Growth Cancer

"Vitamin A acts similarly to some hormones in that it is able to change the amount of proteins in cells by interacting with DNA. This is the primary way that vitamin A affects growth and development. Vitamin A deficiency in children is linked to growth retardation; however, vitamin A deficiency is often accompanied by protein malnutrition and iron deficiency, thereby confounding the investigation of vitamin A’s specific effects on growth and development. In the fetal stages of life, vitamin A is important for limb, heart, eye, and ear development and in both deficiency and excess, vitamin A causes birth defects. Furthermore, both males and females require vitamin A in the diet to effectively reproduce. Vitamin A’s role in regulating cell growth and death, especially in tissues that line and cover organs, suggests it may be effective in treating certain cancers of the lung, neck, and liver. It has been shown in some observational studies that vitamin A-deficient populations have a higher risk for some cancers. However, vitamin A supplements have actually been found to increase the risk of lung cancer in people who are at high risk for the disease, including smokers, ex-smokers, and workers exposed to asbestos. The Beta-Carotene and Retinol Efficacy Trial (CARET), involving over eighteen thousand participants who were at high risk for lung cancer, found that people who took supplements containing very high doses of vitamin A, 25,000 international units, and beta-carotene had a 28 percent higher incidence of lung cancer midway through the study, which was consequently stopped."