In the lexicon of rock, there is surely no more overused word than "baby". "Love" comes a close second, but - as in real life - "baby" comes first. Yet depending on how the word is phrased, it can sound either like a hollow cliche or full of promise. Bonnie Raitt, slide guitarist, and practitioner of roots, soul and blues music, knows the word inside out. Every time she uses it in a song she invests such a sense of sexual knowing in it that it takes a series of cold showers to rid the listener of the effect. "I'm a babe," she informed the world four years ago, at the age of 45. "I'm not a pop babe, I'm a real babe."

Currently supporting Eric Clapton on dates around Europe, the Bonnie Raitt who speaks to me from London professes that life on the road has changed for her over the past 15 years. The most radical point arrived over 10 years ago when she stopped drinking and staying up late. Prior to that, it was almost 20 years of partying. "When you quit drinking," she says in a soft Californian voice, "you flip that scenario around and travel at night. Then you have all day in the next city to bike around or meet friends, or do whatever you want. That's a pretty marked difference, but other than that life on the road is still as much fun, as thrilling, and as daunting. It's still something I must love or I wouldn't be doing it 30 years down the line. The lifestyle change is a necessary part of getting older, otherwise you'd probably kill yourself."

Raitt has grown into her voice, a cool, raspy, smoky instrument that drives the sensuality of her material as much as her effortless slide guitar work and lyrical wounds that weep adult experiences. From her late teens, she drank Jim Beam to give her voice what she calls "the patina of age". As she got older, she fell into disarray in both her personal life and career - a long-standing relationship with her bass player collapsed, and she was dropped by Warner after 16 years on the label. "Me and Van Morrison. We weren't cutting the mustard, so they gave us the big axe. And we're both doing so poorly because of it!" She puts a brave face on it now, but at the time it almost killed her career. "The day-to-day relationship with the record company staff was great, but the powers that be weren't into promoting my records. Perhaps I didn't have a beautiful enough visage or image. I didn't have a powerful manager behind me, and I didn't want to be a star. There wasn't that much of a drive to put someone like me on a commercial radio station, so the record company gave up. I'm not just blaming them - the climate of radio was moving away from the roots music that I do, when songwriters such as John Hiatt and Delbert McClintock weren't being recognised.

"Warner pulled the rug out from under my toes, which I thought was crummy, to put it mildly. It didn't show a lot of integrity for 16 years of a relationship, but I was happy to be out in the market place. Personally, it really devastated me, and financially it was not a fair thing to do to someone who makes a living touring."

Such events opened up a free-falling route into drink and drug habits. She admits to liking the lifestyle, and to having stopped only because it was no longer serving her well. "When you get into your thirties, you can't do the same things you did in your twenties. It eventually catches up. I don't know anyone that trashes themselves these days. I wasn't trashing myself regularly, but in terms of weight and coming back from colds, your immune system being down, and wasting time recovering from an all-nighter - that kind of thing is much harder to do at 37 than it was at 27."

Raitt had a number of other reasons to stop. Firstly, a fan passed her a scribbled note that read, "Bonnie, you got fat. What happened?" Secondly, The Artist (aka Prince) contacted her to co-write songs and appear in a promotional video with him. It was this, more than anything else, she has said, which halted her decline. She promptly checked into rehab and embarked on the 12-step programme, which radically altered her life. Apart from what she coyly terms "the lifestyle change" Raitt sees no differences in her life now compared to 20 years ago.

Very much a political person, Raitt was raised in a Quaker tradition that saw folk musicians as political activists. Initially influenced by The Weavers and later by Pete Seeger, Bob Dylan, and Joan Baez, the young blues guitarist read African Studies at college. In what is a nicely ironic touch, she is now on the board of the Rhythm & Blues Foundation, which helps to improve the financial condition, recognition and royalty rates of a generation of R&B pioneers to whom she feels we owe so much.

"I didn't invent R&B, but I make music based on it," she says. "About 10 years ago, I found that none of my heroes, none of the people that I have in my record collection, ever got a penny from their royalties to this day. I got involved with the R&B Foundation because it's morally the right thing to do. It's not a charity, it's justice. There's a big difference between being a do-gooder and trying to rectify things that are seriously wrong."

Such a sense of morality is rarely misplaced. Narrowing the focus on to men and women, and by extension the standards of morality between the sexes, is something that crucially informs her music. The fact that certain songs of hers are easily the most overtly sexual in the commercial blues/roots canon is clearly a bonus.

`I feel that way about them. That's why I like to sing them. I'm not going to say they're better than sex, but you do get to play for two hours, which you don't often get to do in your personal life! You can get pretty worked up, and sing lyrics that are calling for or expressing your deepest desires and hurts. It's very cathartic, and by the time I've finished my two and a half hour show, and sung Spit Of Love right into I Can't Make You Love Me, it is like a revelation, emotionally. You feel pretty complete. In no small terms it's therapeutic, even if you're not hurting inside.

"The other thing I want people to know is that some of these songs are written by men. It's amazing to me. I'm so thrilled to be able to show that side of the fact that men deeply understand those kinds of emotions in women. The cliche is that men don't understand, which is so limiting. We all have well-developed sides of male, female, child, adult and it's important to sing from all those sides."

Bonnie Raitt disagrees that music and sex are indivisible. She feels such an argument would be limiting to both. "Any art can express any emotion," she says. "Rock'n'roll, R&B, and the blues are incredibly sexy, and that's what the drive to create them came from - a quickening heartbeat, the thickening blood. Sex is not just about getting off. There are very deep waters that associate sex and the soul. All kinds of shadowy, frightening things, and ecstatic transcendental things. Great songwriters such as Paul Brady elevate the sexual relationship to the spirit. I don't want to sound like I'm religious, but it's an exultation."

Bonnie Raitt plays the Olympia Theatre on Friday, November 6th