Food, Calories, and Vitamins

Bill Bryson’s awesome book, The Body: A Guide for Occupants, has a chapter titled “Food, Glorious Food”. It starts with the topic of calories:

“We all know that if we consume too much beer and cake and pizza and cheeseburgers and all the other things that make life frankly worth living, we will add pounds to our bodies because we have taken in too many calories.”

The weird thing about the unit we call ‘calorie’ in the context of food is that it’s really kilocalorie in physics lingo! That’s the amount of energy needed to heat 1 kg of water by 1˚ C:

“But it seems safe to say that no one ever thinks of it in those terms when deciding what foods to eat.”

 

The father of the caloric measurement was Wilbur Atwater. He did his study at a time when people thought the only purpose of food was to give energy:

“Nobody yet understood the concept of vitamins and minerals or even the need for a balanced diet.”

Thus, he concluded wrongly that a pure meat diet was better than one with vegetables because, hey, meat gave more calories.

 

The calorie, as a measure of dietary intake, has many failings. It doesn’t tell whether the food is good or bad for you. And it doesn’t factor for the amount of different foods that get absorbed v/s thrown out. As a species though, we humans are far better at extracting more energy from food than most species. No, that’s not because we have “an exceptionally dynamic metabolism”. Rather, it’s “because of a trick we learned a long time ago: cooking”:

“It kills toxins, improves taste, makes tough food chewable, greatly broadens the range of what we can eat, and above all vastly boosts the amount of calories humans can derive from what they eat.”

A cooked potato, for example, is 20 times more digestible than a raw one. Other primates spend as many as seven hours a day chewing. This may explain our modern-day affliction, as something caused by the fact that in evolutionary time, our body hasn’t yet adjusted for the ability to extract calories via cooking:

“Our tragedy is that we eat more or less constantly anyway.”

 

The discovery of vitamins only happened in the 1920’s, and it has been a chequered history. To start with, vitamins got named in alphabetical order, as they were discovered – A, B, C, D and so on. Then the system began to fall apart. Vitamin B was found to be many vitamins, not one, so it got split into B1, B2, all the way to B12. Then they realized some of them weren’t different after all, so they got dropped, leaving us with “semi-sequential B vitamins”: B1, B2, B3, B5, B6 and B12. Other vitamins came and went, as a result of which scientific literature is filled with “ghost vitamins” like M, P, PP and S.

 

Bryson is very good at explaining while keeping it interesting. Do read the book.