ELi5: How do they measure calories etc for nutritional labels?

Question

I always wonder how “they” can know the exact amount of fiber, protein, carbs and sugars, etc when I’m reading ingredient labels.

PS: couldn’t decide between biology or chemistry flair since I guess my question relates to biochemistry! Haha

In: 527

Answer 1

When I worked for the deli dept in a grocery that eventually became a Whole Foods, the following conversation was routine:

*Customer*: How many calories are in that salad?
*Me*: Well, we haven’t done a nutritional analysis, but that one has nuts, plus the dressing contains honey. I can recommend an alternative that likely has far fewer calories.
*Customer*: I’ll just have some chicken wings.