Olivia Newton-John, devoted to healthy diet

My goodness, Olivia Newton-John looks incredible. She's all glossy, with shining eyes, and radiates that natural, healthy beauty that only Australians seem to have.

She tells me she is 63 - 63! - but she could easily pass for a decade or so younger. I suppose it has always been this way. When she was 29, she played a 17-year-old - Sandy in the 1978 film adaptation of the Broadway musical Grease. "I remember when I got the part, I thought, 'I'm way too old for this!' They had to sew me into the leather trousers. But now, of course, I look back at the film and think, 'Why didn't I realise how young I was?' I mean, 29…" she lets out a puffing sound. "It's nothing!"

To look at Newton-John, you'd never know that 20 years ago she was diagnosed with breast cancer (the same weekend that her father died of cancer). Then again, she does not strike me as a woman who would be given to self-pity. She underwent a partial mastectomy and breast reconstruction, and now calls herself a "cancer thriver". She won't talk about being in remission, "because that makes it sound as if it is still lurking. I'm not in remission - it's over."

The first time I met her was in 2008, when she was three weeks into a 142-mile charity walk of the Great Wall of China. It was a gruelling trip, with long days and long nights sleeping in tents in the Gobi desert, and in scorpion-infested hotels where the sheets didn't seem to have been cleaned for several months. But did the glamorous Newton-John complain? "It was enlightening," she says now. "Whatever doesn't kill you makes you stronger!"

Crucially, though, the trip was worth the trouble, because she raised more than a million pounds to help fund the development of the Olivia Newton-John Cancer & Wellness Centre, which is due to open in Melbourne in June. She proudly shows me pictures of her standing in a hard hat and fluorescent bib in front of the freshly erected building. It will house oncology units and provide palliative care. There will be yoga, acupuncture, massage, meditation and art and music therapy available at the centre.

If that sounds a little too alternative, then it should be said that the centre is an adjunct to a hospital and will work with the Ludwig Institute for Cancer Research, the largest academic institute in the world dedicated to controlling the disease. Newton-John hopes that this is only the beginning, that one day these centres will exist all over the world.

She has also put her name to - and features prominently on the website for - a simple medical device called the Liv that helps women examine their breasts for lumps. Meanwhile, her singing and acting career continues apace. The four-time Grammy-Award winner has just completed a concert tour of South-east Asia (I bet she'd still suit the Spandex look she sported in her famous 1982 video for Let's Get Physical). And then there's her latest movie, A Few Best Men, which premiered and was lauded at the Rome Film Festival last October. She plays a cocaine-snorting, champagne-swilling mother of the bride. Olivia Newton-John? Cocaine? Has she ever done drugs? "No!" she says. "And if I had, I don't think you'd be the person I told."

I don't imagine she's ever done anything naughty at all. She tells me she occasionally eats meat, and that she likes a bit of champagne after a concert "to wind down". When I ask if she has ever been overweight, I am met with silence while she thinks. "Well, only when I was pregnant with Chloe [her daughter, now 26, whom she had with her first husband, an actor called Matt Lattanzi]. And I loved that. It was glorious."

You can taste the Olivia Newton-John lifestyle at the Gaia Retreat and Spa near Byron Bay in Australia, a peaceful hotel that she co-owns, where guests can lose weight, detox and practise yoga.

And now you can eat like she does, with the help of her new cookery book. Livwise contains, as she puts it, "easy recipes for a healthy, happy life". I was expecting bland mung bean and lentil creations, but actually the dishes are pretty palatable - there are omelettes and pancakes, muffins and cookies, and even recipes for burgers. To write the book, Newton-John enlisted the help of the chefs at Gaia, as well as nutritionists she worked with while she had cancer. "I've always been aware of my health - when you are having to go on stage and perform, you need to be feeling good - but when I was diagnosed with a life-threatening illness I became really, really conscious of my health."

She is a big believer in the "you are what you eat" mentality. "I've never been one for faddy diets. I have tried vegetarianism, and I've done the macrobiotic thing, but I believe now in just being balanced. If my body asks for meat, I give it meat."

She eats lots of pulses - chickpeas, borlotti beans - drinks lots of water and only eats organic. Her daughter's best friend died when she was just five years old of a kidney cancer that is believed to be caused by environmental factors, and Newton-John has been organic ever since. "There are countless pesticides out there that have never been tested on humans," she says sadly.

She supports her diet with a range of supplements from the Amazon Herb Company, which is owned by her husband, John Easterling, whom she married in 2008 (When I tried to ask about her former boyfriend, Patrick McDermott, who went missing in 2005 while on a fishing trip in California and was never seen again, I am blocked by Newton-John's PRs). It provides supplements derived from the rainforest, and she has bags of the pills and lotions with her in her hotel room today. What do they do, I ask somewhat sceptically? She goes to get me a bottle of "camu", a nutrient that claims to "fortify the immune system", increase your levels of serotonin (thus cheering you up) and "flood your body with vital micronutrients". It tastes vile, but if it works for her, who am I to argue?

She says that she feels "the healthiest I ever have". How does she relax when she eventually goes home to Florida? "Oh," she beams. "I love to do the washing. It's just so therapeutic."

Livwise by Olivia Newton-John is published by Murdoch