Antioxidants and cancer

Reactive oxygen species (ROS) are by-products of metabolism that increase in the body during inflammation, smoking, and exposure to agents such as radiation and certain drugs. ROS cause damage to DNA and other molecules, and they are implicated in the development and progression of cancer. Antioxidants from endogenous and dietary sources can neutralize and destroy ROS and may play a role in cancer prevention. Experimental and animal studies have shown that treatment with single or combined antioxidants prevents neoplastic transformation of normal cells and inhibits tumor growth. Human observational studies suggest that high intake of antioxidant-rich foods, notably fruits, vegetables, and grains, is inversely related to cancer risk. However, prospective human studies that began to accrue data in the 1990s did not always confirm this relationship. Randomized, controlled clinical trials using specific antioxidant supplementation have also produced mixed results, but study limitations and confounding factors often make it difficult to derive definitive conclusions. Antioxidant supplementation during cancer treatment remains controversial. Radiotherapy and certain chemotherapeutic agents rely on ROS to destroy cancer cells. Although antioxidant supplementation may help protect normal cells from ROS damage and may have palliative effects during cancer treatment, studies suggest that cancer cells may also be protected from ROS damage, thereby reducing treatment efficacy and patient survival. This article reviews evidence for the impact of antioxidant supplementation and antioxidant-rich diets on cancer risk and mortality. It also outlines some of the factors that may have contributed to the conflicting outcomes reported.

Antioxidants

The antioxidants are molecules capable of retarding or anticipating the oxidation of other molecules. Epidemiological results have shown that the persons who consume a rich diet of fruits and vegetables present a minor risk of suffering different types of cancer, cardiovascular and neurological diseases, and a minor mortality than the persons who consume few fruits and vegetables. Others studies suggests that the vitamins are antioxidants like can to decrease hurt oxidative in the physiopathology of many chronic diseases and cancer. Nevertheless, evidence of new studies in mice shows that vitamins can promote the growth of tumors and metastasis and the expression of the gene p53. Current studies indicate that patients with cancer and people who have a major risk of cancer will have to avoid taking complements of antioxidants, due to the fact that it was thought that antioxidants might protect cells against cancer since they neutralize reactive oxygen species (ROS) that can damage the DNA, but in studies of animals, it has been indicated that the presence of major concentrations of antirust exogenous prevents the type of hurt of free radical that has been associated with the formation of cancer.

Food Research International, 2011

The search for therapeutic anticancer agents from plant-based foods became the work of numerous researchers when epidemiological studies showed a relationship between the low incidence of cancer and the intake of plant-based foods. These researchers were especially interested in plant-based foods with high antioxidant capacities because of the important role antioxidants have been postulated to play in the prevention and treatment of certain cancers. However, at present there is no conclusive proof that high antioxidant activity is a good indicator of high anticancer activity. This poses a challenge for researchers to directly test this hypothesis and resolve the debate. This review summarized the data on both sides of the debate.

Nutrition Research Reviews, 1994

Food Chemistry, 2009

Epidemiological studies have consistently linked abundant consumption of fruits and vegetables to a reduction of the risk of developing several types of cancer. In most cases, however, the identification of specific fruits and vegetables that are responsible for these effects is still lacking, retarding the implementation of effective dietary-based chemopreventive approaches. As a first step towards the identification of foods endowed with the most potent chemopreventive activities, we evaluated the inhibitory effects of extracts isolated from 34 vegetables on the proliferation of 8 different tumour cell lines. The extracts from cruciferous vegetables as well as those from vegetables of the genus Allium inhibited the proliferation of all tested cancer cell lines whereas extracts from vegetables most commonly consumed in Western countries were much less effective. The antiproliferative effect of vegetables was specific to cells of cancerous origin and was found to be largely independent of their antioxidant properties. These results thus indicate that vegetables have very different inhibitory activities towards cancer cells and that the inclusion of cruciferous and Allium vegetables in the diet is essential for effective dietary-based chemopreventive strategies.