Which organs have different functions in which people? Do they produce diferent secretions? Are there different blood and lymph functions? Different filtration functions? Elimination? Capacity may vary, but the physiological systems are the same. A varying capacity in no way indicates a need for varied nutritional requirements.
Discussion
I think it's pretty obvious that I'm not arguing that people's organs perform different functions, but they do operate at different levels and aren't all statically identical. People have allergies, sensitivities, genetic differences and body chemistry that makes their needs unique.
If you think realistically that everyone on earth should actually eat the exact same diet, then I don't know what to tell you except stay out of my kitchen.
You should eat whatever you want. Any justifications based on "we are different" rather than nature's design is only self deception. People seem to believe we are the only species on the planet that has different requirements among different members. You're welcome in my kitchen any time. I take no offense at our differing beliefs.