Veganism is a philosophy and lifestyle that seeks to exclude the use of animals for food, clothing, or any other purpose. Vegans do not use or consume animal products of any kind. The most common reasons for becoming a vegan are ethical commitment or moral convictions concerning animal rights, the environment, human health, and spiritual or religious concerns. Of particular concern are the practices involved in factory farming and animal testing, and the intensive use of land and other resources required for animal farming.Various polls have reported vegans to be between 0.2% and 1.3% of the U.S. population, and between 0.25% and 2.24% of the UK population.Vegan diets (sometimes called strict or pure vegetarian diets) are a subset of vegetarian diets, which are credited with lowering the risk of colon cancer, heart attack, high blood cholesterol, high blood pressure, prostate cancer, and stroke. However, vegan diets can be low in levels of calcium, iodine, vitamin B and vitamin D. Vegans are therefore encouraged to plan their diet and take dietary supplements as appropriate.