Source: http://www.npr.org/blogs/thesalt/2014/03...

So, for example, say you want to compare the calories, sugar content and nutrients of mashed potatoes and sweet potatoes? Just type in "compare mashed potatoes and sweet potatoes," and boom, you get photos and an elegant chart revealing that sweet potatoes have 4.2 grams of sugar per 100 grams, compared with 0.5 grams in mashed potatoes. Scroll down and you'll see that sweet potatoes kill mashed potatoes in vitamin A, potassium and calcium content.

As you contrast ingredients, perhaps out of sheer curiosity, perhaps to design a meal plan, you'll learn a lot by playing around with the preparation and cooking method of the food. Tweak the mashed potatoes to "potato, mashed, with milk and butter," and unsurprisingly, the fat content jumps up.

You can even compare apples and oranges (apples are slightly sweeter and have slightly more calories, in case you were wondering). Or analyze foods from totally different food groups — for instance, what do grapes and bacon have in common? Google says it's getting most of its data from the U.S. Department of Agriculture's National Nutrient Database, so you can compare pretty much anything in it.