Cameron Diaz on aging: 'We're being told that we're just not valuable'

She talked about how to have a 15-minute private dance party and how to examine a bowel movement in her first book and now Cameron Diaz is tackling another taboo topic: aging.

The 43-year-old star of films like The Holiday, There's Something About Mary and My Best Friend's Wedding has co-written her second book, The Longevity Book. It follows her debut bestseller The Body Book.

Diaz said the idea to write a book about getting older came to her as she was approaching 40 and fielding questions from media about how the milestone might affect her career.

"Saying to somebody 'you know you're not going to be viable, you know you're not going to count anymore, you know we're going to disregard you', that's a painful, mean, horrible, scary thing to hear from people," she said in an interview in Los Angeles.

"I thought, that's really just not fair. We're being told that we're just not valuable is something that I think we need to take back for ourselves and start to look at what aging really is."

The book, which she wrote alongside Sandra Bark, looks at the science behind aging and how nutrition, exercise, and sleep habits among other factors affect the process.

The Charlie's Angels star joins a growing list of Hollywood A-listers making a name for themselves in the lucrative lifestyle industry. Gwyneth Paltrow's GOOP publication, Reese Witherspoon's Southern-inspired retail brand Draper James, and Jessica Alba's uber-successful Honest company have proven there's a demand for celebrity-endorsed products and practices.

Diaz, who married Good Charlotte guitarist Benji Madden last year, says there's a reason it's so popular — women like her have something to say.

"One of the wonderful things about getting older and having experience is that you have something to share with people," said Diaz. 

"I think people are just looking for things that can help them."