1 A diet low in calcium and vitamin D makes you more prone to bone loss. 2  Medication use. 3  Some medicines increase the risk of osteoporosis. 4  Activity level. 5  Lack of exercise or long-term bed rest can cause weak bones. 6  Smoking. 7  Cigarettes are bad for bones, and the heart, and lungs, too. 8  Drinking alcohol.
Fungus infections of the fingernails can also turn the nails brown or yellow. The texture usually also changes; nails often become very thick and may crack or peel. Nail fungus infections are more common in the toes than the fingers. They affect about 12 percent of Americans and may run in families.
Symptoms of Toenail Trauma. A subungual hematoma can range from a small spot under the nail to a large area of discoloration. Depending on the amount of blood beneath the nail, the nail may come loose. But often the nail does stay intact, and the blood fades as the nail grows out.