If you could do just one thing for your health, says this doctor, it would be to make seasonal, farm-fresh produce the center of your diet.

If you could do just one thing for your health, says this doctor, it would be to make seasonal, farm-fresh produce the center of your diet.

On a sunny Friday, Preston Maring, M.D., the associate physician-in-chief at Kaiser Permanente's Oakland hospital, leaves his office to go food shopping. Just downstairs, on the sidewalk in front of the hospital, a farmers' market is in full swing. Roberto Rodriguez is arranging flats of organic strawberries so fragrant you can smell them from 10 feet away. In the stall next door, stalks of rhubarb and artichokes are piled high near bouquets of garden roses. On a table, paper bags are overflowing with a potpourri of market produce and flowers. "Pick-of-the-market bags," Maring explains. "If you are too busy to shop, you can just reserve one of these." Everywhere, people are smiling and saying, "Hey, Preston!"

If it seems as if Dr. Maring, a tall, graying man, knows everyone at this farmers' market it's because he does: he started it. In 2003, Maring helped to get this market off the ground and then persuaded Kaiser to start farmers' markets at 30 other hospitals. Says Maring: "If we can just get people to eat more fresh fruits and vegetables, we can really impact people's health."

He also set about revamping the hospital food system by getting the health-care company to buy more fresh produce from local farms. In 2006, Kaiser Permanente purchased only 25 of the 250 tons of produce served in 20 Northern California hospitals from local farms. In three years, that amount has risen to 74 tons. The Kaiser project now serves as a model for hospitals around the country and is part of a worldwide initiative to make health care more sustainable, called Health Care Without Harm.

This and other farmers' markets not only cut down on the average 1,500 miles food travels from farm to fork, they also help create local jobs. Strawberry farmer Roberto Rodriguez has hired five more people since Kaiser's Oakland market started, and devoted half of his 37 acres to growing organic berries. "As my 6-year-old daughter gets older, I don't want her playing in fields near so many pesticides," he says. "Now, with the market here, I have buyers for organic strawberries so I can plant almost half my crops organic."

But the most important thing is that the market has done what Maring hoped it would do: it has made people healthier. Take Matt Kinch, the 53-year-old building engineer who has lost 63 pounds since he began shopping at the farmers' market. "Now I have at least two vegetables per meal based on whatever is in season," he says.

In a time when the words antioxidants, omega-3s and probiotics appear on so many packaged foods, Maring's advice to eat more vegetables may seem a little quaint. Yet it's the same message being sent out by dozens of national health organizations. "We know that eating fruits and vegetables as part of a healthy diet reduces the risk of obesity and chronic disease, such as diabetes, some cancers and heart disease," says Heidi Blanck, Ph.D., a senior scientist with the Centers for Disease Control and Prevention. In 2000, national goals were set by federal health agencies of getting more than half of Americans to eat five daily servings of fruits and vegetables by 2010. Yet, according to the CDC's biennial surveys, fruit and vegetable consumption remained essentially static from 1998 to 2007, and latest figures show that fewer than one in four Americans are eating the recommended five a day.

"Think what would happen if more people shopped for their food at farmers' markets-eating the fruits and vegetables as they become ripe each season," Maring continues. "People would discover just how good fresh produce can be-apricots that are picked ripe are so much tastier and more nutritious than those that have to be picked hard to endure shipping," he notes. "Plus, these markets inspire people to try new vegetables, such as kohlrabi or mustard greens, and to cook more at home."

Which is exactly what Maring loves to do. Ever since his son, a trained chef, showed him a few recipes and inspired him to cook more, Maring has become an ardent home cook. Tonight, for instance, he'll take what he's found at the market-some spring leeks, artichokes, carrots in his basket-and make an EatingWell recipe: "Spring vegetable stew," he says, smiling. Followed, perhaps by the Apricot-Almond Clafouti. His shopping is done.

We were so inspired by Dr. Maring's story that we collaborated with him to produce our latest cookbook, EatingWell in Season: The Farmers' Market Cookbook (The Countryman Press). In it, you will find our favorite recipes, organized into seasonal chapters, that include the fruits and vegetables you might pick up at a farmers' market or as part of your community-supported-agriculture share. The book also has a handy guide with shopping, prep, storage and cooking tips for more than 60 fruits and vegetables. Plus we include recommendations for our favorite kitchen tools, profiles of farmers and farmers' markets and information on why eating in season is better for you and for the environment.