It's cool inside the Missoula Food Bank on a recent hot August day. Cans of beans, tomato soup and jars of peanut butter line the shelves of the nonprofit's Third Street store.

When the $80 that M. Buck, 58, receives each month from the Supplemental Nutritional Assistance Program runs out, she gets a three-day emergency food supply from the food bank. It goes quickly. "I'm like halfway through the month when I run out of food stamps," she says.

Buck, who has bipolar disorder, receives $842 from Social Security disability each month. But even with SNAP and Social Security, her income falls below the federal poverty threshold. That leaves her among a growing contingent of Missoulians over the age of 55 who report that they they don't know from day to day whether they'll have enough to eat.

"The increase in need in the senior population is outpacing every other demographic," says Missoula Food Bank Community Relations Director Jessica Allred.

Nearly 16 percent more seniors drew emergency supplies from the food bank this spring than during the same period last year. The pantry is on track to serve more than 9,500 clients over the age of 55 in 2012.

Elder advocates and social service providers say elderly people across the nation are having a tougher time making ends meet. Nationally, food insecurity among elderly Americans increased by 78 percent between 2001 and 2010, according to the Meals on Wheels Association of America. In 2010, nearly 15 percent of all American seniors weren't sure from day to day if they'd have access to food.

"They're a silent community," says Missoula Aging Services's Senior Nutrition Program Manager Curtis Hammond. "But they're there."

Missoula Aging Services, through the Meals on Wheels Program, serves homebound seniors and those who can't shop for or prepare food. Last year, the nonprofit provided 63,900 meals to people over the age of 60.

Montana is positioned to be especially hard hit by a glut of graying Baby Boomers, also known as the Silver Tsunami. The U.S. Census projects that a quarter of the state's population will be composed of elderly people by 2030. That's up from about 15 percent in 2010.

According to the AARP, 18 percent of Montanans 50 years and older now live below the poverty level.

Minkie Medora is a dietician who serves on the Montana Food Bank Network board of directors. She also chairs the Food Security Council, the advocacy arm of the Montana Food Bank Network's board. Between 2009 and 2011, she says, there was an 15.6 percent jump in demand for food among the elderly at Montana food pantries.

Seniors on fixed incomes, including Social Security or pensions, are most likely to experience food insecurity, Medora says. The cost of living is going up and incomes are not. That leaves seniors prioritizing needs that are nearly impossible to rank, such as rent, heat, medicine and food.

"As a nutritionist, I really get concerned," Medora says.

When seniors miss meals, nutrition deficits leave them more prone to illness or injury. Medora says that increases the likelihood they'll end up in the hospital or require long-term care. "It starts a downward spiral," she says. "The cost of keeping a senior in their own home is so much less than keeping them in long-term care."

Even taking into account increases in demand at Montana food pantries, social service providers say there's likely a significant segment of Montanans who, fearful of stigma or limited by other barriers, haven't come forward to ask for help. "What we see more so with the senior demographic," Allred says, "is the pride issue, the stigma. And really, they've probably been needing the help for a lot longer than they've actually committed to coming here."

To better quantify hunger in the community, the Missoula Food Bank is launching a needs assessment to identify existing barriers to food access and form new strategies to address them. "There are things that lead us to believe that there is more probably more need out in the community than we maybe know about," Allred says.

As for Buck, she says when she first decided to seek emergency food assistance, it was tough. "It just really hurt my pride," she says. "I really did have a lot of unease and just embarrassment."

These days Buck volunteers at the Food Bank. She tries not to think too much about her own food insecurity or that of others, those who shop alongside her in the food pantry's air conditioned aisles. "I would be really defeated," she says.