Cancer

Cancer ⁱ/ˈkænsər/, known medically as a malignant neoplasm, is a broad group of diseases involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invading nearby parts of the body. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous; benign tumors do not invade neighboring tissues and do not spread throughout the body. There are over 200 different known cancers that affect humans.^[1]

The causes of cancer are diverse, complex, and only partially understood. Many things are known to increase the risk of cancer, including tobacco use, dietary factors, certain infections, exposure to radiation, lack of physical activity, obesity, and environmental pollutants.^[2] These factors can directly damage genes or combine with existing genetic faults within cells to cause cancerous mutations.^[3] Approximately 5–10% of cancers can be traced directly to inherited genetic defects.^[4] Many cancers could be prevented by not smoking, eating more vegetables, fruits and whole grains, eating less meat and refined carbohydrates, maintaining a healthy weight, exercising, minimizing sunlight exposure, and being vaccinated against some infectious diseases.^[2][5]

Cancer can be detected in a number of ways, including the presence of certain signs and symptoms, screening tests, or medical imaging. Once a possible cancer is detected it is diagnosed by microscopic examination of a tissue sample. Cancer is usually treated with chemotherapy, radiation therapy and surgery. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.^[6]

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Free Radicals

The free radical theory of aging (FRTA) states that organisms age because cells accumulate free radical damage over time.^[1] A free radical is any atom or molecule that has a single unpaired electron in an outer shell.^[2] While a few free radicals such as melanin are not chemically reactive, most biologically-relevant free radicals are highly reactive.^[3] For most biological structures, free radical damage is closely associated with oxidative damage. Antioxidants are reducing agents, and limit oxidative damage to biological structures by passivating them from free radicals.^[4]

Strictly speaking, the free radical theory is only concerned with free radicals such as superoxide ( O₂^- ), but it has since been expanded to encompass oxidative damage from other reactive oxygen species such as hydrogen peroxide (H₂O₂), or peroxynitrite (OONO^-).^[4]

Denham Harman first proposed the free radical theory of aging in the 1950s,^[5] and in the 1970s extended the idea to implicate mitochondrial production of reactive oxygen species.^[6]

In some model organisms, such as yeast and Drosophila, there is evidence that reducing oxidative damage can extend lifespan.^[7] In mice, interventions that enhance oxidative damage generally shorten lifespan.^[8] However, in roundworms (Caenorhabditis elegans), blocking the production of the naturally occurring antioxidant superoxide dismutasehas recently been shown to increase lifespan.^[9] Whether reducing oxidative damage below normal levels is sufficient to extend lifespan remains an open and controversial question.

Source: http://en.wikipedia.org/wiki/Free-radical_theory_of_aging

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Anti Oxidants

An antioxidant is a molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction that transferselectrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When the chain reaction occurs in a cell, it can cause damage or death to the cell. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions. They do this by being oxidized themselves, so antioxidants are often reducing agents such as thiols, ascorbic acid, orpolyphenols.^[1]

Substituted phenols and derivatives ofphenylenediamine are common antioxidants used to inhibit gum formation in gasoline (petrol).

Although oxidation reactions are crucial for life, they can also be damaging; plants and animals maintain complex systems of multiple types of antioxidants, such as glutathione, vitamin C, vitamin A, and vitamin E as well as enzymes such as catalase,superoxide dismutase and various peroxidases. Insufficient levels of antioxidants, or inhibition of the antioxidant enzymes, cause oxidative stress and may damage or kill cells. Oxidative stress is damage to cell structure and cell function by overly reactive oxygen-containing molecules and chronic excessive inflammation. Oxidative stress seems to play a significant role in many human diseases, including cancers. The use of antioxidants in pharmacology is intensively studied, particularly as treatments for stroke and neurodegenerative diseases. For these reasons, oxidative stress can be considered to be both the cause and the consequence of some diseases.

Antioxidants are widely used in dietary supplements and have been investigated for the prevention of diseases such as cancer, coronary heart disease and even altitude sickness. Although initial studies suggested that antioxidant supplements might promote health, later large clinical trials with a limited number of antioxidants detected no benefit and even suggested that excess supplementation with certain putative antioxidants may be harmful.^[2][3][4] Antioxidants also have many industrial uses, such as preservatives in food and cosmetics and to prevent the degradation of rubber and gasoline.^[5]

Source: http://en.wikipedia.org/wiki/Antioxidant

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