Several regions became famous for containing unusual concentrations of people living past a hundred, and their diets and habits were widely promoted. The underlying age records have since been questioned.
The claim rests on verified ages
Identifying a region as exceptional requires knowing how many very old people live there and knowing their ages are correct.
Verification means a birth record created near the time of birth, plus documentation linking that record to the living person, across a century of changing administration.
Where records are incomplete, destroyed or were never created reliably, an age can only be accepted on the basis of testimony.
Errors run in one direction
Age misreporting is not random. Overstatement is far more common than understatement, particularly at very old ages where the claim carries prestige.
Pension systems create a further incentive, since a payment continuing after a death that was never registered produces a record of an implausibly old survivor.
Analyses have found that regions reporting exceptional longevity often correspond to areas with late or poor birth registration, which is the pattern the criticism rests on.
The correlation is the awkward part
If exceptional longevity were driven by diet or environment, the effect should not track administrative record quality, but in several analyses it does.
Introducing reliable registration in some regions has been followed by a fall in reported centenarian numbers, which is difficult to explain biologically.
Defenders of the original work argue that specific communities have been verified individually and that record quality varies between the regions grouped together.
Lifestyle observations were secondary
The dietary and social patterns described in these regions were catalogued after the populations had been identified as exceptional.
That order matters, because features found by looking at a chosen group are not evidence that those features caused the selection.
Any traditional rural community would show plant-heavy diets, daily physical work and strong social ties, whether or not it produced unusual numbers of centenarians.
The advice survives the dispute
Most of the practices attributed to these regions are supported independently by other research, so the recommendations do not stand or fall with the age records.
What the dispute undermines is the specific claim that particular villages have discovered something the rest of the world has not.
It is a useful illustration of how a finding built on a data quality assumption can circulate for years before that assumption is examined.