Antioxidants are compounds that help control cell damage from oxidative stress, a process linked with heart disease, some cancers and other chronic conditions. People who eat plenty of vegetables and fruit, which are rich in antioxidants, have lower rates of chronic disease, but antioxidant supplements have generally not shown the same benefit and can sometimes cause harm. The practical message is to get antioxidants from a colourful, plant-rich plate, not from pills.
What antioxidants are and what they do
During normal activity, your cells produce highly reactive oxygen-containing molecules, often called free radicals. In small amounts they are part of normal body functions. When too many build up, the result is oxidative stress, which can damage cells. The U.S. National Center for Complementary and Integrative Health (NCCIH, part of the NIH) explains that oxidative stress may contribute to chronic diseases such as heart disease and cancer, and that your body has its own defence and repair systems, with antioxidant enzymes being the most important part.
Antioxidants from food add to that defence. Common ones include:
- Vitamin C
- Vitamin E
- Carotenoids such as beta-carotene and lycopene
- Selenium and zinc, minerals involved in antioxidant enzymes
- Polyphenols and other plant compounds (phytochemicals)
Each works differently, and they are not interchangeable. That is one reason a variety of foods matters more than any one “superfood.”
Food versus supplements: what the evidence shows
This is the most important part of the antioxidant story. According to NCCIH, there is extensive evidence that people who eat more vegetables and fruit have lower risks of chronic diseases. But apart from one specific eye condition (age-related macular degeneration), there is currently no evidence that antioxidant supplements have a positive effect on heart disease, cancer, cataracts or Alzheimer’s disease.
Some large trials found harm. Harvard T.H. Chan School of Public Health’s Nutrition Source summarises several:
- Beta-carotene supplements increased the risk of lung cancer in smokers.
- In the SELECT trial, vitamin E supplements increased prostate cancer risk in healthy men.
- High-dose vitamin E can thin the blood and raise bleeding risk for people on blood thinners.
Harvard’s explanation is that antioxidants seem to work best in combination with the many other nutrients and plant compounds in whole foods, something a high-dose single supplement cannot copy. NCCIH also notes that large amounts of antioxidants may interfere with normal cell functions.
Antioxidants and specific health areas
| Area | What we know |
|---|---|
| Heart health | Diets rich in vegetables, fruit, whole grains and nuts are linked with lower heart disease risk. Vitamin E and beta-carotene supplements have not shown protection. |
| Cancer | Eating more vegetables and fruit is linked with lower risk of some cancers. Some supplements increased risk in trials. |
| Eyes | Certain combinations of antioxidants and zinc have been shown to slow the progression of existing macular degeneration, but supplements have not been shown to prevent it or cataracts. This is a decision for you and your eye doctor. |
| Skin and aging | A colourful diet supports overall health; claims that antioxidant products reverse aging are not well supported. |
The best food sources
Harvard’s Nutrition Source lists these sources, which make an easy shopping guide:
| Antioxidant | Good food sources |
|---|---|
| Vitamin C | Broccoli, Brussels sprouts, citrus, kiwi, strawberries, sweet potato, tomatoes, bell peppers |
| Vitamin E | Almonds, sunflower seeds, peanuts, avocado, spinach, Swiss chard |
| Carotenoids | Carrots, apricots, mangoes, pumpkin, winter squash, spinach, tomatoes |
| Selenium | Brazil nuts, fish, shellfish, poultry, brown rice |
| Zinc | Beef, poultry, pumpkin seeds, chickpeas, lentils |
| Polyphenols | Berries, apples, grapes, onions, cocoa |
Herbs and spices such as cinnamon, oregano, turmeric and ginger also contain plant compounds and add flavour without extra salt or sugar.
Canada’s Food Guide recommends regularly eating vegetables and fruits, whole grains and plant-based protein foods, noting that plant-based eating patterns are linked with a lower risk of cancer, heart disease and type 2 diabetes. That pattern naturally delivers a wide range of antioxidants.
How to get more antioxidants every day
You do not need special products. Small, steady additions work well:
- Aim for colour at every meal. Try to include at least two colours of vegetables or fruit on your plate.
- Start the day with fruit. Add berries or kiwi to oatmeal or yogurt.
- Swap snacks. Choose a handful of almonds, an apple or carrot sticks with hummus.
- Use frozen produce. Frozen berries, spinach and mixed vegetables are nutritious, affordable and ready when you are.
- Add beans or lentils to soups, salads and pasta sauces a few times a week.
- Season generously with herbs and spices.
- Blend a smoothie with spinach, frozen berries, banana and milk.
A sample colourful day
- Breakfast: oatmeal with blueberries, ground flaxseed and a spoon of almond butter
- Lunch: spinach salad with chickpeas, red pepper, tomatoes and sunflower seeds
- Snack: an orange and a few Brazil nuts
- Dinner: salmon or lentil patties with roasted sweet potato and broccoli
- Evening: a cup of hot chocolate made with milk and cocoa, or a fruit-infused water
For more on plant-forward eating, see our article on a plant-based diet, and for batch-cooking ideas that make this easier, see our meal prep tips.
Lifestyle habits that matter too
Food is only part of the picture. Not smoking, regular physical activity, enough sleep and managing stress all support your body’s own defences. Skipping alcohol also supports overall health. Our article on nutrition and sleep covers how diet and rest work together.
Common myths
- “More antioxidants are always better.” Very high doses from supplements can cause harm.
- “A supplement can replace vegetables.” Trials do not support this; whole foods provide combinations a pill cannot.
- “Only exotic superfoods count.” Everyday foods like carrots, spinach, tomatoes, apples and beans are excellent sources.
- “Fresh is always better than frozen.” Frozen produce is a convenient and nutritious option.
FAQ
Should I take an antioxidant supplement just in case?
For most healthy people, no. The evidence favours food, and some supplements have caused harm in large trials. If you think you may be low in a specific nutrient, ask your doctor about testing rather than guessing.
Does cooking destroy antioxidants?
Cooking changes some nutrients, lowering a few and making others easier to absorb. Eating a mix of raw and cooked vegetables is a practical way to cover your bases.
When to check with a professional
Talk to your doctor or pharmacist before taking any antioxidant supplement, especially if you smoke or used to, take blood thinners, are being treated for cancer, are pregnant, or take other medications. If you have macular degeneration, ask your eye doctor whether a supplement is appropriate for you.
Key takeaways
- Antioxidants help manage oxidative stress, which is linked with chronic disease.
- Eating more vegetables and fruit is linked with lower chronic disease risk.
- Antioxidant supplements generally have not shown benefit, and some have caused harm.
- Aim for several colours of plants each day; frozen counts.
- Pair a plant-rich diet with activity, sleep, not smoking and skipping alcohol.
- Check with a professional before starting any supplement.