Thursday, January 12, 2012

Antioxidants and Free Radicals

We generally think of oxygen as the stuff of life. After all, if you can’t breathe oxygen, you die. Oxygen is a vital part of respiration and of life itself, but it also has a significant down side. Oxygen is a highly reactive element, which means that it loves to combine and react with other molecules. This is very useful for driving the chemical engines that keep us alive, but byproducts of these reactions (free radicals) can cause significant damage and destruction to living tissue (cell membranes, DNA, etc.). While we absolutely need oxygen to live, we also need some kind of protection from oxygen (and free radicals) in order to prevent the damage it can cause.  

Oxygen may not seem like it would be particularly dangerous to us. But, for an idea of just how damaging oxygen can be, consider that rust is formed when oxygen interacts with iron (i.e. the iron “oxidizes”). While the cells in a human body are different from a piece of iron, the oxidation in this example is very similar to what happens in cells. This “oxidation” reaction (on a larger scale) is also what causes most fires to burn; chemicals (like wood) oxidize and release energy causing physical damage to the surrounding material. Clearly oxidizing reactions are very powerful and potentially dangerous. This is the way that oxygen can damage cells and DNA leading to cell death and premature aging.

To solve this “oxygen” problem, humans evolved the ability to make antioxidants. To understand what an antioxidant does, you just have to look at the word itself. Breaking it down, “anti” means against and “oxidant” basically means a chemical with a reactive form of oxygen. You need antioxidants to protect your body from “oxidative stress” (the cascade of damage done by reactive oxygen molecules created in your body).

Fortunately, antioxidants can prevent and protect us from most of this damage. But what are antioxidants and how can you get or make more of them in your body? What do free radicals have to do with all this and how can you minimize their formation and protect yourself and your health?


Free radicals are types of chemicals which are very chemically reactive (usually by having unpaired electrons). Typically, these chemicals are related to oxygen, which itself is a very reactive element, though other types exist (e.g. nitrogen). These oxygen based free radicals can also be called other names, such as “reactive oxygen species” (ROS).

Free radicals, due to their unpaired electron configuration, strip electrons from other atoms nearby. This sometimes causes the robbed atoms to themselves become free radicals in the process. As this cascade continues, crucial parts of cells get damaged.

When these reactive chemicals are created in your body, they can cause damage to many different types of cells. Many forms of cancer are thought to be the result of reactions between free radicals and DNA, resulting in mutations which can change the ways cells behave. Free radicals interacting with LDL (the bad cholesterol) cause physical damage to the (endothelial) cells which line arteries, leading to atherosclerosis (hardening of the arteries) and heart disease. In fact, damage from free radicals is associated with many different types of chronic illness and disease. Free radicals are thought to play a role in the process of aging as well, though it is unclear as to exactly why or how.

Free radicals aren’t all bad, though. They are created and utilized in many “normal” processes in the body. Small amounts of these reactive chemicals are actually necessary for maintaining the chemical reactions that keep us alive and healthy. When levels of free radicals get too high, and aren’t countered by antioxidants, damage starts to occur.

A certain amount of free radicals are produced by normal metabolism, but other factors can increase the amount drastically. Environmental factors and toxins contribute to much higher levels of free radicals generated in your body. Your body, in processing these and other toxins, uses many different chemical processes to convert the toxins into a form that can be more easily removed. Free radicals are produced in many of these chemical reactions. These free radicals then need to be either processed or neutralized (combined with antioxidants) in order to prevent cellular damage.

Environmental factors contributing to free radical generation include:

  • cigarette smoke
  • pollution
  • radiation (including sunlight),
  • diet (pesticides, alcohol, fructose)
  • heavy metals
  • stress
  • lack of sleep
  • both extremely high and low levels of physical activity

The things which lead to the creation of free radicals are not always obvious. Alcohol, for instance, is essentially a toxin to your body. Most people are aware that drinking lots of alcohol for a long period of time leads to liver damage. This liver damage is primarily due to the free radicals generated while your body converts the alcohol to a form that can be safely removed, rather than directly from the alcohol itself. (Incidentally, the chemical process for removing alcohol is virtually identical to how your body processes and removes fructose, which makes up half of sugar. This helps to explain why fructose is so damaging to both the liver and overall health.)


Antioxidants provide protection from the damage caused by free radicals. Basically, antioxidants are able to donate electrons to free radicals (which are dangerous because of a missing electron) and essentially neutralize them, preventing damage to your cells. Antioxidants also help your body process toxins (primarily in the liver, but every cell in the body in smaller amounts), detoxifying them and making them ready for removal. So, maintaining adequate levels of antioxidants in your body is crucial to overall health.

There are two major categories of antioxidants, based on what parts of cells they protect:

  • Fat-soluble antioxidants protect cell membranes (made up of mostly fats) from a process called “lipid peroxidation” (oxidative damage to the fats that make up cell membranes).
  • Water-soluble antioxidants protect against damage from free radicals in blood plasma (the fluid through which blood cells travel) and cytosol (the fluid inside of cells). Both types are designed to protect your cells from damage caused by free radicals.

The antioxidant system is an incredibly complex system that seeks to maintain some sort of a balance between free radical production and the protection of antioxidants. This system is not entirely understood and is not particularly intuitive. It’s not just as simple as “eat more antioxidants and you get more” because antioxidants are almost entirely produced by your body and eating more does not seem to directly raise the level of antioxidants in your blood. In addition, there are systems in place to remove “excess” levels of antioxidants from your body.

Nonetheless there are a few key chemicals from which antioxidants are manufactured in your body. Vitamin A (carotenoids), vitamin C, vitamin E (tocopherols), and polyphenols are needed for antioxidant production. These nutrients are all powerful antioxidants in their own right, but they do not seem to directly provide antioxidant protection in the body. Rather they are critical precursors and ingredients for the antioxidant production done by your body. Without these essential nutrients, you would be unable to produce antioxidants and, since insufficient levels of antioxidants leads to cell damage or cell death, you would become very ill and probably die. This is why it is essential to get adequate quantities of these key nutrients in your diet or through supplementation.


Antioxidants are found in varying amounts in foods such as vegetables, fruits, grain cereals, eggs, meat, legumes, and nuts. Some foods (e.g. a├žai, gojee berries, pomegranate, etc.) are marketed as particularly good sources of antioxidants. Eating more of these foods should raise levels of antioxidants in your body, right? Well, as intuitive as that seems, it turns out that dietary sources of antioxidants do not actually raise levels of antioxidants in your body.

While many foods do provide a strong dietary source of antioxidants, the way in which food is cooked and later digested prevents most antioxidants from being directly absorbed. Instead, antioxidant chemcials are digested and broken down into smaller chemicals which can then be absorbed by your gut. (Later on, these smaller chemicals can be used by your body in making antioxidants, but they don’t specifically stimulate production) In addition, foods which are stored at room temperature or for long periods of time are also subject to oxidation from the oxygen in air (a big reason why many foods go rancid) which destroys some of the antioxidant chemicals present.

Unfortunately, the studies which focus on dietary supplementation of antioxidants and antioxidant rich foods suggest that there is no significant boost to antioxidant production from either diet or supplements rich in antioxidant chemicals. This is not to say that antioxidant rich foods, which are also full of vitamins, minerals, and other key nutrients are not of any benefit; they are very healthy for many reasons, but they just don’t seem to specifically increase your natural production of antioxidants. Foods essentially provide the building blocks of antioxidants, which allows your body to make them as needed, but there seems to be almost no direct absorption of antioxidants from food.

Eating healthier, however, can still reduce levels of free radicals. A healthy diet can reduce the amount of free radicals generated from food intake. Avoiding refined carbohydrates and sugar (especially fructose) means that your body doesn’t generate as many free radicals during digestion. Eating organic food means you will avoid synthetic pesticides, most of which are known to generate large quantities of free radicals when consumed. Improving levels of cholesterol in your blood can reduce the chances of free radicals combining with LDL (the bad cholesterol) and causing damage to your arteries. Reducing the levels of free radicals generated in your body can have a huge impact, almost as much so as increasing antioxidant levels.


There are many different types of antioxidants which may protect us from free radicals. Let us look at just a few examples:

  • Glutathione - By far, the most widely used antioxidant and processor of toxins in the body is glutathione. Your body tightly regulates how much is available at any given time, as too much or too little is extremely dangerous. It is made up of 3 amino acids,  L-cysteine, L-glutamic acid, and glycine. Unfortunately, glutathione is not absorbed through diet or supplementation, mainly because the amino acids are separated during the digestive process. Glutathione is critical for removing toxins and neutralizing free radicals from normal metabolism, drug metabolism, and immune system responses. Glutathione can be made in almost any cell in the body, but the highest concentrations are found in the liver.
  • Curcumin - Curcumin is found in turmeric and is sometimes used as a (yellow) food coloring. Curcumin is an antioxidant, but it appears that its stimulation of glutathione production is more significant to the body than as an antioxidant itself. While it does not appear that curcumin in diet or as supplements makes it into the blood stream in any significant amount, it does have other beneficial effects in the body. For example, curcumin has valuable antiinflammatory properties.
  • Carotenoids (beta-carotene, alpha-carotene, gamma-carotene, and beta-cryptoxanthin) - Carotenoids are found in plants, where they are used in photosynthesis. Carotenoids stimulate the production of vitamin A in your body, and both exhibit a strong anti-oxidant effect. Eating a diet rich in vegetables, especially those rich in carotenoids (e.g. carrots) is associated with lower risks of cancer and heart disease.
  • CoQ10 - Though not specifically an antioxidant, coenzyme Q10 (CoQ10) is primarily used in the production of energy (ATP) in the body. However, as a part of this process, CoQ10 both gives off electrons and absorbs them. CoQ10’s antioxidant properties are important for protecting mitochondria (the parts of cells that make ATP), lipids (in cell membranes), and DNA proteins (it is one of the only antioxidants that protects all three). CoQ10 is produced almost entirely by your body (since there are so few dietary sources), but levels can get low due to illness or injury. Fortunately, CoQ10 is one of the few antioxidants that can be absorbed through supplementation. It is also very safe to supplement CoQ10, as the amount in the body is regulated so that any excess simply gets removed.
  • Flavonoids - Flavonoids are a subset of very beneficial chemicals called polyphenols, which are found in many plants (as a yellow pigment) and often touted for their health benefits, including being a potent antioxidant. However, flavonoids are very poorly absorbed in the gut (less than 5% absorption). It remains unclear what, if any, direct effect flavonoids have on protecting from free radicals. While it is true that eating flavonoid rich foods (all citrus fruits, berries, ginkgo biloba, onions, parsley, tea, red wine, and dark chocolate with a cocoa content of 70% or greater) stimulates higher levels of antioxidants, this is now believed to be because dietary flavonoids are quickly metabolised (similar to toxins). Since they are treated like toxins, your body produces antioxidants (uric acid) in order to remove them through urine. Flavonoids have many other documented health benefits, and do appear to indirectly contribute to antioxidant production.

Given that almost all antioxidants don’t seem to be very well absorbed through diet or supplementation, the best way to reduce damage from free radicals is to limit free radical production by avoiding toxins or other sources which cause free radicals to form. In addition, upper levels of antioxidants are closely regulated to prevent levels that are too high, so taking supplements only appears to be of benefit under conditions where antioxidant levels are severely depleted.


One of the only ways that has been demonstrated to reliably increase levels of antioxidants is through aerobic exercise. It appears that the increased levels of free radicals generated while exercising (you breathe more and burn more energy) somehow stimulate your body to produce more antioxidants to compensate. This is one of many reasons why regular exercise is such a key part of maintaining health. If you exercise regularly, your baseline levels of antioxidants increase, so you produce more all the time, an overall health benefit.

One caveat, however, is that exercising too much or too little can have a negative impact on levels of both antioxidants and free radicals. Drastically increasing or decreasing your amount of exercise may also have a negative impact, and so exercise levels should be changed gradually to allow your body to adjust accordingly.


Free radicals are dangerous and need to be neutralized by antioxidants. Antioxidants play a crucial role in maintaining health and preventing damage to the cells of your body. While the complex system of antioxidant production is poorly understood, what seems clear is that specifically eating antioxidant rich foods may have very little, if any, effect in helping to boost the levels of antioxidants in your body. On the other hand, regular exercise clearly helps to raise levels of antioxidants, and is a key element in any effort to increase overall health. Finally, preventing the generation of excess free radicals is crucial so that you have enough antioxidants in your body to prevent damage. Exposure to foods or toxins which cause your body to generate extra free radicals just puts more stress on your body by depleting the level of antioxidants your body naturally produces. With all of the toxins and chemicals around us on a daily basis, it’s not that hard for this system to get overwhelmed; a little effort to avoid most of these chemicals goes a long way toward lowering the stress on your body.

In summary, regular exercise, a diet of whole foods grown without synthetic pesticides and the avoidance of toxins in your environment are the best steps to ensure that your body produces enough antioxidants to keep you healthy.

Researched and written by Dr. Rebecca Malamed, M.D. with assistance from Mr. Malcolm Potter.

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