Media playback is unsupported on your device Media caption Three people talk about using food banks: "It means I can eat, it means I can get healthy"

The first time Donna Kennedy visited a food bank, she hung around outside for 20 minutes, gathering courage to go in.

Once a health worker, Donna, from Maghera, Londonderry, could not earn after a series of mini-strokes.

"It was so embarrassing," she says. "I'd been the person providing for the family for so long."

Now a three-year study, focusing on more than 1,000 food-bank users, suggests three-quarters are from homes affected by illness or disability.

The UK-wide project, by researchers from Heriot Watt University with input from the Department for Work and Pensions, was commissioned by the charity Trussell Trust.

Its first annual report indentifies three key elements that leave people "no protection from hunger and poverty":

problems with the benefits system

ill-health and challenging life experiences

too little local support

Donna, 47, is a single mother with two adult children and a 10-year-old son.

Her mini-strokes, five years ago, affected her mobility.

Image copyright Donna Kennedy Image caption Donna worked in hospitals before becoming ill

At first, she borrowed money, "which I know they didn't have", from family members.

And without the food bank, she says: "I don't think my mental health would have coped with it at all."

About one in five food-bank users is a single parent, compared with about one in 20 of the working-age population overall, the research suggests.

The researchers also found many people using food banks had an income of just £50 a week after rent, with almost one in five having no money coming in at all in the month before being referred for emergency food.

The researchers also found most people referred to food banks had experienced a challenging life event in the previous year.

At Hammersmith and Fulham Food Bank, in west London, "Sally", who asked BBC News not to use her real name, says her husband died a year ago.

Aged 50, she had had a good job at the local council but long-term illness and the death of her husband had pushed her into destitution.

"Some nights you get starving," she says. "I've had zero in my cupboards until I came here.

"It means you can eat. It means I can get healthy."

Two-thirds of the food bank users questioned said they had encountered problems with benefits in the past year, including:

reductions in payments

being refused disability benefits

being sanctioned, so benefits were cut

delays to payments, for example the five-week wait for universal credit

In west London, one man, Otis Taylor, says he had been on and off benefits for a year while freelancing as a graphic designer.

When sanctions were put on his benefits account, he was left with less than £50 a month to live on.

Another, Douglas, 32, who works as a builder or handyman when he can, is homeless - either sofa-surfing or sleeping rough.

"Being on the universal credit, you are living on the breadline, so any sort of help is appreciated," he says.

The Trussell Trust wants an end to the five-week wait for universal credit and for benefits payments to cover "the true cost of living".

Funding for crisis support from local councils should be ring-fenced and increased, it says.

"Hunger in the UK isn't about food, it's about people not having enough money," says chief executive Emma Revie.

"Any of us could be hit by a health issue or job loss."

Ms Revie says a key question is why the incomes of people at food banks are so low, despite being supported by the benefits system.

"Our benefits system could be the key to unlocking people from poverty, if our government steps up and makes the changes needed," she says.

"How we treat each other when life is hard speaks volumes about us as a nation."

In a statement, the Department for Work and Pensions said it took the report very seriously and continued to work closely with the Trussell Trust on the issue.

"We spend more than £95bn a year on the welfare safety net but we continue to make improvements to get people the support they need and prevent them falling through the cracks," it said.

"Already we have simplified the benefits system with universal credit, making it easier for people to access support - and this week we have announced working-age benefits will rise in line with inflation from April, giving millions of people more money in their pockets."