All natural protein shake

The other bags had similar labels from other VR sessions of various male crew members that had already completed their one year active cycle onboard the Odyssey. As you came to terms with just having ingested nearly a liter of your shipmates' cum, you vaguely recalled that when male crew members used the ship's VR system for pleasure, they connected a special hygienic tube to their penis which would provide added stimulation and also siphon away any fluids they produced in order to keep themselves and the system clean. Those fluids were then collected in vacuum pouches and placed in cold storage waste containers until the completion of the mission. At that point, they might be used for medical analysis, or simply discarded. Somehow one of those containers had survived the explosion, and your rescuers mistakenly assumed it must be food.

"Is something wrong?" asked the Grey. "The probes are registering a sharply elevated stress level."

Probes? You realized you still had a hose running up your ass, as well as another one that seemed to be inserted into your transplanted vagina, but those were the least of your concerns right now. "This isn't food!" you announced. "Why did you think that this is what we eat?"

"It's not? From the chemical analyses, it appeared the ingredient mixture of carbohydrates, proteins, vitamins, minerals and water should be fully compatible with your digestive system, at least what little of it we could examine.," explained the Grey doctor. "Clearly, it's edible, but if it's not food, then what is this?"

"These contained semen produced by the males of my species. Didn't your analyses figure that out?" you inquired, trying to fight off another round of dizziness as you thought about what you'd just swallowed.

"Yes, our tests confirmed it," the alien exclaimed. "Are you saying that females of your species do not eat semen?"

"Yes...I mean no...it's...it's not like that," you stammered. "Females of my species sometimes eat it, but usually only in small quantities during or at the end of a sexual encounter. It's certainly not something we eat on a regular basis. So yes, it may be edible, but it's not something we consider to be food. Why would you assume otherwise?"

"In the species we have encountered across the galaxy, it is quite common for the females of the species to eat semen regularly. In a few instances, the males do too. Hence, when we found this container with carefully packaged amounts, it seemed likely that it was being kept for you as a food source," the Grey explained. "If you aren't keeping it as food, then what is it used for?"

"It might get studied later for possible effects during space travel, but I suspect most of this was just going to get discarded along with other non-recyclable waste after our voyage," you disclosed.

"You just discard it? How wasteful!" the alien rebuked. "Unless your species has mastered food production and completely eliminated famine across every corner of your inhabited worlds, edible items should not be disposed of so carelessly. Be thankful they kept this much since it's the only thing keeping you alive until we devise a viable substitute."

As the full meaning of that began to sink in, you felt a horrible sinking feeling in the bottom of your...well, not a stomach since you no longer had one. Not only had you just consumed nearly a liter of semen, but you'd have to repeat this every four hours for the rest of your waking life. "Just kill me now," you muttered.