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Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

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Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#321

Post by dumbneurologist »

martingoodson wrote: post #302
sov wrote: post #220

Earlier quoted context omitted.

> Small study Almost entirely irrelevant, provided it's properly powered--and based on the effect size and p-values, it is. Furthermore, for an 18 month trial, 40 people is larger than most. > probably not preregistered I mean, true, and we should definitely promote pre-reg, but, 1. so few are preregistered that I'm not sure it's prudent to disregard a study based on this and 2. it's an academic study, neither a clin…

>> Small study >Almost entirely irrelevant, provided it's properly powered--and based on the effect size and p-values, it is. Sorry to state this so strongly but I feel it's important to point out that this is misinformation of the most egregious kind. There is no examination of statistical power in this article whatsoever so there is no basis for your claim that this study is properly powered. Large effect sizes are…

  Sorry to state this so strongly but I feel it's 
  important to point out that this is misinformation of the 
  most egregious kind.
  
  There is no examination of statistical power in this article whatsoever so there is no basis for your 
  claim that this study is properly powered.
The power is only relevant when you fail to detect an effect. This is a positive study, so the power is simply not relevant to criticizing that particular study.

The nature article you reference talks about literature in aggregate, and the problem created by small studies in general, but it does not allow you to say anything about a single positive study. In fact, the place where those very authors draw their primary conclusion, they state:

  Inflated effect estimates make it difficult to determine an adequate sample size for replication 
  studies, increasing the probability of type II errors
Which means: when you try to replicate it, you might fail because you thought the real effect size was bigger than it is, based on your estimated effect size with small n.

That's well and good, but is a problem for the replicating authors, not for these.

An even more direct point related to the current article: it was preregistered, so you know the authors have not been farming well-designed but small curcurmin studies until they did one than that was positive by chance, and then published it. The act of pre-registration goes a very long way toward addressing the issues raised by Button et al.

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#322

Post by scotty79 »

eni wrote: post #272
sov wrote: post #220

Earlier quoted context omitted.

> Small study Almost entirely irrelevant, provided it's properly powered--and based on the effect size and p-values, it is. Furthermore, for an 18 month trial, 40 people is larger than most. > probably not preregistered I mean, true, and we should definitely promote pre-reg, but, 1. so few are preregistered that I'm not sure it's prudent to disregard a study based on this and 2. it's an academic study, neither a clin…

it's not turmeric, it's curcumin, which is about 2% of turmeric by mass (so, you'd need to eat ~4.5g turmeric daily to match study doses) Typical Indian cooking uses turmeric in pretty much everything. I wouldn't be surprised if daily consumption of turmeric is very close to the figures you mentioned.

Also:

http://www.ijamhrjournal.org/article.asp?issn=2349-4220;year...

> Worldwide, esophageal cancer is the eighth most common cancer [...]. In India, it is the fourth most common cause of cancer-related deaths.

Granted it's probably due to alcohol and tobacco but curry probably won't save you from cancer.

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#323

Post by closed »

dumbneurologist wrote: post #314
YeGoblynQueenne wrote: post #250

From the Wikipedia page on Curcumin (section Research): In vitro, curcumin exhibits numerous interference properties which may lead to misinterpretation of results.[3][6][20] Although curcumin has been assessed in numerous laboratory and clinical studies, it has no medical uses established by well-designed clinical research.[21] According to a 2017 review of over 120 studies, curcumin has not been successful in any c…

None of your criticisms from wikipedia pertain to this publication. The paragraph is essentially making the argument that a randomized, double blind (DB), placebo controlled (PC) clinical trial (RCT) is unlikely to show that curcurmin is effective. yet, the published article is exactly that, and shows a statistically measurable impact on a clinically meaningful endpoint: a direct refutation of the paragraph. the fact…

When a small sample size produces a big effect, it does not mean you can be more confident in the effect!

All things equal, you'd expect confidence intervals / credible regions to be very large.

Another way to say this, is that since the measurement error is large, you expect spurious findings that result from something like p-hacking to be large (they have to be to be significant).

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#324

Post by closed »

dumbneurologist wrote: post #321
martingoodson wrote: post #302

Earlier quoted context omitted.

>> Small study >Almost entirely irrelevant, provided it's properly powered--and based on the effect size and p-values, it is. Sorry to state this so strongly but I feel it's important to point out that this is misinformation of the most egregious kind. There is no examination of statistical power in this article whatsoever so there is no basis for your claim that this study is properly powered. Large effect sizes are…

Sorry to state this so strongly but I feel it's important to point out that this is misinformation of the most egregious kind. There is no examination of statistical power in this article whatsoever so there is no basis for your claim that this study is properly powered. The power is only relevant when you fail to detect an effect. This is a positive study, so the power is simply not relevant to criticizing that part…

> The power is only relevant when you fail to detect an effect.

This is simply not true. It is sometimes called the fallacy of "what does not kill my statistical significance makes it stronger”.

See http://andrewgelman.com/2017/08/17/just-google-despite-limit...

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#325

Post by closed »

sideshowb wrote: post #310
martingoodson wrote: post #302

Earlier quoted context omitted.

>> Small study >Almost entirely irrelevant, provided it's properly powered--and based on the effect size and p-values, it is. Sorry to state this so strongly but I feel it's important to point out that this is misinformation of the most egregious kind. There is no examination of statistical power in this article whatsoever so there is no basis for your claim that this study is properly powered. Large effect sizes are…

Am I right in thinking that statistical power is the true positive rate, so a test that always rejected the null hypothesis (whether correctly or incorrectly) would have the highest possible statistical power?

No, statistical power as a concept is independent of the observed result of a test.

It is widely misunderstood though, so often people try to use an observed result to justify low power.

http://andrewgelman.com/2017/08/17/just-google-despite-limit...

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#326

Post by closed »

pytonslange wrote: post #288
hannob wrote: post #152

Small study, probably not preregistered (didn't find anything about it in the description). Likely Publication Bias or p-hacking. I'm starting to get interested when it's been independently replicated.

It was registered as a clinical trial ( https://clinicaltrials.gov/ct2/show/NCT01383161?term=NCT0138... ). If you are concerned about p-hacking and replicability, what should worry you is that the outcome measures posted during registration are rather vague, i.e. ".. show less evidence of cognitive decline (as measured with neuropsychological assessments)" At baseline, they performed an extensive neuropsychologist te…

That's a good point. After having seen much of the brain training literature (especially its early studies), this wouldn't surprise me at all.

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#327

Post by vanderZwan »

wastedhours wrote: post #289
eni wrote: post #272

Earlier quoted context omitted.

it's not turmeric, it's curcumin, which is about 2% of turmeric by mass (so, you'd need to eat ~4.5g turmeric daily to match study doses) Typical Indian cooking uses turmeric in pretty much everything. I wouldn't be surprised if daily consumption of turmeric is very close to the figures you mentioned.

Interestingly, one of the recent fads I've been seeing has been for "turmeric lattes" - maybe can reach that level even if you're not keen on Indian cuisine?

Apparently, eating more than a teaspoon of tumeric a day increases the risk of kidney stones though, so don't overdo it.

I've been mixing it through my oatmeal, together with chilli-pepper and black pepper, a bit of cardamom, and a teaspoon of real cinnamon (the non-cumerin kind). While it feels like it works, I know that the placebo effect is probably much stronger than any real effect these foods have. Still, a placebo effect is still a real effect on my mood, so that's still a kind of health benefit I guess. If nothing else the spices help me wake up!

Tangent regarding health food fads: these days I mainly use nutritionfacts.org[0] to determine which of those are actually supported by the latest nutrition research. It is the only health food/diet website that I know of that directly cites nutrition research and continuously scours the latest papers for new findings - sources are always linked, and quotes are directly lifted from the papers with no modification (so less likely to suffer from "stronger or opposite of what the paper actually says"-shenanigans often seen elsewhere).

Some of the other things I tried out based on that website have too big of an effect to just be placebo: adding blue-berries to a meal really reduces sugar rushes/crashes in the hours after it[1]. Taking a table spoon of freshly broken flax seeds[2] does a lot to counter the rise in blood pressure due to my ADD medication (I measured it, plus I feel a lot less discomfort in my chest area and less jittery).

Last time I mentioned that website here, it was in a discussion of which diets are healthy. Ironically, it was the only comment in the discussion that attracted multiples downvotes without explanation, while everyone else was sharing their unsourced opinions.

[0] https://nutritionfacts.org/

[1] https://nutritionfacts.org/video/green-smoothies-what-does-t...

[2] https://nutritionfacts.org/video/flax-seeds-for-hypertension...

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#328

Post by roganp »

closed wrote: post #323
dumbneurologist wrote: post #314

Earlier quoted context omitted.

None of your criticisms from wikipedia pertain to this publication. The paragraph is essentially making the argument that a randomized, double blind (DB), placebo controlled (PC) clinical trial (RCT) is unlikely to show that curcurmin is effective. yet, the published article is exactly that, and shows a statistically measurable impact on a clinically meaningful endpoint: a direct refutation of the paragraph. the fact…

When a small sample size produces a big effect, it does not mean you can be more confident in the effect! All things equal, you'd expect confidence intervals / credible regions to be very large. Another way to say this, is that since the measurement error is large, you expect spurious findings that result from something like p-hacking to be large (they have to be to be significant).

This. This is a relevant podcast featuring John Ioannidis (author of "Why Most Published Research Findings Are False.") http://www.econtalk.org/archives/2018/01/john_ioannidis.html

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#329

Post by anentropic »

chiefalchemist wrote: post #153
dumbneurologist wrote: post #135

Earlier quoted context omitted.

I am a neurologist. this is actually the exact opposite of what you should care about, which is "does it work to treat ___" In this trial, and 99% of other trials, there is no mechanism provided by the study, only a measurement of causality (which is the same thing as effectiveness). The authors may think they know based on other, prior, basic science research (as they are postulating here), but it does not affect th…

OK. But without knowing why how can you be certain it's cause and not correlation? Especially in such a small trial?

isn't it because the control and treatment groups are randomised from the same pool?

Re: Curry spice turmeric boosts memory by nearly 30%, eases depression, study finds

#330

Post by vanderZwan »

closed wrote: post #323
dumbneurologist wrote: post #314

Earlier quoted context omitted.

None of your criticisms from wikipedia pertain to this publication. The paragraph is essentially making the argument that a randomized, double blind (DB), placebo controlled (PC) clinical trial (RCT) is unlikely to show that curcurmin is effective. yet, the published article is exactly that, and shows a statistically measurable impact on a clinically meaningful endpoint: a direct refutation of the paragraph. the fact…

When a small sample size produces a big effect, it does not mean you can be more confident in the effect! All things equal, you'd expect confidence intervals / credible regions to be very large. Another way to say this, is that since the measurement error is large, you expect spurious findings that result from something like p-hacking to be large (they have to be to be significant).

What annoys me as a someone not trained in statistics is that these discussions are always abstract in-principle arguments about what proper statistics should be like.

Meanwhile, we have a real paper with real p-values, why not discuss the validity of that?

> SRT Consistent Long-Term Retrieval improved with curcumin (ES = 0.63, p = 0.002) but not with placebo (ES = 0.06, p = 0.8; between-group: ES = 0.68, p = 0.05). Curcumin also improved SRT Total (ES = 0.53, p = 0.002), visual memory (BVMT-R Recall: ES = 0.50, p = 0.01; BVMT-R Delay: ES = 0.51, p = 0.006), and attention (ES = 0.96, p 

I can see that there are a lot of p-values around 0.05, but that the supposed improvements have much lower p-values:

    (ES = 0.63, p = 0.002)  SRT Consistent Long-Term Retrieval
    (ES = 0.53, p = 0.002)  SRT Total 
    (ES = 0.50, p = 0.01)   BVMT-R Recall 
    (ES = 0.51, p = 0.006)  BVMT-R Delay 
    (ES = 0.96, p 
What does this imply? Is it a good sign, or does it actually make it more fishy? pythonslange's comment[0] seems to suggest the latter, claiming that none of the other pre-registered tests are mentioned, without any explanation why.

(eyeing that "attention" one, if this does hold up under scrutiny, could I expect tumeric-based ADD medication somewhere in the future, without all the nasty side-effects of my current amphetamine-based options?)

[0] https://news.ycombinator.com/item?id=16229693

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