Zahra Nazari - Food Quality And Safety Research Department, Food Science And Technology Research Institute, ACECR,Khorasan Razavi Branch, Iran

Vitamins, minerals, trace elements, and other bioactive substances are available as supplements, usually in pill or powder form. These began to be manufactured and marketed after their functions wereidentified, and claims made for their general benefits in prevention of disease and promotion of well being. Many dietary supplements are classed as foods, although some may be regulated medicinal products. Manufacturers of food supplements may market their products using health claims, although in some countries, medicinal claims that the product can prevent, cure, or treat a disease may not bemade. Herbal products may be permitted to make certain claims based on their history of being used for a particular condition. The regulatory status of dietary supplements varies from country to country.Some nutrients such as water-soluble vitamins have been thought to be harmless at pharmacological doses; but there is now evidence, including some summarized and judged in this Report, that this is notalways the case. Other nutrients, including fat-soluble vitamins and all minerals and trace elements, are known to be toxic at pharmacological doses; some of these, selenium being one example, are known to be toxic at relatively low pharmacological levels.Many people take dietary supplements.The evidence that the use of high-dose beta-carotene supplements in tobacco smokers is a cause of lung cancer is convincing. There is limited evidence suggesting that high dose retinol supplements are a cause of lung cancer in this group. The principal cause of lung cancer is smoking tobacco. Calcium probably protects against colorectal cancer. At specific doses, selenium probably protects against prostate cancer. There is limited evidence suggesting that retinol at specific doses protects against squamous cell carcinoma of the skin. There is also limited evidence suggesting that alpha-tocopherol protects against prostate cancer; and also that selenium at specific doses protects against colorectal cancer (ata level of 200 μg/day, the dose used in the studies on which this judgement is based). There is limited evidence suggesting that selenium supplements are a cause of skin cancer. It is unlikely that beta-carotenesupplements, or foods containing it, have a substantial effect on the risk of either prostate cancer or skin (non-melanoma) cancer

Cancer Prevention, Nutrition and Cancer, Cancer Treatment and Management, Targeted Cancer Therapy, Drugs and Cancer