Across the world, chronic diseases such as cardiovascular complications, hypertension, diabetes mellitus Alzheimer's disease, Parkinson's disease and various cancers have been on the rise in recent years.
According to the WHO, it was projected that by this year, chronic diseases will account for almost three quarters of all deaths worldwide. Additionally, the number of people in the developing world with diabetes will increase by more than 250%, from 84 million in 1995 to 228 million in 2025.
Antioxidant nutrients found in fruits and vegetables are believed to provide the body with protective effects against such diseases. Many Health Care Practitioners (HCPs) and health initiatives recommend dietary inclusion of antioxidant-rich fruits and vegetables for those with cardiovascular diseases and cancer.
Yet there is also a growing body of research and advocates supporting not only including antioxidant-rich foods, but the introduction of antioxidant supplements.
However, there is still controversy around the benefits and harmful effects of antioxidant supplements.
Why antioxidant supplements are not ‘fit’ for every patient
There have been no clinical studies and treatments that have produced significant desired results using synthetic antioxidants. Even more so, most of the recent epidemiological data on the treatment with synthetic antioxidants indicate ambiguous results, with a range of responses from toxicity to beneficial treatment.
The National Institute of Health emphasises that most of the data examined on using antioxidant supplements in the prevention of chronic diseases, fail to give reliable evidence as to beneficial effects on health when taken, regardless of dosage.
Antioxidants that can react with molecular oxygen and are reducing agents are able to act as prooxidants. These antioxidants can generate superoxide radicals and dismutate to H2O2 under aerobic conditions. This then reacts with reduced metal ions and superoxide to form toxic reactive oxygen species (ROS).
As found in a recent study that focused on the impact of antioxidants and prooxidants on health, it was recommended that supplementation of antioxidants should be limited to cases where oxidative stress was identified.
When antioxidant supplements are not recommended
Identifying common misconceptions regarding antioxidants – such as “the more antioxidants the better” and “antioxidants cure all disease” – are important to control expectations and focus efforts on sound research. These critical nutritional compounds are not cure-alls or remedies and must be used wisely as a part of a comprehensive health regimen.
There have been recorded cases where antioxidants have shown prooxidant behaviour, where there are at least three factors that can affect the function of an antioxidant (transforming it to a prooxidant). These include: the presence of metal ions; the concentration of the antioxidant in matrix environments and its redox potential.
Vitamin C, beta-carotene, phenolics and flavonoids have all been shown to act as prooxidants either with the right environmental conditions or when taken in high-concentration doses.
It is now widely recognised that it may not be beneficial to increase cellular viability with a high dose of antioxidants such as beta-carotene or vitamin E prior to toxic compound-induced exposure (i.e. ionising radiation, UV radiation or cigarette smoke).
ROS scavengers (for example, ascorbic acid) are able to act as both prooxidants and antioxidants in oxidation-reduction reactions, under the right environmental conditions.
To ensure patient safety, HCPs need to identify all factors that could lead to prooxidant behaviour in each patient. If any of the above-mentioned factors are found to be present, research indicates that supplementary antioxidants can do more harm than good.
When antioxidant supplements are recommended
Antioxidant supplements should be limited to specific population groups where oxidative stress is prevalent and well-documented, such as postmenopausal women, the elderly, infants, workers exposed to environmental pollutants and the obese.
Research shows that the elderly are at particular risk due to deficiency of vitamins (B12 and D) and trace elements. As such, institutionalised seniors tend to show signs of malnutrition. In turn, the elderly may even increase their need for nutrient ingestion because of absorptive and metabolic capacity changes.
Supplements are also recommended when considering vulnerable groups. These include folic acid for women of childbearing age, iron supplements for women with heavy menstrual flow and vitamin D for young children, pregnant women and older (and housebound) individuals.
Magnesium can be used in the management of hypertensive heart disease, Alzheimer’s and osteoporosis. Additionally, omega-3 fatty acids are presumed to lower the risk of cardiovascular disease and cancer. Garlic extracts fight viral and bacterial infections and prevent chronic inflammation.
Furthermore, diets rich in fruits and vegetables, which are rich sources of antioxidants, are beneficial for one’s health and act as anti-aging agents.
In conclusion: There’s no 'one size fits all' for antioxidants
As many HCPs, practices and institutions emphasise, generalised treatments for chronic diseases are no longer as beneficial as they were once thought to be.
Patients suffering from chronic diseases require specialised attention with an individual-focused treatment. In turn, before starting any antioxidant supplementation, oxidative stress should be measured, alongside the identification and elimination of possible free radical sources