One of the biggest dangers of veganism is that the restricted diet may cause malnutrition. This isn't unique to veganism; any restrictive diet can lead to a lack of important nutrients. The main nutrients that can be lacking in a vegan diet include vitamin B12, vitamin D, calcium, iodine and omega-3 fatty acids. These deficiencies can cause ailments such as anemia and osteomalacia, a condition that damages bones. In children these deficiencies can result in rickets and other potentially serious illnesses.