Thin Evidence Base

If we go by the best available studies with the longest follow-ups, including an “unusually lean cohort” in the Oxford Vegetarian Study, then the ideal body mass index (BMI) for the longest life is probably between 20 and 22 (kg/m2). The residents of Okinawa traditionally landed exactly in the middle, namely at a stable BMI of 21. Although it was also considered good manners not to stuff yourself, the fact that they averaged only 1800 calories a day probably had more to do with the quality than the quantity of their diet. In fact, people on Okinawa ate larger amounts, but because whole plant foods have so few calories relative to their mass, it worked out to an 11-percent calorie reduction.

This mild, long-term calorie reduction may have contributed to their extraordinary survival rate, even if what perhaps weighed more heavily here was the fact that their diet consisted almost exclusively of plants. The only population group that lives even longer than the Japanese of Okinawa lives not only 98 percent but 100 percent meat-free.

The vegetarian Adventists in California “may have the highest life expectancy of any population ever formally described.” These men and women live to about 83 and 86 years, respectively. For women, that’s comparable to Okinawa, but the men in California live longer than those on Okinawa. At the very top were vegetarian Adventists who also lived healthfully because they exercised and didn’t smoke. They lived, on average, to 87 and 89 years, respectively. That’s ten to fourteen years more than the general population.

Red, White, and Blue Zone

Unfortunately, the longevity of the people of Okinawa is a thing of the past. There are now more than a dozen KFC outlets there, and since World War II, the saturated fat eaten there has tripled. They went from virtually zero cholesterol a day to the equivalent of a few Big Macs a day. They tripled their sodium intake and now suffer from a potassium deficiency just as massive as Americans do, which means they consume less than half the recommended 4700 milligrams per day. Within just two generations, the people of Okinawa have gone from the leanest Japanese to the heaviest. That’s why health experts are trying to persuade them to follow the Okinawa diet again.

The same can be said about almost all the other Blue Zones, for example those in the Mediterranean region: They are history. Today, only one Blue Zone still lives and thrives, namely the community of Seventh-day Adventists in Loma Linda, California. And one more aspect makes this zone special: It is not clearly bounded but rather surrounded by the rest of society. All the other Blue Zones were geographically isolated from the mainland, mostly islands, which made it easier to maintain their own dietary and lifestyle habits.

The diet in other Blue Zones was also economically driven; people were “forced” to eat more healthfully. For example, the average resident of Okinawa didn’t eat much meat, sugar, salt, cooking oils, or white rice because they simply couldn’t afford it. Okinawa was Japan’s poorest prefecture. After World War II, the sweet potato lost importance; from its position as a staple food, it fell to a share of less than 5 percent because imported white rice and bread displaced the healthier foods. In contrast, the United States, with an annual gross domestic product of more than 65 000 US dollars per capita, is among the richest countries in the world, but in life expectancy it ranks 45th. What can we learn from the Adventists in Loma Linda, the only still-active Blue Zone, right in our midst, who outstrip everyone else in life expectancy? How did they manage to maintain their healthy eating habits while surrounded by the excesses of the modern world?

The Adventists’ health philosophy is based on the Bible, which says the body should be treated like a temple. That’s why they have eaten vegetarian for more than 140 years. In that they are unique, because the majority of them eat no meat or only very little. In the Adventist Health Study-2, for example, which followed more than 100 000 North American Adventists for ten years, about 50 percent of participants lived vegetarian or vegan, and the other half ate meat on average only about three times a week.

Living Religiously

Seventh-day Adventists are a group of Protestant Christians. Does religiosity play a role? A survey of 1000 adult Americans found that 79 percent believed spiritual trust helps you get healthy. Is there a grain of truth to that? A meta-analysis of more than 70 studies on the topic concluded that the degree of religiosity or spirituality was associated with lower mortality rates in healthy populations, but not in ill groups, and there were indications of publication bias—that is, studies that did not portray spirituality positively may have quietly disappeared into a drawer.

Even if the association could be clearly demonstrated, there are important confounding factors. For example, (non-evangelical) Protestants and Jews have the lowest mortality among the largest religious groups in the United States, but they are also disproportionately white, affluent, and educated, and each of these factors contributes to longevity. In addition, the specter of reverse causation also looms here. In these studies, one factor used to measure religiosity is attendance at religious services, and you can imagine that illness prevents attendance.

Religious involvement has also been associated with longer telomeres, but the longest telomeres were found among the least religious people—for example, people who said they never pray or read sacred books like the Bible. Yet among those who were at least somewhat religious, those with closer spiritual involvement had longer telomeres.

Religiosity is often directly connected with lifestyle and its effects on health, for example deciding not to smoke or to drink only in moderation, which is typical of religious people, and in the case of Adventists, it involves a healthier diet. Do believers adhere more closely to lifestyle recommendations because they tend to follow behavioral rules more strictly? Many Adventist rules for plant-based eating and a particular lifestyle were implemented as part of the Complete Health Improvement Program (Pivio) for comprehensive improvement of health. This is the most far-reaching published lifestyle intervention of a community in the medical literature. (In the section on the optimal weight-loss program in How Not to Diet, you can learn all about it.) The influence of religious affiliation on adoption of the program was tested in a group of 7000 participants.

Although Adventists make up less than one percent of the total US population, one in five study participants was a member of this church. How did they do compared to nonbelievers? Massive reductions in cardiovascular risk factors were seen in Adventists as well as others, and some improvements were actually greater among non-Adventists. From this the researchers concluded that Seventh-day Adventists “do not have a monopoly on health …”.

Fertility versus Longevity?