- Best Antioxidant-Rich Foods
- What Are Antioxidants?
- Health Benefits of Antioxidants
- Foods High in Antioxidants
- Bottom Line
- 7 High Antioxidant Foods You Must Eat Regularly
- Wat are the antioxidants?
- ANTIOXIDANTS, WHAT ARE THEY?
- TOP 10
- What’s So Special About Hydroxytyrosol?
- The Science Behind Hydroxytyrosol
- Neuroprotective Effects of Hydroxytyrosol
- Need-to-Know Information
- What are antioxidants?
- Health benefits of antioxidants: what’s the buzz?
- Antioxidant foods hyped to super-status
- Antioxidant supplements and disease prevention: little supportive evidence
- Heart disease
- Lung disease
- Age-related eye disease
- Early death
- Potential hazards of antioxidant supplements
- Antioxidants in food
- Bottom line on antioxidants and disease prevention
- Related posts:
Best Antioxidant-Rich Foods
You’ve probably heard about antioxidants. But what exactly are they? And what do they do? So many foods, especially fruits and vegetables, tout antioxidant benefits. This article provides a definition for antioxidants and a list of antioxidant-rich foods based on the largest antioxidant database ever published.
What Are Antioxidants?
Beyond vitamins, minerals, protein and fiber (and all the other micro- and macronutrients), foods contain many other compounds that are important for our health. According to the National Institutes of Health, antioxidants are defined as naturally occurring or man-made substances that might prevent or delay oxidative damage to a cell. This is a category, meaning there isn’t just one kind of antioxidant. Examples of types of antioxidants include flavonoids (like anthocyanin), carotenoids (like lycopene) and a lot of other compounds that are equally hard to pronounce and that may do the body good.
One way to measure total antioxidant content is with a test called the ferric-reducing ability of plasma assay, FRAP for short. This method quantifies all of the types of antioxidants present in a food. The measurement, expressed in millimoles (mmol) per 100 grams, enables easy comparison of the antioxidant capacity of different foods.
Related: Why You Should Eat the Rainbow When It Comes to Fruits and Vegetables
Health Benefits of Antioxidants
The benefit of antioxidants is spelled out in their name: they prevent oxidation. But what does this mean for us? First off, natural processes in the body are constantly creating unstable molecules called free radicals that can damage cells over time through a chemical reaction called oxidation. Additional sources of oxidative cell damage include environmental factors, such as air pollution, cigarette smoke and excessive sun exposure. Antioxidant substances can scavenge or mop up these free radicals. Oxidative stress, when there’s not enough antioxidant activity in the body to counteract the free radicals, can cause damage to healthy cells and is implicated in diseases like cancer and cardiovascular disease.
In the lab and in animal studies, antioxidant substances have shown promise in protecting against many diseases and chronic conditions. But in people, as the NIH says, “Diets high in vegetables and fruits, which are good sources of antioxidants, have been found to be healthy; however, research has not shown antioxidant supplements to be beneficial in preventing diseases.” The research on the benefits of antioxidants keeps coming and coming; for now, our best bet is to eat plenty of fruits and vegetables. And it can’t hurt to seek out some that are higher in antioxidant activity than others.
Foods High in Antioxidants
Now that we have the basics down, let’s get specific. In 2010, the Nutrition Journal published a database of the antioxidant power for over 3,100 foods, beverages, spices and more. Some experts discourage relying on numbers like these to build a healthy diet, until more is known. For example, the USDA dropped the ORAC database of antioxidant foods from its website in 2012, ostensibly over concerns that scientific evidence of actual human health benefits was lacking.
Nevertheless, it’s interesting to look at the numbers. Antioxidant values can vary depending on where foods are grown and how they’re processed, but the numbers give a general way to compare foods, and some tend to rise to the top. We’ve put together a list of five foods that are particularly high in antioxidants. And some of them may surprise you.
14 mmol per 100 g (3 shots)
Let’s hear it for the coffee lovers! Three espresso shots in one sitting may be a bit much, but cholorogenic acid, a potent antioxidant polyphenol found in coffee beans, is being studied for its health benefits.
Don’t Miss These: Healthy Coffee Drink Recipes
Walnuts: 22 mmol per 100 g (1 cup, halved)
Pecans: 9 mmol per 100 g (1 cup, halved)
Again, 100 grams of any nut is definitely way more than a standard serving—it’s about four servings. However, the science shows that regular consumption of nuts may be good for your heart and brain health, among other benefits. They also provide a yummy crunch to salads, baked goods and more.
Pictured Recipe: Walnuts with Dark Chocolate
11 mmol per 100 g (about one king-size bar)
The dark chocolate analyzed for this database contained 70-99% cocoa. Many store-bought chocolates have a lower percentage of cocoa than this (even bars labeled as dark), so be sure to read labels if you want to indulge in an antioxidant-rich way.
Blueberries: 9.2 mmol per 100 g (2/3 cup)
Berries may be one of the most potent sources of antioxidants on the list. Some less-available berries, such as dried bilberries, had numbers as high as 50, but the highest value for a common berry was blueberries. The antioxidants in blueberries especially seem to promote healthy aging and may have anticancer properties. It is well worth your while to sprinkle some blueberries on your yogurt parfait or keep some around as a sweet after-dinner snack.
Pictured Recipe: Fresh Berries with Warm Tequila-Lime Foam
Cinnamon: 115 mmol per 100 g (3/4 cup)
Allspice: 102 mmol per 100 g (3/4 cup)
Mint (dried): 72 mmol per 100 g (3/4 cup)
Cloves: 126 mmol per 100 g (3/4 cup)
Yes, 100 grams of any spice, which is around 3/4 cup, is an absurd amount for one sitting. However, these values show that using a variety of spices regularly can help boost your antioxidant intake. Using spices can also help you cut down on other less-nutritious flavor boosters, like salt or added sugar. For a more comprehensive list, check out the Top Fresh and Dried Herbs and Spices for Antioxidants.
There are a lot of foods that contain a variety of antioxidants. Some heavy hitters include fruits, vegetables and spices, but foods like coffee and chocolate show high levels as well! Enjoy a variety of food, with an emphasis on being plant-based, in appropriate servings, and the antioxidants will follow.
Related: The Health Benefits of Eating a Plant-Based Diet and How to Get Started
7 High Antioxidant Foods You Must Eat Regularly
By now you may have heard about antioxidants – in food articles, from health experts or on nutrition labels. You’ve been told to eat foods that are good for your stomach and those that protect your heart but what about replenishing the cells that make up these critical organs in our body? The buzzword is antioxidants. Let’s begin by understanding some basics.
What are Antioxidants really?
Antioxidants are compounds or substances that naturally occur in certain fruits and vegetables. You may have heard of flavanols in chocolate, resveratrol in red wine, lycopene in tomatoes or beta-carotene in carrots. These are all different types of antioxidants.
How do Antioxidants keep us healthy?
They work to protect the cells by damage caused by oxidants. Oxidants, on the other hand, are free radicals that your body produces to defend itself against bacteria and viruses. When they become too many in number, they may start attacking and harming the cells and even put us at the risk of serious diseases like heart trouble and cancer. You may also encounter oxidants from the external environment from pollutants, smoke or alcohol. Antioxidants help the body by neutralising and removing these oxidants from your bloodstream.
It’s important to maintain the balance between antioxidants and oxidants in the body for good health. However, the free radicals or oxidants usually outnumber the antioxidants naturally produced in the body. Therefore, it is important to have a continuous supply of antioxidants from an external source to maintain this balance. Your diet is this external source and it must be packed with good quality antioxidants. This, in turn, provides other benefits like slowing down the signs of ageing, making your skin look youthful and lowering the risk of heart disease. A diet rich in antioxidants is also known to keep your brain active and your gut healthy. Needless to say, all these factors help in improving the quality and length of your life.Here are seven antioxidant rich foods that you must eat regularly and add to your daily diet if you haven’t already:
1. Dark chocolate
Good news for all chocolate lovers! Chocolate is actually quite healthy so no need to feel guilty indulging in your chocolate love every now and then. Dark chocolates and cocoa pack a big antioxidant punch and are rich in flavanols and polyphenols. A popular study conducted by Harvard experts and published in the online Journal Heart suggests that is actually good for your heart especially, the one with 70% cocoa. Too much chocolate can, of course, add to you daily calorific intake so moderation is the key here.
Also read: (Top 6 Health Benefits of Dark Chocolate)
2. Kidney beans
All kinds of beans – black, pinto, red and kidney beans are high-octane sources of antioxidants. Beans are also rich in muscle-boosting protein, have no cholesterol and little fat. Combing them with grains helps in making them a complete protein. Use them in salads, sandwiches or to make famous Punjabi Rajma. If you find them difficult to digest, drink a lot of fluids through the day.
If you’re looking to load up on antioxidants, have a handful of raisins. Dark raisins are packed with anthocyanins that give you an energy boost. Sprinkle them on your breakfast oats, throw them in a salad or blend some with your smoothie. Interestingly, raisins contain at least three times the amount of antioxidants as grapes
This ancient grain is trending again and for good reason. Barley is known for its powerful antioxidant properties that make you stronger from within. Also, it has been found that when grains like barley are soaked and sprouted the antioxidant levels increase. Moreover, they become more digestible and it is easier for the body to absorb their nutrients.
Also read: (5 Amazing Barley Water Benefits: Drink Up This Elixir to Good Health)
In the recent years, this humble vegetable has created a lot of noise because of its cancer-fighting antioxidants. Out of all the cruciferous vegetables, broccoli is one of the best sources of antioxidants like carotenoids lutein, zeaxanthin and beta-carotene. The best way to have broccoli is to steam it. Remember that some antioxidants like Vitamin C are completely destroyed by heat while others like beta-carotene become more potent on cooking the vegetable.
Also read: (10 Best Broccoli Recipes)
Juicy tomatoes are packed with three types of antioxidants – Lycopene (that gives tomato its bright red colour), Vitamin C and Vitamin A. Vitamin C is one of the most potent kind of antioxidants that you can derive from fruits and vegetables. The lycopene in tomatoes is best absorbed when they are cooked.
CommentsMost nuts are super healthy and experts recommend that you must have at least a handful or 30 grams of nuts daily. Walnuts are cholesterol-free, low in sodium and loaded with antioxidants. They offer huge amounts of antioxidant – polyphenols.
It is also important to note that the cooking method greatly impacts the levels of antioxidants in these foods. According to the Journal of Food Science, griddles, microwaving and oven cause less antioxidant destruction in veggies as compared to frying, boiling or cooking in a pressure cooker.
Wat are the antioxidants?
ANTIOXIDANTS, WHAT ARE THEY?
Antioxidants are very important for the body, they help to protect the cells against damage caused by free radicals. Free radicals are very active molecules that can cause cardiovascular disease, certain types of cancer and other disease related to ageing. The best way to protect against free radicals is a good diet. Some foods are more effective than others. We have created a TOP 10 of the foods highest in antioxidants.
Prunes is probably one of the fruits highest in antioxidants.
It is a highly nutritious food that contains vitamin E and A. It is well known for its effectiveness against ageing.
Red fruit has the best antioxidants after prunes ! Blueberries, blackberries, cranberries or raspberries are all packed with antioxidants.
Garlic is considered as a powerful antioxidant. Among its many virtues, is contains quercetin that helps to control ” bad ” cholesterol.
Turmeric root contains curcumin. It is known for its anti-inflammatory and antioxidant properties. Tip : combined with black pepper or ginger, it gets absorbed quicker by the body and its effects are enhanced.
Broccoli like many members of the cabbage family are high in vitamin C. It contains alpha lipoic acids; a powerful antioxidant that helps to burn sugars instead of stocking them in the body.
The Goji berry is one of the superfoods high in antioxidants and protein. Only recently its virtues on revitalising the skin have come to light.
This root hides its virtues well. It contain lots of antioxidants, it is an anti-inflammatory, helps digestions and against nausea. Combined with garlic or onions, its virtues get enhanced !
Pure chocolate gets its virtues from the cocoa. Cocoa is high in flavonoids and minerals (zinc, manganese and copper) and it has great antioxidant virtues. It is supposed to be 2 or 3 times more effective than tea or wine. So do take a little bit of dark chocolate after your meal.
These nuts contain the highest levels of antioxidants. They are true energy bombs and well known for their nutritional value.
And last but not least: Cloves ! One of the spices highest in natural antioxidants. It also helps digestions, against cough and is a powerful antiseptic.
Antioxidants are incredibly important because they help protect your cells against free radicals, which are thought to play a significant role in numerous health issues. You’ve probably heard a lot about the fact that antioxidants can be found in foods and supplements like green tea, vitamin C, vitamin E, CoQ10 and alpha-lipoic acid. But actually, the world’s most powerful antioxidant is something you may have never even heard of –– it’s a little polyphenol called hydroxytyrosol.
Hydroxytyrosol is truly the superstar of antioxidants – the most powerful discovered to date! It has an ORAC value (Oxygen Radical Absorbance Capacity – its ability to absorb cell-damaging free radicals) of 68,576 – which is considered to be 15 times higher than green tea and 3 times higher than CoQ10.
It is not well-known yet because its discovery, and extensive studies of its properties, are so recent. Yet hydroxytyrosol is already being recognized by scientists for its powerful anti-inflammatory, antibacterial, antioxidant and cardioprotective properties.
What’s So Special About Hydroxytyrosol?
Hydroxytyrosol is primarily found in the olive – its fruit, leaves and pulp. It was first discovered and extracted from the wastewater that resulted when green olives were rinsed in the process of making olive oil.
For decades olive oil has been known for its many healthy properties. It has long been noted that Mediterranean countries have lower rates of cardiovascular disease and cancer than other Western countries. And since the most characteristic element of the Mediterranean diet is olive oil, researchers began studying it, looking for the compound that was responsible for the anti-inflammatory and cholesterol-lowering effects.
Traditionally, the benefits of olive oil have been ascribed to its oleic acid content. However, other foods like pork and chicken are also rich in oleic acid but do not provide the same cardiovascular protection as olive oil. So scientists began to search for other properties of olive oil that might be responsible for its health-promoting effects.
That’s when they found hydroxytyrosol – the polyphenol thought to be responsible for olive oil’s anti-inflammatory effects. Its ability to absorb free radicals and protect cells and mitochondria from damage is quite impressive.
Hydroxytyrosol boasts the highest level of free radical absorption activity ever reported for a natural antioxidant.
Hydroxytyrosol has some other very special characteristics that contribute to its effectiveness. It is:
- Rapidly absorbed into the bloodstream and tissues, where it can perform its free radical scavenging duties.
- The only phenol that is able to cross the blood-brain barrier, which allows it to also absorb free radicals throughout the central nervous system.
- A metabolite of the neurotransmitter dopamine, which means it may play a role in neuroprotection.
- Both fat and water soluble, giving it the highest bioavailability of any antioxidant.
The Science Behind Hydroxytyrosol
In numerous human, animal and in vitro studies, hydroxytyrosol has been shown to:
- Reduce markers/indicators of inflammation including IL-10, PEG-1, C-reactive protein, COX-2, TNF-a, iNOS and others.(1)
- Support healthy mitochondrial function and significantly increase ATP energy production.(2)
- Help suppress bone loss.(3)
- Help improve blood lipid profiles.(4)
- Boost eye health.(5)
- Have a therapeutic effect on the cardiovascular system.(6)
- Protect against oxidative DNA damage in human breast cells.(9)
- Reduce the effects of peripheral neuropathy.(10)
Additional research shows that hydroxytyrosol holds great promise for a wide variety of potential health benefits.
Neuroprotective Effects of Hydroxytyrosol
A two-part German study in 2007 investigating the effect of hydroxytyrosol on mitochondrial membranes in the brains of mice concluded, “…the ex vivo data provide the first evidence of neuroprotective effects of oral hydroxytyrosol intake.”(7)
In 2010, the same group of researchers conducted a study to determine whether hydroxytyrosol reduces the risk of age-dependent neurodegeneration and cognitive decline. They concluded, “The results we obtained mainly confirm our previous observation of promising cytoprotection of brain cells…”(8)
Purity and Potency: The hydroxytyrosol in ProHealth’s Hydroxytyrosol Extreme is extracted from organic olive leaves and is the first pure hydroxytyrosol sold in the U.S. It contains a minimum of 25% hydroxytyrosol, which means you get 25 mg of pure hydroxytyrosol per 100 mg capsule.
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Safety: Hydroxytyrosol has an excellent safety profile. No adverse effects have been demonstrated even at very high doses. The FDA has granted hydroxytyrosol GRAS (generally recognized as safe) status.
Dosage: The suggested dosage as a dietary supplement is one 100 mg capsule daily, which provides 25 mg of pure hydroxytyrosol, or as otherwise recommended by your health care professional.
Hydroxytyrosol is the most powerful natural antioxidant currently known. Well-documented studies confirm its anti-inflammatory, antibacterial, antioxidant and cardioprotective health benefits. Although still relatively new to most people, hydroxytyrosol promises to soon become a staple in natural health care.
This article, originally published June 22, 2012, was updated on December 17, 2019.
Karen Lee Richards is ProHealth’s Editor-in-Chief. A fibromyalgia patient herself, she co-founded the nonprofit organization now known as the National Fibromyalgia Association (NFA) in 1997 and served as its vice-president for eight years. She was also the executive editor of Fibromyalgia AWARE magazine. After leaving the NFA, Karen served as the Guide to Fibromyalgia and Chronic Fatigue Syndrome for the New York Times website About.com, then worked for eight years as the Chronic Pain Health Guide for The HealthCentral Network before coming to ProHealth. To learn more about Karen, see “Meet Karen Lee Richards.
4. Gonzalez-Santiago M, et al. One-month administration of hydroxytyrosol, a phenolic antioxidant present in olive oil, to hyperlipemic rabbits improves blood lipid profile, antioxidant status and reduces atherosclerosis development. Atherosclerosis. 2006 Sep;188(1):35-42. DOI: 10.1016/j.atherosclerosis.2005.10.022
5. Zhu L, et al. Hydroxytyrosol protects against oxidative damage by simultaneous activation of mitochondrial biogenesis and phase II detoxifying enzyme systems in retinal pigment epithelial cells. J Nutr Biochem. 2010 Nov;21(11):1089-98. DOI: 10.1016/j.jnutbio.2009.09.006
Note: This information has not been reviewed by the FDA. It is for general information purposes; is not intended to prevent, diagnose, treat or cure any illness, condition or disease; and should not replace the personal attention of a qualified healthcare professional. It is very important that you make no change in your healthcare plan or health support regimen without researching and discussing it in collaboration with your professional healthcare team.
Often used as a marketing buzzword, learn about the role of antioxidants beyond the hype, and some of the research on health and disease prevention.
–What are antioxidants?
–Health benefits of antioxidants: what’s the buzz?
–Studies of antioxidant supplements and disease prevention
–Antioxidants in food
–Bottom line on antioxidants and disease prevention
What are antioxidants?
The body’s trillion or so cells face formidable threats, from lack of food to infection with a virus. Another constant threat comes from chemicals called free radicals. In very high levels, they are capable of damaging cells and genetic material. The body generates free radicals as the inevitable byproducts of turning food into energy. Free radicals are also formed after exercising or exposure to cigarette smoke, air pollution, and sunlight.
Free radicals come in many shapes, sizes, and chemical configurations. What they all share is a voracious appetite for electrons, stealing them from any nearby substances that will yield them. This electron theft can radically alter the “loser’s” structure or function. Free radical damage can change the instructions coded in a strand of DNA. It can make a circulating low-density lipoprotein (LDL, sometimes called bad cholesterol) molecule more likely to get trapped in an artery wall. Or it can alter a cell’s membrane, changing the flow of what enters the cell and what leaves it. An excessive chronic amount of free radicals in the body causes a condition called oxidative stress, which may damage cells and lead to chronic diseases.
We aren’t defenseless against free radicals. The body, long used to this relentless attack, makes many molecules that quench free radicals as surely as water douses fire. We also extract free-radical fighters from food. These defenders are labeled “antioxidants.” They work by generously giving electrons to free radicals without turning into electron-scavenging substances themselves. They are also involved in mechanisms that repair DNA and maintain the health of cells.
There are hundreds, probably thousands, of different substances that can act as antioxidants. The most familiar ones are vitamin C, vitamin E, beta-carotene, and other related carotenoids, along with the minerals selenium and manganese. They’re joined by glutathione, coenzyme Q10, lipoic acid, flavonoids, phenols, polyphenols, phytoestrogens, and many more. Most are naturally occurring, and their presence in food is likely to prevent oxidation or to serve as a natural defense against the local environment.
But using the term “antioxidant” to refer to substances is misleading. It is really a chemical property, namely, the ability to act as an electron donor. Some substances that act as antioxidants in one situation may be pro-oxidants—electron grabbers—in a different situation. Another big misconception is that antioxidants are interchangeable. They aren’t. Each one has unique chemical behaviors and biological properties. They almost certainly evolved as parts of elaborate networks, with each different substance (or family of substances) playing slightly different roles. This means that no single substance can do the work of the whole crowd.
Health benefits of antioxidants: what’s the buzz?
Antioxidants came to public attention in the 1990s, when scientists began to understand that free radical damage was involved in the early stages of artery-clogging atherosclerosis. It was also linked to cancer, vision loss, and a host of other chronic conditions. Some studies showed that people with low intakes of antioxidant-rich fruits and vegetables were at greater risk for developing these chronic conditions than were people who ate plenty of those foods. Clinical trials began testing the impact of single substances in supplement form, especially beta-carotene and vitamin E, as weapons against chronic diseases.
Even before the results of these trials were in, the media and the supplement and food industries began to hype the benefits of “antioxidants.” Frozen berries, green tea, and other foods labeled as being rich in antioxidants began popping up in stores. Supplement makers touted the disease-fighting properties of all sorts of antioxidants.
The research results were mixed, but most did not find the hoped-for benefits. Most research teams reported that vitamin E and other antioxidant supplements didn’t protect against heart disease or cancer. One study even showed that taking beta-carotene supplements actually increased the chances of developing lung cancer in smokers. On the other hand, some trials reported benefits; for example, after 18 years of follow-up, the Physicians’ Health Study found that taking beta-carotene supplements was associated with a modest reduction in the rate of cognitive decline.
These mostly disappointing results haven’t stopped food companies and supplement sellers from banking on antioxidants. Antioxidants are still added to breakfast cereals, sports bars, energy drinks, and other processed foods, and they are promoted as additives that can prevent heart disease, cancer, cataracts, memory loss, and other conditions.
Often the claims have stretched and distorted the data: While it’s true that the package of antioxidants, minerals, fiber, and other substances found naturally in fruits, vegetables, and whole grains helps prevent a variety of chronic diseases, it is unlikely that high doses of antioxidant supplements can accomplish the same feat.
Antioxidant foods hyped to super-status
Some foods reached “superfood” status because of their high antioxidant content. In 1991, a rating tool called the Oxygen Radical Absorbance Capacity (ORAC) was created by scientists from the National Institute on Aging and the United States Department of Agriculture (USDA). It was used to measure the antioxidant capacity of foods. The USDA provided an ORAC database on its website highlighting foods with high ORAC scores, including cocoa, berries, spices, and legumes. Blueberries and other foods topping the list were heavily promoted in the popular press as disease-fighters even if the science was weak, from cancer to brain health to heart disease. However, 20 years later the USDA retracted the information and removed the database after determining that antioxidants have many functions, not all of which are related to free radical activity. Learn more about the history and hype around so-called superfoods.
Antioxidant supplements and disease prevention: little supportive evidence
Randomized placebo-controlled trials, which can provide the strongest evidence, offer little support that taking vitamin C, vitamin E, beta-carotene, or other single antioxidants provides substantial protection against heart disease, cancer, or other chronic conditions. The results of the largest trials have been mostly negative.
Vitamin E, beta-carotene, and other antioxidants in supplement form aren’t the silver bullet against heart disease and stroke that researchers were hoping for. A modest effect of vitamin E has been found in some studies but more research is needed.
- In the Women’s Health Study, 39,876 initially healthy women took 600 IU of natural source vitamin E or a placebo every other day for 10 years. At the study’s end, the rates of major cardiovascular events and cancer were no lower among those taking vitamin E than those taking the placebo. However, the trial did observe a significant 24% reduction in total cardiovascular mortality. Although this was not a primary endpoint for the trial, it nevertheless represents an important outcome.
- Earlier large vitamin E trials, conducted among individuals with previously diagnosed coronary disease or at high risk for it, generally showed no benefit. In the Heart Outcomes Prevention Evaluation (HOPE) trial, the rates of major cardiovascular events were essentially the same in the vitamin E (21.5%) and placebo (20.6%) groups, although participants taking vitamin E had higher risks of heart failure and hospitalization for heart failure. In the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico (GISSI) trial, the results were mixed but mostly showed no preventive effects after more than three years of treatment with vitamin E among 11,000 heart attack survivors. However, some studies suggest potential benefits among certain subgroups. A recent trial of vitamin E in Israel, for example, showed a marked reduction in coronary heart disease among people with type 2 diabetes who have a common genetic predisposition for greater oxidative stress.
- Beta-carotene, meanwhile, did not provide any protection against heart disease or stroke, as demonstrated by the Physicians’ Health Study.
- What about combinations? In the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI.MAX) study, 13,017 French men and women took a single daily capsule that contained 120 mg vitamin C, 30 mg vitamin E, 6 mg beta-carotene, 100 mcg selenium, and 20 mg zinc, or a placebo, for seven and a half years. The vitamins had no effect on overall rates of cardiovascular disease.
- In the Women’s Antioxidant Cardiovascular Study, vitamin E, vitamin C, and beta-carotene had similar effects as a placebo on myocardial infarction, stroke, coronary revascularization, and cardiovascular death, although there was a modest and significant benefit for vitamin E among women with existing cardiovascular disease.
A 2014 study from the Journal of Respiratory Research found that different isoforms of vitamin E (called tocopherols) had opposing effects on lung function. The study analyzed data from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort and measured serum levels of alpha- and gamma-tocopherol in 4,526 adults. Lung function was tested using spirometric parameters: higher parameters are indicative of increased lung function, while lower parameters are indicative of decreased lung function. The study found that higher serum levels of alpha-tocopherol were associated with higher spirometric parameters and that high serum levels of gamma-tocopherol were associated with lower spirometric parameters. Though the study was observational in nature, it confirmed the mechanistic pathway of alpha- and gamma-tocopherol in mice studies.
When it comes to cancer prevention, the picture remains inconclusive for antioxidant supplements. Few trials have gone on long enough to provide an adequate test for cancer.
- In the long-term Physicians’ Health Study, cancer rates were similar among men taking beta-carotene and among those taking a placebo. Other trials have also largely shown no effect, including HOPE.
- The SU.VI.MAX randomized placebo-controlled trial showed a reduction in cancer risk and all-cause mortality among men taking an antioxidant cocktail (low doses of vitamins C and E, beta-carotene, selenium, and zinc) but no apparent effect in women, possibly because men tended to have low blood levels of beta-carotene and other vitamins at the beginning of the study.
- A randomized trial of selenium in people with skin cancer demonstrated significant reductions in cancer and cancer mortality at various sites, including colon, lung, and prostate. The effects were strongest among those with low selenium levels at baseline.
- A six-year trial, the Age-Related Eye Disease Study (AREDS), found that a combination of vitamin C, vitamin E, beta-carotene, and zinc offered some protection against the development of advanced age-related macular degeneration, but not cataracts, in people who were at high risk of the disease.
- Lutein, a naturally occurring carotenoid found in green, leafy vegetables such as spinach and kale, may protect vision. However, relatively short trials of lutein supplementation for age-related macular degeneration have yielded conflicting findings. A follow-up trial to the AREDS, the AREDS2, examined lutein/zeaxanthin supplementation on late age-related macular degeneration (AMD) in men and women for up to five years. It found a favorable but not significant effect of the supplements on AMD.
- A Cochrane review of 19 randomized controlled trials compared antioxidant vitamin/mineral supplements (multivitamin, vitamin E, lutein, zeaxanthin, zinc) with placebo or no intervention in people with AMD. The participants were generally well-nourished. The study found that people taking the vitamins were less likely to progress to late-stage AMD and vision loss. However, the study authors noted that taking lutein and zeaxanthin alone or vitamin E alone did not have a beneficial effect on these eye conditions.
- The Selenium and Vitamin E Cancer Prevention Trial (SELECT) Eye Endpoints Study, which followed 11,267 men for a mean of five years, did not find that vitamin E and selenium supplements, in combination or alone, protected from age-related cataracts.
- The Physicians’ Health Study II, a randomized trial giving 50 mg beta-carotene supplements or a placebo to 5,956 men older than 65 years, found that longer-term supplementation for at least 15 years provided cognitive benefits.
- The Prevention of Alzheimer’s Disease by Vitamin E and Selenium (PREADViSE) trial followed more than 3,700 men ages 60 and older for six years. It did not find that antioxidant supplements of vitamin E or selenium, alone or in combination, protected against dementia compared with a placebo.
- A meta-analysis of 68 antioxidant supplement trials found that taking beta-carotene and vitamin A and E supplements increased the risk of dying. Although healthy participants were included in 21 of the trials, most of the studies included people who already had some type of serious illness. It was also difficult to compare interventions because the types of supplements, the dosages taken, and the length of time they were taken varied widely.
- The same authors conducted another systematic review of 78 randomized clinical trials on antioxidant supplements including beta-carotene, vitamin A, vitamin C, vitamin E, and selenium (alone or in combination). Again, the majority of trials included people with various established diseases. The study found that both people who were healthy and those with diseases taking beta-carotene and vitamin E supplements had a higher rate of death. The duration of the studies varied widely from one month to 12 years, with varying dosages.
Potential hazards of antioxidant supplements
If antioxidants were harmless, it wouldn’t much matter if you took them “just in case.” A few studies, though, have raised the possibility that taking antioxidant supplements, either single agents or combinations, could interfere with health.
- The first inkling came in a large trial of beta-carotene conducted among men in Finland who were heavy smokers, and therefore at high risk for developing lung cancer. The trial was stopped early when researchers saw a significant increase in lung cancer among those taking the supplement compared to those taking the placebo.
- In another trial among heavy smokers and people exposed to asbestos, beta-carotene was combined with vitamin A. Again, an increase in lung cancer was seen in the supplement group. Not all trials of beta-carotene show this harmful effect, however. In the Physicians’ Health Study, which included few active smokers, no increase in lung cancer or any other adverse affect was seen even after 18 years of follow-up.
- In the SU.VI.MAX trial, rates of skin cancer were higher in women who were assigned to take vitamin C, vitamin E, beta-carotene, selenium, and zinc.
- Vitamin E supplements were found to significantly increase the risk of prostate cancer by 17% in healthy men compared with those who took a placebo. These results came from the Selenium and Vitamin E Cancer Prevention Trial (SELECT) that followed 35,533 men for up to 12 years.
High-dose antioxidant supplements can also interfere with medicines. Vitamin E supplements can have a blood-thinning effect and increase the risk of bleeding in people who are already taking blood-thinning medicines. Some studies have suggested that taking antioxidant supplements during cancer treatment might interfere with the effectiveness of the treatment. Inform your doctor if starting supplements of any kind.
Antioxidants in food
One possible reason why many studies on antioxidant supplements do not show a health benefit is because antioxidants tend to work best in combination with other nutrients, plant chemicals, and even other antioxidants.
For example, a cup of fresh strawberries contains about 80 mg of vitamin C, a nutrient classified as having high antioxidant activity. But a supplement containing 500 mg of vitamin C (667% of the RDA) does not contain the plant chemicals (polyphenols) naturally found in strawberries like proanthocyanins and flavonoids, which also possess antioxidant activity and may team up with vitamin C to fight disease. Polyphenols also have many other chemical properties besides their ability to serve as antioxidants. There is a question if a nutrient with antioxidant activity can cause the opposite effect with pro-oxidant activity if too much is taken. This is why using an antioxidant supplement with a single isolated substance may not be an effective strategy for everyone.
Differences in the amount and type of antioxidants in foods versus those in supplements might also influence their effects. For example, there are eight chemical forms of vitamin E present in foods. However, vitamin E supplements typically only include one form, alpha-tocopherol.
Epidemiological prospective studies show that higher intakes of antioxidant-rich fruits, vegetables, and legumes are associated with a lower risk of chronic oxidative stress-related diseases like cardiovascular diseases, cancer, and deaths from all causes. A plant-based diet is believed to protect against chronic oxidative stress-related diseases. It is not clear if this protective effect is due to the antioxidants, other substances in the foods, or a combination of both. The following are nutrients with antioxidant activity and the foods in which they are found:
Bottom line on antioxidants and disease prevention
Excessive free radicals contribute to chronic diseases including cancer, heart disease, cognitive decline, and vision loss. This doesn’t automatically mean that substances with antioxidant properties will fix the problem, especially if they are taken out of their natural context. The studies so far are inconclusive but generally don’t provide strong evidence that antioxidant supplements have a substantial impact on disease. Keep in mind that most of the trials conducted have had fundamental limitations due to their relatively short duration and inclusion of people with existing disease. At the same time, abundant evidence suggests that eating whole in fruits, vegetables, and whole grains—all rich in networks of naturally occurring antioxidants and their helper molecules—provides protection against many scourges of aging.
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