If you're a vegan, vegetarian or just prefer fruits and vegetables to meat most of the time, you may face a challenge getting enough protein into your diet. Animal products contain all the amino acids the body needs to maintain itself. Relying on other sources like nuts, grains, seeds and vegetables for nutrients is doable, but without some know-how and judicious monitoring, forgoing animal protein on a regular basis can lead to deficits.
Vitamin B12 is an essential nutrient present in animal products, but it's often harder to find in sufficient quantities from other sources. A B12 deficiency can cause dark nails or nails that tend to curve. It can also cause tiredness, light headedness, bleeding gums, constipation and other symptoms. Although gray or brownish nails are an indication of vitamin B12 deficiency, the dark coloration can also be a symptom of illness, particularly if the condition is recent or presents with thickened nails, concave nails or nails that are lifting from the nail bed. Yellowish nails can also be a symptom of a zinc or iron deficiency, too.