You’ve read the blog posts telling you to eat more blueberries, or drink more green tea or indulge in more dark chocolate because these foods are packed with healthy antioxidants that are crucial for gobbling up nasty free radicals that do your body harm.
These foods and several others do contain significant amounts of antioxidants, but is it true that simply eating more blueberries or eating more dark chocolate will prevent damage by free radicals?
Have you actually seen the evidence?
What about the health benefits of antioxidant supplements such as vitamins C and E, selenium, glutathione, and beta-carotene? There’s a multi-million dollar industry marketing them to the public as wonder supplements.
But do they work in your body to neutralize free radicals and thus make you a healthier individual or could they actually harm your health?
Let’s take a closer look at antioxidants and see if dietary antioxidants can really improve your health. This post is rather long, but I guarantee you’ll be surprised by what you find out.
What Are Free Radicals And Antioxidants?
To get a clear understanding of what free radicals and antioxidants are, let’s go back to chemistry class. Below is an oxygen atom. It consists of 8 protons, 8 neutrons, and 8 orbiting electrons.
When two or more atoms are linked together, they form a molecule. This is an example of a water molecule consisting of two hydrogen atoms and one oxygen atom. As you can see when they bond, they share paired electrons. This molecule is quite stable as all the electrons are paired.
During metabolism, the human body will either break down larger molecules into smaller molecules (catabolism) or organize smaller molecules into larger molecules (anabolism).
For example, this is a molecule of a monounsaturated fatty acid found in olive oil. Your body will take this molecule and metabolize it into a phospholipid. Phospholipids are one of the building blocks of our cell membranes.
However, during metabolism, it’s also possible for some types of molecules to lose an electron.
These new molecules, that are now missing an electron, are referred to as “free radicals” or Reactive Oxygen Species (ROS). In the example below an oxygen atom is bonded to a hydrogen atom. However, because the oxygen atom has an unpaired electron the molecule formed is a type of radical called an hydroxyl free radical.
Since free radicals don’t like having an unpaired electron, they are highly reactive and will seek to steal an electron from other molecules in their path.
If there happens to be a cell membrane phospholipid in its vicinity, the free radical can react with it, steal its electron, and turn it into a free radical.
This could set off a chain reaction of phospholipids being turned into free radicals which could lead to damage of the cell membrane. This is called lipid peroxidation. Lipid peroxidation appears to have a strong link to heart disease.
In order to prevent damage by free radicals, antioxidants come to the rescue. These molecules are stable enough to donate an electron to an out of control free radical and neutralize it, thus reducing its ability to cause damage.
In your body, antioxidants and free radicals should be in equilibrium. If free radicals outweigh antioxidants, then there is an unhealthy situation called oxidative stress.
Let’s take a look at oxidative stress.
Free Radicals And Oxidative Stress
Free radicals can accumulate in your body by a number of different ways.
First, your body itself produces free radicals as a result of normal metabolic processes. These radicals are not necessarily bad. They are important for cell growth, differentiation, and normal cell death. They are also produced by your body to kill pathogenic microbes.
Secondly, free radicals can accumulate in your body from external sources. This includes:
- Air pollution.
- Cigarette smoke.
- Alcohol intake.
- High blood sugar levels.
- Consuming large amounts of polyunsaturated fatty acids.
- Radiation, including excessive sun exposure.
- Infections by bacteria, fungi or viruses.
- Excessive systemic presence of metals such as iron and copper.
- Intense and prolonged exercise.
- Excessive intake of antioxidants.
- Antioxidant deficiency.
When the critical balance between free radical generation and antioxidant defenses is upset, free radicals can roam wild causing damage to lipid and protein molecules, cell structures, DNA molecules, and even cell death. This situation is termed oxidative stress.
Oxidative stress has been linked to several negative health consequences. These include:
- Certain types of cancer.
- Cardiovascular disease.
- Neurologic disease including Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS), memory loss, depression.
- Pulmonary disease
- Rheumatoid arthritis
While oxidative stress has been linked to the above diseases, it’s not always clear whether oxidative stress causes the disease or vice versa.
Oxidative stress has also been implicated in what is referred to as the “free radical theory of aging. ” This theory states that organisms age because cells accumulate free radical damage over time. See here and here.
To prevent oxidative damage by free radicals, antioxidants step into the picture.
Antioxidants To The Rescue
Antioxidants are your body’s defense from the perils of free radicals. They can be divided up into two types.
Type 1: Endogenous Antioxidants
Endogenous Antioxidants are antioxidants produced by your own body. The most common ones are:
- Superoxide Dismutase (SOD)
- Alpha Lipoic Acid (ALA)
- Catalase (CAT)
- Coenzyme Q10 (CoQ10)
- Uric Acid
These antioxidants work by directly reducing (neutralizing) free radicals.
Type 2: Exogenous Antioxidants
Exogenous antioxidants are antioxidants that you consume either through your diet or by supplementation. These can further be divided into the following groups. I have included some foods with high concentrations of the specific antioxidant.
- Vitamin C (oranges, red peppers, kale, brussels sprouts, broccoli, strawberries and from supplements)
- Vitamin E (almonds, spinach, sweet potato, avocado, olive oil, shellfish and from supplements)
- SOD, CAT, Glutathione, CoQ10, ALA, melatonin (from supplements)
- Carotenoids – Carotenoids are responsible for the bright red, yellow, orange and green hues in many fruits and vegetables. Some example of antioxidants in this category include:
- beta-Carotene (carrots, sweet potato, spinach, kale, cantaloupe, and from supplements)
- lutein and zeaxanthin (eggs, corn, orange peppers, kiwi fruit, grapes, spinach, orange juice, zucchini, and different kinds of squash)
- lycopene (tomatoes, watermelons, red peppers)
- Polyphenols – Polyphenols are plant-based chemicals that have antioxidant capacity. There are over 5,000 of them. Here are some examples.
Dietary antioxidants are not limited to plants. All animals produce them as well. However, plants contain the highest concentrations of antioxidants.
The Antioxidant Nature Of Vitamins C and E
Because your body cannot produce the antioxidants vitamins C and E, you must get them in adequate amounts from your diet.
They are essential for carrying out the process of reducing free radicals.
Vitamin C reduces radicals that threaten blood vessels. It also has an important co-antioxidant relationship with vitamin E.
Vitamin E is well absorbed by your body and uniquely suited to neutralize radicals responsible for lipid oxidation of cell membranes.
However, when a molecule of Vitamin E neutralizes a free radical, it then becomes a free radical itself and its antioxidant capacity is lost. Vitamin C can then step in and regenerate vitamin E.
In turn, glutathione can regenerate vitamins C and E back into their active forms.
So vitamins C and E are important dietary antioxidants that absolutely reduce free radicals in your body.
However, the role exogenous phytochemicals (carotenoids and polyphenols) play in human health is not so clear cut.
What Role Do Phytochemicals Play In Neutralizing Free Radicals
Observational studies confirm that people with diets high in phytochemicals (plant antioxidants) are healthier in general (eg. Mediterranean Diet, see here). There is also evidence that phytochemicals are beneficial in preventing chronic diseases. See here, here, here, and here.
Researchers know from in vitro (in the lab) studies that phytochemicals are potent antioxidants. However in vivo (in the body) studies don’t really confirm this. There are no clear studies showing that phytochemicals act as free radical scavengers inside the human body.
Concerning the antioxidant capacity of phytochemicals Jeffrey B. Blumberg, PhD, a professor and the director of the Antioxidants Research Laboratory at Tufts University, in a study on flavonoids (see types of flavonoids above) noted,
Evidence from observational studies indicates that regular consumption of foods containing flavonoids may reduce the risk of several chronic conditions, including neurodegenerative diseases, atherosclerosis, and certain forms of cancer.
Okay, Blumberg confirms what many researchers have already confirmed. A diet high in antioxidant foods will confer health benefits.
However, he also pointed out that,
Although flavonoids are commonly defined as dietary antioxidants and their putative health benefits commonly attributed to this mechanism, it now appears their principal actions are mediated in vivo via other biochemical and molecular pathways.
In other words, phytochemicals antioxidant don’t work by neutralizing free radicals in your body. Blumberg is echoing what many researchers are now finding. There is no clear evidence that phytochemicals exhibit classic antioxidant activity.
One of the reasons for this is that researchers don’t believe that phytochemicals reach high enough concentrations in plasma and tissues to be effective. See here.
So when you hear that blueberries are good for you because they’re high in antioxidants, that doesn’t mean that antioxidants from blueberries will enter your body and automatically start zapping free radicals.
Phytochemicals are important for good health; however, researchers just aren’t exactly sure how they function as antioxidants.
Professor Blumberg reminds us of an important fact about phytochemicals,
Today, antioxidant research is where most vitamins were about 60 years ago. We’re still trying to characterize what these compounds are, their bioavailability, and active principles.
Phytochemicals And Hormetic Stress
Many researchers now believe that phytochemicals may work by increasing the activity of your own endogenous antioxidants through a process called hormetic stress.
Hormetic stress is a biological phenomenon whereby a beneficial effect (improved health, stress tolerance, growth or longevity) results from exposure to low doses of an agent that is otherwise toxic or lethal when given at higher doses.
A good example of this is exercise. When exercise occurs at a high enough level to disrupt homeostasis but low enough that it doesn’t create exhaustion, your body will adapt to the stress and get stronger.
It appears that plants contain phytochemicals, principally in their skin and leaves, that protect them from predators and diseases. These compounds, when consumed in low doses, are not toxic to your body, but they do elicit a stress response when consumed.
When your body recognizes the phytochemical stressor, it adapts to it by activating pathways that induce the expression of endogenous antioxidant enzymes and several other cell protective processes.
So it does appear that phytonutrients are absolutely necessary for good health but just not in the way we are usually told.
Be Wary Of Antioxidant Supplements
Here comes the practical low down. You have been told that antioxidants are good for you. Does that mean you should add antioxidant supplements to your diet? The more antioxidants the merrier?
There have been scores of studies done on the efficacy of supplementary antioxidants. They’ve not been very promising.
A 2013 metanalysis of 294 478 participants found that there is no evidence to support the use of vitamin A, C, and E and other antioxidant supplements for prevention of cardiovascular diseases.
Another study of 5220 patients over a seven-year period receiving vitamins C and E, β-carotene, zinc, and selenium showed they received no benefit in avoiding metabolic syndrome. For more studies see here.
There have also been important studies performed showing the dangers of antioxidant supplementation.
A 2007 JAMA study looked at 68 trials with over 230,000 participants and found that treatment with beta-carotene, vitamin A, and vitamin E may actually increase mortality. The potential roles of vitamin C and selenium on mortality were inconclusive.
What about supplementation with phytonutrients? Not a lot of research has been done on this but two fairly recent studies found that no health benefits were received from resveratrol supplementation. See here and here.
The strength of evidence is really quite limited for antioxidant supplements. To go from red wine to thinking the benefits are only about resveratrol and then from the miniscule doses of resveratrol in red wine to taking gram quantities of resveratrol in supplements is jumping the gun.
There are several reasons to be wary of antioxidant supplements
- While glutathione is one of the most popular antioxidant supplements, there still seems to be a great deal of controversy over whether it can reach concentrations in the body that make it useful. It may really just be an expensive protein pill.
- During exercise, your body produces free radicals. It appears that these free radicals induce your body to express antioxidants that have a positive association with enzymes that regulate insulin sensitivity. Studies showed that vitamin C supplementation can interfere with this process. See here.
- Over-consumption of antioxidants can interfere with the hormetic stress mechanism.
The biggest reason to be wary of antioxidant supplements might be the possibility of antioxidative stress.
Antioxidants and free radicals should always be in balance. In order to maintain this balance, there is an interplay and synergy among antioxidants. When an antioxidant reduces a free radical, it itself is oxidized and must be reduced.
However, if there is an overload of one antioxidant through supplementation, there may not be a corresponding antioxidant available to reduce it. This is known as antioxidative stress.
These “pro-oxidants” can now act as free radicals and cause a cascade of free radical production.
Ron Prior, Ph.D, a nutritionist and research chemist in the department of food science at the University of Arkansas, states,
People think that antioxidants are good for them, and more is better. One of the problems is that when you start isolating some of these compounds, such as antioxidants, and take them singly [in pill form], they may have an opposite effect—they may act as pro-oxidants.
This could be one of the reasons for the poor clinical results found from antioxidant supplementation. See here.
The Take Away: Consume More Whole Foods
Your body has been created with a wonderfully intricate system of antioxidation that works interactively and synergistically with the food you consume.
To keep this system working optimally, the best course would be to consume a diet of a wide array of whole plant foods. These foods provide high levels macronutrients, micronutrients, vitamins, and phytonutrients.
Because phytochemicals work interactively and synergistically, you want to consume a rainbow of different fruits and vegetables.
This means choosing fruits and vegetables that have deeper colors such as reds, oranges, blues, and greens. This variety of different colors are indicators of different phytochemical profiles.
It appears the best (and healthiest) strategy to ensure adequate intake of antioxidants, is a diet rich in various vegetables and fruit, along with other healthy dietary habits.
Low-dose supplementation, such as in multivitamin tablets, may be beneficial if you are deficient in certain nutrients or unable to follow a healthy diet. If this refers to you, definitely check with you health practitioner before taking megadoses of supplements.
Also remember that lessening oxidative stress can lower your need for antioxidants. This includes things like getting proper sleep, exercising daily, eliminating toxins, reducing stress, reducing omega-6 PUFA’s, and reducing fructose intake.
As is often the case, we are what we consume.