Actually it's neither. White marks (called leukonychia) on the nail are from minor traums - like banging your nails. People who use their hands a lot generally have more.
From what I've read, white marks aren't necessarily a result of just one cause. There could be a number of reasons why they are that way, and both zinc deficiency and minor trauma are frequently thought by doctors to be two of the possible causes.
Generally, if there is any kind of deficiency, it will show up on *all* your nails and usually the entire nail is white, not just random spots. Nails are mostly protein - both calcium and zinc are present in less than 1/10% of the nail and deficiencies show up bodily before they show up in your nails. The only time white spots may be a cause for concern is if you have them on *all* your nails - a lot - and you arent overly rough on your hands. Then you need to see a doctor because certain heart problems can cause that to happen.
Also: don't be fooled into buying nail polish that promises to fill in your deficincies. It all comes from the inside so be sure you're getting enough of all you need.
I Remember Getting White Marks on my nails from when i was little i would always bang my nails against the metal fence bars it stayed for a few years i suppose but has now left. i actually took it as a good thing and something "unique" about me weirdly...