Puzzled by parse_bbcode function - help :(

[cinq]

I can trying to parse the content using the parse_bbcode function.
However the page is loading very slow because of the parsing , and I cannot figure out why.
If I use the bottom code instead ( ie. dont parse but the result is not what I want ), the page loads fast.

How come ?

$newsmain['content'] = parse_bbcode($newsmain['content'], '1', 1, 0, '', 1, 0);
$newscontent = $newsmain['content'];

vs.

$newscontent = $newsmain['content'];