SAN DIEGO (AP) — Six months ago, Jim Wiseman didn’t even have a spare nutrition bar in his kitchen cabinet.

Now, the 54-year-old businessman and father of five has a backup generator, a water filter, a grain mill and a 4-foot-tall pile of emergency food tucked in his home in the expensive San Diego suburb of La Jolla.

Wiseman isn’t alone. Emergency supply retailers and military surplus stores nationwide have seen business boom in the past few months as an increasing number of Americans spooked by the economy rush to stock up on gear that was once the domain of hardcore survivalists.

These people snapping up everything from water purification tablets to thermal blankets shatter the survivalist stereotype: they are mostly urban professionals with mortgages, SUVs, solid jobs and a twinge of embarrassment about their newfound hobby.

From teachers to real estate agents, these budding emergency gurus say the dismal economy has made them prepare for financial collapse as if it were an oncoming Category 5 hurricane. They worry about rampant inflation, runs on banks, bare grocery shelves and widespread power failures that could make taps run dry.

For Wiseman, a fire protection contractor, that’s meant spending roughly $20,000 since September on survival gear — and trying to persuade others to do the same.

‘‘The UPS guy drops things off and he sees my 4-by-8-by-6-foot pile of food and I say ’What are you doing to prepare, buddy?’’’ he said. ‘‘Because there won’t be a thing left on any shelf of any supermarket in the country if people’s confidence wavers.’’

The surge in interest in emergency stockpiling has been a bonanza for camping supply companies and military surplus vendors, some of whom report sales spikes of up to 50 percent. These companies usually cater to people preparing for earthquakes or hurricanes, but informal customer surveys now indicate the bump is from first-time shoppers who cite financial, not natural, disaster as their primary concern, they say.

Top sellers include 55-gallon water jugs, waterproof containers, freeze-dried foods, water filters, water purification tablets, glow sticks, lamp oil, thermal blankets, dust masks, first-aid kits and inexpensive tents.

Joe Branin, owner of the online emergency supply store Living Fresh, said he’s seen a 700 percent increase in orders for water purification tablets in the past month and a similar increase in orders for sterile water pouches.

He is shipping meals ready to eat and food bars by the case to residential addresses nationwide.

‘‘You’re hearing from the people you will always hear from, who will build their own bunkers and stuff,’’ he said. ‘‘But then you’re hearing from people who usually wouldn’t think about this, but now it’s in their heads: ’What if something comes to the worst?’’’

Online interest in survivalism has increased too. The niche Web site SurvivalBlog.com has seen its page views triple in the past 14 months to nearly 137,000 unique visitors a week. Jim Rawles, a self-described survivalist who runs the site, calls the newcomers ‘‘11th hour believers.’’ He charges $100 an hour for phone consulting on emergency preparedness and says that business also has tripled.

‘‘There’s so many people who are concerned about the economy that there’s a huge interest in preparedness, and it pretty much crosses all lines, social, economic, political and religious,’’ he said. ‘‘There’s a steep learning curve going on right now.’’

Art Markman, a cognitive psychologist, said he’s not surprised by the reaction to the nation’s financial woes — even though it may seem irrational. In an increasingly global and automated society, most people are dependent on strangers and systems they don’t understand — and the human brain isn’t programmed to work that way.

‘‘We have no real causal understanding of the way our world works at all,’’ said Markman, a professor at the University of Texas, Austin. ‘‘When times are good, you trust that things are working, but when times are bad you realize you don’t have a clue what you would do if the supermarket didn’t have goods on the shelves and that if the banks disappear, you have no idea where your money is.’’

Those preparing for the worst echo those thoughts and say learning to be self sufficient makes them feel more in control amid mounting uncertainty — even if it seems crazy to their friends and families.

Chris Macera, a 29-year-old IT systems administrator, said he started buying extra food to take advantage of sales after he lost his job and he was rehired elsewhere for $30,000 less.

But Macera, who works in suburban Orange County, said that over several months his mentality began to shift from saving money to preparing for possible financial mayhem. He is motivated, too, by memories of the government paralysis that followed Hurricane Katrina.

He now buys 15 pounds of meat at a time and freezes it, and buys wheat in 50-pound bags, mills it into flour and uses it to bake bread. He checks survivalist Web sites for advice at least once a day and listens to survival podcasts.

‘‘You kind of have to sift through the people with their hats on a little bit too tight,’’ said Macera, who said his colleagues tease him about the grain mill. ‘‘But I see a lot of things (on the Web) and they’re real common sense-type things.’’

‘‘I don’t want to be a slave to anybody,’’ he said. ‘‘The more systems you’re dependent on, the more likely things are going to go bad for you.’’

That’s a philosophy shared by Vincent Springer, a newcomer to emergency preparedness from the Chicago area.

Springer, a high school social studies teacher, says he’s most worried about energy shortages and an economic breakdown that could paralyze the just-in-time supply chain that grocery stores rely on.

In the past few months, Springer has stockpiled enough freeze-dried food for three months and bought 72-hour emergency supply kits for himself, his wife and two young children. The 39-year-old is also teaching himself to can food.

‘‘I’m not looking for a retreat in northern Idaho or any of that stuff, but I think there’s more people like me out there and I think those numbers are growing,’’ he said.