Vitamin A and Cancer - issues and controversies
Surveys suggest an association between diets rich in beta-carotene and vitamin A and a lower risk of many types of cancer. A higher intake of green and yellow vegetables or other food sources of beta carotene and/or vitamin A may decrease the risk of lung cancer.
However, a number of studies that tested the role of beta-carotene supplements in cancer prevention did not find them to be protective. In the Alpha-Tocopherol Beta-Carotene (ATBC) Cancer Prevention Study, over 29,000 men who regularly smoked cigarettes were randomized to receive 20 mg beta-carotene alone, 50 mg alpha-tocopherol alone, supplements of both, or a placebo for 5 to 8 years. Incidence of lung cancer was 18% higher among men who took the beta-carotene supplement. Mortality was 8% greater in these men, as compared to those receiving other treatments or placebo.
Similar results were seen in the Carotene and Retinol Efficacy Trial
(CARET), a lung cancer chemoprevention study that provided subjects
with supplements of 30 mg beta-carotene and 25,000 IU retinyl palmitate
(a form of vitamin A) or a placebo. This study was stopped after
researchers discovered that subjects receiving beta-carotene had a 46%
higher risk of dying from lung cancer.
The IOM states that "beta-carotene supplements are not advisable for the general population," although they also state that this advice "does not pertain to the possible use of supplemental beta-carotene as a provitamin A source for the prevention of vitamin A deficiency in populations with inadequate vitamin A nutriture".
I have decided to start an active promotion of this website, so that we get more visitors soon. And it would be a waste of time if we didn't allow for discussion and sharing of informations. In light of that, discussion forum will be officially launched on June 21st.
I hope it will serve a positive function in opening alternative horizons in the area of general information about vitamins.