what is the quantity of vitamins you can bring into China ?

I am a US citizen working and living in china , I am back in the US and will be going back to my home in South China. I want to bring back some western vitamins , one because they are cheaper in the USA and second I know they are made in the USA and not knock offs. I would like to know the quantity's of Lecitin - Calcium -and fish oil(omega3). I do live in china and come back once a year or so. Many thanks Albert