We have all heard that antioxidants are important in skincare. Do you know why? Do you know what they are? How they protect skin? How they make life possible?
Without them, we’re all dead.
Most women realize topical antioxidants provide important anti-aging benefits to skin. They are less likely to understand how and why they are beneficial. If oxygen is so critical to life, why would one want to counteract it? What does the term antioxidant even mean? This post provides answers to that apparent paradox.
Oxygen is 49.2% of the mass, and most abundant element, in the earth’s crust. It is a major constituent of the silicon dioxide and metal oxides found in rock, clay and sand. Rust-colored soil and rock are evidence of oxygen combined with iron. When oxygen combines with hydrogen to create water, it comprises 89% of the mass of the molecule.
Because oxygen has such enormous propensity to chemically combine with other elements, there was no free oxygen in the atmosphere for much of earth’s history. Atmospheric oxygen first appeared about 2.3 billion years ago when cyanobacteria (capable of photosynthesis) began to produce free oxygen at a rate greater than it was chemically captured by iron or organic matter. It took 200 million years for oxygen in the atmosphere to increase to levels capable of sustaining forms of life dependent upon it for energy production
Oxygen – good and bad?
To understand the role anti-oxidants play in health, and why they are actually indispensable to life itself, one must acknowledge the two-edge sword the element oxygen poses to all life forms that depend on it for their very existence.
Oxygen is the cause of good and bad effects in organisms of all types. It is required to convert foodstuffs into the metabolic energy that powers the physiologic processes of life. Yet, too much oxygen is detrimental, even deadly. On a macroscopic level, the human nervous system, eyes, and lungs are particularly susceptible to oxygen injury. At the cellular or microscopic level, all cells are at risk.
The power of life – reduction-oxidation chemical reactions (a.k.a. redox)
Elemental oxygen was discovered in 1774. In 1790 the term oxidation was coined from the words oxygen and acid to indicate a chemical reaction in which oxygen combined with another substance. The term oxidizer has since been adopted to include any substance that behaves in a way similar to oxygen i.e. it accepts electrons from other substances. The substance giving up electrons to oxygen is therefore “oxidized.” Oxidization can be extremely fast or extremely slow.
The chemical redox process in a rocket flame that propels a spacecraft into orbit is identical to that which causes a wrecked car to slowly crumble into a pile of rust over decades, or apple slices to brown in the air. How is that possible, you ask? It has to do with the concept of electronegativity, which refers to the relative propensity of a substance to donate or accept electrons in redox reactions.
For some substances the value is positive, for other the value is negative, but that is only part of what determines which substance is an oxidizer and which is a reducer in a chemical reaction between two specific reagents. It is the absolute difference in value between the two substances that ultimately determines which way and at what rate electrons will flow in a chemical reaction.
The greater the difference between the two substances chemically reacting determines how rapidly a reaction occurs. In the case of chemical reactions within the human body, all differences must be very small – we want (and, indeed, must have) our chemical reactions to more resemble the rusting automobile than the rocket flame.
The reason is obvious when one considers how our bodies utilize oxygen to transform the stored energy in our food into usable biologic energy. This occurs through oxidization of small carbon-based molecules of fuel within the mitochondria of our cells.
The process is controlled by enzymatic catalysts that release the stored energy in a stepwise gradual fashion, converting it into ATP (adenosine triphosphate), the form in which it powers our body processes. The energy is used to synthesize tissue, contract muscle, or power ion and molecular pumps that move charged particles across membranes, creating the conditions required to enable neurons to “fire”, reabsorb solutes to concentrate urine, and remove toxins from the blood as it transits the liver.
How food is created: storing the sun’s energy for later release.
All animal food ultimately has its source in solar energy. Plant chlorophyll activated by sunlight enzymatically combines water and atmospheric carbon dioxide into sugars or polymers of sugar (cellulose). Carnivores also get their food from the sun’s energy because somewhere down the food chain a plant-eater is eaten as food.
Sunlight-activated chlorophyll enables solar energy to be stored by pushing electrons against the electronegativity gradient that exists between oxygen and carbon. Because all food is carbon- based, food it is essentially “stored” solar energy. The return of the electrons, in incremental stepwise fashion back to oxygen within intracellular mitochondria, releases the energy that powers life.
Reactive oxygen species (ROS) – by-products of cellular respiration that also electron “hungry”
ROS are oxygen containing intermediate molecules created during the electron transfer of carbon to oxygen within mitochondria. ROS are also electron “hungry.” They react with molecules in their vicinity, most notably molecules found within mitochondria or cellular membranes. ROS are also called “free radicals”, defined as molecules lacking enough electrons to balance their electrical charge. Like oxygen, free radicals are always seeking their missing electron – and could care less where they get it.
Antioxidants are valuable in combating the deleterious effects of ROS because they supply the “missing” electron instead of it being “stolen” from a molecule within the cell structure. Unless an antioxidant supplies the electron that “neutralizes” an ROS molecule, it will grab it wherever it can. Because ROS are created as part and parcel of the way in which our bodies utilize food for energy, they are major contributors to aging in all tissues.
Food for thought: It is known that calorie restriction is an effective means of prolonging life (animals and people that eat less live longer). The scientifically plausible reason is reduction in mitochondrial energy production because of reduced calorie intake means reduced creation of ROS, and hence, less accumulation of cellular damage from free radicals.
While the production of free radicals are an intrinsic part of the process of cellular respiration (the oxidizing of carbon-based molecules derived from food), ROS are also created by other means, most notably solar radiation on the skin, smoking, environmental toxins, and repetitive micro trauma. Regardless of origin of the ROS, inflammation is triggered when free radicals damage cells and tissues. Because inflammation is never restricted only to damaged cells, surrounding normal tissue can be negatively affected. Antioxidants are therefore essential in combating the aging effects of inflammation on the skin.
Intrinsic anti-oxidant systems at work in all living organisms
Both plants and animals have metabolic functions that create ROS, in plants the most notable one being photosynthesis. Even in the production of the food that powers life, oxygen is both friend and foe. Elaborate systems have therefore evolved to manage the ROS in all life forms. This was an evolutionary necessity because ROS also play an important role in “signaling” functions i.e. modulating biochemical processes. Too many ROS is bad, but so is too few. Total elimination of ROS is neither possible nor desirable.
Three intrinsic systems enzymatically manage ROS levels in animals. They are: superoxide dismutase (SOD), catalase, and glutathione peroxidase. These enzymes are manufactured within the interior of the cell and are our major inherent defense against free radical damage. With age, however, the efficiency of these systems deteriorates and extrinsic antioxidants become more and more important. The effectiveness of the intrinsic enzyme systems declines most significantly after the hormonal changes of puberty occur.
Extrinsic antioxidants are either eaten or applied topically and include, in particular, vitamins E and C. Vitamin E is fat soluble; vitamin C is fat soluble. Both are important because of the need to provide antioxidant activity to the lipid (fat) and water containing portions of cells and tissues. Because oral vitamins have limited ability to protect the skin, it is well recognized that topical application is an essential part of an effective anti-aging skincare regimen.
There are other antioxidants that can help protect skin from damage caused by free radicals. Many are plant derived including resveratrol and green tea. Retinol, a form of vitamin A, has antioxidant effect in addition to its benefit in promoting skin cell turnover. Because of the damaging “cascade effect” when one free radical creates another as they sequentially “steal” an electron, it is important to extinguish the process early.
Topical antioxidants do just that.