We've all heard of antioxidants, but what are they and what do they do?
🕒 3 min read
Antioxidants are substances that have the ability to help neutralise damaging oxidation reactions, which are triggered by chemicals known as free radicals. To understand the important role they play in our health, we must first look at how they work.
What are free radicals?
A free radical is a molecular fragment that carries a negative electric charge. This makes it highly unstable, causing it to collide with other molecules and cell structures in an attempt to shake off the charge.
This process, known as oxidation, passes on the negative-charge in a rapid, damaging cascade of chain reactions that mean our cells are under constant attack.
Are all oxidation reactions bad?
No. Some oxidation reactions, such as those used by white blood cells to fight infections, are beneficial, however, excess oxidation reactions are associated with premature ageing.
When proteins are oxidised, they may cross-link and change shape – as happens when collagen in the skin loses elasticity, leading to wrinkles.
What problems can excess oxidation cause?
A lack of antioxidant consumption in conjunction with a moderate level of oxidation is now thought by many researchers to be an underlying cause of heart disease, stroke, cataracts, macular degeneration, and inflammatory diseases such as arthritis, and degenerative nervous system conditions, such as dementia.
For example, when 'bad' LDL-cholesterol is oxidised, scavenger cells recognise the fat as foreign and engulf it. If these become over-laden they form bloated 'foam' cells, which become trapped in artery walls as they try to leave the circulation, contributing to hardening and furring-up of the arteries.
- Colourful fruit and veg
- Soy products
- Dark chocolate
How can you protect against free radical damage?
Protection against free radicals is one of the reasons that we are urged to eat at least five servings of fruit and vegetables per day, as several vitamins and minerals act as antioxidants.
Of these, the most important are vitamins A, C, E and selenium, while other powerful antioxidants include carotenoids, such as lutein found in spinach, soy isoflavones, pine bark extracts (pycnogenol), co-enzyme Q10 and polyphenols found in tea leaves, dark chocolate and wine.
People with the highest intake of fruit and vegetables have the lowest blood pressure, lowest total and LDL-cholesterol levels, and the lowest risk of developing diabetes, coronary heart disease and stroke.
Why are there sometimes negative news stories about antioxidants?
Every now and then headlines suggest that antioxidants are not beneficial or even harmful in some way. These negative stories are usually based on studies that give antioxidants to experimental animals with genetically programmed diseases, or adding them to human cancer cells in a laboratory.
These situations do not reflect what happens when we eat antioxidants in the form of fruit and vegetables, or take them as supplements to safeguard dietary intakes.
While diet should always come first, there is no evidence that antioxidant supplements are harmful – if they were they would rapidly be banned from sale!
Free radicals are generated as a result of:
- Normal metabolic reactions
- Abnormal metabolic reactions (e.g. in diabetes)
- Vigorous exercise
- Smoking cigarettes
- Drinking excessive amounts of alcohol
- Exposure to environmental pollutants
- Exposure to x-rays
- Exposure to UVA sunlight
- Some medications (e.g. antibiotics, paracetamol)