gelatin, tryptophan depletion, and memory

barefooter

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I've been planning to try taking more gelatin for sleep, and I was doing some research and heard mention that tryptophan depletion from gelatin can cause reduction in memory function. Obviously this seems to go against what Peat says, but has anyone heard about it, and can you help debunk it. It does seem like there's some research on this. I haven't looked a lot, but I did find this study.

http://www.ncbi.nlm.nih.gov/pubmed/18515454
"Memory impairments in humans after acute tryptophan depletion using a novel gelatin-based protein drink."
"Abstract
Acute tryptophan depletion (ATD) can be used to decrease serotonin levels in the brain. Traditionally, ATD has been established by administering amino acid (AA) mixtures and studies using this method showed that serotonin is involved in learning and memory processes. This study used a recently developed gelatin-based protein drink to examine whether it 1) is superior to the traditional AA method in controlling the tryptophan levels in the placebo condition, 2) impairs long-term memory and 3) differentially affects episodic and spatial memory. Sixteen healthy subjects participated in a double-blind, placebo-controlled study. Memory was assessed using a visual verbal learning test and an object relocation task (spatial memory). Tryptophan ratio significantly decreased after ATD and did not significantly increase in the placebo condition. Delayed recall in the verbal learning test and delayed relocation of objects to positions in the spatial task were impaired after ATD. Spatial short-term memory, however, improved. The current results indicate that the tryptophan levels were essentially neutral in the placebo condition compared with those in the traditional AA mixture. Our study provides further evidence that impairment in long-term episodic and elementary spatial memory after ATD is related to lowered tryptophan levels in plasma."

EDIT:

here's another study

http://www.ncbi.nlm.nih.gov/pubmed/25176356
"Dose-dependent effects of tryptophan on learning and memory."
Abstract
The concentration of 5-hydroxytryptamine (5-HT, Serotonin) varies as a result of physiological changes in the availability of its precursor tryptophan to the serotonergic neurons in the brain. Increase in brain tryptophan occurs following an increase in plasma tryptophan concentration. Tryptophan intake increases brain serotonin metabolism and enhances memory. The Present study was designed to investigate the effects of oral administration of tryptophan (TRP) at different doses (100, 300 and 500mg/kg) for two weeks on learning and memory functions and Neurochemical changes in rats. Control rats were given drinking water. Assessment of memory in rats was done by using the water Maze. on the 14th day trail training of water Maze was given to rats and after 1h of this 2nd trial of these rats were done. On the next day (After 24h of trail) long-term memories of these rats were monitored. After 1 hour of this all rats were killed by decapitation using guillotine. Brain and blood was collected and stored at -70°C. Neurochemical estimations of Plasma and brain tryptophan, 5-HT and 5-HIAA in brain were made by HPLC-EC. Result showed that administration of tryptophan enhanced performance on water Maze test. Tryptophan treated animals exhibited higher level of Plasma as well as brain tryptophan. 5-HT and 5-HIAA levels were also increased in tryptophan treated rats. Findings are discussed in context with the role of 5-HT metabolism in learning and memory process in rats. Results may help to understand the 5-HT changes following long term TRP administration in a dose dependent manner and will help to suggest the use of TRP in serotonin related illnesses.
 

Giraffe

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barefooter said:
post 118065 I've been planning to try taking more gelatin for sleep, and I was doing some research and heard mention that tryptophan depletion from gelatin can cause reduction in memory function. Obviously this seems to go against what Peat says, but has anyone heard about it, and can you help debunk it. It does seem like there's some research on this. I haven't looked a lot, but I did find this study.

I found the full texts.

Memory impairments in humans after acute tryptophan depletion using a novel gelatin-based protein drink.
Overnight fasted participant drank 100 g gelatine in 200 ml water within 15 min.:barf :barf

"Two female participants did not finish the study. One of them complained of nausea and had to throw up during the placebo condition. The other participant did not return for the second session after she had had tryptophan depletion during the first. A third female participant was excluded from analysis because she had to throw up during the placebo condition and showed complaints of nausea at T4."
:tease


So they had only 6 participants in the placebo group and 7 in the ATD group. When you look at the results, you see that the baseline already differs between the two groups. In my opinion, the results are not reproducible.

post 118065 delayed recall in the verbal learning test
No, similar trends in both groups.

post 118065 delayed relocation of objects to positions in the spatial task were impaired after ATD. Spatial short-term memory, however, improved
In other words, the results are all over the place. In total the trytophan depleted group showed better trends.

In that test 10 objects were presented for 30 s on a computer screen. The objects then disappeared from the square in which they had been and reappeared above it. The participants had to place them back.

OTP means there where dots on the screen to help place back the objects into the square. COM means there were no dots.
immediate: How many errors made the participants directly after they have seen the objects?
delayed: How many errors did they make 30 minutes later?

.............tryptophan depleted group ...... placebo group

OTP immediate, errors: T4 = baseline .......400% increase
OTP delayed, errors: 146% increase ........ T4 = baseline
COM immediate, errors: 42 % decrease .....114% increase
COM delayed, errors: 14% increase ........ 59% increase



Dose-dependent effects of tryptophan on learning and memory.

post 118065 Assessment of memory in rats was done by using the water Maze

Weakness of the Morris water-maze test
"When the searching times for the platform in the target quadrant are reduced in the probe trial, this is seen as direct evidence that the spatial memory of the mouse must be impaired. However, many times the reason for a lengthier amount of time spent looking for the platform, or the lack of searching in the target quadrant, has nothing to do with an effect on the mouse's spatial memory, but is actually due to other factors. A large study of performance in mice concluded that almost half of all variance in performance scores was due to differences in thigmotaxis, the tendency of animals to stay close to the walls of the pool. About 20% of the variability was explained by differing tendencies of mice to float passively in the water until "rescued" by the experimenter. Differences in spatial memory were only the third factor, explaining just 13% of the variation between animals' performance."

https://en.wikipedia.org/wiki/Morris_wa ... ation_task
 

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barefooter

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Giraffe said:
I found the full texts.

Thanks for the excellent analysis Giraffe! I was reading more from the thread on serotonin and the formation of traumatic memories, which I think sheds some light on this. In that thread, it's noted that serotonin increase, and other acute stressors can improve memory in the short term, likely as some kind of survival mechanism. So, even if a study does prove that a substance improves memory in the short term, it may still be harmful to cognitive function in the long term.
 

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