The vegan is one such type of vegetarian. They are also referred to at times as strict or pure vegetarians. This is because vegans do not eat anything which is either the flesh of an animal or is derived in any way from an animal. This includes not just meat, poultry or fish but also dairy products (milk, cheese, cream, etc.), eggs, gelatin (which is derived from animal collagen) and in some extreme cases even honey.
Most vegetarians only refuse the eating of actual animal flesh, and thus will eat eggs, dairy products, gelatin and honey without a problem. Some are surprised when they learn this, some are surprised when they learn that a vegan will not eat such foods. However studies have shown that persons following a vegan diet are quite rare.
In 2004, for example, there was a Time/CNN poll run to determine the amount of vegetarians in the United States of America. According to the results of the poll, about 4% of the American population were self-described vegetarians. Of this already small 4% of the population, only 5% of self-described vegetarians described themselves as vegans, meaning that only 0.2% of the population actually followed a vegan lifestyle.
A later poll run in 2006 found the numbers to be somewhat higher. This poll, run by Harris Interactive, did not ask respondents to self-identify but rather asked them to identify which sort of foods they would or would not eat. According to this poll, 1.3% of the American population followed a vegan diet, meaning they did not eat dairy products, eggs, meat, poultry, fish, etc. The only animal derived product not mentioned was honey, which generally is not too big of an issue for vegans. Interestingly enough, this poll showed that vegan diets are slightly more common among men than women (1.4% of the male population versus 1.3% of the female population).
One primary issue of concern not only for vegans but for vegetarians in general is that of vegetarian nutrition. While more traditional diets are known to be high in fat and cholesterol (which is a bad thing), many worry that vegans and vegetarians are going to be lacking in some very important nutrients which are typically found in meat and meat-by-products. This is especially true for the vegan, who does not eat any animal products whatsoever, a source that most vegetarians tap to get many of these nutritional benefits.
Especially of concern are calcium deficiencies. Studies have shown that vegans typically have weaker bones than meat eaters and traditional vegetarians both, because of a lack of calcium in their diets. Iodine and Vitamin B12 are two other areas of concern. In order to make up for these deficiencies, many doctors recommend that vegans try to bulk up on foods that provide these nutrients or take a nutritional supplement to assist them with keeping proper levels in their systems.