According to majority of the scholars this is impermissible. Every business and its dealings are different. We should consult a scholar on exactly what the business is and in this very case food supplement, if it is halal or haram, and how the profits are shared among members.
The problem comes in when you sit idle do nothing and make money. And most of the networking and pyramid schemes are fraud or have some strings attached which are not very clear to normal people. It sometimes is accounted as gambling as a person doesn't know if its a profit or loss without real hard work. Also is the product not adultered? Would you recommend it to your family. These are some ethical questions but do factor in.
Not stepping on any ones toes. Just explaining from what I've learned. Consulting a scholar with specifics is the best option. And Allah knows best...