Initially no, perhaps because I could guess based on prior discussions on Mg.

But, reread after reading your comment and yes I can see that it can cause confusion. They should have been more clear in the title.

Felt the same here. Title gives the indication that magnesium, even a little, is bad.

no, it doesn't. it's your "level" of english ^^

It's not. The title is ambiguous. You're used to read headlines in a "headline tone" and you know/assume the meaning because you internalised the fact that magnesium is not bad for you, which is correct. If someone knows perfect English, but doesn't take that fact as axiomatic, the title is ambiguous.

Yes I thought the same.

While English may be at fault for allowing many ways to parse the same strings, it's excuse is it's not a conscious entity that chose anything.

What is the excuse of an article author who has no other job than to communicate?

Yes! I basically read the headline as “too much” magnesium is bad. Which, was a surprising headline to me.