Added the following two bits to "Issues in Vegetarian Diets" by Vexen Crabtree:
Vitamin A (retinol) is found in animal liver (in abundance), cheese, eggs, oily fish (such as mackerel), milk, fortified margarine and yoghurt7. It only comes from animal sources. There is a chemical similar to vitamin A, called beta-carotene "a substance that the body can convert into vitamin A"[Byrnes 2000]. Dr Byrnes also notes that this conversion, however, only takes place efficiently when animal fats are present. Otherwise the amount coverted into vitamin A is very small. We can't convert all our beta-carotene into vitamin A though, because beta-carotene is itself an important part of our diet and in addition. Some people cannot do it at all. "Infants and people with hypothyroidism, gall bladder problems or diabetes (altogether, a significant portion of the population) either cannot make the conversion, or do so very poorly".
“Iron deficiency, which causes tiredness, is the world's most common nutritional problem. In the UK around 20% of women are anaemic. Iron is the least plentiful nutrient in the typical British diet. It can come from plant sources (inorganic iron) or from animal tissues (haem iron). Haem iron is absorbed around five times more efficiently than inorganic iron - this is why eating red meat is recommended for preventing anaemia. Lead researcher Dr Andrew McKie said: "Currently pregnant women suffering from anaemia are given supplements of inorganic iron, but these are poorly absorbed and poorly tolerated.”
BBC News, 2005 Sep 10
It is dangerous for women to remain on a vegetarian diet during pregnancy. Not only is substitute iron less efficient, but some people cannot tolerate it at all. If a woman's baby is intolerant to inorganic iron, a vegetarian diet can be fatal for the baby and harm the mother more than normal as her iron requirements are much higher and only iron obtained typically from red meats is adequate and efficient for her.
Vitamin A and Iron deficiencies in Vegetarians
January 8th, 2007