Oxidation of pectin produces a small quantity of formaldehyde as a metabolite. I’m not suggesting that you shouldn’t eat fruit or jams by the way, it’s just an example of how something considered broadly healthy still produces toxins that require elimination. Metabolism by its very nature produces energy and “exhaust” in the form of heat and metabolites. To be clear, you’re getting a lot more methanol metabolism from a drink of alcohol than an apple, so eat the fruit. No matter what we do we’re. It living forever based on diet, we should just try to avoid too much excess and accept that living isn’t a thermodynamically favorable process.