Warnings Signs Your Fingernails May Be Sending (vertical ridges = amino acid deficiency, diet is low in protein or weak digestive juices. Making sure to get enough easy to digest protein is key. White spots on nails = low zinc status (and low stomach acid ). A zinc deficiency doesn’t mean you need a zinc supplement, but more a sign of a poor diet and/or weak digestive juices due to slowed metabolism).
Vertical ridges or white spots on your nails are usually harmless, but black streaks in your nails may be due to melanoma skin cancer. http://articles.mercola.com/sites/articles/archive/2015/12/07/10-nail-symptoms.aspx