Like ... food? This is an amino acid, the building block of protein. Many amino acids have pronounced effect in the body or when lacking.
Our bodies are fine-tuned to be somewhat fault-tolerant, but evolution is extraordinarily slow. If our diets diverge over a few hundred years, there haven't been nearly enough evolutionary cycles to compensate for whatever effect that has; particularly if it's minor annoyances like getting jittery with coffee, which was consumed far less as far back as a few hundred years ago.
Wouldn't this entirely depend on selection pressure, rate of mutation, and turnover of, er, subjects? Certainly bacteria can evolve extremely rapidly and it's been noted in animals too, cf http://discovermagazine.com/2015/march/19-life-in-the-fast-l...
Like ... food? This is an amino acid, the building block of protein. Many amino acids have pronounced effect in the body or when lacking.
Our bodies are fine-tuned to be somewhat fault-tolerant, but evolution is extraordinarily slow. If our diets diverge over a few hundred years, there haven't been nearly enough evolutionary cycles to compensate for whatever effect that has; particularly if it's minor annoyances like getting jittery with coffee, which was consumed far less as far back as a few hundred years ago.