LOS ANGELES — There have been days since her son Ezekiel was born 11 months ago that Los Angeles mom Beth Capper has gone without food to keep up her supply. One friend was arrested for stealing some.

It’s not drugs or alcohol or even baby formula that has put her in such a bind. It’s diapers.

“There’s no way around buying them,” said Capper, a 41-year-old single mother who doesn’t work because of a disability.

Across the country, mothers like Capper are facing the same predicament. According to a report published Monday in the journal Pediatrics, diaper need — the inability to afford to keep a child in clean diapers — affects a “substantial” number of low-income Americans, with nearly 30 percent of mothers questioned in New Haven, Conn., reporting that they did not have enough for their children.

It’s a problem that often goes unnoticed.

“I call it the silent epidemic,” said Caroline Kunitz, who runs L.A. Diaper Drive, which will distribute 1.5 million diapers this year.

Parents in need can get subsidized health care through Medicaid and subsidized food through the Special Supplemental Nutrition Program for Women, Infants and Children. But there are few places to turn when they need help paying for diapers.

Keeping a young child dry and clean can cost a pretty penny; the average is $18 a week. A single mother earning $15,080 a year in a minimum-wage job would need to devote more than 6 percent of her pay to diapers, according to the Pediatrics study.

Add in the fact that many lower-income families can’t afford to buy diapers in bulk at stores like Costco and Target and the expense becomes prohibitive. Cloth diapers are often not an option because they require frequent and expensive trips to the laundromat.

Fanning out across New Haven to schools, stores, bus stops, beauty parlors and other locations where mothers might congregate, the research team asked women about their health, medical care, use of social services and access to basic needs such as food, housing and diapers.

They found that 27.5 percent of the women in the study reported diaper need. They didn’t have enough to change their children as often as they’d like, and they had turned to social service agencies, friends or family for help or had “stretched” the diapers they had.