Viola Crowson does daily stretching exercises to keep her muscles strong and flexible.Viola Crowson does daily stretching exercises to keep her muscles strong and flexible. (Forbes.com)According to the U.S. Census Bureau, there are about 500,000 centenarians in the world, and almost 100,000 in the United States. And the population is rapidly growing.

The agency projects by 2050 there will be 1.1 million centenarians in America alone. Meanwhile, researchers at Boston University predict there will be even more, estimating some 3 million baby boomers will live to be 100 or older.

This begs the question: How can you live healthfully into your 100s? Experts say having good genes is half the battle, but lifestyle clearly contributes too.

ForbesWoman asked current 100-year-olds to share their secrets for healthy living. Medical professionals insist that beginning these practices early can easily add decades to your lifetime — though it's never too late to start.

You are what you eat

Daisy McFadden, a longtime resident of the Bronx, N.Y., will celebrate her 100th birthday this November. Still active and alert, she believes her eating habits have greatly contributed to her longevity. For years she's eaten a breakfast of oatmeal, cranberry juice and a banana. For lunch she usually has a salad with beets, cucumbers, tomatoes and either chicken or fish. Dinner is a plate of steamed vegetables and lean meat. Fresh fruit often follows for dessert.

Her diet resembles that of the people of Okinawa, Japan, a community with the world's largest concentration of healthy centenarians. The Okinawa diet is high in grains, vegetables and fish. It's low in eggs, dairy and meat. Okinawans also drink a lot of water.

"I don't drink soda at all, and never have," says McFadden, a retired nurse. Instead she opts for milk, water, juice or iced tea. She doesn't drink alcohol much anymore, but says that throughout her life she occasionally had a glass of wine or a Bloody Mary.

McFadden's doctor, David Prince, M.D., director of cardiac recovery at Montefiore Medical Center in New York, says McFadden is doing it right. "There is not enough fiber or vegetables in the American diet," he says. "If you eat more fiber, fruits and vegetables, it will push out the bad stuff." Plus, Prince agrees that just about anything is better than soda — including diet soda — and notes that studies show having two to three alcoholic drinks a week can extend your life.

Got a perpetual sweet tooth? Don't despair. Occasionally indulging will keep a smile on your face well into old age. McFadden says she can't live without chocolate chip cookies and eats them regularly. Louis Sussman, 101, has eaten a scoop of chocolate ice cream almost every day for as long he can remember, and Viola Crowson, 100, breaks up a steady diet of lean meats and leafy greens with the occasional brownie or a Hardy's hamburger.

"It's important not to feel deprived," Prince says. "Have a treat once or twice a week, but maintain portion control. The simplest rule is to split what you like with a friend."

Simple exercise makes a difference

"If you want to live to be 101, you have to live an active life both mentally and physically, and you do not want to be overweight," says Eric Rackow, M.D., professor of medicine at New York University and chief executive of at-home health care provider SeniorBridge.

Crowson, who lives in Alabama, says she gets fully dressed every morning. She doesn't take any prescription drugs, still cooks for herself — three squares a day — and keeps her house immaculate. She busies herself with chores like raking leaves, vacuuming and scrubbing dishes, and every two weeks gets a manicure and a haircut. For most of her life, and well into her 90s, she walked to and from church every week. Now she does daily stretching exercises to keep her muscles strong and flexible.

McFadden also enjoys regular exercise. As a New Yorker, she spent most of her life walking to work. Today she goes to her local senior center at least three times a week to walk on the treadmill, bicycle or use a rowing machine.

'I believe in being happy and enjoying life, and I love to be with other people.'—Mary Malecha

In South Carolina, Opal Prater, 99, enjoys Wii bowling, and Mary Richardson, 98, cares for all the indoor and outdoor plants in her retirement community on a daily basis. Harry Fox in California, 95, still likes to dance. And Elizabeth Louis of Maryland, 97, spends time working on her art.

Prince says that regular activity is one of the strongest predictors of a long, healthy life, and it doesn't have to entail gym visits. "Walk more, carry more and take the stairs," he advises.

Studies show that focused attention, like doing puzzles or reading, will help keep your mind young. Every day McFadden wakes up at 5 a.m., reads the newspaper and completes a crossword puzzle. Every evening she watches Jeopardy and plays along. Likewise, Sussman reads his newsweekly cover-to-cover every week. "People who have those lifelong interests have better mental faculties throughout their lives," Prince concludes.

Enjoy yourself!

"We live in a stressful world," says Rackow. "You need to be able to take time for yourself and enjoy what you do."

For most of the pre-retirement population, that means reducing job stress and finding meaningful work. In Fort Lauderdale, Fla., Sussman looks back on his job change early in life. After working what he calls excruciatingly long days as a pharmacist and store owner, Sussman's wife suggested he do something more fun. So in 1946 he started his own business selling ice cream, a venture that was less stressful and more profitable. It allowed him more family time, and eventually the time and money to travel the world with his wife.

Which brings us to the next healthy-living staple: "Stay married," says Rackow. Studies show that married people live longer, healthier lives, which probably can be attributed to the psychological benefits of having close peer relationships. Experts agree that having good friends and family is key to reaching age 101.

Mary Malecha, 103, of Minnesota, has surrounded herself with friends her entire life. She says her fondest memories are from when she was 19 and recently married, spending most of her time with friends and at dances. For the next several decades she had a core group of girlfriends she could laugh with. She stills regularly visits with friends, playing games like Uno and Bingo. "I believe in being happy and enjoying life, and I love to be with other people," she says.

Malecha also keeps healthy spiritually; for her entire life she has prayed every morning and evening. In fact, a recent survey of centenarians by health care provider Evercare found that 62 per cent of the 100-plus crowd prays, meditates or engages in another spiritual practice every day. Maintaining a positive attitude and taking time for introspection will increase your odds of long-term health.

And despite industries devoted to wrinkle creams and hair dyes, age is a blessing after all. McFadden says, "I don't fear age. If you don't get old, you die young."