system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do we actually know what vitamins and minerals are in the foods we eat

Bananas , sweet potatoes , and squash, are all high in vitamin k. Aside from Google and health books, how can we find those vitamins and what do they look like ?
gpt
We have data from processing samples in a Mass Spectrometer. The sample is broken down into its chemical components and the spectrometer identifies the quantities of each chemical. So we get the exact amount for the small sample and the scientists scale up and give an educated guess as to how much for a full serving/individual food.