sciencetalk

Het kan in de lever opgeslagen worden vanwaaruit als het nodig is beschikbaar komt voor de aanmaak van vitamine A. Teveel aan vitamine A is schadelijk, dit in tegenstelling tot een overmaat aan caroteen.

It has been shown in trials that the ingestion of beta carotene at about 30 mg/day increases the rate of lung cancer and prostate cancer, and increases mortality in smokers and people with a history of asbestos exposure.

An article on the American Cancer Society says that The Cancer Research Campaign has called for warning labels on beta carotene supplements to caution smokers that such supplements may increase the risk of lung cancer.[12]

The New England Journal of Medicine published an article[13] in 1994 about a trial which examined the relationship between daily supplementation of beta carotene and vitamin E (alpha-tocopherol) and the incidence of lung cancer. The study was done using supplements and researchers were aware of the epidemiological correlation between carotenoid-rich fruits and vegetables and lower lung cancer rates. The research concluded that no reduction in lung cancer was found in the participants using these supplements (beta-carotene), and furthermore, these supplements may, in fact, have harmful effects.

The Journal of the National Cancer Institute published an article in 1996[14] about a trial that was conducted to determine if vitamin A (in the form of retinyl palmitate) and beta carotene had any beneficial effects to prevent cancer. The results indicate an increased risk of lung cancer for the participants who consumed the beta-carotene supplement.

A randomised trial into the use of β-carotene and vitamin A for prevention of lung cancer had to be stopped early due to the apparent increase in the incidence of lung cancer in those with lung irritation from smoking or asbestos exposure.[15]

A review of all randomized controlled trials in the scientific literature by the Cochrane Collaboration published in JAMA in 2007 found that beta carotene increased mortality by 5% (Relative Risk 1.05, 95% confidence interval 1.01-1.08).[16]