1 - Avoid seed oils (also known as vegetable oils) - almost everything now is made with seed oil, 100 years ago when there was very little degenerative disease, there was virtually no seed oil. People used traditional fats like butter, olive oil, and beef tallow. You can find a good alternative for a lot of seed oil products if you look. For example, here's a list i found of where to
get fries without seed oil.
2 - There's some pretty unfortunate chemical contamination in foods.. You can look up a report on the pesticide content in food at the store. More than half the bread has detectable pesticides in it. (might be why people feel better going grain-free... it isn't the grain, it's the chemicals!) So I go for certified organic stuff, and generally avoid store-bought grains anyway. Also filter my water to remove pesticides and the other nasty chemicals that get in there.
3 - Lifestyle. Get enough sleep, don't strain, don't be filled with bitterness
These will destroy health. "Consider the lilies of the field" is one of my favorite verses, and good advice for health too! Funny how that works out
Just my opinion! But it's worked pretty well for me and my family. (One thing I would say is to not do anything strange or excessively restrictive in the name of health, like going vegan, or low carb, or getting obsessed with some "protocol." Usually pretty unhelpful to do that kind of thing, and can even be BAD for health I think.)