Lewis Hamilton on Thursday said there "is a lot going on in my life" as he responded to critics of his recent emotional social media postings by conceding that he is only human after all.

However, he added that his growing concerns over the environment have seen him sell his private plane and introduce a complete ban on plastics in his daily life.

The five-time world champion, who is on the brink of possibly claiming a sixth title at this weekend's Mexican Grand Prix, revealed a fleeting despair at the state of the world when he used Instagram to declare that the world was "a messed-up place" and he felt he wanted "to give up".

That commentary, including revelations about his vegan lifestyle, led to him being accused of hypocrisy and, during a news conference at the Autodromo Hermanos Rodriguez, faced a series of questions on his mental condition ahead of Sunday's potential title showdown.

"I'm only human," he replied. "Like everyone, we have up and down days. That's what I've been really trying to convey.

"I think it is very difficult for people watching on social media to be able to relate to certain individuals and to live in a celebrity world.

Lewis Hamilton says he will keep highlighting his environmental concerns
Lewis Hamilton says he will keep highlighting his environmental concerns AFP / Toshifumi KITAMURA

"There is a lot going on in my life at the moment, but coming into this weekend I'm feeling very positive and I'm back to doing what I love doing."

Hamilton said he intended to make himself carbon-neutral by the end of this year, explaining that he is swapping his fuel-reliant road cars for electric cars.

"I don't allow anyone in my office, but also within my household, to buy any plastics," he said.

"I want everything recycle-able down to deodorant, down to toothbrush, all these kind of things.

"I sold my plane over a year ago. I fly a lot less now. I try to fly less through the year and mostly fly commercial so that's been a big change in my habits."

Hamilton, 34, switched to a plant-based diet in 2017.

Sebastian Vettel supports Hamilton
Sebastian Vettel supports Hamilton AFP / Behrouz MEHRI

'Not quick fix'

His career in Formula One has been accompanied by close media attention since he made a spectacular debut, in 2007, as the sport's first black race-winning driver and his mood swings, when under pressure, have often attracted additional analysis.

The mixed-race child of separated parents, he was an exceptional talent in karting who embraced social media to retain control his own narrative, so far as he could, as he conquered F1.

"Lots of people have their opinions how I utilise my social media, but ultimately it's my platform and we all have a voice," he explained to reporters on Thursday.

"It's how you want to use it. I know it's not the easiest for me because I know we are travelling around the world and racing Formula One cars, (and) our carbon footprint is higher than the average homeowner who lives in the same city.

"But that doesn't mean you should be afraid to speak out about things. I'm always looking at things and how I can improve the effect that I'm having on the world.

"It's something over time I have become more aware of and it takes a while. It's not a quick fix. It takes time to understand the implications and I think it's just about education.

"I'm trying to highlight areas, whether people choose to look into those is up to them. I'd feel like I wasn't doing anything positive if I didn't mention it."

Hamilton's Ferrari rival Sebastian Vettel spoke in support of the Briton.

"I'm not active on social media, but the point is very clear," said Vettel.

"You would be ignorant if you wouldn't look at it.

"As Lewis said, it's difficult for us to get acceptance from the outside because we don't have the smallest footprint. The races happen around the world -- we have to travel, so it's part of our jobs.

"But in general, F1 should do more. It's a worldwide operating platform and I think we should send a much stronger message.

"I think everybody can do something. Contribute a little bit. If the whole world acted like that it would be a huge difference."