Zoe Ball has said the death of her boyfriend last year left her with "lots of questions," as she prepares for a cycle challenge to raise mental health awareness.
Cameraman Billy Yates, found dead at his home last May, had been living with mental health issues for years.
Ball will also film a documentary about mental health while taking part in the Sport Relief challenge.
"I wanted to do something for him," said Ball.
Speaking to Chris Evans on his Radio 2 Breakfast Show, she added: "One in four people is living with mental illness. That's a lot of people struggling."
'Close to my heart'
The Strictly Come Dancing: It Takes Two host has been out training ahead of her challenge.
Details of the route, including the distance and locations, are yet to be revealed, but she admitted it was "a long way" for a novice cyclist.
Ball said Sport Relief was supporting mental health issues this year, adding: "It's very close to my heart."
"I think lots of people know that I lost my boyfriend last year, who lived with depression for a very, very long time.
"I was really touched and moved by the amount of people who got in touch with me, who have been through the same, or living with the same issues.
"Mental health resources are under huge pressure and there are a lot of people who are not necessarily getting the support they need in time."
'How can we help?'
Speaking about Yates' death, she added: "I was left with lots of questions. While we're doing the challenge, we're making a documentary. I'm going to visit projects helping people living with mental illnesses - that can be anything from self-harm, anxiety, depression, bereavement, bullying - all of those issues.
"I have lots of questions about what are we doing? How can we help? How do people find the right help?
"There are some incredible organisations helping people."
She said the challenge was about "spreading some awareness and hopefully helping people find the right help and some hope".
In her interview with Evans, she told him: "I wanted to raise some awareness. I wanted to do something for him - I wanted to do something for everyone else."
She has already got tips from Davina McCall, who completed her own Sport Relief challenge in 2014. McCall has given some "top tips" on "looking after undercarriages", said Ball.
Unveiling news of her mission on BBC Breakfast, she said: "I've ridden shopping bikes. My dad held my saddle and pushed me along when I was five. I've had a go on a BMX.
"But road bikes is a whole new thing. Cleats? Oh my goodness me.
"I've had an altercation with a kerb, I've had an angry driver, I've had two slow-motion falls."
She joked: "I look the part - all the gear, no idea."
Sport Relief is taking place from 17 to 23 March.