According to the rules of IAAF, a sportsman can receive a nutrition in two cases:
1) At the official feeding station (it's also allowed to prepare the nutrition at the feeding station in advance, if it's allowed by the officials).
2) Keeping your nutrition with you (in hands, on the belt, it's up to you), beginning from the start
It's prohibited to get the nutrition from the others (trainer, friends, fans, other runners) outside of the feeding station.
It's not strictly controlled among non-leaders. However, we ask our runners to keep to these rules. They are not so difficult.