I could eat anything with no difference in ride performance when I was in my twenties and thirties. Now that I am in my 70's I need to be more careful with carbs and take various supplements. The older we get the less efficient our bodies are at absorbing nutrients from the food we eat and with industrial farming the food has far less nutrients as well and more carcinogens.
My riding buddy has always suffered from saddle sores and with him it is that he rides commando with no underwear and so bacteria builds up in the chamois of his riding shorts. I have always worn cotton jocky shorts under my bike shorts and I have never had a problem with saddle sores.
While riding it is carbs that fuel the body and it becomes a matter of which carbs are most easily digested. Bananas and raisins are good fuel food and easy to carry along on a ride. Staying hydrated is important although the recommended volumes are to me crazy. Potasium, magnesium, and calcium are used by the muscles including heart muscle and so having these in short supply will cause problems. And recommended daily dosages are going to be understated for older people as the only time they are included is when the study uses a nursing open or mental institution and then wildly extrapolates the "findings".
One generation back most adults, in particular men, died before they reached 60 and so it is new ground in terms of trying to find reliable information that does not have a big pharma or AMA bias. It helps if you have a GP that practices sports medicine or functional medicine but these are few in number in the USA.