Antioxidants: When Do They Benefit Our Health and When Do They Cause Harm?

Every day we are exposed to a wide variety of environmental factors than can impact our health, such as UV radiation from the Sun, exhaust gas from vehicles with combustion engines, and even meat that is being barbecued. These items can potentially be dangerous for our health because they emit “free radicals”, which can damage healthy cells and subsequently cause cancer. Fortunately, there are effective counterparts called antioxidants. But to what extent are antioxidants healthy for our body?

What are Antioxidants?

Antioxidants are substances that can slow down or prevent cell damage caused by free radicals, so they have a reputation for promoting health. This is accomplished by their ability to scavenge harmful free radicals and thus reduce oxidative stress in the human body by protecting its cells. Some antioxidants can be produced in the human body, while others must be ingested through food. Vitamin A, C and E are some examples of antioxidants, these and others are found in many different types foods, but especially in colorful vegetables and fruits. Others can be found in certain spices, beans, cereals and teas.

Research has largely shown that antioxidants have anti-carcinogenic activity, which means they can inhibit the development of cancer in our bodies.

What are free radicals?

Free radicals are highly unstable oxygen species with an unpaired electron, which is responsible for their high reactivity. For this reason, they are also called Reactive Oxygen Species (ROS). Since free radicals are missing an electron, and in order to complete that electron gap, they look for molecules from which they can snatch an electron from including ones from a healthy cell in the human body. When they “steal” the required electron from a cell the process is called oxidation, where the cell loses an electron to the free radical. Once they have stolen their electron the process can cause damage in the cell that had its electron stolen. This damage is usually in the cellular DNA which can lead to mutations that can result in various diseases, such as cancer or heart disease.

Free radicals are produced in the body naturally as a result of the oxygen metabolism or by environmental impacts such as UV-light, ionizing radiation, heavy metals, or tobacco smoke. Free radicals have extremely short lifetimes, but they can still damage our DNA in that short time. A healthy immune system can normally control free radicals to prevent this process and can also get rid of damaged cells caused by this process. However, if our body contains an overload of free radicals, this can cause “oxidative stress”. That happens as a result of the imbalance between production and detoxification of free radicals. This phenomenon leads to cell and tissue damage which can subsequently lead to cancer.

Anti-carcinogenic activity of antioxidants

Antioxidants can help stop the oxidation process mentioned above. They achieve this by donating an electron to free radicals and thus prevent our own cells from being attacked by free radicals in their quest for an electron. In this way, they prevent oxidation, hence the name “anti-oxidants”. After this process, they are also missing an electron, however, they do not take it from our cells, but from other antioxidants.


Antioxidants can therefore prevent our genetic material from being damaged, cells from mutating and dividing uncontrollably, which is responsible for cancer. Skin cells are also protected in this way, which has a positive effect on the appearance of the skin. In addition to that, it has been proven that sufficient supply of antioxidants can improve sperm quality, as some of the male infertility cases are caused by oxidative stress.

Can an excess amount of antioxidants worsen cancer growth?

Taking too many antioxidants can be dangerous for people with cancer, because of two issues. First of all, researchers using cell cultures as well as mouse models have found that antioxidants may promote the metastatic ability of melanoma cells, which induces a type of skin cancer. A proposed mechanism for this is via a protein called BACH1. Cancer cells increase the sugar consumption by activating the BACH1 protein and therefore, grow faster and spread. But they can only do this in an environment with low oxidative stress. Antioxidants reduce the oxidative stress on cancer cells and allow them to activate the BACH1 protein and spread. And secondly, having some oxidative stress triggers the immune system, thereby allowing it to fight with cancer cells. If there is not enough free radicals, our immune system may have a difficult time fighting with cancer cells.

Maria Tyutina

A research group from Gothenburg University in Sweden tested the antioxidant substances N-acetylcysteine (NAC) and vitamin E in a mouse model of melanoma and on human melanoma cell lines. In the mouse model, N-acetylcysteine increased the number of lymph node metastases. However, the number and size of primary tumors did not change. Similarly, vitamin E increased the migration of the melanoma cells, but did not have any impact on their proliferation, which is described as the division activity of the tumor cells. The results were similar with the experiments with cell cultures. The question that pops in our mind is: “Should individuals with cancer take antioxidant supplements?” Until there are more research results on this topic, people who are diagnosed with cancer should be very cautious with their dietary supplements and always consult their physicians.

Quick Summary

To put it in a nutshell, antioxidants reduce oxidative stress in the human body, which can help decrease the risk of developing cancer. This effect might be desirable in healthy cells but can be dangerous in tumor cells. In this case, antioxidants could help tumor cells survive, which is undesirable for us.