[dogtorwoof]

Strength training with weights + adequate protein intake, more than ok, if not probably even better frankly, to include whey protein powders maybe a couple times a week.

Commonality of many of the people who live well (i.e remain functional and independent, 90+ years old) is proximity to hills. Make what you will of that, but exercise involving uphill steps is probably important.

Community / friends, ideally with some sort of bond over hobbies or common interests. It’s one thing to sit together and chat but it’s another for them to get creative together.

Omega 3? Probably, but not through supplements. A balanced diet (Mediterranean diet probably easiest to look up) with good amounts of fish.

Only supplements that have ever made sense to me (apart from a very clear/documented deficient in something) are vitamin D and iron.