A vegan diet might increase your risk for osteoporosis or low bone density and bone fractures, according to Vanderbilt University Health Psychology Department. Vegans tend to have lower levels of calcium and vitamin D than non-vegans. However, vegans with high calcium intake have similar fracture risk to non-vegans. If you adopt a vegan diet, pay extra attention to high-calcium foods, such as kale, collard greens, bok choy and broccoli. Oranges are also a good vegan-friendly source of calcium, and many commercial soy milks, cereals and pasta are fortified with calcium. Low calcium and vitamin D levels in vegan diets may lead to rickets in children, a condition characterized by soft and deformed bones.