N=30 short-term ensures minimum chance of detecting side effects to provide plausible deniability to the FDA. Age range 40-60 excludes the less wealthy <40 and those higher risk of death age ranges >60.
Nutrition studies of the general population with N<1000, without any qualifying factor such as “extremely rare cancer subgroup”, ought to be banned at HN.
So, AFAIK these studies are often based on questionnaires (=fuzzy indicators, easily skewed as people want to decorate their answers for the better etc.) and the sample sizes are limited, so the results cannot be directly ingested as facts.
But that’s often the best we have due to the state of affairs. Option is to not do the studies at all, which seems counterproductive. At least we can duplicate the studies if the results seem promising, maybe combine some other dietary studies for a meta-analysis to try to improve the accuracy.
Not to downplay the risk of science-clad marketing with food&nutrition, what I said does not mean I carefully read the study or that it’s correct. Just wanted to contribute the general view I’ve adopted for these types of studies — the field is NP hard if you want to produce concrete facts as results, so read them with an inquisitive mind. And yeah, check for independece, it certainly doesn’t hurt :-)
Got sidetracked for a bit, but summa summarum: they probably did questionnaires, and had to live with people commonly using those mixes of spices since they cannot really insist them on using just one (or factor out the effect of other spices, since people mix in the other stuff anyways, if ask if they spice with turmeric).
This is by itself interesting too.
Not perfect for efficacy of one substance, but...their money.
Sometimes I have the impression that these type of studies are more common among studies initiated by a company. Here it was some supplements company.
I think it is important to remember that by testing random mixes, any company can produce an arbitrary amount of studies and then publish the one with the best looking results and use it for marketing.