. But DHA is the star when we are talking about brain structure. And the best natural sources of DHA are animal foods from the aquatic food chain, fish, shellfish, and roe. So perhaps the modern diet has made a terrible mistake. We become obsessed with feeding the body while forgetting to feed the brain. We pushed grains, seed oils, ultra-processed foods, and low fat advice. We frightened people away from animal fats and seafood. We treated the brain as if it could run on vague balanced diet slogans. But the brain is not vague. It has a certain chemistry, it has its structure, it has requirements, and one of those requirements appears to be DHA. So if there is one practical takeaway from this interview that we saw with Dr. Michael Crawford, it is this. Do not just ask whether you are getting enough protein. Ask whether you're getting the nutrients your brain is actually made from and needs. That means DHA. That does mean seafood. That means respecting animal foods, especially marine animal foods, as part of the story of how humans became human. And if all else fails, remember this. The humble sardine may not look glamorous, but it may have done more for human intelligence than half the modern food industry combined. Which to be fair is is is a pretty low bar, but still credit where it's due. Now the interesting thing for me about this is up until age fifty, I was allergic to seafood. So you can obviously do okay. I think I'm doing okay, where you don't have a lot of seafood. Only by the time I got to age fifty and started low carb and then keto and then carnivore did all my allergies pretty much go away from seafood and I really thoroughly enjoy it. I think I do feel fitter and healthier and more alert since I've included seafood in the diet. And yes, there are some issues with packaging and how it's processed and how it's called. So definitely be mindful To whether it's farmed or whether it's wild caught. All of those things are important. But anyway, the key part of this is about DHA, and I hope you enjoyed learning a little bit about the omega-3 fatty acids. If you did enjoy this, please consider liking, sharing, and subscribing. If you didn't like this and you've got to the end, well, I take my hat off to you for getting this far. Maybe drop a comment on what you didn't agree with, and maybe we can do a video covering the other side of the story. Anyway. With that said, I want to thank you for watching and I look forward to seeing you on the next one.