Help please

Everyone should be careful about their health.(informal)

Everyone should be careful about his or her health.(formal)

Thanks. But I got another idea after posting the question and I'm hesitating using it either before conformation. If I say "One should be careful about one's health" would it give the same meaning as the one stated earlier? Kindly tell me which one is more suitable for formal use. Thanks again.

Everyone should be careful about their health.(informal)
Everyone should be careful about his or her health.(formal)

"One should be careful about one's health" is better than the above sentences..

Thank you so much.