Dear Holly,
Everyone talks about ANTI oxidants being good for you, and how many are found in plants. But don't we need oxygen to live? What is so bad about oxygen? Is this a dumb question?
Sylvia in Colorado
Dear Sylvia,
It's an excellent question! It's so good, that I have to give an especially long answer, so forgive me for this.
Most school kids learn that blood delivers oxygen from the lungs to the rest of the body, and that oxygen is required for life. Most people don’t know why it is needed, but mistakenly believe that oxygen is somehow intrinsically good. Indeed, many health fads capitalize on this misconception by trying to sell you oxygen, as if you could not breathe it already. Because wares designed to increase oxygen are peddled as health aids, we receive the idea that oxygen does something nebulously good. As a matter of fact, oxygen is very toxic and corrosive, and you would do well to think twice about buying anything claiming to increase oxygen. Just think about how it rusts and corrodes metal. Most “oxygen-boosting” products do not actually increase your oxygen, thank goodness. They merely deplete your cash.
You can shell out a lot of money for “oxygenated water”, which is great if you are a fish. All water exposed to air is oxygenated anyway, otherwise, fish could not breathe in it. Oxygen from the air dissolves down into water naturally. The oxygen you obtain from breathing is significantly in excess of any you could possibly derive, if any, from drinking even super-oxygenated water. Assuming you could absorb the oxygen dissolved in water through your digestive tract, which is iffy, you would have to drink a ridiculous number of liters of the stuff to match the amount of oxygen you get from one breath.
Many claims for oxygenated water and special waters violate so many fundamental laws of chemistry, they make me dizzy. Several of the companies making these claims have been fined by the FTC, yet continue selling oxygenated water, boasting supportive clinical trials, which they never release for anyone to actually read. One company, for example, claims to have even shrunk the water molecules in their product, to make room for more oxygen! No scientist has ever shrunk a molecule. All water molecules are identical, and have the same size. If you change a molecule, the process is called a reaction, and it is not the same molecule, anymore. Unless you have gills, do not give oxygenated water a second glance.
Magnet sellers argue that their magnets attract the iron in the blood, and thus bring oxygen-bearing blood to the magnetized body area. But there are many different forms of iron. The iron in blood is actually of a sort which is never capable of being attracted to a magnet, so this claim is utterly false. Magnetic iron requires that many iron atoms be crammed together into a clump, and also requires that each iron atom in the clump has unpaired electrons all spinning in the same direction, which cooperatively create a magnetic field. A hemoglobin molecule has four distantly spaced iron atoms, (or more properly, ions, because each is missing two electrons and thus has a positive charge). They are so far apart that they cannot create a magnetic field. You can always prick your finger and wait for your blood to approach a nearby magnet, but you will wait a long time.
“Oxygen bars” are so-called health establishments where you can pay to stick tubes up their nose and have oxygen piped through, often accompanied by your favorite scent. Unless you are a whale or dolphin, mammals such as ourselves do not store oxygen well, so there are no positive long-term benefits; breathing pure oxygen beforehand cannot prevent you from suffocating later, and it could even do real damage. I recently visited an oxygen bar, out of curiosity, which sported all sorts of massage chairs, fountains, and festively colored lights. I would like to try the massage chairs some day, for the sake of research, but will decline the oxygen. I was told the oxygen that they sold was a different sort of oxygen, so it could not hurt you. All oxygen molecules are the same, so I cannot imagine how their oxygen could be of a different kind.
Pressurized oxygen therapy is a successful, accepted medical treatment for extreme cases of necrotic, gangrenous tissue, or crush injuries, where oxygen has been cut off from cells. Supplying the oxygen to the previously deprived cells can accelerate tissue healing. It is also used for anaerobic bacterial infections, which thrive in low oxygen concentrations. Even in these cases, medical personnel must be specially trained to deliver the least amount of oxygen that has a therapeutic effect, because too much oxygen causes injury.
There is a very real risk of harming tissues by subjecting them to too much oxygen. Excess oxygen shuts down critical cell reactions, causing cell death and tissue injury. Oxygen overdose oxidizes, or “rusts” the iron in blood, such that the iron is no longer of a form capable of carrying oxygen. The iron capable of carrying oxygen has two missing electrons, and is called iron II ion, or ferrous ion. Excess oxygen removes one more electron from iron, resulting in iron III ion, or ferric ion. Ferric ion cannot carry oxygen and ironically (no pun intended) produces anoxia, or oxygen deprivation. Premature infants given oxygen risk permanent blindness. Scuba divers who dive excessively deep, or who use a high oxygen-percent mixture called Nitrox, must worry about “oxygen toxicity”, which entails nausea, dizziness, vision problems, seizures, and fluid in the lungs, the dreaded “pulmonary edema”. Why is oxygen so toxic?
The oxygen that we require for life is unfortunately a biradical, that is, it has two unpaired electrons, and thus it is a free radical, and does all the bad things that free radicals do. You might think that the two unpaired electrons on oxygen ought to simply pair up, resolving the problem, but the reason why this cannot occur involves the mathematically allowed and forbidden energies of electrons. Not only is oxygen a free radical, but oxygen is also very good at generating other free radicals and free radical generators. Hydrogen peroxide (the active ingredient in peroxide bleach), superoxide, and hydroxyl radical are the customary oxygen-generated saboteurs. Scientists call these bad guys collectively “reactive oxygen species”, frequently abbreviated “ROS” in scientific papers. They are also called oxidizing agents.
Since we continually inhale oxygen to stay alive (and I will explain why, shortly,) we are constantly generating these toxic oxygen by-products, in addition to subjecting ourselves to damage done by oxygen itself. Fortunately we also have enzymes, such as catalase and superoxide dismutase, which perpetually convert oxidizing agents into relatively harmless molecules like water. The cells of healthy people also constantly produce a good number of non-enzyme molecules, which chemists call reducing agents. They inactivate oxidizing agents, and repair the damage that is done by them. The more common term for reducing agent is antioxidant.
Every experienced breathing person knows that we need oxygen, yet so few know why. We need oxygen to accept electrons in an energy-generating event called “the electron transport chain”. In this process, electrons are shuttled from one protein to another in a cellular structure known as a mitochondrion. High school biology students dutifully learn and regurgitate the phrase “the powerhouse of the cell” in reference to mitochondria. This electron transfer flows easily, because of the proteins’ relative abilities to successively accept them. As a mill uses a river’s current to grind flour, the electron flow is used to construct an energy-carrying molecule called adenosine triphosphate, or ATP, for short. ATP is needed for all sorts of cellular processes that require energy to run. The old phrase “the energy currency molecule” is what the same high school students apply to ATP. The problem with the electron transport chain is that all of these flowing electrons have to end up somewhere, and that is where oxygen comes into the picture. The very last acceptor of electrons is oxygen.
When combined with electrons and hydrogen in this process, oxygen usually becomes water, which is relatively harmless, and that is the end of the oxygen. Occasionally, however, oxygen does not pick up enough electrons, and it then becomes either the superoxide radical, or hydrogen peroxide, and both of these, like hardened sub-microscopic vandals, damage nearby molecules. Their formation is more likely to occur when there are too many oxygen molecules competing for electrons. Without somewhere for the electrons to ultimately go, the electron transport chain backs up and stops, so oxygen is required for this energy-generating process. About ninety percent of the oxygen we breathe is used for this purpose.
So, oxygen is both good and bad. We can’t survive without it, but like a criminal whose fingerprints keep turning up at crime scenes, oxygen is a prime suspect for accelerating aging and disease. Unless you have a lung disease like emphysema, or are climbing Mount Everest, you have enough oxygen, I promise you.
We hear of things “getting oxidized”, and we know it relates to the aging of a material, but what is really happening? Oxygen readily changes other molecules, and in doing so is said to “oxidize” them. For the oxidation we are interested in, we need to focus on organic, or carbon-containing molecules. Organic molecules are required for life and are present in all organisms. A more precise definition says that oxidation is the loss of electrons. Oxygen tends to be greedy with electrons, and when it attaches to a less greedy atom, pulls electrons away from that atom. Since oxygen tends to pull the electrons in a bond toward itself, attaching it to a carbon causes the carbon to “lose” some electron density through the bond to oxygen. If the carbon in a molecule makes more bonds to oxygen atoms, we say it “got oxidized”. The most oxidized, electron-depleted form of carbon is carbon dioxide. Hydrogen is more electron generous, and likely to push electrons in its bonds toward carbon, so a molecule can also get oxidized when the carbons in it lose bonds to hydrogen.
The reverse process bears a little discussion, because it is what antioxidants do. The reverse of oxidation is called reduction, so reduction is the gain of electrons. This sounds backwards, because usually reduction means the loss of something, as in weight reduction. But electrons are negatively charged, so this reduction refers to the drop in numerical charge that occurs when electrons are gained. When the carbon in a molecule loses bonds to electron-greedy oxygen, or gains bonds to electron-generous hydrogen, we say the molecule got reduced. Molecules that enable this are termed reducing agents, but most people call them antioxidants. They are good, because they prevent oxidation. But what is so bad about getting oxidized?
We actually benefit from oxidizing our own molecules, but in a very controlled sort of way, in order to generate energy. Another term for combining-with-oxygen is combustion, or burning. When we burn fuels, the fuel molecules combine with oxygen. When the fuels contain carbon, the ultimate product is carbon dioxide, where carbon is as oxidized as it can possibly get. In fact, for each gallon of gasoline we burn, we generate an astonishing twenty pounds of carbon dioxide, (a figure I find easy to remember, because it is the weight of my largest cat.) Our bodies also burn organic molecules, and produce carbon dioxide as a waste product. As with burning things, oxidizing molecules always releases energy, and that energy can either be lost as heat, or it can be channeled into more useful forms. When we “burn carbohydrates,” or any other carbon-containing molecules for that matter, we are using up the molecule’s potential to generate energy, and that energy is stored in some other form, like ATP. This process involves successive additions of oxygen and removals of hydrogen from the nutrient. Since oxidation is the loss of electrons, oxidizing food removes electrons from the food molecules, and these electrons are then used for the electron transport chain, which, as I described above, generates energy.
Highly reduced molecules have carbons with the least oxygens attached and the most hydrogens attached. Since the molecule starts off with a lot of potential places to add oxygen, it requires the most steps to become oxidized, and will provide the most energy. Fats and oils fall into this category, as well as fuels like gasoline, propane, butane, and methane, which are known as hydrocarbons. The more oxygen a molecule has attached, the more oxidized or “burned” it is already, and the less energy it can provide. This is not bad in itself; we require both highly reduced molecules, like fats and oils, as well as partially oxidized molecules, like carbohydrates, for energy. Uncontrolled oxidation, however, cripples essential molecules.
Scientists are extensively researching this phenomenon, which they term oxidative stress.
This uncontrolled molecular oxidation is accelerated by all sorts of disease processes, aging, and both short- and long-term exposure to a large number of toxins. Oxidation of molecules alters them, and when you indiscriminately alter molecules, they do not function properly. Oxidative stress, in turn, exacerbates aging and disease processes, creating a vicious circle. Organisms combat oxidative stress by producing numerous antioxidants, and some of these are vitamins, but many are not.
One of the most ubiquitous non-vitamin antioxidants is glutathione, which I am personally fond of, because my graduate research focused on it. Glutathione’s depletion is clearly associated with aging, toxins, and disease, and boosting cell’s production of it often improves the outcome of the situation. When consumed orally, glutathione is broken down, and is no longer glutathione anymore. Too bad! However, some of its constituents and related molecules (cysteine and N-acetyl cysteine,) often increase glutathione production in situations where glutathione is already depleted. One of my jobs, in graduate school, was to synthesize glutathione-boosting drugs. These drugs did help prevent the customary liver destruction caused by an overdose of acetaminophen, and I remain impressed by glutathione for this and several other reasons.
The association of other cellular antioxidants and oxidant-destroying enzymes is very often associated with positive outcome in studies, as well, and these studies are far too numerous for me to mention here. Bear in mind that some studies do fail to link antioxidants with positive outcome. However, fewer studies actually show a negative outcome. A popular theory for how regular exercise maintains good health involves oxygen. Exercise subjects cells to mild oxidative stress, which stimulates antioxidant defense systems. The suggestion that dosing oneself with antioxidants could slow down the aging process seems logical, at least, but just because something seems logical does not make it true!
As you may imagine, the exciting prospect of slowing aging has scientists vigorously pursuing this topic. While the theory certainly seems sound, it has yet to be proven that consuming antioxidant supplements prolongs the lives of actual people. What is clear is that consuming more plants, which contain lots of antioxidants, enhances your health. So, it seems you are better off following the famous motherly request, and eating your fruits and vegetables, than trying to get them in a pill. The only studies that clearly demonstrate life-prolongation due to diet involve calorie restriction in lab animals. Animals that lived longer were given less food. Isn’t that depressing! What is interesting about these studies is that some show this dietary restriction decreases the production of free radicals, oxidizing agents, and inflammation, perhaps because there are fewer molecules around to get oxidized.
While you can’t “reverse aging”, you can lower the risk of certain age-related diseases by maintaining the antioxidant status of your body. Plants contain a dazzling array of different antioxidants, which are associated with numerous health benefits.
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