Genetic Vitamin A Deficiency (Retinol Deficiency)
Almost half of British women could be suffering from chronic vitamin A deficiency caused by a previously undiscovered genetic variation. Vitamin A, also known as retinol, is an important fat-soluble vitamin that has numerous important functions in the body. It is involved in the maintenance of healthy skin and the mucous membranes in the digestive and respiratory tissues, it promotes a healthy immune system and fights infection, it is essential for reproductive processes, and — last but not least — it promotes good vision (especially in low light). Vitamin A deficiency (VAD or hypovitaminosis A) is most prevalent in developing countries, particularly among children. Children with a severe vitamin A deficiency suffer a significantly increased risk of death, blindness and infections.
As vitamin A is a fat-soluble nutrient (as opposed to water-soluble), large doses of vitamin A can accumulate in the body and become toxic over time. As a result, many health care professionals have been recommending beta-carotene as the preferred source of vitamin A. Beta-carotene is a precursor to vitamin A (also known as pro-vitamin A) and can be converted to real vitamin A by the body. Beta-carotene is abundant in many yellow, orange and green fruits and vegetables such as carrots, sweet potatoes and broccoli.
The results of a study led by Dr Georg Lietz and carried out by a group of scientists from England's Newcastle University question the usefulness of beta-carotene as an effective source of vitamin A. The researchers found that 29 women out of the 62 study participants, or 47 percent, carried a genetic variation which prevented them from effectively converting beta-carotene into vitamin A. These women were also not eating enough foods rich in retinol (preformed vitamin A) which is present in foods of animal origin such as calf's liver, egg yolks, cod liver oil and dairy. With an inability to convert beta-carotene into vitamin A and a low consumption of foods that contain retinol, these women were clearly not getting enough vitamin A.
Younger women with the genetic variation seem to be particularly susceptible to vitamin A deficiency as they typically consume less food that contains retinol. Following a vegetarian, vegan or a low-fat diet will further increase the risk of chronic vitamin A deficiency in these women. The older generations appear to be less at risk as they tend to eat eggs, dairy and other retinol rich foods on a regular basis.
The US Food and Drug Administration (FDA or USFDA) has set the Recommended Daily Intake (RDI) for vitamin A at 5000 International Units (IU). One IU is equivalent to 0.3 mcg retinol, or of 0.6 mcg beta-carotene in the US and in Canada.