I’m nearing 40. Are you sure it’s normal to feel terrible most of the day when eating right, exercising, and getting enough sleep? This doesn’t sound normal to me.
Can I overdo things and feel like shit? Yeah but mostly I feel great.
My knees are kind messed up but that is from running 500 miles every summer during middle school and high school.
So no, being in your 40s shouldn’t mean feeling like shit.
As to the topic at hand, I use two supplements in addition to prescription blood pressure medications. I take my blood pressure 3 times daily. I can see in the cold hard numbers if I forget to take them.
That point being: All of us deteriorate. We all reach an age/state where conventional medicine has reached its limit and snake oil begins to be look attractive. Not all of it is proven wrong, none of it is proven right.
It falls short of feeling like shit, but there is a kind of death by many cuts that changes the baseline for feeling normal in the wrong direction.