In The Guanacaste Journal, a study was reported stating that Nicoyans are among the people who reach the highest lifespan in the world. To follow up on this topic, several theories have been proposed to try to explain this phenomenon; one of them is the so-called "Blue Zones."

A Blue Zone is a particular place in the world that has special conditions for people to live many years, even beyond 100; that is, good health conditions that are passed from parents to their children. So far, four hot spots of longevity have been identified: the mountainous Barbagia region of Sardinia, an island off the coast of Italy; the Japanese island of Okinawa; a community of Seventh-day Adventists in Loma Linda, Calif., about 60 miles east of Los Angeles; and the Nicoya Peninsula of Costa Rica, in Central America. Last November, Oprah Winfrey and Dr. Oz spoke with Dan Buettner, a National Geographic independent writer who has been researching these special regions of the world for seven years, and who wrote about them in his book Blue Zones: Lessons for Living Longer From the People Who've Lived the Longest. He appeared on the Ophra Winfrey show to talk about his research.

Buettner said one of the secrets of Nicoyans' lifespan can be found in the water that flows through the hills. Their water is among the hardest in Costa Rica, which means it's chock-full of minerals. "Hard water means stronger bones. It also means your muscles are probably working better, especially when you get old," he said.

Dr. Oz said hard water has proven benefits. "Calcium, magnesium and water — it relaxes your arteries, it builds bone strength and it has a huge benefit across the board in how your body functions," he explained.

Having strong bones is actually one of the most important ways to live a long life. "One of the biggest killers of older people in this country is simply falling down and breaking a bone," Buettner said. "If you take calcium and couple it with vitamin D, your bones don't deteriorate as quickly."

Families stay together in Nicoya, which is another important key to living a long life, Buettner and Dr. Oz explained. During their visit to Guanacaste, both corroborated first hand the customs of Nicoyans, such as preparing tortillas after having processed corn on stone metates like their Mesoamerican ancestors used to do.

Buettner and Dr. Oz featured the 65-year-old daughter of a centenarian. For lunch, she made them corn tortillas from scratch. First, she soaked the corn in ash and lime to break it down. Then, she smasheed it in the metate. Then, she cooked the corn patties without oil. "It's a lot of hard work, and there's no electricity, so she can't do it any other way," Dr. Oz said. "And it's a good workout."

Another crucial factor to Nicoyan longevity is diet. On his land, another centenarian, Jose, has 14 different kinds of trees that produce ripe fruit all year long.

But the real secret may be in what Buettner calls the "Mesoamerican trifecta" that is the predominant diet in much of Central America — and has been for 3,500 years. The diet consists of lightly salted corn tortillas, beans and squash. "It's arguably the best longevity food ever invented," Buettner said.

Another important aspect of the Nicoyan diet is that they tend to eat their larger meals in the morning, with progressively smaller meals throughout the day. This not only leaves Nicoyans craving fewer calories during the day, it also lets them transition into sleep much more easily when darkness falls.

"A hundred years ago, when the sun went down, the brain would start making more melatonin. And with more melatonin, you'd get tired, you'd get drowsy," Dr. Oz said. "Today, the reason half of us don't sleep normally is because the last thing we see is a computer screen or the tube. That actually does the opposite to your brain — it stimulates it. So of course you can't fall asleep. You've got to glide to sleep."

During their visit to Guanacaste, both Buettner and Dr. Oz had the chance to meet several Nicoyans, such as Pachita (102 years old), Felipa (86), Serillo (95), Patron (107), and Jose (99), who exemplified the lifestyle of the Blue Zones.