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We often consider antioxidants as protectors from harmful free radicals, just like friends.
In fact, free radicals do not always cause harm, and antioxidants do not exclusively offer benefits. Maintaining a balance between the actions of antioxidants and the creation of free radicals is crucial for a healthy and long life. We require both types of compounds.
What are free radicals and why can they be harmful to health?
Free radicals can assume various forms, sizes, and chemical configurations, but share the common ability to extract an electron from any molecule they interact with.
Free radicals significantly change the structure and properties of compounds by taking electrons from them. This process damages DNA, vessel walls, and cell membranes, resulting in a disturbance of substance transport into and out of the cell.
“Incomplete” chemical molecules known as free radicals require a pair of electrons. They take an electron from other molecules with fully paired electrons. Consequently, the affected molecules transform into free radicals and begin searching for a complete molecule to acquire their missing electron.
Two types of free radicals exist.
- Endogenous, or internal. They are formed in cells as a result of their normal functioning, for example, during activation of immune cells or in the process of respiration.
- Exogenous, or external. These are formed from substances that enter the body through air pollution, cigarette smoke, alcohol, medications, and other sources.
Active oxygen forms constitute the majority of free radicals in our organism, which damage cells causing oxidative or oxidizing stress. Research suggests that oxidative stress plays a key role in the development of many chronic diseases like diabetes, cancer, Alzheimer’s disease, and cardiovascular disease.
Sometimes, the body requires free radicals at low and moderate levels to function correctly. Immune cells will fail to eradicate microbes, and signaling between cells will suffer if they are absent. Additionally, cell structure maturation, along with other processes, will be impacted.
When there are too many free radicals, they can become dangerous. The body works to prevent them from causing harm by utilizing antioxidants.
| Factor | Effect |
|---|---|
| External free radicals: Air and water pollution, heavy metals, pesticides | Damages cells and tissues, leading to chronic diseases |
| Internal free radicals: Respiratory chain, which operates in cell organelles called mitochondria | Natural byproduct of cellular metabolism, can cause oxidative stress and damage |
| Cigarette smoke | Damages lungs, increases risk of cancer and other diseases |
| Ozone | Can cause respiratory problems and aggravate existing conditions |
| Ultraviolet and X-ray radiation | Can damage DNA and increase risk of cancer |
| Medications | Can have side effects and may contribute to organ damage over time |
| Food prepared by smoking, frying at high temperatures | Can produce harmful compounds that increase risk of cancer and other diseases |
Antioxidants benefit health. What do antioxidants do?
A molecule with antioxidant properties donates an electron to a free radical, thereby neutralizing it. As a consequence, the antioxidant loses its ability to neutralize other similar molecules, since it has no extra electrons remaining.
Antioxidants are also divided into internal – endogenous and external – exogenous. Internal ones are produced by the body itself, while external ones come from food.
Endogenous antioxidants
Endogenous antioxidants can take the form of large protein molecules, enzymes, or low molecular weight compounds that lack enzymatic activity.
There are various enzymes in the human body that can eliminate free radicals, such as superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase.
The body’s primary internal antioxidant system is the glutathione system, which includes several enzymes like glutathione reductase and a low-molecular weight compound made up of the amino acids glycine, glutamate, and cysteine.
Glutathione, a small molecule, acts independently to neutralize free radicals and also helps the antioxidant enzymes within its system to function properly, making it the central component of this system.
In addition to glutathione, internal antioxidants include compounds such as the amino acid L-arginine, coenzyme Q10, melatonin hormone, and others.
Exogenous antioxidants
External antioxidants that come from food also help neutralize free radicals. There are a lot of them.
Some of the external antioxidants are vitamins, which are essential for human life. These include vitamins C, E, and beta-carotene, which is converted into vitamin A in the body.
Microelements such as manganese and selenium are sometimes considered to be essential external antioxidants. These substances do not have antioxidant activity on their own, but the internal systems that fight free radicals cannot function without them.
Do free radicals cause aging and do antioxidants rejuvenate?
Sometimes, people consider free radicals as the primary cause of aging because these molecules can harm cells. It is believed that they contribute to the disturbances in cellular structures that are always related to aging.
Scientists believed that an increase in free radicals in the body accelerates aging. Therefore, by taking antioxidants, individuals can delay the aging process.
In fact, the complexity is much higher. Fast aging cannot be directly attributed to increased levels of free radicals. Also, antioxidants do not seem to prolong youth.
The naked mole rat, an unusual rodent living underground, caught the attention of scientists who observed that its lifespan surpassed that of other rodents of the same size by eight times. However, the naked mole rat’s tissues contain a low level of antioxidants and undergo many oxidative damages.
Scientists later explained the paradox of the naked mole-rat as an evolutionary adaptation in which animal cells gradually adapted to living in a high oxidative stress state.
However, data on other long-living organisms undergoing significant oxidative stress doesn’t entirely support this hypothesis.
By genetically engineering it, researchers suppressed the internal antioxidant synthesis of roundworms and mice. The mutants they created were found to have either the same lifespan as healthy individuals or a longer one, despite not having had thousands of years of evolution to adapt to high oxidative stress living conditions.
The data obtained does not disprove the harmful effect of high levels of free radicals and oxidative stress, as well as their involvement in the development of several chronic diseases. However, the findings from these experiments challenge the theory that it is specifically free radicals that initiate the aging process.
Is it worth taking antioxidants in the form of food supplements?
Antioxidant additives are compounds that are obtained either from food products or by chemical synthesis. The composition of additives always differs from what is contained in natural products.
The theory of oxidative stress, which arises due to an excess of free radicals and harms health, suggests the benefit of taking supplements with antioxidants. However, in serious clinical trials, such hypothetical benefits have not been proven.
The research results are ambiguous. Most of them either do not confirm the benefits of dietary supplements with antioxidants or indicate possible harm.
In 2020, a major review of most reliable clinical studies of antioxidant dietary supplements conducted over the years was published in the journal Frontiers in Physiology.
Summing up the results of the clinical data, the authors of the review came to the following conclusions:
- More doesn’t always mean better. Free radicals are also necessary for the human body, and an excess of antioxidants can be harmful.
- The use of dietary supplements with antioxidants does not overcome the negative impact of an unhealthy lifestyle and poor nutrition.
- Antioxidants are not interchangeable. Each has its own unique biological activity, so taking one compound does not compensate for the lack of others.
- Many antioxidants are not well absorbed by the body from supplements, only from food.
- Antioxidants in natural fruits and vegetables often have a different chemical configuration. They work quite differently from those that have been isolated from products or synthesized in the laboratory.
- Taking supplements with antioxidants may only benefit certain groups of patients, for example with proven deficiencies of certain substances. But it is useless for healthy people as a preventive measure against diseases or protection against aging.
Specialists today discourage taking antioxidant supplements, as they deem it irrelevant for those with chronic diseases, including diabetes, cancer, and cardiovascular diseases, where oxidative stress has a significant impact, as well as healthy individuals.
The American Cardiology Association and the American Diabetes Association advise that individuals should take dietary supplements with antioxidants on the prescription of a doctor and after an analysis has revealed a deficiency in specific compounds with antioxidant activity.
In all other cases, people should consume antioxidants in their natural form from food.
Additionally, evidence suggests that high doses of antioxidant dietary supplements can pose a grave health risk in certain situations. For instance, smokers who take high doses of beta-carotene may have an increased likelihood of developing lung cancer. The risk of prostate cancer and stroke also increases as a result of high doses of vitamin E.
Certain medications may interact with other antioxidant supplements, so it is always necessary to consult a treating physician before taking them.
People taking anticoagulants have an increased risk of bleeding when they consume supplements containing vitamin E. Antioxidant supplements’ effects on cancer therapy are conflicting as some studies show benefits while others indicate harm.
Which foods have antioxidants?
Consuming a diverse and balanced diet is the only proven method to obtain essential antioxidants without compromising your health.
Vegetables and fruits contain a majority of antioxidant compounds, which are believed to reduce the risk of certain diseases and improve overall health. Although it is uncertain whether the benefits are due solely to antioxidants or other factors in these foods.
| Antioxidant | Foods containing it |
|---|---|
| Vitamin E | Vegetable oils, nuts and seeds, avocado, leafy greens |
| Vitamin C | Sour fruits, green vegetables, tomatoes |
| Beta-carotene | Carrots, greens, zucchini, spinach |
| Lycopene | Tomatoes that have been heat-processed, tomato juice and sauce |
| Flavonoids | Green tea, grapes, apples, natural cocoa, turmeric, berries, onions, broccoli |
Main Myths About Antioxidants
Antioxidants are the same as vitamins
Some vitamins have antioxidant activity. But there are also vitamins that are not antioxidants, and many antioxidants that are not vitamins.
The human body does not produce antioxidants, so they must always be obtained through food
Some important antioxidants, such as vitamin C, are actually not produced in the body and must be obtained through food. At the same time, the human body has its own antioxidant systems that effectively destroy free radicals.
Free radicals are absolute evil
Free radicals are only dangerous in high concentrations. In small and moderate amounts, they are vital to the body.
Antioxidants are so beneficial that they can be consumed in unlimited quantities
However, taking supplements with antioxidants in high doses can be harmful to health. For example, an excess of vitamin E is just as dangerous as a deficiency.
If you consume a lot of antioxidants, you can delay aging
The excess of free radicals and the lack of antioxidants are related to a condition called oxidative stress, which, in turn, is associated with many chronic diseases. But there is no scientific proof for the hypothesis that antioxidants are a pill for aging.
Taking supplements with antioxidants does not guarantee a healthy diet or lifestyle, as it is still possible to eat improperly and lead an unhealthy life
The negative impact on health from harmful habits and a deficiency in fruits, vegetables, and whole grains – which are rich in vitamins, minerals, fiber, and natural antioxidant compounds – cannot be compensated for by any dietary supplement.
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