Antioxidant and Free Radicals

Noni is a powerful antioxidant.
An antioxidant is a substance that reduces the oxidative damage caused by free radicals.

Antioxidants

Antioxidants are phytochemicals, vitamins and other nutrients that protect our cells from damage caused by free radicals. In vitro en in vivo studies have shown that antioxidants help prevent the free radical damage that is associated with cancer and heart disease. Antioxidants can be found in most fruits and vegetables but also culinary herbs and medicinal herbs can contain high levels of antioxidants. Dragland S and colleagues showed in their study entitled "Several Culinary and Medicinal Herbs are Important Sources of Dietary Antioxidants", and published in the Journal of Nutrition (2003 May) that the antioxidant level of herbs can be as high as 465 mmol per 100 g.A study in 2006 by Thompson HJ showed that a botanical diversity of fruits and vegetables plays a role in the biological effect of antioxidant phytochemicals. The consumption of smaller quantities of many phytochemicals may result in more health benefits than the consumption of larger quantities of fewer phytochemicals.

What are free radicals?
Free radicals are formed as part of our natural metabolism but also by environmental factors, including smoking, pesticides, pollution and radiation. Free radicals are unstable molecules which react easily with essential molecules of our body, including DNA, fat and proteins. All organic and inorganic materials consist of atoms, which can be bound together to form molecules. Each atom has a specific number of protons (positively charged) and electrons (negatively charged). Most single atoms are not stable because they have to few or to may electrons. Atoms try to reach a state of maximum stability by giving away or receiving electrons from other atoms, thereby forming molecules. Free radicals are molecules with have one electron too much or to less in order to be stable. Free radicals try to steal or give electrons to other molecules, thereby changing their chemical structure.

When a free radical attacks a molecule, it will then become a free radical itself, causing a chain reaction which can result in the destruction of a cell. Antioxidants have the property to neutralize free radicals without becoming a free radicals themselves. When antioxidants neutralize free radicals by receiving or donating an electron they do not become antioxidants themselves because they are stable in both forms. In other words, antioxidants are chemicals that offer up their own electrons to the free radicals, thus preventing cellular damage. However, when the antioxidant neutralizes a free radical it becomes inactive. Therefore we need to continuously supply our body with antioxidants. The action of free radicals could increase the risk of diseases such as cancer and hearth problems and could accelerate ageing. Antioxidants have the property to neutralize the free radicals and prevent damage. Well known examples of antioxidants are the vitamin C, E and beta-carotene. These three vitamins are often added to the so called ACE drinks. But there are numerous other rather unknown antioxidants such as lycopene, and lutein.

Benefits of antioxidants
Numerous studies with plant phytochemicals show that phytochemicals with antioxidant activity may reduce risk of cancer and improve heart health.

Antioxidants reduce the risk of cancer

Not all results are conclusive but many studies show that antioxidants may reduce the risk of cancer. A large randomized trial on antioxidants and cancer risk was the Chinese Cancer Prevention Study (1993). This study showed that a combination of the antioxidants beta-carotene, vitamin E and selenium significantly reduced incidence of cancer. However, the Alpha-Tocopherol / Beta-Carotene Cancer Prevention Study (1994) showed that intake of beta-carotene increased lung cancer rates of male smokers.

Antioxidants protect the heart

Everyone knows that cholesterol causes heart diseases and tries to limit cholesterol intake. But a more important cause of fatty buildups in the arteries is the oxidation of low-density lipoprotein cholesterol. The use of dietary supplements of antioxidants could reduce the risk of cardiovascular disease, but there is no hard evidence. At this stage, studies only show that the intake of foods, naturally rich in antioxidants reduces this risk.

Antioxidant claims on foods

Antioxidants can be found in most foods, especially in fruits and vegetables, but we see more and more food products on the shelves with antioxidant claims. These antioxidant claims crop up everywhere: from beverages to chocolates. Food producers do this because of the very high consumer awareness of the term antioxidants. Consumers believe that a high intake of antioxidants will protect them from ageing, cancer, heart disease and other diseases. This awareness already started in the 1990s when mainly beverage producers launched so called ACE drinks, which contained the three antioxidant vitamins vitamin A, C and E. Now food producers are adding supper fruits such as red berries, pomegranate and acai. When the food producer claims antioxidants, they are mainly looking at the total content of antioxidants and not at their biological activity. The antioxidant activity of foods is mainly expressed as FRAP, ORAC or TEAC values, all of which are measured in a test tube. In future the antioxidant activity should be measured in humans, by determining the quantities absorbed in the blood and tissues.

What are free radicals?

Free radicals are atomic or molecular species with unpaired electrons in the outermost bonding orbital and are likely to take part in chemical reactions. Electrons prefer to be in pairs and when an electron is alone in its orbital in will try to take an electron from another atom to become more stable. When the other atom loses its electron it tries on its turn to steal an electron from another atom, often resulting in a dangerous chain reaction. Free radicals can cause damage to our cells but they also play an important role in a number of biological processes, such as the intracellular killing of bacteria by white blood cells and some cell signalling processes.

Types of free radicals

Most free radicals are coming from oxygen atoms and are called Reactive Oxygen Species (ROS), such as superoxide ion, hydroxyl radical, hydrogen peroxide and singlet oxygen.

Superoxide ion (or reactive oxygen species) is an oxygen molecule with an extra electron. This free radical can cause damage to mitochondria, DNA and other molecules. Our body can neutralize superoxide ions by producing superoxide dismutase.

Hydroxyl radical is formed by the reduction of an oxygen molecule in the electron transport chain. It is a neutral (not charged) form of the hydroxide ion. Hydroxyl radicals are highly reactive and form an important part of radical biochemistry. Unlike superoxide the hydroxyl radical cannot be eliminated by an enzymatic reaction. Is has a very short half-life and will only react with molecules its vicinity. Because of its high reactivity it will damage most organic molecules such as carbohydrates, DNA, lipids and proteins.

Singlet oxygen is formed by our immune system. Singlet oxygen causes oxidation of LDL cholesterol.

Hydrogen peroxide is not a free radical but it is involved in the production of many reactive oxygen species. Hydrogen peroxide is a byproduct of oxygen metabolism and is neutralized by peroxidases.

Sometimes reactive nitrogen atoms are involved and these free radicals grouped under Reactive Nitrogen Species (RNS). Nitric acid is the most important RNS. Some transitional metals, such as iron and copper, have many numbers of unpaired electrons and can also act as free radicals. These metals do not have that strong electron affinity but can easily accept and donate electrons.

Oxidative damage

Free radicals can damage DNA in different ways. They can disrupt the duplication and maintenance of DNA, brake open the DNA molecule or they can alter the structure by reacting with the DNA bases. Lipids in cell membranes are very prone to oxidative damage because some free radicals tend to concentrate in the membrane and cause oxidative damage, known as lipid peroxidation. Many forms of cancer are thought to be the result of reactions between free radicals and DNA, resulting in mutations that can lead to malignancy. Other diseases such as atherosclerosis, Parkinson's disease and Alzheimer's are also attributed to free radicals.