Of course it is ambiguous. I was speaking broadly.
And it is true. Catalysts are needed for many substances to react.
True enough, but when we're talking about digestion and nutrient absorption, we're not talking about "reactions", per se. Once the nutrients (vitamins, minerals, etc.) are past the gut lining and being transported to where they are needed, catalysis of reactions is in many instances needed, but that catalysis can then obvious take place because the nutrients and catalysts have both been absorbed and are ready for use, regardless of the source form which they were originaly obtained.