Antioxidants can prevent or slow cell damage caused by free radicals. Free radicals are unstable molecules that the body produces as a reaction to environmental and other pressures. They can increase the risk of inflammation and various health issues.
They are sometimes called “free-radical scavengers.”
The sources of antioxidants can be natural or artificial. Certain plant-based foods are thought to be rich in antioxidants. Plant-based antioxidants are a kind of phytonutrient, or plant-based nutrient.
The body also producesTrusted Source some antioxidants, known as endogenous antioxidants. Antioxidants that come from outside the body are called exogenous.
Free radicals are waste substances produced by cellsTrusted Source as the body processes food and reacts to the environment. If the body cannot process and remove free radicals efficiently, oxidative stress can result. This can harm cells and body function. Free radicals are also known as reactive oxygen species (ROS).
Factors that increase the production of free radicals in the body can be internal, such as inflammation, or external, for example, pollution, UV exposure, and cigarette smoke.
Oxidative stress has been linkedTrusted Source to heart disease, cancer, arthritis, stroke, respiratory diseases, immune deficiency, emphysema, Parkinson’s disease, and other inflammatory or ischemic conditions.
Antioxidants are said to help neutralize free radicals in our bodies, and this is thought to boost overall health.
Antioxidants can protect against the cell damage that free radicals cause, known as oxidative stress.
Activities and processes that can lead to oxidative stress include
- mitochondrial activity
- excessive exercise
- tissue trauma, due to inflammation and injury
- ischemia and reperfusion damage
- consumption of certain foods, especially refined and processed foods, trans fats, artificial sweeteners, and certain dyes and additives
- smoking
- environmental pollution
- radiation
- exposure to chemicals, such as pesticides and drugs, including chemotherapy
- industrial solvents
- ozone
Such activities and exposures can result in cell damage.
This, in turn, may lead to:
- an excessive release of free iron or copper ions
- an activation of phagocytes, a type of white blood cell with a role in fighting infection
- an increase in enzymes that generate free radicals
- a disruption of electron transport chains
All these can result in oxidative stress.
The damage caused by oxidative stress has been linked to cancer, atherosclerosis, and vision loss. It is thought that the free radicals cause changes in the cells that lead to these and possibly other conditions.
An intake of antioxidants is believed to reduce these risks.
According to one studyTrusted Source: “Antioxidants act as radical scavenger, hydrogen donor, electron donor, peroxide decomposer, singlet oxygen quencher, enzyme inhibitor, synergist, and metal-chelating agents.”
Other research has indicatedTrusted Source that antioxidant supplements may help reduce vision loss due to age-related macular degeneration in older people.
Overall, however, there is a lack of evidenceTrusted Source that a higher intake of specific antioxidants can reduce the risk of disease. In most cases, results have tended to show no benefit, or a detrimental effect, or they have been conflicting.
Types
There are thought to be hundreds and possibly thousands of substances that can act as antioxidants. Each has its own role and can interact with others to help the body work effectively.
“Antioxidant” is not really the name of a substance, but rather it describes what a range of substances can do.
Examples of antioxidants that come from outside the body include:
- vitamin A
- vitamin C
- vitamin E
- beta-carotene
- lycopene
- lutein
- selenium
- manganese
- zeaxanthin
The best sources of antioxidants are plant-based foods, especially fruits and vegetables.
Foods that are particularly high in antioxidants are often referred to as a “superfood” or “functional food.”
To obtain some specific antioxidants, try to include the following in your diet:
Vitamin A: Dairy produce, eggs, and liver
Vitamin C: Most fruits and vegetables, especially berries, oranges, and bell peppers
Vitamin E: Nuts and seeds, sunflower and other vegetable oils, and green, leafy vegetables
Beta-carotene: Brightly colored fruits and vegetables, such as carrots, peas, spinach, and mangoes
Lycopene: Pink and red fruits and vegetables, including tomatoes and watermelon
Lutein: Green, leafy vegetables, corn, papaya, and oranges
Selenium: Rice, corn, wheat, and other whole grains, as well as nuts, eggs, cheese, and legumes
Other foods that are believed to be good sources of antioxidants include:
- eggplants
- legumes such as black beans or kidney beans
- green and black teas
- red grapes
- dark chocolate
- pomegranates
- goji berries
Effect of cooking
Cooking particular foods can either increase or decrease antioxidant levels.
Lycopene is the antioxidant that gives tomatoes their rich red color. When tomatoes are heat-treated, the lycopene becomes more bio-available (easier for our bodies to process and use).
However, studies have shown that cauliflower, peas, and zucchini lose much of their antioxidant activity in the cooking process. Keep in mind that the important thing is eating a variety of antioxidant-rich foods, cooked and raw.
The following tips could help increase your antioxidant intake:
- Include a fruit or a vegetable every time you eat, meals and snacks included.
- Have a cup of green or matcha tea every day.
- Look at the colors on your plate. If your food is mostly brown or beige, the antioxidant levels are likely to be low. Add in foods with rich colors, such as kale, beets, and berries.
- Use turmeric, cumin, oregano, ginger, clove, and cinnamon to spice up the flavor and antioxidant content of your meals.
- Snack on nuts, seeds, especially Brazil nuts, sunflower seeds, and dried fruit, but choose those with no added sugar or salt.
Understanding free radicals requires a basic knowledge of chemistry.
Atoms are surrounded by electrons that orbit the atom in layers called shells. Each shell needs to be filled by a set number of electrons. When a shell is full; electrons begin filling the next shell.
If an atom has an outer shell that is not full, it may bond with another atom, using the electrons to complete its outer shell. These types of atoms are known as free radicals.
Atoms with a full outer shell are stable, but free radicals are unstable and in an effort to make up the number of electrons in their outer shell, they react quickly with other substances.
When oxygen molecules split into single atoms that have unpaired electrons, they become unstable free radicals that seek other atoms or molecules to bond to. If this continues to happen, it begins a process called oxidative stress.
Oxidative stress can damage the body’s cells, leading to a range of diseases and causes symptoms of aging, such as wrinkles.
It is hard to watch television without seeing at least one commercial that promises to fight aging with antioxidants. Antioxidants are molecules that prevent the oxidation of other molecules.
Antioxidants are chemicals that lessen or prevent the effects of free radicals. They donate an electron to free radicals, thereby reducing their reactivity. What makes antioxidants unique is that they can donate an electron without becoming reactive free radicals themselves.
No single antioxidant can combat the effects of every free radical. Just as free radicals have different effects in different areas of the body, every antioxidant behaves differently due to its chemical properties.
In certain contexts, however, some antioxidants may become pro-oxidants, which grab electrons from other molecules, creating chemical instability that can cause oxidative stress.
Antioxidant foods and supplements: Do they work?
Thousands of chemicals can act as antioxidants. Vitamins C, and E, glutathione, beta-carotene, and plant estrogens called phytoestrogens are among the many antioxidants that may cancel out the effects of free radicals.
Many foods are rich in antioxidants. Berries, citrus fruits, and many other fruits are rich in vitamin C, while carrots are known for their high beta-carotene content. The soy found in soybeans and some meat substitutes is high in phytoestrogens.
The ready availability of antioxidants in food has inspired some health experts to advise antioxidant-rich diets. The antioxidant theory of aging also led many companies to push sales of antioxidant supplements.
Research on antioxidants is mixed. Most research shows few or no benefits. A 2010 study that looked at antioxidant supplementation for the prevention of prostate cancer found no benefits. A 2012 studyTrusted Source found that antioxidants did not lower the risk of lung cancer. In fact, for people already at a heightened risk of cancer, such as smokers, antioxidants slightly elevated the risk of cancer.
Some research has even found that supplementation with antioxidants is harmful, particularly if people take more than the recommended daily allowance (RDA). A 2013 analysisTrusted Source found that high doses of beta-carotene or vitamin E significantly increased the risk of dying.
A few studies have found benefits associated with antioxidant use, but the results have been modest. A 2007 studyTrusted Source, for instance, found that long-term use of beta-carotene could modestly reduce the risk of age-related problems with thinking.
Studies suggest that antioxidants cannot “cure” the effects of free radicals – at least not when antioxidants come from artificial sources. This raises questions about what free radicals are, and why they form.
It is possible that free radicals are an early sign of cells already fighting disease, or that free radical formation is inevitable with age. Without more data, it is impossible to understand the problem of free radicals fully.
People interested in fighting free radical-related aging should avoid common sources of free radicals, such as pollution and fried food. They should also eat a healthful, balanced diet without worrying about supplementing with antioxidants.