Evolutionary Psychiatry

The hunt for evolutionary solutions to contemporary mental health problems.

Eat Your Egg Yolks

Choline and possible decreased schizophrenia risk

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Recently in the American Journal of Psychiatry, a new paper was published tying nutrient supplementation in pregnant women to positive changes in the brains of their offspring. One of the nutrients that may be less predominant in our modern diets than in traditional diets is the phospholipid known as choline. Phospholipids are exceedingly important for brain development and neuron signaling. I’ve discussed them before in these posts:

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Zombieland II

In the current study, 100 pregnant women were randomized to receiving a daily choline supplement (equivalent to the amount of choline found in 3 large eggs) or placebo. After the babies were born, the choline babies continued to get a supplement equal to 100mg of choline daily (the institutes of medicine recommend total daily choline in infants to be 125mg daily), and at measurements of “cerebral inhibition” were taken at about one month and three months of age. Cerebral inhibition is a term used to describe the ability of the brain to tune out a stimulus that happens over and over. For example, if you are trying to work, and someone is running a jackhammer on the street outside, if you have intact cerebral inhibition, your brain will respond less and less to the sound of the jackhammer as it continues. Presumably this change would allow you to focus on more important things, such as the work at hand.

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In some brain disorders, such as schizophrenia, cerebral inhibition is impaired. For someone with schizophrenia, the signal from the jackhammer would be just as strong the second and the third and the seventh and the eighth times. You can imagine how you might be affected if you couldn’t tune anything out, if your brain was constantly taking in more stimulation and unable to sort through what was necessarily important or not. It could be this lack of cerebral inhibition (which begins with brain development in utero and early infancy) is one of the central causes of developing schizophrenia later on. The brain, so overwhelmed with stimuli, stops making sense of it, leading to psychosis and eventually the degeneration of neurons. 

Cerebral inhibition is typically measured by a test called the p50 evoked potential. Electrodes are placed on the scalp, and then the subject is exposed to a sensory stimulus, in this case, paired sounds. With intact cerebral inhibition, the second time the brain processes the sound, the wave amplitude of the auditory evoked potential 50 milliseconds after the sound will be much less than the first time. (Go to this image from the American Journal of Psychiatry to see what the waveforms look like in healthy controls and subjects with schizophrenia.

P50 evoked potential abnormalities can be seen in infants, and genes that are associated with a higher risk of schizophrenia are also associated with these abnormal evoked potential tests. Choline is known to cross the placenta and help with the brain development of certain receptors that normalize cerebral inhibition. In the study of pregnant women receiving choline supplements, 76% of the infants whose mothers got choline had normal p50 evoked potential tests at age one month. Only 43% of the infants of the mothers who received placebo had tests consistent with intact cerebral inhibition. In addition, a gene known as CHRNA7 correlated with diminished cerebral inhibition in the placebo group of infants, but not in the choline group. That means that it is possible (though there is way too little data to know) the choline supplementation could reduce the risk of schizophrenia in these infants. The ScienceDaily write up of the study can be found here.

Schizophrenia risk is higher in the offspring of malnourished mothers. There is also a known gene that reduces choline levels that is associated with a higher risk of schizophrenia. Choline is also sequestered in the mother’s liver during trauma, anxiety, or depression, depriving the fetus. Measures of developmental delay and other developmental problems are also associated with later risk of schizophrenia.

Nicotine activates but also profoundly desensitizes the same receptor that choline seems to protect and activate (the alpha-7 nicotinic receptor). 90% of people with schizophrenia smoke, and smoking normalizes p50 evoked potential tests is schizophrenia. Smoking in mothers has been associated with poorer infant cerebral inhibition and later childhood behavioral problems, whereas choline has only been shown to be beneficial for brain development. One difference between the two compounds (among many!) is that choline does not desensitize the alpha-7 nicotinic receptor at all, leaving it active so it can play its presumed role in helping with intact cerebral inhibition.

While choline supplementation is the interest of researchers, I’m more interested in having pregnant women eat their meat and egg yolks, the best sources of choline in the diet. Egg yolks are jam packed with great nutrients for the brain, not only choline, but also B vitamins and other fatty acids important for nerve growth. Bananas also have more choline than you would expect for a fruit. Choline levels in the diet have fallen recently with folks restricting their egg and organ meat consumption. These traditional foods have some important nutrients that we don’t want to skimp on in our diets.

 


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Photo credit

Photo credit 

Emily Deans, M.D., is a psychiatrist with a practice in Massachusetts.

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