A Polish numismatist, Zbigniew Żabiński, came up with trofa (from Greek trophe 'alimentation'), a universal measure of the value of money. One trofa is defined as an average person's daily ration of food typical for the given place and time. Altogether, it has 3000 kcal: 1800 kcal in 450 g of carbohydrates, 900 kcal in 100 g of fat, and 300 kcal in 75 g of protein.
For instance, in late 1970s' Poland, one trofa consisted of 400 g of rye bread, 100 g of wheat flour, 250 g of potatoes, 100 g of beef, 100 g of sugar, 80 g of butter, and 1/2 litre of milk. Assuming that its content has not changed, you take the cost of the food (8.70 PLN in 2016), add 20% for condiments and preparation, and get 10.50 PLN as the 2016 price of a trofa in Poland.[0]
In Octavian's times, one denarius could buy you 2 trofas (with content appropriate for ancient Mediterranean lands),[0] Judas's 30 pieces of silver were worth 60 trofas,[1] etc.
Unfortunately, Żabiński published in Polish behind the Iron Curtain so the trofa is virtually unknown outside Poland. The Big Mac index is its pale reflection.
While it's an interesting idea, this only captures relative wealth. Places that have higher quality food as standard would be seen as less rich. It's much cheaper to get calories from staples such as rice and potatoes, but a lot more difficult to get it from protein. It's possible to survive on a diet of mostly carbs and little protein, but that can also make you more susceptible to malnutrition, especially if famines are abound.
Also, 3000 kcal per day means that everyone gets fat. The amount of intense physical activity you have to do for an average person to use up that many calories is on the level of modern athletes.
Just to mention that staples like grain have indeed much protein, so your sentence actually doesn't make much sense.
The conception of food consisting of vegetable + meat/fish + staple (rice, bread, potato, ..) is an utterly modern one.
All across history in most settled cultures will have lived principally of local plants of some kind, with meat being a rate treat. The exception being fishing villages but even there vegetables/grains will always have been a principal source of calories and nutrients.
Yes, and people nowadays are taller, smarter, and live longer. A large part of the Flynn effect is usually attributed to nutrition. Humans can survive with poor nutrition (not getting the right amount of nutrients they need) for a very long time, but it usually has consequences, especially when it happens during childhood.
Another thing to keep in mind is that humans didn't evolve to be farmers. We evolved to be hunter-gatherers. Just because for a slice of our existence people ate one way doesn't mean that that's the diet most suited for us.
By the way, there's a difference between animal proteins and protein in grain. They aren't quite the same composition of amino-acids.
Curious - why food? Why not clothing for a year, or transportation, or the cost of raising a child, or a night at an inn, or what it cost to bribe a Senator? So many simple comparables besides food-for-a-day.
The purpose is to compare pricing across history. Food prices is a good yardstick since everybody throughout history need food. You cant really measure the price of "a night at an inn" for a culture without inns, for example. The cost of transportation is not that useful when most people walk everywhere.
Well, you get the idea. Food is subject to very particular customs, environments and traditions. Much more so than other things. So likely a skewed measure. Got to be other things that make at least as much sense.
For instance, in late 1970s' Poland, one trofa consisted of 400 g of rye bread, 100 g of wheat flour, 250 g of potatoes, 100 g of beef, 100 g of sugar, 80 g of butter, and 1/2 litre of milk. Assuming that its content has not changed, you take the cost of the food (8.70 PLN in 2016), add 20% for condiments and preparation, and get 10.50 PLN as the 2016 price of a trofa in Poland.[0]
In Octavian's times, one denarius could buy you 2 trofas (with content appropriate for ancient Mediterranean lands),[0] Judas's 30 pieces of silver were worth 60 trofas,[1] etc.
Unfortunately, Żabiński published in Polish behind the Iron Curtain so the trofa is virtually unknown outside Poland. The Big Mac index is its pale reflection.
More information in Polish:
[0] A table of trofa's price from Octavian's Rome to contemporary Poland: http://blognumizmatyczny.pl/2016/03/14/trofa-miernik-wartosc...
[1] Thirty pieces of silver: http://bazhum.muzhp.pl/media//files/Collectanea_Theologica/C...
[2] The purchasing power in medieval Balkans: https://repozytorium.amu.edu.pl/bitstream/10593/8080/1/11_Zb...
[3] Google search: https://www.google.com/search?q=Żabiński+trofa