As I said in the last paragraph, it is unlikely that one of the regions that was selected by the Blue Zone analysis would be doing anything particularly horrible. If you have too many bad things, those will balance the good and drop you into the norm. If we assume that diet makes a significant impact on longevity, then their diet must not be terrible. But, that’s an assumption.
Let’s say that we know through science that the important thing that a person can choose to do in their life to stay healthy is to eat a well-balanced diet and get exercise of different intensities.
In a few regions in the US, maybe the rural, small farm regions eat like trash. But, across the entire planet, most rural, small farm regions are going to have a lifestyle of eating a well-balanced diet of whole foods and getting exercise of different intensities working on the farm.
So we have 90% of rural, small farm regions that are doing the right thing and they should be topping out the scale. But, in practice, only a few are. Okinawa is doing well but those small farm regions in Ghana are doing crapy. What’s different? Farm exercise is probably equivalent between the two so - since we’ve limited our view to food and exercise - the answer must be the food…right?
Okinawa’s secret could be purple potatoes, sure. But it could also be that Okinawa is part of Japan - a first world country with modern medicine, indoor plumbing, minimal poverty, minimal violence, etc. and Ghana is not those things. It could be that Okinawans have good genetics, that they suffered a life extending period of famine, etc.
We could imagine that plants native to Western Africa might be more healthy and life extending than the plants native to Okinawa. Maybe chufa, elephant ear (plants), goat, and breadfruit are a better diet for longevity than purple potato, fish, mizuna, and pickled daikon. Likely, pickled foods undo high antioxidant foods, if nothing else. But, between smoking, violence, a life of dysentery, HIV, poorly insulated homes, and bad genetics, Ghanaians live shorter lives despite their healthier diet.
The reality on the ground might be that the Ghanaian diet is healthier than the Okinawan. Okinawa jumps to the top of the pack not because of their diet but because of other factors - governance, economy, technological development, WWII, etc.
So should we eat chufa or purple potato? One is devoured by people who die young and the other by people who die extra old, and that’s not nothing, but that’s sort of a nonsense comparison when you’re comparing people with indoor plumbing and electricity to people who live on a dirt floor and smoke hashish like chimney pipes.
A random selection of regions, looking for any statistical anomaly will give you a territory of small farms. In terms of lifestyle, the norm will be eating whole foods and a good amount of exercise. The specific vegetables that they eat could be the differentiator. But it’s also possible that the differences in whole food diets, from one region to another, is largely negligible. Maybe you eat blueberries (antioxidants, yay!) and spinach (oxalic acid, boo!), and they cancel each other out. Maybe Okinawans eat purple potato (antioxidants, yay!) and pickled foods (nitrates, boo!) and those cancel each other out. For almost any regional diet, for any “good” food there’s also an equally bad food, also in the diet. After all, these foods weren’t chosen to be life extending, they’re just what grows natively in that region and the people were going to eat whatever that is, so long as its effects aren’t immediately worrisome. Between the dozens of things in a regular human diet, there’s too much variety for any one good or bad thing to really pull ahead, until you exit the realm of whole foods and start looking at regions with ultra-processed foods. Then you can get a diet that does something significant (in the negative direction).
It’s certainly true that Okinawa has more long-lived people per capita than the normal. But, if that’s because of genetics, WWII, plumbing, or whatever other thing then that’s not useful to us when we’re looking at diet. Knowing that they live longer doesn’t tell us what the cause was. Taking the assumption that it’s that one thing in their diet doesn’t make it so. It may be, but it also might not be.