Ultimate Guide to Antioxidants

Antioxidants, free radicals, and reactive oxygen species (ROS). If you’re like most people, you get a little confused by what these are, the science behind them, and why it matters to your health and antiaging. If you’re looking for a comprehensive guide that translates heavy scientific information into something easily digestible and easy to understand, then this Ultimate Guide to Antioxidants is your jam. 

As a Registered Nurse in Critical Care, I want you to be healthy. So, I dug into the research and answered the most popular questions about antioxidants. I decoded the scientific and medical journals and made it easier to understand. You can take positive actions towards improving your health, reducing your risks for diseases, and slowing the signs of aging. And this Guide can help.

What Are Antioxidants

In scientific terms antioxidants are defined as, “a compound that removes reactive species, mainly those oxygen-derived.” This translates to ‘antioxidants are little molecules that roam your bloodstream looking for unstable oxygen molecules to devour.’

Antioxidants are vitamins, lipids, flavonoids, polyphenols, and other free radical taming, redox regulating molecules. 

Why is this important?

Unstable molecules, or free radicals, are damage-causing, havoc-wreaking baddies. 

You’ve probably read that they crash into cells and organs causing an immune response known as inflammation while literally damaging the healthy cell walls of normal cells. And yes, this is true. But most of us haven’t heard about the latest research finding that they also cause damage from within cells, not just on the outside. Over time and if left uncontrolled, antioxidants cause disease and signs of aging.

To understand this more, let’s dive into the nitty gritty of free radicals. 

What Are Free Radicals

Free radicals are a term that describes 2 different molecules, ROS and RNS.

In scientific terms, free radicals are defined as, “The free radicals, both the reactive oxygen species (ROS) and reactive nitrogen species (RNS), are derived from both endogenous sources (mitochondria, peroxisomes, endoplasmic reticulum, phagocytic cells etc.) and exogenous sources (pollution, alcohol, tobacco smoke, heavy metals, transition metals, industrial solvents, pesticides, certain drugs like halothane, paracetamol, and radiation).”

This translates into meaning that reactive oxygen species (ROS) and reactive nitrogen species (RNS) are molecules that accumulate in the body and we get them from either processes from our body’s natural processes (endogenous) or from our environment (exogenous). ROS and RNS work together to cause oxidative stress on the body.

High levels of ROS have been associated with aging and disease. 

Reactive Oxygen Species (ROS)

Until about 2011, the leading hypothesis about ROS said that it was a toxic by-product of the body’s endogenous processes. Endogenous means that free radicals from processes inside the body. 

Overtime, as ROS builds up in the bloodstream and more and more of them accumulate, the body can no longer keep them in check and they cause harm to healthy cells. This is known as the, “structural damage-based oxidative stress” hypothesis.  It literally says that unstable oxygen-carrying molecules crash into cell walls causing damage. Like a vacuum crashing into a coffee table when you clean takes bits off the wood, a little at a time. The damage isn’t massive, but over time it’s enough to cause noticeable damage. 

But ROS isn’t all bad. Without ROS, the cell wouldn’t be able to regulate genes, regulate redox (we’ll explain what this is next), and communicate with the body. The key is to keep ROS balanced. 

The Latest Research on ROS

Then, as more research was done, Scientists realized that the amount of damage to cells and signs of aging caused by ROS was too much to be caused by structural damage alone. 

In other words, it didn’t make sense that only cell wall damage (all by itself!) would cause the massive amounts of damage and disease they were finding in aging populations compared to younger ones. Even when huge amounts of antioxidants were consumed or applied to the skin by these groups, still massive cell damage from ROS was happening. 

Scientists decided it was out of proportion to the ROS they were measuring in these age groups.  So, another hypothesis was formed, the “redox stress hypothesis.” 

In scientific terms, it says, “aging-associated functional losses are primarily caused by a progressive pro-oxidizing shift in the redox state of the cells, which leads to the overoxidation of redox-sensitive protein thiols and the consequent disruption of the redox-regulated signaling mechanisms.” This translates to ‘ROS causes damage from inside cells somehow making cells cause internal damage, not just free radicals banging into cell walls.’ 

Of note, ROS and RNS are closely related to each other and play a central role in the ‘redox’ or oxidation–reduction biology. RNS and something called reactive sulfur species (RSS) are derivatives of ROS. For simplicity sake, we’re going to stick to calling them all ‘ROS.’ 

They are all considered to be disease-associated agents and when out of balance, have been linked to diseases like, “diabetes, cancer, heart and lung disease, autoimmune disease and a host of other maladies including ageing and various infectious diseases.”

To understand more about this process, I need to explain ‘redox.’ 


In scientific terms, “redox, or oxidation-reduction biology, is a vital process of all aerobic life.” Any living thing that uses oxygen to survive is called ‘aerobic life.’ Think animals, plants, and some microbes. It is literally a function of cell metabolism which means cells use this process to carry out their daily functions, live, and die. 

When ROS accumulates the state known as “redox homeostasis” gets messed up and cells show signs of damage. Homeostasis is a scientific word that is fancy for, “balance.” So this translates to, ‘ROS messes us the natural balance of cells causing damage.” 

Diseases associated with oxidative stress include:

  • Diabetes Mellitus
  • Neurodegenerative disorders
    • Parkinson’s disease
    • Alzheimer’s disease
    • Multiple Sclerosis 
  • Cardiovascular diseases
    • Atherosclerosis
    • Hypertension)
  • Respiratory diseases
    • Asthma 
  • Cataract development
  • Rheumatoid arthritis
  • Various cancers
    • Colorectal
    • Prostate
    • Breast 
    • Lung 
    • Bladder


Whenever our cells are damaged, they release something called ‘cytokines’ which cause inflammation. 

Inflammation is our body’s natural response to help heal itself. The chemicals released from cell damage ‘call in the troops’ of our immune system in an attempt to heal damaged cells. It’s great for the short term because it heals our cells, but when cytokines just keep coming it spells trouble for your body. Think about when you get a paper cut and it turns red at first but ends up healing. Your body releases cytokines which brings your immune system to the paper cut helping it heal. 

But inflammation over a long period of time and throughout your whole body is what’s known as chronic inflammation and it causes disease and accelerates the process of aging.  

This makes it important to keep redox homeostasis in check and balanced. The body will naturally keep ROS in check but problems happen when the ROS gets out of control and the body can no longer keep them at bay. Control the things you can, like quitting smoking (damages lung cells), only drinking alcohol moderately (damages liver cells), getting regular exercise (increases the body’s ability to control inflammation and maintain a healthy weight), and eat mostly unprocessed healthy foods as free from chemicals as possible (go organic, if you can!). 

Other ways you can help maintain redox homeostasis and prevent cell damage is with antioxidants. 

What Do Antioxidants Do

In the 1990’s news about antioxidants really started to make an appearance in the public eye. At the time, Scientists were discovering how “oxygen-triggered free radical reactions in the body play a key role in aging-associated chronic diseases.” This was the start of loads of research that led to the beliefs Scientists have now about the role of antioxidants in stopping the damage of ROS and even preventing it from happening both inside and outside the cell wall, in the first place. 

Scientists believe that by controlling free radicals and ROS we can slow, reduce, or even halt the aging process and certain diseases. 

However, there is some research to suggest that in people with certain types of cancers, antioxidants can actually make the cancer worse. So it’s important to discuss any antioxidant regime with your doctor if you’re looking to add it as a treatment for cancer. 

Antioxidants naturally create a balance in redox. Taking too many will actually make redox become imbalanced and may cause more harm than good. Scientists tend to agree that antioxidant supplements should only be taken to replace a lack of them. 

How Do Antioxidants Work

We’ve gone over a lot of backstory, so now let’s talk about how, exactly, scientists believe antioxidants control free radicals and ROS. 

We know that healthy cells are damaged by free radicals when they either cause structural damage to the cell wall which releases cytokines and causes inflammation or bind to other molecules and cause abnormal cell growth, which can lead to cancer. producing nasty bits that damage them or deleting the good bits that help protect healthy cells. 

Scientists have come up with 4 distinct lines of defense lines of defense for how antioxidants work to defend the body:

  1. Prevention of new free radicals 
  2. As a scavenger seeking and destroying free radicals
  3. Repairing cell walls and DNA
  4. Adapting to the cell and literally generating the enzymes it needs to repair itself (um, amazing!)

What Vitamins are Antioxidants

Of these 4 lines of cellular defense that we just discussed, there are 3 that scientists have decided use certain vitamins, proteins, fatty acids, minerals, or other building blocks of cells. 

Here are the different antioxidant vitamins that help fuel each line of cellular defense:

  1. Preventing free radicals from forming
    1. Includes proteins that bind metals like ferritin and ceruloplasmin, plus minerals like selenium, copper, and zinc
  2. Scavenging free radicals
    1. Includes vitamin C, vitamin E, carotenoids, flavonoids, glutathione, and albumin 
  3. Repairing damaged cells
    1. Includes lipases, proteases, DNA repair enzymes, transferases, and methionine-sulfoxide reductases

We’ll discuss the antioxidant micronutrients vitamin C, vitamin E, and carotenoids. 

Vitamin C

Vitamin C is probably the most popular antioxidant. It’s a necessary nutrient for humans to ingest and prevent diseases like scurvy, which we don’t typically see in developed countries in this modern day. But, its ability to prevent and reverse chronic disease is something that the Scientific community can’t quite agree on. 

They do agree that diets high in fruits and veggies reduce the risks of cardiovascular disease, stroke, longer life, and certain types of cancers but they can’t quite agree that it’s only because of vitamin C.  

Antioxidant Serum 

Something most people don’t know is that vitamin C serum has to be applied topically, meaning directly onto the skin. This is actually the only way vitamin C will reach the epidermis, or outermost layer of skin. 


Since dark spots, or hyperpigmentation, develop on the epidermis, this makes vitamin C serum necessary to fade dark spots. To fix wrinkles, which form in the dermis, the vitamin C molecules have to soak through the epidermis to reach the dermis directly. Vitamin C molecules are too large to reach these layers from the bloodstream when vitamin C is ingested as a supplement or in your diet.    

If you’re looking for a good one, these are our favorite picks for an all natural vitamin C serum. Remember that some brands need to be kept in the fridge to prevent oxidation. 

Vitamin E

In scientific terms, vitamin E, or α-tocopherol, is “a potent peroxyl radical scavenger, is a chain-breaking antioxidant that prevents the propagation of free radical damage in biological membranes.” This translates to ‘vitamin E seeks and destroys free radicals (ROS/RNS) and prevents them from causing more damage to cell walls.’ It’s considered a lipid antioxidant which means that it stops the ROS from being produced during the oxidation process of fats. 


Carotenoids are pigments that are in plants and help protect them from sun damage. But, good news, they protect humans, too. They are what give fruits and veggies their pretty colors. There are more than 600 species of them, but you may have heard of lycopene, lutein, beta carotene, and alpha carotene.  

Carotenoids have been found to work better when paired up with other antioxidants. They have a synergistic relationship and really give those free radicals a run for their money. They are especially effective in preventing sun damage. This is one reason eating lycopene-rich tomato paste before going out in the sun can actually prevent a sunburn.  


What Foods Are High in Antioxidants

The short answer is to eat a healthy diet full of fruits and vegetables and avoid processed foods. 

Epidemiological studies show that diets high in fruits and vegetables are associated with lower risk of cardiovascular disease, stroke and cancer, and with increased longevity.

These foods are high in antioxidants are packed with lycopene, flavonoids, vitamin C, vitamin E, and carotenes:

  • Tomatoes
  • Tomato sauce
  • Tomato juice
  • Strawberries
  • Pomegranate juice
  • Blueberries
  • Green leafy vegetables, especially spinach and kale
  • Sweet potatoes
  • Cranberries
  • Red grapes
  • Green tea
  • Black tea
  • Saffron
  • Cherries
  • Citrus fruits
  • Broccoli
  • Raspberries
  • Chocolates (yay!)
  • Coffee
  • Red wine (1 glass)
  • Outer leaves of onions
  • Mushrooms
  • Buckwheat

Final Thoughts

Our bodies are constantly undergoing a process called redox and it can have by-products of free radicals and ROS. Antioxidants help the body keep these molecules in balance. When they get out of balance our cells can become damaged. This often leads to the development of diseases and signs of aging. By eating a healthy diet full of antioxidant foods we can help maintain balance. Along with a healthy diet, maintaining a healthy weight through exercise, not smoking, and drinking alcohol only in moderation will help you stay strong and healthy for many years to come.