Antioxidants are (man-made or natural) substances that inhibit the oxidation of other molecules and may therefore protect cells from the damage caused free radicals. Antioxidants are found in many foods, especially fruits and vegetables. There are literally thousands of different substances that can act as antioxidants. Some of the most popular antioxidants are, beta-carotene, selenium, vitamin A, ascorbic acid (vitamin C), tocopherol (vitamin E), ubiquinol (coenzyme Q).
Since 1990’s, antioxidants have gained in popularity as scientist realized that free radical or oxidative damage was involved in the early stages of artery-clogging atherosclerosis  and may contribute to cancer , vision loss , and some chronic conditions.
Antioxidants have now become synonym for good health. Due to their high popularity and demand supplemental antioxidants also found their way to supermarket shelves. However, more and more well-designed studies show that antioxidants, in supplement form, do not deliver promised health benefits. Therefore, we decided to dig in to scientific literature to bring you the facts about this very popular supplement.
What are Antioxidants, Free Radicals, and What is Oxidative Stress?
Free radicals (reactive oxygen species or harmful oxidants) are highly unstable molecules that are naturally formed during exercise, sun exposure, cigarette smoking, and when your body converts food into energy . They may cause a cell damage via process called oxidative stress.
Oxidative stress is described as increased production of oxidants or a significant decrease in the effectiveness of antioxidants, which may potentially lead to damage . Betteridge  defined oxidative stress as “disturbance in the balance between the production of reactive oxygen species (free radicals) and antioxidant defenses”. Severity of damage caused by oxidative stress depends upon the size of changes. It can cause anything from small deviations in the cell to cell death .
To prevent free radical damage the body has a defense system of antioxidants. They are produced by our bodies to fight off the free radicals formed by normal body processes. They can also be ingested by eating health diet or as supplement.
Exercise and Oxidative Damage
Strenuous physical exercise can increase oxygen consumption from 10 to 15 times over the resting, which leads to oxidative stress via increased production of free radicals and lipid peroxidation . This fact raised a few questions, does this increased oxidative stress enhances damage to muscles and other tissues and do athletes need to supplement with antioxidants? Well, luckily our bodies can adapt to regular physical exercise via improved antioxidant defense system . Whether athletes should ingest extra antioxidants remains controversial. However, diet rich in fruits and vegetables is suggested.
Why Don’t Antioxidant Supplements Work as Marketed?
Widespread use of antioxidants has failed to put an end to the current pandemic of cancer, diabetes, and cardiovascular disease and it also failed to reverse the aging process. Furthermore, most clinical randomized, double-blind, controlled trials in humans using supplemental antioxidants have failed to provide substantial health benefits .
The Women’s Antioxidant Cardiovascular Study  failed to show any effects of ascorbic acid (500 mg/d), vitamin E (600 IU every other day), or beta carotene (50 mg every other day) on cardiovascular events among women at high risk for cardiovascular disease. Same was reported in a large-scale study in men where neither vitamin E (400 IU every other day) nor C (500 mg/d) supplementation reduced the risk of major cardiovascular events . Meta-analysis of randomized trials  discouraged the use of vitamin supplements containing beta-carotene and vitamin A, beta-carotene’s biologically active metabolite, because this family of agents is associated with a small but significant excess of all-cause mortality and cardiovascular death.
Furthermore, beta-carotene and vitamins C and E had no effect on the age-related lens opacities or visual acuity loss in 4,757 participants (who were followed for 6.3 years) . Findings of Hercberg et al.  study advised against supplementing with vitamins and trace element antioxidants as they may not always provide beneficial effects. In 13,017 men and women rates of skin cancer were higher in women (but not in men) who were assigned to take vitamin C, vitamin E, beta-carotene, selenium, and zinc.
According to National Center for Complementary and Alternative Medicine several reasons may contribute to these findings, including :
– Relationship between free radicals and health is more complex than previously thought as in some cases free radicals may actually be beneficial. Some recent data shows that cells use reactive oxygen species as part of the signaling process responsible for activating an important mechanism for eliminating cancer cells .
– Health benefits from diet rich in vegetables and fruits may be caused by other substances present in such food rather than antioxidants.
– High doses of antioxidants used in studies may have different effect on the body than small amounts found naturally in foods. Differences in the chemical composition of antioxidants in foods versus those in supplements may also influence their effects.
– For some diseases, specific antioxidants may be more suitable than others.
Potential Hazards of Antioxidants
Not only that most studies failed to show health benefits of antioxidants, a few raised the possibility that taking antioxidant supplements, alone or combinations, could interfere with health. For example, a study in Finish male smokers found an 18% excess of lung cancer in participants receiving beta-carotene compared to placebo after 6 years and increased the incidence of cardiac death and the risk for major coronary events . The trial was stopped early due to increase in lung cancer among those taking the supplement. Excess in lung cancer (28%) was also reported in another trial where 18,314 smokers, former smokers and workers exposed to asbestos were given beta-carotene and vitamin A for 4 years. The trial was stopped 21 months early.
It is well established that diet rich in vegetables and fruits is healthy. However, how much of this benefits can be credited to their antioxidant content remains unclear. Just because oxidative stress contributes to some chronic diseases and vision loss that doesn’t mean that antioxidant supplements will fix the problem. The studies are thus far controversial and in general don’t provide strong evidence that antioxidant supplements have a considerable impact on disease.
If you decide to take dietary antioxidants keep in mind that they may interact with some mediations as their combination may cause serious problems like kidney damage, bleeding problems, nerve damage and may interfere with absorption of medications used . Do not use antioxidant supplements to replace a healthy diet or conventional medical care . Also, try to get as much information as you can from reliable source.
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Anderson, Robert E., Frank L. Kretzer, and Laurence M. Rapp. “Free radicals and ocular disease.” Free Radicals in Diagnostic Medicine. Springer US, 1994. 73-86.
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