There is a great blog on Evolutionary Psychiatry Dr Emily Deans click here. Emily’s post on depression and inflammation, genetics and evolution is very interesting and links to a paper on this topic full free text here. Like all GP’s I get to see a lot of depression and it is a challenging condition, even with the most dedicated specialist treatment, and total patient cooperation.
My interest in the ideal neuro-developmental diet dates back to my days when I was involved in a community group preventing lead poisoning . Lead has profound effects on the brain, causing reduced IQ, and ADHD and sociopathy. And lead poisoning was almost universal in the USA until 1990. This made it clear to me that the brain is affected by things other than genetics. Later when I became interested in the Paleolithic diet I eventually discovered that it is the ideal neuro-developmental diet and some interesting work has already gone on, including the Ghent conference where Cunnane gave this interesting appraisal including his own original theory. Prof Michael Crawford in London does some ground breaking work in this field.
The brain is the biggest loser in the Neolithic Diet. It is no coincidence that the diet of our Paleolithic forebears was associated with an explosion in brain size. Every modification of our diet since, has had a negative impact on the brain.
To understand the issue we need to forget about the complexities of the brain and focus on 2 general issues- wiring and firing. Wiring is the structure of the brain, size and position of nuclei (clusters of neurons) and the interconnections (synapses) made by axons and dendrites. Firing describes the release of neurotransmitters- where 2 nerves connect, they communicate when an electrical impulse arrives, not by sharing the impulse, but by the first nerve releasing chemicals (neurotransmitters) into the connection (synapse).
The modern diet is low in long chain omega 3. (Ultimate Reference Book= The Omega Diet by Simopoulos and Robinson) Bad for wiring as the synapses are made of omega 3. Bad for firing as neurotransmitters are packaged into “synaptic vesicles” using omega 3. This is why fish oil helps depression.
Next problem, let us go past folic acid which is a vitamin needed for the methyl cycle, and remember that it is just one of 4 methyl amigos. The 4 methyl amigos are folic acid, Vitamin B12, Vitamin B6 and Choline (the forgotten one). We all know that folic acid or B12 deficiency affect cell migration in the embryo (this deficiency may cause spina bifida). Let us also remember that methyl vitamins are needed to produce serotonin, and I think also dopamine and norepinephrine (don’t quote me). So stress on this system can reduce production of these neurotransmitters, which is of course central to depression.
Wind back to CHOLINE. Now this only became a vitamin in 1999, and is needed to make Acetyl Choline, one of the main neurotransmitters, and the target of many Alzheimers drugs (But no papers on Alzheimers and simple supplements of choline as they are too cheap). Now 70% of the population are deficient in choline. Whoopsy. Back to square one.
The deficiency of choline makes it likely that our brains are structurally disorganised due to poor cell migration. It would also contribute to reduced production of neurotransmitters to make matters worse. Increased homocysteine makes it worse again.
Agreed that brain inflammation is undesirable and there are many avenues cited in Loren Cordain’s epic paper Cereal Grains: Humanity’s Double Edged Sword. The seminal single reference on paleolithic diet and health and disease. See also www.paleodiet.com and www.thepaleodiet.com .
And on it goes. Neolithic life is also associated with very high risk of lead poisoning (though Americans born after 1990 might be low in lead, which is why their IQ is higher). And a few other issues such as iodine deficiency (though unusual in USA and Canada but common in Australia and Europe).
If the incidence of depression has increased in recent decades, then the increased inflammation may not be entirely evolutionary (as the time frame is decades rather than millenia). Since the early 1900’s (detoxified cottonseed oil) there has been an increased intake of short chain omega 6 oil (pro inflammatory) which became a flood in the late 1960’s with the widespread recommendation of safflower and sunflower oil consumption. These oil have physiological effects on our bodies, which is to say they are drugs. It was made worse again by adding lots of trans fats to solidify them to mimic butter or give processed foods a good “mouth feel” or extend shelf life etc.
This highly inflammatory diet change has been associated with asthma, arthritis, cancer, depression, ADHD, macular degeneration to name a few diseases.
The Pathos-D paper makes the unwarranted assumption that depression is a genetic illness simply because of the association of some alleles with depression. There is a simple reason why dietary diseases look like genetic diseases which I have posted about before. If everyone smoked we would think lung cancer was genetic. Similarly everyone eats a harmful Neolithic diet, so we think that dietary diseases are genetic. Everyone eats a lot of salt so we might once have thought that hypertension was largely genetic, but everyone knows it is largely due to the massive amounts of salt added by food companies.
I used to confuse phenotype (our health or illness or other character) with genotype (the architect’s plans), but have fortunately downgraded the status of the gene in comparison to diet (with the exception of the small but important number of true genetic diseases). We can upgrade to the GDE model- genes diet and exercise cause most variations in PHENOTYPE. An analogy is that if your house falls down- who do you blame? The architect (genes), the building materials (diet) or the workmanship (exercise). Anyone who has built of renovated a home knows that the work of the architect is generally superior but there are often problems with the materials or workmanship.
Weston Price’s classical text Nutrition and Physical Degeneration, 1939, details his world journeys looking at the links of diet and dental disease and other disease. He is perhaps the second Darwin, the Darwin of food. He did not encounter any cases of depression. The one case of suicide was due to intractable dental pain, due to cavities from introduced Western foods such as flour and sugar.
The Omega Diet tells us that more recent investigators in Japanese fishing villages found not one case of depression when surveying elderly people.
Dethrone King Gene. The Phenotype is King and is mostly determined by diet and exercise (otherwise we might as well give up). If everything is genetic then what point is there in diet and exercise? None at all. However we all have seen and felt and know that diet and exercise is critical. Don’t be sold down the river by the gene.
What is the psychology of the widespread acceptance of genetic explanations?
I would venture that they are overly accepted because they are esoteric, doctors themselves are bit confused. Doctors and scientists rather like genetic explanations as they are intelligent, and if intelligence is primarily genetic (which I dispute) then it makes them fundamentally and naturally superior (and their families and offspring) so there is an appeal to the ego. And genetic studies get a good percentage of research funding grants. Genetics always promises that all the answers are just around the corner, just like the magic software program that doesn’t actually work, the share investment system that never beats the index funds, and anything else that is sold heavily but doesn’t deliver. Yes, it’s time to deliver some healthy skepticism to the geneticists and ask “where are your results?”. Obviously DNA has delivered a range of excellent PCR pathology tests, and recombination DNA protein products, but for the man is the street, genetic testing might pick a handful of useful results. And for the man with depression, how many have been helped?