An article in the latest Nutrition Journal says that a “proprietary” extract of chicken meat, called CMI-168, improved brain function. From the abstract:
Normal, healthy subjects were supplemented with either placebo or CMI-168 for 6 weeks. The subjects were given a series of cognitive tests to examine their levels of cognitive functioning at the beginning and end of supplementation, as well as two weeks after termination of supplementation. The combination of these tests, namely Digit Span Backwards, Letter-Number Sequencing, and the Rey Auditory Verbal Learning Test (RAVLT), was used to assess the subjects’ attention and working memory. . . . Subjects supplemented with CMI-168 showed significantly (p < 0.01) better performance in all cognitive tests after 6 weeks’ supplementation compared to [placebo] and [their] superior performance was maintained even 2 weeks after termination of supplementation.
This is the first time I’ve heard that something in chicken improves brain function. The abstract understates the strength of the evidence; p < 0.001 (not 0.01) in almost all relevant comparisons.
However, several details make me question the claim.
1. Two of the five authors work for the company that sells the chicken extract.
2. The subject recruitment makes no sense. “A total of 46 healthy male and female subjects aged between 35 and 65 years were recruited either as walk-in or referred from their general practitioners for counseling for life-style related issues.” Walk-in? “Life-style related issues”? “Counseling”? I have never heard of such things in this context. Nothing is said about payment or the fraction of people who declined to participate.
3. Vague statistics. I cannot tell if pre-treatment scores were used to make the treatment scores more sensitive. Someone who does better than average before treatment is likely to do better than average after treatment — you want to adjust for that.
4. No apparent learning effect. Subjects in the placebo group did not clearly improve from test to test. There is usually a big learning effect with such tests. Nothing is said about learning effects.
5. Vague supporting evidence. “Anecdotal evidence has long associated EOC [essence of chicken] with improving cognitive performance, especially related to learning and memory, as well as executive function,” says the paper. It provides no documentation of this evidence.
6. Uniformly positive results. The paper emphasizes results from nine different tests of brain function. All showed significant improvement at the same p value (p < 0.001). When I used four different tests to measure the brain effects of flaxseed oil, different tests had widely different sensitivities.
I haven’t been able to find anything supporting the idea that chicken meat (or extract) improves memory other than what this company says. I asked a Chinese friend about this; she too had never heard this claim. The company behind this (Brand’s) is more than a hundred years old, and essence of chicken has been their main product. In spite of my doubts, however, I would still like to test the product to see what effect it has on my reaction-time measure of brain function.
Strangely enough, after writing this post weeks ago, I noticed by accident that duck seemed to improve my brain function. I was stunned — as I said, I had never heard such a thing. I’ll describe the data later.