I think people should be mindful of it since they were 18 - it's something that progresses over decades. You can have a lot bigger impact making changes when you're young rather than at 40
But yeah I agree with your message. Focus on the big impact macro level things. Hyper-optimizing it is a waste of energy
If I'm not wrong, it takes 20 years to revert the damage of smoking.
I don't think you need to care at 18, but the effects will be seen over the course of 20 years
Lots of the damage done can't be undone when it comes to heart diseaese.
Notably risk goes up with the time spent with bad numbers, so the most leverage you have on affecting your lifetime risk is caring as early as possible.
It's an area under the curve situation. Waiting until you start experiencing symptoms is putting a band-aid on an open wound compared to avoiding injury at all by focusing on high impact habits related to diet and exercise.
The article is fantastic with only one caveat. Recommending 1.6 g of protein per kg of body weight to people who are only meeting, not exceeding, physical activity recommendations is foolish. 1.6 if amount that one needs to build maximum muscle mass in the shortest possible time. Leading protein intake researchers (think people like Stu Philips) state that that recommendation is excessive for most people and he instead suggests 1.2 g for nearly everyone.
But yeah I agree with your message. Focus on the big impact macro level things. Hyper-optimizing it is a waste of energy