THE ANTIOXIDANTS STORY CONTINUED #3

A Review of the Literature: A Definition and Identification -

CONTINUED FROM YESTERDAY

The proposed definition is based on three criteria:

1) the substance is found in human diets;

2) the content of the substance has been measured in foods commonly consumed; and

3) the substance decreases the adverse effects of the types of free radicals known as reactive oxygen (ROS) and nitrogen species (RNS) in humans.

As such, a dietary antioxidant is defined in the IOM's report as a substance in foods that significantly decreases the adverse effects of ROS, RNS, or both on normal physiological function in humans. The report determines that beta carotene and other selected carotenoids, vitamin C, vitamin E and selenium should be evaluated to find if adequate data is available. The review also states that the review of antioxidant substances may include other related compounds not addressed by the panel such as flavonoids, polyphenols, phytoestrogens and lipoic acid. The significance of an IOM panel possibly deciding that there should be DRIs for these substances as antioxidants would be that a mainstream medical organization will define antioxidant function as beneficial to human health.

Antioxidant compounds such as the ones mentioned above are present in essential nutrients found in fruits and vegetables. Vitamin E is fat-soluble and is most significantly found in the lipids of cell membranes and in circulating low-density lipoproteins. It is able to become localized in cell membrane, and as free radicals are formed by oxidation, vitamin E quenches them before they damage cellular structures. Vitamin E, of which d-alpha tocopherol is the most prominent natural alternative, is particularly effective at protecting tissues that contain higher levels of polyunsaturated fatty acids. A derivative of vitamin E is tocotrienols, which differ as a result of the presence of three double binds in the carbon side chain of the tocotrienol molecule. This hydrocarbon tail is thought to give tocotrienols greater mobility and access within cell membranes and lipoproteins (and subsequently greater antioxidant activity) than tocopherols.

Vitamin C prevents oxidation of water-soluble molecules and is therefore thought to be a particularly effective antioxidant in the liquid areas of the body, including the blood plasma, lung fluid, eye fluids and in between cells. Beside neutralizing free radicals, Beta carotene prevents free radical formation by quenching singlet oxygen, a highly reactive form of oxygen that creates free radicals by transferring excessive energy to stable molecules. Beside these three nutrients, essential trace minerals, particularly selenium, have been shown to possess antioxidant-like properties.

Many plant sources beside fruits and vegetables are rich in flavonoids, which have been shown to possess antioxidant activity. The two most well-known sources for flavonoids are grape seed extract and pine bark extract. Both extracts contain a class of flavonoids called proanthocyanidins (also termed procyanidins) that have been shown to be extremely effective antioxidants. The seeds of grapes are not the only portion of the fruit indicated to have antioxidant activity. Resveratrol, a phenolic constituent found in the skin of grapes, is a substance that is one of a group of compounds called phytoalexins produced in plants during times of environmental stress. Green tea, which also contains polyphenols, is also touted as an antioxidant. For example, a Japanese "matcha" tea by Maitake Products Inc. contains four primary polyphenols: epicatechin, epicatechin gallate, epicallocatechin and epicallocatechin gallate.

Another substance indicated to have antioxidant potential is alpha lipoic acid. Some of this vitamin-like substance is converted by the body to dihydrolipoic acid, which quenches free radicals in both lipid and aqueous domains. It has also been suggested that alpha lipoic acid can replenish and/or recycle other antioxidants such as vitamins C and E. Coenzyme Q10 (CoQ10) is also a vitamin-like substance and has been found to be a potent antioxidant that is being utilized by some cardiologists in the treatment of heart failure. In simple terms, CoQ10 increases the energy output of a heart, making it stronger. Produced within the body itself, glutathione--a sulfur containing tripeptide formed in the body from amino acids--helps neutralize free radicals in cells. Levels of glutathione in the body can be increased through supplementation with selenium, N-acetyl cysteine and alpha lipoic acid.

http://www.naturalproductsinsider.com/articles/1999/01/winning-the-medical-community-over-to-antioxidants.aspx

http://www.depsyl.com/

http://back2basicnutrition.com/

http://bionutritionalresearch.olhblogspace.com/