B3 as niacin (nicotinic acid) or niacinamide (inositol hexanicotinate)? Both are called B3, but they act differently. Or do you have links to studies? The methods sections will say which was used.
I'd also suggest that anyone taking niacin should also take a methyl donor (e.g. TMG/Betaine, DMG, lecithin - which is in egg yolks) as methylation is required to turn it into the active form - and many/most of us don't have excess methyl donors.