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I've really enjoyed this talk by Molly Crockett: Beware neuro-bunk. The speaker outlines the limitations of modern neuroscience when accessing the effectiveness of dietary supplements intended to enhance cognition. I believe the speaker mentioned that 68% of (americans?) take dietary supplements for a variety of reasons.

I've done some research, and these compounds typically go into "neuro enhancing" products:

  • DMAE
  • GABA
  • N-Acetyl-L-Tyrosine
  • Vinpoceitine
  • 5-HTP
  • Vitamin B complex

This got me thinking: How does one assess the effectiveness of dietary supplements on cognition? These are low- dose compounds that may be taken at random times of a day, combined with assorted other supplements. How does one study the effects of something like that? Is there a "gold standard" study that I can take a look at to understand how this is done?

What I'm interested in is how do they account for the time of day, and other supplements/drugs/activity that happened and followed the study.

When thinking about "real psychoactive drugs", their effect is much more profound, and thus easier to study, with a fairly well defined onset times, intensity curves. For example, I can go to erowid.org and see curves like the one below for

cannabis onset intensity curve

alcohol onset intensity curve

With a graph like that, one can with a reasonable certainty estimate the duration and intensity of effects. But what about dietary supplements? Is it just big placebo?

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    $\begingroup$ those are metabolic rates, measuring the amount of the drug in your body. and yes, you could make a similar chart for any drug. $\endgroup$ – Jeff Dec 19 '12 at 18:51
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    $\begingroup$ I think there is an issue here, in that "real psychoactive drugs" aren't meant to be taken for extended time periods (I mean, you can...). Whereas dietary supplements (and other 'medicines') are meant to be taken over an extended time-period to effect a change in self/personality/life after time. They can take time to build up in the body (think SSRI's, also). $\endgroup$ – BenCole Dec 19 '12 at 19:52
  • $\begingroup$ Though most likely the lack of studies is the result of difficulties with performing well-controlled, longitudinal studies for common dietary supplements that marketers can make more money off of without scientific backing...(these statements are not FDA-approved). $\endgroup$ – BenCole Dec 19 '12 at 19:54
  • $\begingroup$ Good point about making money without scientific backing. I"m looking at this search result for (Vinpocetine metabolic rate -calories) smart-drugs.net/info-vinpocetine.htm The claims make it seem like a super drug, but it doesn't say how long it works, how quick the onset is, if it has to be taken extended period of time and what the benefit %increase is. It would be great to see a study that deals with the points above. $\endgroup$ – Alex Stone Dec 20 '12 at 1:30
  • $\begingroup$ There is a bit of information (and linked studies) at the Wikipedia page for Vinpocetine. Looks like a serious lack of information in general, but they have some basic information like half-life and bio-availability. $\endgroup$ – BenCole Dec 20 '12 at 14:47
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To the general question of how to test the claims , there's a couple things you want to show:

  • 1) that the body absorbs the supplement (measure the absorption rate)
  • 2) that the supplement crosses the blood brain barrier
  • 3) that the supplement actually plays the role of agonist, antagonist, or allosteric modulator (or possibly even has a toxic effect). These are biochemical roles that depend on molecular properties like shape and charge distribution, as well as kinetic interactions (chemistry).
  • 4) that the interaction of the ligand or effector (or toxin) with the receptor (or system) that's being affected by the supplement produces a cognitive benefit.

The first three are feats of biochemistry, the fourth of behavioral/psychological biology. So this is a complicated interdisciplinary task in the first place. Now if we want to consider all the control situations (especially 4) it becomes even more complicated.

Known cognitive benefits are come from substances like caffeine, nicotine, chocolate (it has theobromine), amphetamines, and other stimulant-like drugs.

GABA, on the other hand, exists naturally in the brain. It's part of an integrated molecular system and is tightly controlled by the citrus cycle (aka Krebs Cycle) and the GABA shunt. If you have more of it, but you don't need it, your body will just break it down or convert it (it's part of a very dexterous set of metabolic molecules).

The best cognitive benefit you can get is simply from eating right, not having nutrient deficiencies, omega 3's are good for long-term brain health. Circulatory health is good for long-term brain health (so exercise and less cholesterol). Pretty much all your typical healthy habits. Most of the evidence for the nutrititional/exercise claims I provided in this thread

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  • $\begingroup$ Amazing answer! I especially appreciate you putting the 4 points to test and specific keywords, like allosteric modulator. $\endgroup$ – Alex Stone Dec 27 '12 at 15:31
  • $\begingroup$ I'm glad I could answer your question. I've updated with some links to explain the GABA shunt on modulators a bit. $\endgroup$ – Keegan Keplinger Dec 30 '12 at 7:42

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