NEW YORK (CNS) — Quite a few stand-up comedians are known for their off-color language. So it's perhaps no surprise that some gratuitous vulgarity crops up in "The One and Only Dick Gregory," which premieres on Showtime Sunday, July 4, 9-11 p.m. EDT.

Considered as a whole, however, the program registers as a fascinating and affecting portrait of the titular performer who, in addition to his work in show business, also was a social activist and health guru.

African American filmmaker Andre Gaines wrote, directed and produced the profile. Its executive producers include actor Kevin Hart and former "Saturday Night Live" cast member Rob Schneider, both of whom also appear as commentators.

The phrase "the one and only" is a standard way to introduce comics before they take the stage. But it aptly describes Gregory, who — always evolving — was a true original.

The film begins with a 1963 encounter between Gregory and New York Times journalist Robert Lipsyte. At the time, Gregory — who died of heart failure in 2017, aged 84 — was the highest paid comic in the country. The then-25-year-old sportswriter had been hired to help him pen his autobiography.

Lipsyte, now an octogenarian, recalls finding the wealthy, famous man curled up in the fetal position on his hotel bed, weeping. Gregory was mourning the four African American girls killed a day earlier in the bombing of 16th Street Baptist Church in Birmingham, Alabama, by white supremacists. Gregory, Lipsyte observes, "had missions to accomplish. He wasn't just making jokes."

Gregory's life had been transformed the year before by an invitation from fabled civil rights leader Medgar Evers to come to Mississippi in support of a voter registration drive. According to biographer Sheila Moses, "From the moment he went to Mississippi, he never stopped putting his life on the line" for the cause of racial equality.

In 1967, Gregory engaged in a 40-day fast — the first of many he would eventually undertake — to call for an end to the Vietnam War. That experience changed his life in a different way. His weight dropped from 288 pounds to 98, and the former smoker turned himself into a health advocate.

Gregory developed a concoction of vitamins and nutrients called the 4X formula, which he believed could solve the problems of hunger and obesity. 4X became the foundation of what Gregory dubbed the Bahamian Diet.

Its popularity in the 1980s made selling the regimen a lucrative venture. Eventually, though, in-fighting between Gregory and his partners precipitated the former's economic decline.

Mature themes as well as the crudity already mentioned suggest an adult audience for the show. Grown viewers will appreciate the price Gregory was willing to pay to advance his ideals as well as the question he proposed as the measure of each person's legacy: "How much service did you give to your fellow human beings?"