There are two main types of vegetarian diets: lacto-ovo, which includes eggs and dairy but not meat, and vegan, which includes no animal products. Teenagers on a lacto-ovo diet can get sufficient nutrients with careful planning, while vegans have a higher risk of deficiencies in vitamins D and B12, calcium, iron, zinc, and other minerals needed for growth. A vegetarian diet requires careful planning to ensure adequate nutrition, and the more restrictive the diet, the harder it is to meet nutritional needs. Non-animal sources of nutrients that may be lacking in vegan diets include fortified foods and supplements for vitamin B12 and D, calcium from tofu and greens,