Are the Blue Zones real?

Two of them hold up well on modern records, and three are disputed. Nicoya has a follow-up of 16,300 older Costa Ricans showing men with a death rate ratio of 0.80. Loma Linda has a 73,308-person study showing a death risk score of 0.88 for vegetarians. Sardinia, Okinawa's oldest generation and Ikaria rest on older records. A study posted online since 2019 found those regions matched areas poorer and shorter-lived than their national averages, and that US records of the very oldest people fell 69 to 82 percent once states brought in birth certificates.

Has the records criticism been peer reviewed?

No. It has been on bioRxiv, a site for studies that have not been peer reviewed, since 2019, and was revised in 2024, but it has not been published in a peer-reviewed journal. That is a real limitation, and it does not make the analysis wrong. A narrower version of the same argument was published in PLoS Biology in 2018: errors in recorded ages, and in mixing birth groups, at rates below 1 in 10,000 are enough to make it look as if death rates level off in old age. A separate analysis of US Social Security records reached a similar conclusion.

What happened to Okinawa?

Its generations split. An analysis of life tables since 1975 found very favourable death rates in those born before the war, and death rates clearly higher than mainland Japan in those born after it. Okinawa fell from 4th to 26th of Japan's 47 prefectures for male life expectancy in 2002. The paper's own conclusion calls for careful checking of the ages of the oldest residents.

Is there a Blue Zone diet I can follow?

Not one, and that is the honest answer, not a dodge. The Okinawan diet is heavy on sweet potato and very low in protein. The Nicoyan one is described by its own researchers as rice, beans and animal protein. Loma Linda is Adventist vegetarian, and Sardinia includes sheep dairy and wine. What they share is high fibre, little processing and beans, and those are tested under their own names elsewhere on this site. No trial of any Blue Zone diet has been run.

If it is not the diet, what is it in Nicoya?

Nobody knows, and the data narrows it in interesting ways. The advantage is in men only, not in women, does not depend on income or social conditions, comes entirely from fewer heart and blood vessel deaths, and disappears in people who move away. A separate gene study of forty people found more Indigenous American ancestry in the oldest group, with 2.32 times the odds per 10 percent more ancestry. Moving away wiping out the effect points at something about living there. The ancestry finding points somewhere else entirely, and it rests on forty people.

Plant-forward7 studies in people cited

Blue Zones

Written by Aaron CuhaReviewed Sep 2026

Also called: Longevity hotspots, Power 9, Okinawan pattern, Sardinian pattern, Ikarian pattern

Five regions picked because their records showed unusual numbers of people living to 100, and the records are the disputed part. A study posted online since 2019, not yet peer reviewed, found that in the US, records of supercentenarians, the very oldest people, fell 69 to 82 percent once a state brought in birth certificates.

What it actually is

Not one diet. Five regions picked from population records for having lots of people reaching very old age: the mountain centre and east of Sardinia, Okinawa, the Seventh-day Adventist community of Loma Linda in California, the Nicoya peninsula of Costa Rica, and Ikaria in Greece. The shared diet drawn from them is plant-forward, heavy on beans, low in meat and low in processed food. The Power 9 idea adds natural daily movement, purpose, ways to unwind, moderate eating, wine, faith, family and friends. The key point for reading everything below: these places were picked after the fact, because of the outcome. The idea was not set out in advance and then tested.

How its fans say it works

Here is the argument at its strongest, and it is a serious one. Five populations, unrelated by place or genes, share a similar way of eating and living. All five show less disease late in life and unusual survival, so the shared features could be the causes. The diet half fits with the rest of this site: high fibre, food that is not calorie-dense, beans, very little processed food, and habitually eating a moderate amount. Buettner's own view in his 2024 keynote goes somewhere different from how the idea is usually sold, and the direction is worth noting. There is no silver bullet. Making each person responsible for building a healthy life does not work. Long life comes from a whole set of surroundings that make the healthy choice easy and automatic. That is an argument about environments, not about menus.

What happened when calories were controlled

Best kind of study available: tracked, not tested

Nobody was given a diet. People who choose a diet differ from people who do not in other ways too, so this shows a link, not a cause.

Never, and it cannot be. There is nothing here to control. No trial of any Blue Zone diet has ever been run, the diet data looks backward, and the most serious criticism of this field holds that some of the age records are wrong.

The Sardinian zone was defined by working out what share of people born on the island between 1880 and 1900 reached 100, then smoothing that across the map. Its standout feature is the ratio of male to female 100-year-olds: 1.35 inside the zone against 2.43 outside. The paper that defined it says plainly that nobody knows why. It raises marriage between cousins and low immigration as possible explanations instead of lifestyle, and notes that none of the world's long-life hot spots had been fully checked at that point.
The main criticism is a study that has not been peer reviewed, and both halves of that sentence matter. Newman's analysis found that in the US, being recorded as a supercentenarian, one of the very oldest people, was predicted by a lack of birth and death records. When a state brought in birth certificates, those records fell 69 to 82 percent. In Italy, England and France, extreme old age was instead predicted by poverty, low income, shorter life expectancy, higher crime, worse health, more hardship, fewer people aged 90 and over, and living in remote or overseas areas. Poverty in old age alone predicted more than half of the regional differences in England and France. Only 18 percent of fully checked supercentenarians had a birth certificate, falling to zero percent in the USA, and their recorded birthdays cluster on days divisible by five. The named zones of Sardinia, Okinawa and Ikaria matched regions with low incomes, low literacy, high crime and short life expectancy compared with their national averages. This has been posted on bioRxiv since 2019, revised through 2024, and has not finished peer review. It is both the most important criticism in this field and unpublished, and neither fact cancels the other.
The peer-reviewed version of the narrower argument is Newman 2018, which is about extreme-age data in general, not about Blue Zones. Errors in recorded ages, and in mixing birth groups, at rates below 1 in 10,000 were enough to make it look as if death rates slow down or level off in very old age. Real error rates in birth and death records predicted how big that slowdown looked in humans. Correcting for them with a statistical model removed both the slowdown and the levelling off, without needing any biology to explain them.
A separate population analysis reached a similar conclusion by a different route. Using US Social Security death records, one birth year at a time and month by month of age, death rates kept rising steadily with age (following what is called the Gompertz law) up to ages 102 to 105, with no noticeable slowdown. Earlier reports of a slowdown before 100 seem to come from mixing birth groups and from snapshot data, with people overstating their age named as one cause.
Population experts have now studied Okinawa on its own terms. Life tables since 1975 split the population into people born before and after the Second World War. The older generations show very favourable death rates. The younger generations show death rates clearly higher than mainland Japan. Okinawa fell from 4th to 26th of Japan's 47 prefectures for male life expectancy in 2002, which locals called a shock. The paper's own closing argument is a plea for careful checking of ages, and it names the possibility that some of the oldest people's ages are wrong among the things that may explain the pattern.

What happened when people just ate it

What has actually been measured varies hugely by zone, and the two zones with modern records tracked person by person are the two quoted least. Loma Linda's evidence is the Adventist Health Study 2, which followed 73,308 people. All vegetarians together had a death risk score of 0.88, where one means no difference. For vegans it was 0.85, too uncertain to call, and for vegetarians who ate fish, 0.81. Nicoya is the best measured zone. A follow-up of 16,300 older Costa Ricans found men in Nicoya had a death rate 0.80 times that of other men between 1990 and 2011. For a 60-year-old Nicoyan man, the chance of reaching 100 was seven times that of a Japanese man, and life expectancy was 2.2 years longer. The advantage does not show up in women, does not depend on income or social conditions, disappears in people who move away, and comes from fewer heart and blood vessel deaths, at a death rate ratio of 0.65. Nicoyans are leaner and taller, and have better heart-related blood tests, longer telomeres (the protective caps on chromosomes) and higher levels of the hormone DHEA-S. That paper describes the diet as plain and full of traditional foods like rice, beans and animal protein, with lots of fibre and foods that raise blood sugar slowly. A separate gene study complicates the diet story. 20 Nicoyans aged 99 and over had 43.3 percent Indigenous American ancestry, against 36.0 percent in 20 Nicoyans aged 60 to 65, a clear result. Each 10 percent more ancestry went with more than twice the odds of living very long (2.32 times). That is forty people in total. Ikaria's evidence is a one-time questionnaire. 1,420 people signed up in 2009, 187 of them over 80. Most reported daily exercise, healthy eating, not smoking, seeing friends often, midday naps and very low rates of depression. There was no comparison group, and no health outcomes were measured. Okinawa's diet evidence is an analysis of six decades of stored population data on residents aged 65 and over. It reports eating few calories, and burning more than they ate, when younger, little weight gain with age, low BMI for life, fairly high DHEA in old age, and few deaths from age-related diseases. The diet was the lowest in fat and highest in carbs of the diets it was compared with, driven by sweet potato and green leafy vegetables.

Protein, and whether it muddies the result

The five zones do not agree with each other on protein, which is a problem for anyone quoting them as one plan. The traditional Okinawan diet is about as low in protein as any recorded human diet. The Nicoyan diet is described by its own researchers as full of animal protein. There is a line of animal research, in insects and mice, that found the longest lifespans on low protein, high carb diets eaten freely. In those animals, the ratio of protein to carbs was almost the same as the traditional Okinawan one. That is not a finding in people, and it does not belong next to the death rate data above. Pulling the other way, the PROT-AGE expert group puts the floor for keeping muscle after 65 at 1.0 to 1.2 g/kg a day. No Blue Zone study measured muscle, muscle function or protein intake in anyone. The measured protein intakes, and what they did, are in the protein section of this site.

The measured intakes behind the protein figures are on the protein page.

What reliably moves

Measure	Direction	From
Death rates in Nicoya men	Down	A death rate ratio of 0.80 for men from 1990 to 2011, in a follow-up of 16,300 older Costa Ricans. No advantage in women, and the advantage disappears in people who move away.
Heart and blood vessel deaths in Nicoya	Down, and this is where the whole advantage comes from	A death rate ratio of 0.65. Nicoyans also measured leaner and taller, with better heart-related blood tests, longer telomeres and higher DHEA-S.
Death rates among Loma Linda Adventists	Down a little	A risk score of 0.88 for all vegetarians together, in a 73,308-person study that followed people forward, with the vegan figure at 0.85 and too uncertain to call. The only Blue Zone with a modern long-term study and modern birth and death records.
Death rates in Okinawans born after the war	Up, compared with mainland Japan	Life table analysis since 1975 splits the population in two. Okinawa fell from 4th to 26th of 47 prefectures for male life expectancy in 2002. The good pattern belongs to those born before the war.
Body weight over a lifetime in Okinawa	Little gain with age, low BMI for life	From six decades of stored population data on residents aged 65 and over, along with eating few calories, and burning more than they ate, when younger. This is an analysis of population records, not a study that tracked what each person ate.
Indigenous American ancestry in the oldest Nicoyans	Higher	43.3 against 36.0 percent, in 20 people aged 99 and over against 20 aged 60 to 65, a clear result. Each 10 percent more ancestry went with 2.32 times the odds of living very long. Forty people in total, and it points at ancestry, not diet.
Records of the very oldest people once birth certificates arrive	Down by 69 to 82 percent	From the study, not yet peer reviewed, that makes up the main criticism of this field. The same analysis found only 18 percent of fully checked supercentenarians had a birth certificate, zero percent in the USA, and that recorded birthdays cluster on days divisible by five.

Long term, and serious health events

Everything on this page is long-term data, so the useful question is which parts hold up. Two zones rest on modern records tracked person by person, and they give effect sizes that studies of this kind can honestly support. In Nicoya, men have roughly 20 percent lower death rates, all of it from fewer heart and blood vessel deaths, and none of it in women or in people who move away. In Loma Linda, vegetarians have 12 percent lower death rates, in a 73,308-person study that followed people forward. Those are believable and modest. The other three zones rest on records whose quality is truly disputed. One of them, Okinawa, has a peer-reviewed population analysis that concludes its post-war generations now die earlier than mainland Japan, and calls for checking the ages of its oldest residents. The unpublished analysis that has done most to reshape the field found the named zones matched regions with low income, low literacy, high crime and short life expectancy compared with their national averages. That is the opposite of what a long-life hot spot should look like, and exactly what a bad-records hot spot should look like. Against all that, no trial of a Blue Zone diet exists, no trial big enough to measure health outcomes has ever been proposed, and the single foods the zones share are tested elsewhere on this site under their own names.

Sources

Study in people2004
Identification of a geographic area characterized by extreme longevity in the Sardinia island: the AKEA study
Experimental Gerontology
This paper defined the first Blue Zone, in Sardinia. It mapped people born from 1880 to 1900 who lived to extreme old age. Among people who reached extreme old age, men and women were more evenly matched in number inside the zone (a ratio of 1.35) than outside it (2.43). The authors say the cause is unknown. They name family intermarriage and few newcomers as possible reasons besides lifestyle, and note no longevity hot spot had been fully checked.
The paper that defined the first Blue Zone. Extreme longevity index from births between 1880 and 1900, smoothed geographically. Male to female centenarian ratio 1.35 inside the zone against 2.43 outside. States the mechanism is unknown, raises consanguinity and low immigration as an alternative to lifestyle, and notes that no longevity hot spot had been fully validated.
Review of studies2019
Supercentenarian and remarkable age records exhibit patterns indicative of clerical errors and pension fraud
bioRxiv preprint, not peer reviewed
This paper was posted online in 2019 and updated through 2024, but never passed peer review. In the US, claims of extreme old age were most common where births went unrecorded, and fell 69 to 82 percent once birth certificates came in. In Italy, England and France, extreme old age went with poverty, shorter lives and more crime. Only 18 percent of checked supercentenarians had a birth certificate, and none in the USA. Sardinia, Okinawa and Ikaria were poorer and shorter lived than their countries overall.
Preprint first posted 2019 and revised through 2024, never published in a peer-reviewed journal. US supercentenarian status predicted by absence of vital registration, with birth certificate introduction associated with a 69 to 82 percent fall in records. In Italy, England and France remarkable longevity predicted by poverty, low income, shorter life expectancy and higher crime. 18 percent of validated supercentenarians hold a birth certificate, zero percent in the USA. Sardinia, Okinawa and Ikaria corresponded to regions poorer and shorter-lived than their national averages.
Review of studies2018
Errors as a primary cause of late-life mortality deceleration and plateaus
PLoS Biology
A peer reviewed paper on a narrower point. Tiny errors in recorded ages, fewer than 1 in 10,000, are enough to make death rates seem to level off in very old age. Real error rates predict how big that effect looks in people. Correcting the errors makes the leveling off disappear, with no need for a biological explanation.
The peer-reviewed version of the narrower argument. Age estimation and cohort blending errors below 1 in 10,000 are sufficient to produce late-life mortality deceleration and plateaus; observed registration error rates predict the magnitude in humans; correcting for them eliminates both without any biological model.
Review of studies2011
Mortality Measurement at Advanced Ages: A Study of the Social Security Administration Death Master File
North American Actuarial Journal
Researchers used US Social Security death records, one birth year at a time. The risk of dying kept rising with age in the usual pattern up to ages 102 to 105, with no slowing. Earlier reports of slowing below 100 look like errors from mixing birth years and using snapshot data, helped along by people overstating their age.
Single-year birth cohorts at monthly age intervals. Hazard rates followed the Gompertz law to ages 102 to 105 with no noticeable deceleration. Earlier reports of deceleration below 100 appear to be artifacts of mixing cohorts and using cross-sectional data, with age exaggeration named as a contributor.
Study in people2024
Exceptional longevity in Okinawa: Demographic trends since 1975
Journal of Internal Medicine
Researchers split Okinawa's people into those born before and after the war. The older generations died at low rates. The younger generations died at clearly higher rates than mainland Japan. Okinawa fell from 4th to 26th of 47 regions for men's life expectancy in 2002. The authors call for careful checks of ages and say some of the oldest ages may be wrong.
Life table analysis splitting Okinawa into pre-war and post-war generations. Older generations show a highly favourable mortality pattern; younger generations show mortality definitively higher than mainland Japan. Okinawa fell from 4th to 26th of 47 prefectures on male life expectancy in 2002. The authors call for in-depth age validation and name plausible invalidation of the age of some of the oldest.
Study in people2013
The Nicoya region of Costa Rica: a high longevity island for elderly males
Vienna Yearbook of Population Research
Researchers followed 16,300 older people in Costa Rica from 1990 to 2011. Men in the Nicoya region died at a lower rate than other Costa Rican men, mostly from fewer heart and blood vessel deaths. This did not hold for women, did not depend on wealth, and vanished in men who moved away. Their diet was plain, heavy on rice, beans and animal protein.
Survival follow-up of 16,300 elderly Costa Ricans. Nicoya male death rate ratio 0.80 (0.69 to 0.93) from 1990 to 2011, absent in females, independent of socio-economic conditions, gone in out-migrants, and driven by cardiovascular mortality at 0.65. Diet described as prosaic and abundant in rice, beans and animal protein.
Study in people2018
Amerindian ancestry and extended longevity in Nicoya, Costa Rica
American Journal of Human Biology
Researchers compared the genes of 20 Nicoyans aged 99 and over with 20 aged 60 to 65. The oldest group had more Native American ancestry, 43.3 against 36.0 percent. More of that ancestry went with better odds of living very long. It was forty people, and it points to ancestry rather than diet.
464 ancestry informative markers in 20 Nicoyans aged 99 and over against 20 aged 60 to 65. Amerindian ancestry 43.3 against 36.0 percent (p = 0.04), with each 10 percent increase associated with an odds ratio of 2.32 (1.03 to 5.25) for being long-lived. Forty people, and it points at ancestry rather than diet.
Study in people2013
Vegetarian dietary patterns and mortality in Adventist Health Study 2
JAMA Internal Medicine
This is the Loma Linda Adventist study, the only Blue Zone with a large modern study that followed people over time. It tracked 73,308 people, and 2,570 died. Vegetarians as a whole had a lower death rate. For vegans the drop was not clear, while vegetarians who ate fish did better. Diet was asked about once, at the start, and people chose what they ate.
The Loma Linda evidence, and the only Blue Zone with a modern prospective cohort. 73,308 participants, 2,570 deaths. All vegetarians combined HR 0.88 (0.80 to 0.97); vegans 0.85 (0.73 to 1.01), not significant; pesco-vegetarians 0.81 (0.69 to 0.94). Observational, single baseline food frequency questionnaire.
Study in people2007
Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world's longest-lived people and its potential impact on morbidity and life span
Annals of the New York Academy of Sciences
Researchers looked back over six decades of records on Okinawans aged 65 and over. When younger, they ate few calories and ate less than they burned. They gained little weight with age, stayed lean for life, had fairly high levels of the hormone DHEA when old, and rarely died of age related diseases. These are records for the whole group, not data on what each person ate.
Six decades of archived population data on Okinawans aged 65 and over. Low caloric intake and negative energy balance at younger ages, little weight gain with age, lifelong low BMI, relatively high plasma DHEA at older ages and low mortality from age-related diseases. Ecological analysis of archived records, not individual exposure data.
Review of studies2009
The Okinawan diet: health implications of a low-calorie, nutrient-dense, antioxidant-rich dietary pattern low in glycemic load
Journal of the American College of Nutrition
This paper describes what the traditional Okinawan diet was made of, next to the Mediterranean and DASH diets. It was the lowest in fat, especially saturated fat, and the highest in carbs, mostly from sweet potato and green leafy vegetables. It describes the diet and does not measure any health results.
Composition of the traditional pattern against Mediterranean and DASH. Lowest in fat, particularly saturated fat, and highest in carbohydrate, driven by sweet potato and green leafy vegetables. A dietary characterisation rather than an outcome study.
Animal study2016
New Horizons: Dietary protein, ageing and the Okinawan ratio
Age and Ageing
In insects and mice. The animals lived longest when they could eat freely on a low protein, high carb diet. The authors note its protein to carb ratio is almost the same as the traditional Okinawan diet. This is not evidence about people.
Animal work, reported separately from the human data on this page. Nutritional geometry studies in insects and mice found the longest lifespans on ad libitum low-protein high-carbohydrate diets, at a protein to carbohydrate ratio the authors note is almost identical to the traditional Okinawan one. Not evidence about people.
Study in people2011
Sociodemographic and lifestyle statistics of oldest old people (>80 years) living in ikaria island: the ikaria study
Cardiology Research and Practice
A survey of 1,420 people on the island of Ikaria in 2009, 187 of them over 80. Most said they were active every day, ate well, did not smoke, saw friends often and napped at midday. Very few were depressed. There was no comparison group and no health results were measured.
1,420 people enrolled in 2009, of whom 187 were over 80. The majority reported daily physical activity, healthy eating, no smoking, frequent socialising, mid-day naps and extremely low rates of depression. Cross-sectional questionnaire with no comparison population and no measured outcomes.
Review of studies2016
Blue Zones: Lessons From the World's Longest Lived
American Journal of Lifestyle Medicine
This is how the people who came up with Blue Zones describe it. It tells how a trip found the five regions, the shared habits they call the Power 9, and the community projects that followed. It is a story of the idea, with no new data and no comparison group.
The framing as its originators state it. Describes the expedition that identified the five regions, the Power 9 commonalities distilled from them, and the subsequent community projects. A narrative account of the concept, with no new data and no comparison group.
Review of studies2025
Lessons From the Blue Zones: There is No Silver Bullet (or Magic Pill) for a Long, Healthy Life
American Journal of Lifestyle Medicine
A 2024 keynote speech, published as a paper. It restates the Blue Zones method and the Power 9. It argues that long life comes from living where healthy choices are easy and automatic, not from chasing health through diet, supplements or exercise. That runs against how the idea is usually sold.
A 2024 keynote address, published as such. Restates the methodology and the Power 9, and argues that longevity comes from an environment that makes healthy choices easy and unconscious rather than from an intentional pursuit of health through diet, supplements or exercise. Notable because it argues against the way the framing is usually sold.

What people report

These are things people say about their own eating. Nobody checked them, so they are not evidence. They are here because they tell you what to expect and what to watch for, which the studies do not. They cannot tell you whether anything works.

Bean-heavy eating described as cheap, filling and easy to keep up, the most common positive report, and in line with what the plant-forward studies measure.
The social and purpose parts described as what people actually kept, with the food changes slipping first.
No measurable change in any blood test or other marker after taking up the pattern, reported often. That is no surprise, since it is a whole way of living, not a plan with a target.
Frustration that the pattern has no rules, no numbers and no end point, the most common reason people move to something more defined.
Disappointment after coming across the records criticism, reported more and more since 2024, often along with dropping diet changes that were sensible for other reasons.
Trouble hitting protein targets while training, reported by people who took the Okinawan ratio literally.
Cost and access for the specific regional foods, which the pattern does not require, though the marketing around it often implies it does.

Sources: Blue Zones Project community materials, general longevity forums, and the popular books and TV built on the idea, several of which have money riding on it. Note that the disclosure runs both ways here. Most of the supporting material comes from an organisation that sells the concept, and the main criticism is an unpublished study by a single author. Unchecked self-report throughout.

Who this is wrong for

Anyone treating the five zones as one diet. The Okinawan diet is heavy on sweet potato and about as low in protein as a recorded human diet gets. The Nicoyan one is described by its own researchers as rice, beans and animal protein. Loma Linda is Adventist vegetarian, and the Sardinian diet includes sheep dairy and wine. They contradict each other on the nutrient that matters most for ageing muscle.
Anyone over 65 reading the Okinawan protein ratio as a target. That ratio comes from stored diet records and from animal research. The expert paper on protein in older adults puts the floor for keeping muscle at 1.0 to 1.2 g/kg a day. No Blue Zone study measured muscle or muscle function in anyone.
Anyone who needs the underlying records to be right. The main criticism of this field is that the age records in three of the five zones are unreliable, and that criticism has not been peer reviewed. Read it, and keep that in mind.
Anyone expecting a diet effect. In the best-measured zone, the advantage is in men only, from heart and blood vessel deaths only, and it disappears in people who move away. That points at something about living there, not about eating that way.
Anyone buying a product because of it. The idea's own author said in a 2024 keynote that there is no silver bullet, and that what works is the environment, not chasing health on purpose through diet, supplements or exercise.
Anyone who wants an answer from a real trial. There is none. This is a description of populations, and the diet parts it points to are tested under their own names elsewhere on this site.

Questions

Are the Blue Zones real?: Two of them hold up well on modern records, and three are disputed. Nicoya has a follow-up of 16,300 older Costa Ricans showing men with a death rate ratio of 0.80. Loma Linda has a 73,308-person study showing a death risk score of 0.88 for vegetarians. Sardinia, Okinawa's oldest generation and Ikaria rest on older records. A study posted online since 2019 found those regions matched areas poorer and shorter-lived than their national averages, and that US records of the very oldest people fell 69 to 82 percent once states brought in birth certificates.
Has the records criticism been peer reviewed?: No. It has been on bioRxiv, a site for studies that have not been peer reviewed, since 2019, and was revised in 2024, but it has not been published in a peer-reviewed journal. That is a real limitation, and it does not make the analysis wrong. A narrower version of the same argument was published in PLoS Biology in 2018: errors in recorded ages, and in mixing birth groups, at rates below 1 in 10,000 are enough to make it look as if death rates level off in old age. A separate analysis of US Social Security records reached a similar conclusion.
What happened to Okinawa?: Its generations split. An analysis of life tables since 1975 found very favourable death rates in those born before the war, and death rates clearly higher than mainland Japan in those born after it. Okinawa fell from 4th to 26th of Japan's 47 prefectures for male life expectancy in 2002. The paper's own conclusion calls for careful checking of the ages of the oldest residents.
Is there a Blue Zone diet I can follow?: Not one, and that is the honest answer, not a dodge. The Okinawan diet is heavy on sweet potato and very low in protein. The Nicoyan one is described by its own researchers as rice, beans and animal protein. Loma Linda is Adventist vegetarian, and Sardinia includes sheep dairy and wine. What they share is high fibre, little processing and beans, and those are tested under their own names elsewhere on this site. No trial of any Blue Zone diet has been run.
If it is not the diet, what is it in Nicoya?: Nobody knows, and the data narrows it in interesting ways. The advantage is in men only, not in women, does not depend on income or social conditions, comes entirely from fewer heart and blood vessel deaths, and disappears in people who move away. A separate gene study of forty people found more Indigenous American ancestry in the oldest group, with 2.32 times the odds per 10 percent more ancestry. Moving away wiping out the effect points at something about living there. The ancestry finding points somewhere else entirely, and it rests on forty people.