As others have stated, I do not see any white spots, either.
Here's what Andrew Weil, MD wrote on the matter, back in 2005:
"The white spots on nail you notice are not caused by a calcium deficiency. These white spots in fingernails are called 'leukonychia' and are very common. Most of the time the white spots simply are a sign of some past injury to the matrix (base) of your nails. By the time the white spot shows up (about six weeks after the injury) you’ve probably forgotten all about banging or knocking your fingers. Sometimes, the injury can stem from a manicure that put excessive pressure on the base of the nails. White fingernail spots also can be a sign of an allergic reaction to nail polish or nail hardeners and, sometimes, are a symptom of a mild infection.
Whatever the cause, white spots on fingernails are temporary and will grow out as your nails grow. However, it can take more than eight months for nails to grow out completely so the spots may be around for a while.
Sometimes, a change in the appearance of your nails does indicate an underlying disease, but these changes would be more dramatic than just the occasional white spot. Nails that turn completely white, for example, can indicate liver disease, but by the time this happens, you probably would have other symptoms.
Incidentally, in addition to the myth that white spots in fingernails are a sign of calcium deficiency, you may also have heard that they indicate a zinc deficiency. That isn’t true either. Neither is the well known but bizarre notion that the spots are due to eating too much Hellmann’s mayonnaise (I’m not making this up)."
I don't have white spots on my nails, but I have ridges/lines that run lengthwise on all my nails. After reading many sources on the matter, like most things, it seems there are lots of theories and opinions, but no single cause that can be confirmed. If there were, then no one would still have streaks (or spots).
Other less common and rare (emphasis mine) causes of spots/streaks on the nails are attributed to such conditions as:
* Heart Disease
* Renal (Kidney) Failure
* Psoriasis or Eczema
* Arsenic Poisoning
Although I'm not a Doctor, I would imagine if a person had such serious conditions such as Heart Disease or Renal Failure, white spots/streaks on nails would not likely be the first symptom.
Other suggested sources of spots include parasites and heavy metals. Again, just more speculation.
If I were to place a bet on what might be the cause, I would say either:
But, again, this is just a guess.