is prepared to do the shipping at a loss to generate income.
Because the items are very light they can be sent in the post very cheaply.
The mark up on vitamins is pretty big, so they can afford to take a small hit on the postage.
Providing their sales volume is large enough to compensate it is a pretty good business model, because they are giving a better service than competitors.
Shipping from places with cheap post is a good idea, if you can set up distribution from (say China) you could offer free postage.