best shampoo not to loose hair, also vitamins

A recommendation would be Nioxin shampoo and conditioner.  I purchased the economy-sized duo at a JCPenney salon on sale with a JCP coupon paying $20-25 which is the cost of a large pizza I wasn't eating.  The word "thinning" better described my hair situation starting at three months post-op and lasted about six months.  However, I still use Nioxin today because I like how it makes my hair look better than how pizza made my body look.

Biotin gave me a lovely batch of facial hair.  Also grew hair on my legs much faster but the hair on my head stayed thin.  Nothing will stop the initial hair loss, but mine was still painfully thin at over two years out.  I did go with Nioxin and my hair did come back much fuller.  Now I use Wen.

I will say I have found a shampoo/conditioner that I like.  I have lost  a lot of hair since surgery and my hair was fine to begin with.  This shampoo doesn't prevent it from falling out but does make the hair that is left look fuller and thicker.  The brand OGX Biotin/Collagen. You can get it at Wal-mart.  It is in a purple bottle and sales for about $5 so not bad price wise.  I hope this helps it did for me.