I think Mercola is mixed, a lot of what he says is fine, but sometimes he promotes a particular type of product for financial reasons / ties to the manufacturer (e.g. krill oil), and at other times he uses fallacious arguments (e.g arguing that microwave use is unsafe because if you microwave blood, as one nurse did accidentally, and then try to put it in a patient it will harm the patient). He also tends to say that if anything is unnatural it's automatically bad, which although is generally the case isn't a universal rule that applies to 100% of cases -- there are plenty of natural foods that are more harmful than artificial foods (e.g. poison mushrooms are worse than Pop Tarts), and he tends to recommend against vitamin usage except in rare cases.