Logic Tree diagram

How to Increase Your Intake of Antioxidants

Key Takeaways
  • Antioxidants are compounds that minimize the damage that free radicals do to your body’s cells.
  • One useful way to understand the many different types of antioxidants is through three broad categories based on their enzymatic properties, the types of free radicals they target, and their solubility.
  • Consuming a variety of antioxidants from different sources in your diet may reduce your risk of certain diseases and the effects of aging. However, doctors will be quick to point out that evidence supporting these claims is generally lacking.

To increase your intake of antioxidants, some experts — and common sense — say to get them from a variety of natural sources as part of a normal diet.

But with no intake guidelines and scant nutritional information available about antioxidants, what does this rule of thumb mean?

After all, one person’s idea of a healthy diet is often much different than the next person’s.

As you probably know, antioxidants are chemicals that scavenge free radicals in your body that damage cells in a variety of ways.

“An ounce of prevention is worth a pound of cure.” — Benjamin Franklin

But scientists and doctors will warn you that there is such a thing as too much of a good thing. And excessive intake of antioxidants can be counterproductive.

Furthermore, there’s a lack of scientific evidence supporting many of the health claims of antioxidant proponents.

Few would argue, however, that eating a diet rich in a wide variety of healthy plants does more harm than good. And, for the most part, antioxidants come from these sources. In other words, eating a diet full of healthy plants will likely be your primary approach.

However, you may choose to be more deliberate in your approach, complementing your healthy diet with additional foods, beverages, and supplements based on their antioxidant profile.

Complicating matters, there are thousands of antioxidants. And researchers continue to discover new ones while many of those already discovered are not fully understood.

Furthermore, waiting for well-designed studies to elucidate the unknown benefits (and risks) of antioxidants in a system that rewards expensive, patent-protected treatments to diseases is unlikely a viable strategy.

So how do you make sense of antioxidants and take a common-sense approach that increases your likelihood of enjoying a long and healthy life?

For starters, it helps to understand what the different types of and sources of antioxidants are so that you can make smart, informed decisions about what you put in your body.

And trying to make sense of it all in an independent and objective way is the goal of this article.

Section Highlights
  • Most antioxidants target reactive oxygen species free radicals, but some target reactive nitrogen species.
  • Most antioxidants are non-enzymatic, but some are enzymatic, meaning that they support enzymatic processes that manage free-radical damage.
  • Some antioxidants are water soluble with others are fat soluble, which affects where in your body they are active and how long they stay in your system.

Categories of Antioxidants

There are different ways to categorize antioxidants. And, for the purposes of this article, we will focus on three different ways to categorize them:

Some antioxidants are water soluble with others are fat soluble, which affects where in your body they are active and how long they stay in your system.

  • Enzymatic vs. non enzymatic
  • Reactive nitrogen species (RNS) vs. reactive oxygen species (ROS)
  • Water soluble vs. non-water soluble

Enzymatic vs. Non-Enzymatic Antioxidants

Enzymatic and non-enzymatic antioxidants serve the same general purpose of neutralizing harmful free radicals but do so through different mechanisms.

  • Enzymatic Antioxidants. These are enzymes that catalyze reactions to neutralize free radicals and reactive species. They typically require co-factors like selenium, zinc, or copper to function. Examples include superoxide dismutase (SOD), catalase, and glutathione peroxidase. These enzymes are part of the body’s internal defense system and are highly specific and efficient in their action.
  • Non-Enzymatic Antioxidants. These are molecules that neutralize free radicals by donating an electron, without the need for enzymatic catalysis. They include vitamins like C and E, as well as various phytochemicals like flavonoids, carotenoids, and tannins. These antioxidants are generally obtained from the diet and are not as specific or efficient as enzymatic antioxidants but offer a broader range of action.

RNS vs. ROS Antioxidants

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are both types of free radicals and reactive molecules that can cause oxidative stress and damage to cells. Antioxidants targeting each have specific roles in mitigating these effects.

  • Reactive Oxygen Species (ROS) Antioxidants. These antioxidants are specialized in neutralizing reactive oxygen molecules like superoxide anion, hydrogen peroxide, and hydroxyl radicals. These species are commonly produced in the mitochondria as byproducts of cellular respiration or by various enzymatic reactions. Antioxidants like Vitamin C, glutathione, and various enzymatic antioxidants like superoxide dismutase target ROS specifically.
  • Reactive Nitrogen Species (RNS) Antioxidants. These antioxidants neutralize reactive nitrogen molecules like nitric oxide and peroxynitrite. These species often arise from the reaction of nitric oxide with superoxide or through other nitrogen-centered reactions. Selenium, for example, is an antioxidant mineral that supports enzymes neutralizing both ROS and RNS.

While both ROS and RNS can damage cells, they do so in slightly different ways and in different locations within the cell. Also, the body uses different antioxidant systems to neutralize each. Some antioxidants are versatile and can neutralize both ROS and RNS, while others are more specialized.

Water-Soluble vs. Fat-Soluble Antioxidants

Water-soluble and fat-soluble antioxidants differ in their solubility, which impacts where they act within the body and how they are stored and eliminated.

  • Water-Soluble Antioxidants. These antioxidants are soluble in water and typically act in the aqueous environments of the cell, such as the cytosol and plasma. Since they are not stored in the body, regular dietary intake is necessary. Common examples include Vitamin C and glutathione. These antioxidants are generally excreted quickly through urine when in excess.
  • Fat-Soluble Antioxidants. These are soluble in lipids and often act within the lipid portions of cells, including cell membranes. They are more likely to be stored in fatty tissues and the liver, and thus can accumulate in the body. Examples include Vitamin E and beta-carotene. Due to their storage potential, excessive consumption can sometimes lead to toxicity.

Both types of antioxidants are crucial for protecting different parts of the cell and complement each other in the body’s overall antioxidant defense system.

No Two Antioxidants Work the Same

You might be wondering whether two antioxidants that are from the same categories — for example, two antioxidants that are both non-enzymatic, reactive oxygen species, and water soluble — would have similar effects in the body.

The answer is that they will usually differ considerably. For example, while water-soluble antioxidants that target reactive oxygen species (ROS) may share some general characteristics, they can still have distinct biological functions, mechanisms of action, bioavailability, and interactions with other molecules and physiological systems. Here’s why two antioxidants in the same category could still be quite different:

  • Mechanism of Action. Even if they are water-soluble and target ROS, different antioxidants may neutralize free radicals through different chemical pathways, bind to different molecules, or even have different rates of reaction.
  • Bioavailability. How readily an antioxidant is absorbed, distributed, and utilized in the body can vary significantly. For example, some may easily cross cell membranes, while others may not.
  • Synergistic or Antagonistic Effects. Antioxidants can act synergistically to enhance each other’s effects, or they may compete for absorption, resulting in decreased effectiveness. They may also interact with other nutrients or drugs in complex ways.
  • Specificity. Some antioxidants may be more effective against particular types of ROS or in specific cellular locations. For instance, some might be effective in the lipid portion of cells, while others might act in the aqueous environment.
  • Additional Biological Roles. Many antioxidants are also involved in other biological functions, such as immune modulation, anti-inflammatory effects, or even hormone regulation.
  • Metabolism and Excretion. How an antioxidant is metabolized and excreted can affect its overall impact. Some antioxidants may be rapidly metabolized and excreted, thereby having a shorter duration of action.
  • Dosage and Toxicity. The effective concentration and potential for toxicity can vary among antioxidants, even those within the same category.
  • Molecular Size and Structure. Even slight differences in molecular structure can have significant effects on function and effectiveness.
  • Endogenous vs. Exogenous. Some antioxidants are produced by the body (endogenous), while others are obtained from the diet (exogenous). Endogenous antioxidants often have specialized roles and may be regulated differently than exogenous ones.

So, even within a group defined by solubility and target species, antioxidants can be quite different in terms of their biological activity, health benefits, and potential risks.

Examples of Antioxidants

To provide straightforward breakdown, the following sections divides antioxidants into three categories:
1. Enzymatic antioxidants
2. Fat-soluble non-enzymatic antioxidants
3. Water-soluble non-enzymatic antioxidants

Enzymatic Antioxidants

Superoxide Dismutase (SOD)
  • What It Does. Converts superoxide radicals into hydrogen peroxide and oxygen.
  • Dietary Sources. Green leafy vegetables, melons, corn, and wheatgrass.
  • Supplement Sources. Available as SOD supplements, often derived from melons or other plant sources.
  • What It Does. Converts hydrogen peroxide into water and oxygen.
  • Dietary Sources. Fruits like watermelon, avocado, and grapefruit, as well as green leafy vegetables.
  • Supplement Sources. Available in catalase-specific supplements or multi-antioxidant formulations.
Glutathione Peroxidase
  • What It Does. Reduces hydrogen peroxide and lipid hydroperoxides to water and alcohols, respectively. It uses glutathione as a substrate.
  • Dietary Sources. Selenium-rich foods like Brazil nuts, tuna, and turkey can support the activity of this enzyme.
  • Supplement Sources. Selenium supplements can support the function of glutathione peroxidase.
Glutathione Reductase
  • What It Does. Regenerates reduced glutathione, which is used by glutathione peroxidase.
  • Dietary Sources. Selenium-rich foods like Brazil nuts and sunflower seeds.
  • Supplement Sources. Selenium supplements.
Glutathione S-Transferase
  • What It Does. Involved in the detoxification of xenobiotics and can also remove peroxidized lipids.
  • Dietary Sources. Consuming sulfur-rich vegetables like garlic, onions, and leeks can support the activity.
  • Supplement Sources. N-acetyl cysteine (NAC) supplements can help replenish glutathione, a substrate for this enzyme.
Methionine Sulfoxide Reductase
  • What It Does. Repairs proteins that have been damaged by oxidation.
  • Dietary Sources. Methionine-rich foods like eggs, fish, and poultry can support the activity.
  • Supplement Sources. Methionine supplements, though not commonly recommended.
Coenzyme Q10 (Ubiquinone)
  • What It Does. Not an enzyme itself but acts as a cofactor in the mitochondrial electron transport chain, helping to prevent oxidative stress.
  • Dietary Sources. Oily fish, organ meats, and whole grains.
  • Supplement Sources. Widely available as CoQ10 supplements.

Fat-Soluble Non-Enzymatic Antioxidants

Vitamin E (Tocopherols and Tocotrienols)
  • What It Does. Primarily defends against lipid peroxidation and protects cell membranes.
  • Dietary Sources. Nuts (especially almonds), seeds, vegetable oils, and leafy greens.
  • Supplement Sources. Vitamin E capsules, often containing alpha-tocopherol.
Vitamin A (Retinol and Carotenoids like Beta-Carotene)
  • What It Does. Protects against free radicals, supports the immune system, and is essential for vision.
  • Dietary Sources. Animal liver, fish liver oil, carrots, and sweet potatoes.
  • Supplement Sources. Vitamin A capsules, beta-carotene supplements.
Coenzyme Q10 (Ubiquinone)
  • What It Does. Helps generate energy in cells and acts as an antioxidant.
  • Dietary Sources. Meat, poultry, fish, and whole grains.
  • Supplement Sources. CoQ10 supplements are widely available.
  • What It Does. Known for its potent antioxidant effects that protect against lipid peroxidation.
  • Dietary Sources. Primarily found in marine organisms like krill, algae, and salmon.
  • Supplement Sources. Astaxanthin supplements, often sourced from algae.
  • What It Does. Known for protecting against prostate cancer and may help prevent heart disease.
  • Dietary Sources. Tomatoes, watermelons, and pink grapefruits.
  • Supplement Sources. Lycopene supplements are available but less common.
Lutein and Zeaxanthin
  • What It Does. Primarily known for eye health, protecting against macular degeneration.
  • Dietary Sources. Leafy green vegetables like spinach and kale, as well as corn and eggs.
  • Supplement Sources. Available as standalone supplements or in multivitamins.
Gamma Oryzanol
  • What It Does. Exhibits antioxidant activity and is also known for its potential to improve cholesterol levels.
  • Dietary Sources. Rice bran oil primarily.
  • Supplement Sources. Available as a supplement often marketed for cholesterol management.
Alpha Lipoic Acid
  • What It Does. Although not purely fat-soluble (it’s both water and fat-soluble), it’s known for its wide range of antioxidant actions.
  • Dietary Sources. Spinach, broccoli, and animal organ meats.
  • Supplement Sources. Available as a standalone supplement.
  • What It Does. Known to reduce cholesterol levels, they also exhibit some antioxidant properties.
  • Dietary Sources. Plant oils, nuts, and legumes.
  • Supplement Sources. Phytosterol supplements are available, sometimes combined with other heart-healthy ingredients.
Palm Tocotrienols
  • What It Does. Similar to tocopherols, they protect cell membranes and have other potential health benefits like cardiovascular protection.
  • Dietary Sources. Palm oil, rice bran oil.
  • Supplement Sources. Available as specialized supplements focusing on tocotrienols.
  • What It Does. Acts as a precursor to steroid hormones and also has antioxidant properties.
  • Dietary Sources. Olive oil, shark liver oil.
  • Supplement Sources. Available as standalone supplements, often sourced from olives.
  • What It Does. The reduced form of Coenzyme Q10, with superior bioavailability and antioxidant properties.
  • Dietary Sources. Similar to Coenzyme Q10 — meat, poultry, and fish.
  • Supplement Sources. Ubiquinol supplements are available, often promoted as a more bioavailable form of Coenzyme Q10.
  • What It Does. Known for its antioxidant, anti-inflammatory, and anti-cancer properties.
  • Dietary Sources. Brown seaweeds like kombu and wakame.
  • Supplement Sources. Available as standalone supplements, often derived from seaweed.
  • What It Does. Has antioxidant properties and is often used as a food colorant.
  • Dietary Sources. Natural sources are few, but it’s often added to animal feed to color egg yolks and farmed fish.
  • Supplement Sources. Available as a standalone supplement, though less commonly found.

Water-Soluble Non-Enzymatic Antioxidants

Vitamin C (Ascorbic Acid)
  • What It Does. Protects cells from oxidative damage, helps with wound healing, boosts immune function.
  • Dietary Sources. Citrus fruits, bell peppers, strawberries, and tomatoes.
  • Supplement Sources. Vitamin C tablets, capsules, and powders.
  • What It Does. Protects cells and promotes liver health.
  • Dietary Sources. Spinach, avocado, and asparagus.
  • Supplement Sources. Glutathione supplements in various forms, including oral and sublingual.
Flavonoids (Quercetin, Myricetin, etc.)
  • What It Does. Have various health benefits including anti-inflammatory and anticancer properties.
  • Dietary Sources. Apples, onions, dark chocolate, and grapes.
  • Supplement Sources. Available as flavonoid complex supplements.
Catechins (EGCG)
  • What It Does. Known for anti-inflammatory and cancer-protective effects.
  • Dietary Sources. Green tea, black tea.
  • Supplement Sources. Green tea extract supplements.
  • What It Does. Known for their anti-inflammatory and cardiovascular benefits.
  • Dietary Sources. Berries like blueberries, blackberries, and cherries.
  • Supplement Sources. Berry extract supplements.
  • What It Does. Powerful anti-inflammatory and antioxidant properties.
  • Dietary Sources. Turmeric spice.
  • Supplement Sources. Curcumin or turmeric supplements.
  • What It Does. Acts as an antioxidant and is also known for its role in neurological development.
  • Dietary Sources. Meat and fish.
  • Supplement Sources. Available as standalone taurine supplements.
Chlorogenic Acid
  • What It Does. Known for its effect on reducing blood sugar and potential anti-cancer effects.
  • Dietary Sources. Coffee, sunflower seeds.
  • Supplement Sources. Green coffee bean extract.
  • What It Does. Has a range of health benefits including heart protection and anti-aging effects.
  • Dietary Sources. Red wine, peanuts, and some berries.
  • Supplement Sources. Available as standalone resveratrol supplements.
  • What It Does. Known for liver-protective effects.
  • Dietary Sources. Milk thistle.
  • Supplement Sources. Milk thistle extract supplements.
  • What It Does. Known for anti-inflammatory properties and vascular support.
  • Dietary Sources. Buckwheat, apples, and citrus fruits.
  • Supplement Sources. Available as standalone rutin supplements.
Ellagic Acid
  • What It Does. Has anti-cancer and liver-protective effects.
  • Dietary Sources. Raspberries, strawberries, and pomegranates.
  • Supplement Sources. Pomegranate extract supplements often contain ellagic acid.
Ferulic Acid
  • What It Does. Known for its anti-aging effects and protection against UV radiation.
  • Dietary Sources. Whole grains, coffee, and apples.
  • Supplement Sources. Often found in skincare products and less commonly as an oral supplement.
  • What It Does. Exhibits antioxidant and anti-inflammatory properties.
  • Dietary Sources. Citrus fruits like lemons and grapefruits.
  • Supplement Sources. Citrus bioflavonoid supplements.
  • What It Does. Known for its anti-inflammatory and potential cardiovascular benefits.
  • Dietary Sources. Citrus fruits like oranges and grapefruits.
  • Supplement Sources. Available as a standalone supplement or as part of citrus bioflavonoid complexes.