Which one of these sentences is correct?
1 By using this method, they found that sugar is important in diet.
2 By using this method they found that sugar is important in diet.
Do we need a comma to separate two sentences?
CMOS (The Chicago Manual of Style) leaves the choice on whether to follow introductory adverbial clauses with commas with you:-)
It recommends though - but not very forcefully - skipping the comma for short ones.