All About Antioxidant Supplements: How They Work and When to Use Them

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    Antioxidants are powerful nutrients that can combat the oxidative stress associated with everyday life.

    You have probably heard of antioxidants and associate them with good health. And rightly so – antioxidants play a major role in managing the impact of some of the oxidative stressors the body encounters on a daily basis. While antioxidants are beneficial in the body, it is important to be smart about dosing if you choose to supplement.

    In this article, we’ll discuss the role of antioxidants, the role they play in fighting oxidative stress, and sources of antioxidants and their potential health benefits.

    What are antioxidants?

    Antioxidants are compounds naturally occurring in foods that help protect and repair the body from damage caused by free radicals.

    Some vitamins are antioxidants (think vitamins C and E) while some minerals can act as antioxidants with their properties (think selenium and zinc). These vitamins and minerals must be obtained from dietary sources. Other non-vitamin compounds in plants can also act as antioxidants in the body.

    In addition, there are a variety of antioxidants produced endogenously, or made in the body. These include glutathione, melatonin, and CoQ10, just to name a few. Glutathione, for example, plays such a major role in antioxidant capacity of cells that it is often referred to as the “master antioxidant.”

    Free radicals versus oxidative stress versus antioxidants

    Oxidative stress can occur from daily bodily processes, including exercise and additional stressors like environmental toxins, injury, an unhealthy diet, and lack of sleep. It is also a normal part of aging.

    As a result of these processes, free radicals are formed. Free radicals, also called Reactive Oxygen Species (ROS), are natural byproducts of cellular processes that use oxygen to produce energy. Free radicals are widely known for the damage they can cause, especially in the progression of aging.

    However, not all free radical formation is bad. In fact, some free radical formation is the product of necessary and normal metabolism. Free radicals can even play a key role in stimulating the immune system, like in making the body stronger after exercise. However, many external sources of free radicals from modern life – such as pollution, cigarette smoke, unhealthy diet, and blood sugar imbalances – can lead to an excess of free radicals.

    This is when antioxidants can work their magic to neutralize the excess of free radicals.

    Overall, oxidative stress is an essential process in normal body function but can lead to damage when occurring in excess. Antioxidants, both internal and from external sources of food and supplements, can be beneficial in cleaning up excess oxidative stress.

    Health benefits of antioxidants

    As stated, antioxidants play an important role in keeping oxidative stress in check.

    Oxidative stress is known for its role in the development of a variety of potential health issues.

    Antioxidants, both endogenous and from dietary intake, are known to play a role in promoting optimal health.

    The production of the antioxidant glutathione in the body, for example, is thought to promote longevity and maintain health. Research points to glutathione levels in the body as a potentially important marker of health risk, with optimizing glutathione levels as a strategy for health promotion. Dietary intake of protein, omega 3 fats, cruciferous vegetables, and vitamins and minerals like vitamins E, C, and selenium have been shown to support glutathione levels in the body.

    Research suggests that higher intakes of antioxidant-rich foods, like fruits, vegetables, and legumes, are associated with a lower level of oxidative stress.

    What does science say about antioxidant supplements?

    Numerous studies show that antioxidant supplements can boost antioxidant activity in the body. There is some conflicting research, however, on the use of antioxidant supplements.

    However, we know that deficiency in essential nutrients can disrupt the body’s natural metabolic processes. The ultimate goal is to make sure you get adequate nutrients from eating a balanced diet and can then fill in any nutrient gaps with supplements. The key is meeting your Recommended Dietary Allowances (RDA) for nutrients and maintaining optimal nutrient levels not supplementing in excess. More is not always better.

    Of note, while antioxidant vitamins and minerals have established RDA values, other types of antioxidants in foods and supplements do not.

    Taking high doses can be harmful

    As discussed, some free radical formation can provide essential metabolic functions. Therefore, it is important to avoid over-eliminating free radicals through excessive use of antioxidants, which could have negative health effects.

    General consensus is that levels of antioxidants obtained from food intake is acceptable. However, supplementing with high doses of antioxidants may be linked to potential issues in some cases.

    Avoid mega dosing with antioxidants, and be sure to tell your healthcare providers about your supplement intake.

    Antioxidant supplements

    Given the many inputs of stress in our modern lives, getting an antioxidant boost from supplements may be helpful when done appropriately. We’ll discuss the science on four key antioxidant nutrients and how to supplement.

    Vitamin C

    As humans, we cannot make vitamin C in our body, so we must get it from food.

    Research shows that vitamin C’s antioxidant properties help support healthy levels and function of white blood cells, an important type of immune cells in our body. In addition, vitamin C is needed for the body to make collagen.

    Citrus fruits are a popular source for vitamin C, but other foods rich in vitamin C include peppers, broccoli, Brussels sprouts, kiwi, strawberries, papaya, oranges and pineapple.

    The best way to get it is to consume these foods raw. If your diet lacks these foods, you may be getting less than the daily recommended amount of vitamin C. The RDA of vitamin C is 75-90 mg. Avoid taking more than 1,000-2,000mg per day to avoid potential gastrointestinal disturbances.

    Whole food forms and extracts of vitamin C may be more effective than the synthetic ascorbic acid commonly found in many commercial supplements. Whole food sources of vitamin C also contain numerous additional compounds like bioflavonoids that likely work synergistically with vitamin C to exert its health promoting effects in the body.

    Care/of’s Vitamin C contains vitamin C from acerola cherries and also includes helpful bioflavonoids often present in vitamin C rich foods.

    Vitamin E

    Vitamin E is a fat-soluble vitamin and known as a potent antioxidant. This vitamin’s oxidative stress-reducing capabilities are well documented in research both in vitro (lab studies) and in vivo (human studies). In particular, vitamin E can manage oxidation of lipids, fatty components essential in cell membranes all across the body.

    So widely used as an antioxidant in the body, vitamin E can get depleted when cleaning up oxidative stress. Vitamin C can actually help the body to restore levels of vitamin E in a synergistic process called “vitamin E recycling.”

    Proper doses of vitamin E are important for safety, since very high doses of vitamin E may have a pro-oxidation effect in the body. Doses up to 1,000 mg per day in adults appears to be safe, although more data is needed on testing for longer durations.

    The RDA of vitamin E is 15 mg. Some of the food sources highest in vitamin E include sunflower seeds, almonds, wheat germ oil, hazelnuts, salmon and avocado.

    A pro tip: alpha tocopherol is the preferred form of vitamin E used by the human liver. Be sure to look for that compound on supplement labels when choosing a vitamin E supplement.


    Selenium is a key mineral in thyroid health and reduces oxidative stress in the body. Proper functioning of the thyroid gland requires several elements, including selenium, zinc, copper, and iodine.

    One of the key ways in which selenium supports antioxidant activity in the body is through promoting glutathione production. Research shows that glutathione levels in the body tend to decrease with age. Accumulation of oxidative stress over the lifetime is considered a key promoter of the aging process.

    One study showed that selenium-enriched foods boost the activity of the glutathione peroxidase antioxidant complex in the body.

    The RDA of selenium is 55 mcg. Some of the foods highest in selenium include Brazil nuts, shellfish, beef, poultry, eggs, beans and lentils.


    Zinc is an essential trace mineral involved in numerous functions in the body and especially immune health.

    The strength of the intestinal cell barrier, a critical structure of the immune system, requires sufficient zinc for optimal function. Neurons also depend on zinc for proper functioning. Deficiency in zinc is strongly associated with neuronal and immune system issues.

    While zinc is not considered an antioxidant, it can, however, exert antioxidant-like effects. Zinc acts as a cofactor for the Copper-Zinc-superoxide dismutase enzyme, an essential antioxidant defense system in the body. One important function of this system is to reduce the free radicals produced in stressful situations.

    Do not take zinc in excess of the tolerable upper intake level of 40 mg per day for more than about 2 weeks, unless medically prescribed by your doctor. Long term higher doses of zinc can result in copper deficiency.

    Pro-tip: supplement zinc with up to 2 mg of copper or increase foods rich in copper when taking higher levels of zinc to prevent mineral deficiencies, since zinc and copper compete with one another in the body.

    The RDA of zinc is 8-11 mg per day. Foods richest in zinc include meat, fish, seafood, eggs, and dairy. In fact, oysters contain more zinc per serving than any other food.

    Care/of’s Zinc supplement contains a blend of 15 mg of zinc and 2 mg of copper for mineral balance.

    Antioxidants in food

    As discussed, certain vitamins and minerals can act as antioxidants in the body.

    Polyphenols are another type of antioxidants found in plant foods and can provide significant protection against oxidative stress.

    One way to get more antioxidant-rich foods in your diet is to aim for a variety of colors. Polyphenol compounds are often responsible for giving the fruits and vegetables their color, such as the anthocyanins in blueberries that give the fruit their purple-blue hue.

    Aim for a variety of plant foods rich in antioxidants, including:

    • Spices, such as turmeric, cinnamon, and thyme
    • Fruits, especially berries and citrus
    • Vegetables, such as dark leafy greens and tomatoes
    • Legumes, such as beans and lentils
    • Nuts and seeds, such as walnuts, chia seeds, and flax seeds
    • Tea
    • Cocoa

    In addition to plant foods, many protein-rich animal foods provide good sources of the antioxidant supporting minerals selenium and zinc.

    Overall, a diet rich in a variety of plant and animal foods can provide antioxidants – and supplements can help fill in the gaps.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Our Editorial Staff
    Freelance Contributor
    The Care/of Editorial Team is made up of writers, experts, and health enthusiasts, all dedicated to giving you the information you need today. Our team is here to answer your biggest wellness questions, read the studies for you, and introduce you to your new favorite product, staying up to date on the latest research, trends, and science. Each article is written by one of our experts, reviewed both for editorial standards by an editor and medical standards by one of our naturopathic doctors, and updated regularly as new information becomes available.