Have you heard about the antioxidants in blueberries and green tea? Wait, that’s a silly question because I know you have. The better question is: do you have any idea what an antioxidant is and why it really matters? And perhaps the best question is: did you know that too many antioxidants can also cause damage, if we’re not careful, so finding the right balance is important for overall health?
Because many of us probably don’t get enough antioxidants, but getting too many of them can be detrimental, let’s get you the information you need to make good choices, starting at the beginning…
What is a Free Radical and what do they do?
“Free radicals” are atoms or molecules that are missing an electron. You may remember from chemistry class that all atoms and molecules like to have their electrons in pairs. After all who doesn’t want a friend to do things with?! When an atom or molecule is missing an electron, it is unbalanced and unhappy and is considered to be in a state of oxidation. These unstable molecules are highly reactive (meaning they are dying to cause a reaction) and bounce around trying to steal an electron from another molecule.
Stealing electrons from healthy cells can lead to all sorts of problems as a result of oxidative stress, a state resulting from damage to cellular membranes and other organelles within the cell. Oxidative stress can lead to:
- Oxidation of fats in the blood stream
- Loss of enzyme activity due to damaged proteins that make the enzyme
- DNA mutations
- Degenerative conditions like degenerative disc disease
- Rheumatoid arthritis
- Many chronic conditions such as:
- Cardiovascular disease (many people believe the link between serum cholesterol or LDL and cardiovascular disease is not simply the presence of a large amount of LDL, but rather the oxidized LDL damages the walls of the arteries and veins)
- Neurological diseases such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), memory loss ,and depression
- Respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD)
- Kidney (aka, renal) diseases such as glomerulonephritis, chronic renal failure, proteinuria (protein in the urine), and uremia (urine in the blood)
- Eye conditions such as macular degeneration and cataracts
- Pregnancy concerns such as stunted fetal growth and pre-eclampsia
Although it may sound extreme that a molecule missing an electron can lead to all of the above, keep in mind that there is never just one free radical. The initial steal usually leads to a cascade of electron stealing because the molecule that was forced to give up an electron is now a free radical and needs to find an electron to steal.
Although stealing of electrons is usually a bad thing, as evidenced by the list above, the fact is that sometimes our bodies purposefully create free radicals and this is helpful, as you will see in the next section.
Side note: because of their reactivity and the fact that the free radicals created through our body’s natural processes usually contain oxygen or nitrogen, certain free radicals are also called reactive oxygen species (ROS) or reactive nitrogen species (RNS).
Where do Free Radicals come from?
There are many things that can cause a molecule to become oxidized. Essentially anything internal or external to the body that steals or removes an electron creates a reactive molecule. The following is a partial list of the sources of free radicals:
- Exposure to:
- Cigarette smoke
- Air pollutants
- Industrial solvents
- Radiation such as x-rays and UV light
- High levels of oxygen, sometimes related to ischemia or reperfusion injury (happens when a part of the body has been deprived of oxygen for a period of time and then receives it again)
- Phase 1 detoxification of:
- Normal physiological processes such as:
- Defending against microbes
- Breaking down fatty acids
- Creation of energy in the mitochondria
- Creation of prostaglandins
As you can see from that last section, the creation of free radicals isn’t a bad thing when it is done by our bodies for a higher purpose. Taking one example, some phagocytes (white blood cells that consume microbes) create free radicals and “shoot them” at microbes. These bullet-like free radicals kill the microbe by stealing electrons. Because microbes are so small, losing a few electrons is enough for them to die and then our bodies clean up the debris that’s left.
The problem isn’t when we create free radicals as part of our process of living, it’s when we get a whole bunch of free radical creation from other sources like air pollution.
What is an Antioxidant?
Antioxidants are substances that purposefully donate an electron to a free radical in order to bring the receiving molecule into balance. This takes the free radical out of an oxidative state and makes it balanced and happy. Being reduced (i.e., receiving an electron) by an antioxidant prevents them from stealing an electron from an unintended source. Not that you need to remember it, but the acronym for this electron giving and receiving process is:
Although antioxidants are a good and necessary thing, keep in mind that an antioxidant that has given up its electron is now oxidized… and that means it needs an electron from somewhere else! Fortunately, many of the antioxidants work together to keep the giving and receiving within the family (so to speak), which prevents other molecules from having to get involved. The following diagram illustrates some, but not all of these interactions:
But two things about that:
- It doesn’t always work and sometimes a free radical is “quenched” by taking an electron from an unintended source.
- Antioxidants work in specific ways, so having enough of each antioxidant and a balance between all of them is crucial to prevent oxidative stress.
Let me repeat that last bit… we need to have the right amount and the right balance of antioxidants to keep ourselves healthy right down to the cellular level.
What are the Antioxidants and where are they found?
Finally, we are down to the whole point of this article, now that you know you need all of and the right amounts of the antioxidants! Remember, many of these antioxidants are somewhat specific, in that they can only give their electron to certain free radicals and not to just any unbalanced molecule. As well, some of them are water soluble (which means they can take care of free radicals in the blood or inside cells), others are fat soluble (so they quench free radicals in fat tissue or in the cell membrane which is mostly fat), and a few are both.
The following is the list of antioxidants and the best sources for them:
- A / carotenoids: apricots, broccoli, cantaloupe, carrots, dark green leafy vegetables, romaine lettuce, peas, sweet peppers, sweet potato and winter squash (ex: acorn, butternut, pumpkin)
- C: bell peppers, broccoli, brussels sprouts, dark green leafy vegetables, guava, kiwi, orange, papaya, pineapple, strawberries
- E (aka, tocopherols): almonds, asparagus, avocado, dark green leafy vegetables, olive oil, peanuts, shrimp, spinach, sunflower seeds, trout
- Copper: cashews chickpeas (aka, garbanzo beans), lentils, lima beans, mushrooms, oysters, sesame seeds, soybeans, sunflower seeds, walnuts
- Iron: beef (especially liver), poultry (especially liver), pork, oysters, clams, shrimp, eggs, beans / legumes, dark green leafy vegetables, molasses
- Manganese: bass, brown rice, chickpeas, cloves, hazelnuts, mussels, pineapple, pumpkin seeds, soybeans, spinach
- Selenium: beef, brazil nuts (especially!), fish, lamb, mushrooms, oysters, pork, poultry, sunflower seeds, trout
- Zinc: beef, cashews, cocoa, crab, lobster, oysters (especially!), pork, poultry, spinach, wheat germ
- Thiols (aka sulfur-containing compounds which are found in the onion family and cruciferous vegetables), including:
- Glutathione: internal creation, whey protein, milk thistle, in addition to sulfur-containing foods
- Alpha lipoic acid: internal creation, organ meats, spinach, broccoli, tomatoes, peas, brussels sprouts
- Thioredoxin: internal creation
- Plant polyphenols like resveratrol and catechins: colorful fruits and vegetables, legumes, nuts, seeds, green tea and herbal teas
- Ubiquinol (aka, coenzyme Q10): broccoli, cauliflower, chicken, fatty fish (ex:herring, mackerel, sardines), meat (especially organ meat), peanuts, pistachios, sesame seeds, spinach, soybeans
- Uric acid: internal creation
- Metallothionein: internal creation
Note: Some of the above are considered antioxidants because they are cofactors in a reaction to reduce free radicals. In other words, they are necessary for the enzyme that actually moves an electron from one molecule to another to work. (Check out this blog post for a slightly more extensive explanation of cofactors.) Also, there are enzymes (examples: superoxide dismutase and catalase) that can eliminate free radicals by facilitating a reaction that simultaneously neutralizes two free reactive oxygen species, so do not need an antioxidant to provide the needed electron.
As you move forward on your health journey, I hope that you will include plenty of foods in your diet whose antioxidants can quench free radicals and keep you away from oxidative stress. If you are following my basic guidelines for healthy eating, you won’t have any trouble at all getting all the antioxidants you need in the right amounts to stay healthy.
Image courtesy of FoodiesFeed.
— Cleveland Clinic. Anemia & iron-rich foods. In Diseases & Conditions. Accessed on June 7, 2016.
— Dunne S. Spring Cleansing, Phase 1 Detoxification and Antioxidant Support. May 18, 2016.
— Gropper SS, Smith JL. Advanced Nutrition and Human Metabolism. 6th ed. Belmont, CA: Wadsworth Cengage Learning; 2013.
— Linus Pauling Institute. Lipoic acid. In Dietary Factors. Reviewed in April 2012. Accessed on June 7, 2016.
— Lobo V, Patil A, Phatak A, Chandra N. Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy reviews. 2010;4(8):118.
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