The biggest example for this IMO is Vitamin D. If you can spend time in the Sun regularly every day, you won't ever need to touch vitamin D. But how realistic is that for most people ?
The only supplement I've encountered so far that has a noticeable effect that cannot be reproduced with any realistic diet is creatine.
Personally think it's probably equally valuable for women but can't get my wife to take it (worried about the bloating which is a thing).
To your point it would be very difficult to get the equivalent creatine from your diet. Would take a lot of steak.
Haven't asked him about his cardio training but he's moving more weight around than he did before and that's creating benefits for him overall.
Creatine is one of the most studied supplements out there though so would think the empirical data supports it at this point.
I'm speaking anecdotally of course. I used to cycle creatine but now I just always take it. When I'd cycle off I'd lose 5-10 lbs every time. Thats mostly water weight but my lifts would decrease about 10% as well. Not to mention the extra energy (more reps not just more weight)
It makes a significant difference for me.
Does it have downsides in the body?
- helps build skeletal support muscles which reduces osteoarthritis and treats osteopetrosis
- helps strengthen the heart muscle
- the brain also uses atp, increased brain function (anecdotally, can help reduce brain fatigue)(Parkinson's, als, Huntingtons, possibly Alzheimer's
Downsides:
Increased load on the kidneys - which combines with an increased load from muscle breakdown (which it can reduce, but most likely the workout with it will increase muscle breakdown) - don't take it and workout hard if you are approaching renal failure.
Some stomach upset, diarrhea, and muscle bloating.