WASHINGTON — Cynthia Heimel, a humor columnist whose biting, ribald commentary on sex, romance, and late-century womanhood were collected in books including ‘‘Sex Tips for Girls’’ and ‘‘Get Your Tongue out of My Mouth, I’m Kissing You Good-Bye,’’ died Feb. 25 at an assisted-living community in Los Angeles. She was 70.

The cause was complications from dementia, said her son Brodie Ransom. Ms. Heimel had been diagnosed about a year ago.

In her books and columns, Ms. Heimel wrote about bad boys, bad dates, bad sex, and bad birth control, with the occasional reminiscence of blissed-out pleasure thrown in. ‘‘God protects drunks, infants, and feisty girls,’’ she once observed, and in a tumultuous, three-decade writing career, she was feistier than most.

‘‘Everyone in the world seems to think that they are codependent and that they come from dysfunctional families,’’ she wrote in one 1989 column for Playboy. ‘‘They call it codependency, I call it the human condition.’’

Comparing her favorably to the noted wit Dorothy Parker, New York Times culture critic Stephen Holden once wrote that Ms. Heimel was ‘‘an urban romantic with a scathing X-ray vision that penetrates her most deeply cherished fantasies.’’

For her part, Ms. Heimel described herself as a ‘‘card-carrying hippie,’’ absent the snotty self-righteousness she saw in other aging members of her generation.

In her 20s, she supported herself and her son on child welfare payments as well as occasional paychecks from freelance writing and secretarial jobs. She was working as an assistant in the advertising department at the now-defunct SoHo Weekly News in the 1970s when she published her first major story — an article about an anarchists’ conference in New York. The activists, she noted, seemed to miss the irony of their organized gathering.

Ms. Heimel soon turned to sex, focusing on what she described as a lack of self-esteem among young women and a society that had, she wrote, ‘‘taught women to hate themselves.’’

For readers of Vogue, the Village Voice, Playboy, and New York magazine, she became a conduit to the women’s issues of the day, a sexual ambassador for men, and an inspiration for women.

‘‘You must just acknowledge deep in your heart of hearts that people are supposed to [have sex],’’ Ms. Heimel wrote in her best-selling first book, ‘‘Sex Tips for Girls’’ (1983), using a characteristically blunt four-letter word. ‘‘It is our main purpose in life, and all those other activities — playing the trumpet, vacuuming carpets, reading mystery novels, eating chocolate mousse — are just ways of passing the time until you can [have sex] again. Well, maybe not eating chocolate mousse. If it is made with good Swiss chocolate and topped off with Devon cream, eating chocolate mousse is almost as good as [having sex].’’

Ms. Heimel ‘‘taught so many of us women who came up after her to talk about sex without shame,’’ said Anna March, publisher of the online feminist magazine Roar. ‘‘We don’t always stop to think about how revolutionary that was, but 30 years ago when I was 18, it sure was.’’

Cynthia Joan Glick was born in Philadelphia on July 13, 1947. Her father worked in pharmaceutical sales, and her mother — sometimes described in Ms. Heimel’s columns as ‘‘my enemy,’’ the upbraiding parental force who insisted she lose weight, find a man, and fix her hair — was an administrative assistant at Temple University.

She attended Cheltenham High School in Wyncote, Pa., where her classmates included future Israeli Prime Minister Benjamin Netanyahu, and ran away from home at 17 to immerse herself in painting and the arts. She also dabbled in journalism, working for several years as a contributor to the Distant Drummer newspaper in Philadelphia.

After having a son in 1970 with her first husband, radio broadcaster Steven Heimel, she kicked around in communes in London before settling in New York and becoming art director at the SoHo Weekly News. She also had a short-lived stint as a columnist at the New York Daily News, where she said an editor once summoned her to his office and scolded her: ‘‘Our readers are slobs. You have to write slobbistic.’’

Ms. Heimel, who soon quit to write her first book, discussed sex on late-night television with Jay Leno and David Letterman, adapted her first book into a play, ‘‘A Girl’s Guide to Chaos,’’ and published the collections ‘‘But Enough About You’’ (1986), ‘‘If You Can’t Live Without Me, Why Aren’t You Dead Yet?’’ (1992), and ‘‘If You Leave Me, Can I Come Too?’’ (1995).

She also wrote for the television sitcoms ‘‘Dear John’’ and ‘‘Kate & Allie,’’ which Ms. Heimel said nearly drove her to become an alcoholic, and in 2003 published a sequel to her first book, ‘‘Advanced Sex Tips for Girls: This Time It’s Personal.’’

Her marriages to Heimel and journalist Abe Opincar ended in divorce. In addition to her son, of Los Angeles, she leaves a sister and four grandchildren.

Ms. Heimel said she struggled with depression, and for years her columns were filled with self-deprecating barbs and acknowledgments that the confidence and poise she urged upon other women was not something she always possessed. Even the art of loving another person, which formed the backbone of her work, was something she said she ‘‘figured out’’ only ‘‘too late.’’

Still, she wrote in ‘‘If You Can’t Live Without Me,’’ ‘‘I regret nothing. I’m miserable because I was one of the first, and I believe that women my age are a sacrifice to the future. It’s not going to be the same for our daughters. They will have a much better chance of ‘having it all.’

‘‘Whatever that means.’’