As a longevity researcher, I've spent the past 20 years studying the habits of people who live to 100 years old or longer, particularly the foods they eat.

And in a tucked-away corner of Nicoya, Costa Rica, I may have found the world's healthiest breakfast.

Under a red-tiled roof, a dozen or so people of the Cooperativa Nicoya wake each morning at 4:00 a.m. They stoke wood fires in clay ovens, put cauldrons of spicy beans to boil, and mix corn dough with wood ash.

A woman pinches off a golf ball-sized piece of dough on a piece of waxed paper and rotates it with mechanical precision into a perfectly round patty. She slaps it onto a hot clay plate, where it expands to a puffy disc before collapsing into a perfect tortilla.

At the other end of the stove, three others mix beans with onions, red peppers and local herbs. The beans cook slowly for about an hour to tender perfection and are then mixed with rice.

What makes this hearty longevity dish so healthy?

The corn tortillas, chewy with a nutty flavor, are an excellent source of whole-grain, low-glycemic complex carbohydrates.

The wood ash breaks down the corn's cell walls, making niacin (a B vitamin that plays a role in cell signaling and DNA repair) available, and freeing amino acids so the body can absorb them.

The black beans contain the same pigment-based anthocyanins (antioxidants) found in blueberries. They're rich, colon cleansing, blood pressure lowering, and insulin regulating, and they are filled with folates like potassium and B vitamins to boot.

The bean-and-rice combination creates a whole protein, which is to say all the amino acids necessary for human sustenance.

The coffee here, made from a local strain of "pea berry" beans, provides a boost of antioxidants plus metabolism-boosting caffeine.

The chilero, made with vinegar, carrots and searingly hot peppers, offers a probiotic boost to the breakfast along with curcumin, a compound shown to possess antioxidant, anti-inflammatory and anticancer properties.

Total cost of the breakfast: $4.23. A very fair price to discover Nicoya's secrets to longevity. You can do as the Nicoyans do — make a large batch of bean soup and then enjoy it all week

Nixtamal Tortillas

Nixtamal refers to corn that has been soaked and partially cooked with wood ash or lime. This releases the amino acid niacin in corn, which helps to reduce bad cholesterol and increase good cholesterol and also aids in digestion.

Corn itself is high in fiber, folate, and vitamins B and C. You can buy your nixtamal corn flour from the ethnic food aisle, from Mexican or Latin grocery stores, or online.

Total cook time: 15 minutes

Makes: 5 servings

Ingredients:

• 2 cups masa harina (corn flour)
• 1/4 teaspoon baking soda
• 1 1/2 cups warm tap water, plus more as needed
• Plastic wrap
• Waxed paper, as needed

Steps:

1. In a large bowl, whisk the masa harina and baking soda together.
2. Add water and stir until a soft dough forms (if the mixture won't form a soft ball of dough, add warm water in one tablespoon increments until it will).
3. Cover with plastic wrap and set aside for five minutes.
4. On a clean, dry work surface, knead dough gently for one minute. Divide it into 16 equal balls, each about the size of a small plum.
5. Roll out dough between pieces of waxed paper into 6-inch rounds.
6. Set a griddle or cast iron skillet over high heat until smoking.
7. Set dough on the griddle and cook for 30 seconds. Flip with kitchen tongs and cook until lightly toasted, with tiny bubbles in the tortilla, about 30 more seconds. Work in batches.
8. Transfer to a clean kitchen towel and wrap gently. Serve warm.

Technique tip: Cool any unused tortillas to room temperature and store in the refrigerator, tightly wrapped in a kitchen towel, for up to one day. Reheat on a baking sheet four to six inches from a heated broiler for 10 seconds.

Jose Guevara's Gallo Pinto

I last visited Jose Guevara in Costa Rica in 2015, when he was 105 years old. This recipe he gave me is his version of Costa Rican rice and beans, or gallo pinto.

The genius of the Costa Rican kitchen is its ability to make a humble bean dish so delicious that you could eat it every day. Many Costa Ricans eat it for breakfast, lunch and dinner.

It's often topped with eggs and Salsa Lizano (a bottled condiment, slightly sweet and acidic, that you can find on every restaurant table).

Total cook time: 20 minutes

Makes: 3 servings

Ingredients:

• 1 1/2 tablespoons vegetable oil
• 1 onion, chopped
• 1 clove garlic, minced
• 2 tablespoons Worcestershire sauce
• 1 1/2 cups cooked black beans (or one 8-ounce can black beans, drained)
• 3 cups cooked long-grain white rice
• Salt and pepper (optional)
• 1/2 avocado, sliced, for topping (optional)
• Chilero hot sauce (optional garnish)
• Chopped cilantro (optional garnish)

Steps:

1. In a large skillet, heat oil over medium heat. Add onion and sauté until it starts to soften, about four minutes.
2. Add garlic and cook for another five to seven minutes, or until vegetables are browned.
3. Add Worcestershire sauce and beans; turn heat to low and stir. Cook for two to three minutes more.
4. Add rice and stir to combine. Cook and stir until rice and beans are evenly distributed and heated through. Season with salt and pepper.
5. Top with sliced avocado, hot sauce and chopped cilantro, if desired.

Tender Bean, Potato and Onion Stew

Total cook time: 1 hour

Makes: 6 servings

Featured in almost every Nicoyan meal, black beans contain high levels of anthocyanins, the important flavonoids in red onions and blueberries, and have 10 times the antioxidants of an equivalent serving of oranges.

These one-pot meals are staples in Costa Rican kitchens. They are easy to make, high in nutritious vegetables and spices, and cost less than $1 a serving. Rich and hearty, they will serve as a main meal paired with corn tortillas or rice.

Ingredients:

• 1 pound dried kidney beans, soaked overnight (or three 15-ounce cans, drained)
• 1 cup low-sodium vegetable broth
• 1 chayote squash, diced
• 1/2 carrot, peeled and diced
• 3 red, orange, or yellow sweet peppers, seeded and diced
• 2 large potatoes, peeled and diced
• 2 teaspoons chopped culantro coyote
• 1 small onion, diced
• 2 cloves garlic, minced
• Salt and pepper (optional)

Steps:

1. If using dried beans, drain the beans; discard the soaking water.
2. Place beans in a large pot and add vegetable broth. Add water, as necessary, to cover beans. Bring broth to a boil; then immediately turn down to simmer. Cook for 25 minutes.
3. Stir in the rest of ingredients; cook for about 25 more minutes, or until beans are tender, stirring occasionally to keep from burning.
4. Add salt and pepper to taste before serving. Enjoy alone or with tortillas or rice.

Dan Buettner is an explorer, longevity researcher, National Geographic Fellow, and award-winning journalist and producer. He is also the author of the best-selling books "The Blue Zones: Lessons for Living Longer from the People Who've Lived the Longest" and "The Blue Zones Solution: Eating and Living Like the World's Healthiest People." Follow Dan on Instagram @danbuettner.

Don't miss:

• At 101 years old, I'm the 'world's oldest practicing doctor': My No. 1 tip for keeping your brain sharp
• Longevity doctor shares the No. 1 diet he follows to 'beat diseases and live longer': It's a 'unique blend' of foods
• I talked to 263 of the world’s longest-living people—their 9 ‘non-negotiables’ for a long, happy life

Want to be smarter and more successful with your money, work & life? Sign up for our new newsletter here

Get CNBC's free Warren Buffett Guide to Investing, which distills the billionaire's No. 1 best piece of advice for regular investors, do's and don'ts, and three key investing principles into a clear and simple guidebook.

This is an adapted excerpt from "The Blue Zones Kitchen: 100 Recipes to Live to 100" by Dan Buettner, published by National Geographic. Copyright © 2019 by Dan Buettner.