The science is complex and the health claims extravagant. But what are antioxidants
This article explains what you need to know and answers the important questions
- What are antioxidants?
- How do they work? (or at least, what do we know?)
- How do you get the antioxidants you need from ordinary food?
- Do you need expensive superfoods or supplements? (you don’t!)
I dip into the science, but never too deep. This is a practical, nutritionist’s guide to antioxidants. Just the information you need – no more.
So what are antioxidants?
An antioxidant is a substance that prevents oxidation.
In biology, oxidation isn’t always a bad thing. But when we’re talking nutrition, oxidation is often a problem. And antioxidants are usually beneficial. Because they reduce oxidation caused by free radicals and lower oxidative stress.
OK – But what is oxidation? And what are free radicals and oxidative stress? And how do they fit into the antioxidant picture?
Without getting too deep into the chemistry, oxidation is one half of an oxidation-reduction reaction. A reaction that involves the transfer of electrons between molecules or atoms. Essentially, oxidation is the loss of electrons. And the substance that loses the electrons is oxidised.
Oxidation is happening everywhere. It’s the process that rusts iron, turns the cut edge of a pear brown and causes cooking oils to go rancid. And your body’s metabolism couldn’t function without oxidation-reduction reactions. For example, your cells oxidise glucose to produce energy.
But electrons like to be in pairs. And oxidation can produce molecules with unpaired electrons. These molecules are known as free radicals.
Free radicals are atoms or molecules with one or more unpaired electrons.
In biology, the most important free radicals are oxygen-derived radicals (1). For example, superoxide with one unpaired electron and peroxide with two unpaired electrons.
Technically oxygen free radicals are known as reactive oxygen species. But, for simplicity, I’m going to stick with the generic, catchier and more popular free radical label.
You’ll remember electrons like to be in pairs. Having unpaired electrons makes free radicals unstable, highly reactive and potentially toxic.
The free radical chain reaction
Left unchecked free radicals
Your body’s fats and proteins are the most vulnerable. Free radicals can damage your cells’ outer membranes, the DNA they contain and LDL cholesterol. And this damage is linked to many of their harmful effects.
Free radical damage is thought to contribute to the natural ageing process. And to diseases like cancer, cardiovascular disease, Alzheimer’s, diabetes and even vision loss.
Not all free radicals are bad
Still, labelling all free radicals bad would be a mistake (2). They’re a by-product of many natural metabolic reactions essential to life. Your cells use them for internal signalling and to communicate with other cells. Immune cells produce them to help fight off disease. And free radicals may have a positive effect on cell division and multiplication – essential for the growth, repair and maintenance of your body.
We live on an oxygen rich planet. Free radicals are inevitable. And life has adapted to cope with their negative effects. Over billions of years, complex antioxidant systems have evolved to deal with free radicals. Your body produces antioxidants and antioxidant enzymes to defend itself against them. And it uses the antioxidants in your diet to help neutralise free radicals.
To limit oxidation damage, your body balances antioxidants and free radicals.
Antioxidants prevent oxidation. They step in and donate electrons to free radicals. And crucially they can do this without becoming free radicals themselves. The free radical chain reaction is interrupted and damage to your cells is prevented.
Although the principle is simple, the reality is far more complex. There are hundreds and possibly thousands of antioxidants (3). Their effect is frequently multi-stage and interactive. And often they only act in very specific circumstances.
The scientific interest in antioxidants began in the late ‘80s. And it’s intensified as our knowledge has expanded. But still, science doesn’t have all the answers and has arguably only scratched the surface.
But we do know that if the antioxidant and free radical balance is disrupted it’s a bad thing. And left uninhibited free radicals cause damage.
This is known as oxidative stress.
The causes of oxidative stress are an overproduction of free radicals or a lack of antioxidant capacity (4). It’s a harmful process and an influential driver of cell damage, ageing and disease.
Despite your body’s best efforts, some free radical damage is unavoidable. And it repairs the damage. However, oxidative stress overwhelms your body’s ability to fix free radical damage.
So, what can stimulate an overproduction of free radicals and cause oxidative stress?
Your lifestyle and environment can increase oxidative stress
Your lifestyle and environment can provoke your body into higher free radical production. And if your antioxidant systems struggle to cope it causes oxidative stress.
Unfortunately, loading up on antioxidants isn’t the magic solution to a life of free radical abuse. Yes, there are plenty of studies to suggest antioxidants are beneficial. But we must be realistic.
Take a couple of studies looking into the effect of antioxidants on smokers’ cancer risk as an example. Higher antioxidant consumption led to a statistically significant reduction in the risk of lung cancer (7) and gastric cancer (8). But the reductions were trivial compared to the reduction associated with not smoking.
Avoiding lifestyle and environmental causes of oxidative stress should be your first option. But maybe like me, you enjoy the odd glass of wine or sometimes test your body’ training limits. Should you boost your antioxidant intake with a superfood smoothie or a supplement?
Marketing antioxidant myths
Skin cream, supplements, nutritional therapies and superfoods. Marketers love antioxidants. And it’s easy to understand why.
Complex science. Lots of studies. Marginal health gains. And importantly no easily measurable short-term benefits. In marketing terms, antioxidants are the perfect storm. So many opportunities to separate the consumer from their cash with credible pseudoscience.
Yes, antioxidants play an important role in your body’s management of free radicals. And in the prevention of oxidative stress. But we need to be clear. The science doesn’t support the overwhelming benefit of specific antioxidant superfoods. And it doesn’t support the antioxidant benefit of many active ingredients at the concentrations available in foods.
There are thousands of different antioxidants in food. And our understanding of their role in health is constantly growing. But the current research is only scratching the surface.
Your body’s antioxidant system is complex with built-in redundancy and regulation. And much of the heavy lifting is done antioxidants your body synthesises for itself.
Studying single or small groups of antioxidants needs a reductionist approach. And science often ignores the larger context by necessity. At the same time oxidative stress has become a less specific term. And marketers exploit the smallest suggestion that antioxidants protect against or heal illnesses.
But it’s not realistic to suggest one antioxidant or small group of vitamins can alter the whole oxidation-reduction balance of your body (9).
Arguably, vitamin C and vitamin E are the most well-researched antioxidants. And there is a synergy to their antioxidant effect. But they aren’t efficient scavengers of all free radicals (10). And they’re plentiful in ordinary (i.e. “non-super”) foods – just like other antioxidants.
The evidence doesn’t support antioxidant supplementation
The antioxidant supplementation industry is thriving. It sells concentrates of the active antioxidant ingredients of many foods and spices. And antioxidants the body can produce for itself without help.
But the benefit of antioxidants in natural foods is not replicated by antioxidants in isolation.
Research is ongoing into the clinical potential of natural antioxidants. But it’s very early days and little conclusive evidence has emerged. And this area of research has nothing to do with the supplementation industry.
Antioxidant supplementation is a modern take on snake oil. The supplement producers make claims that the evidence doesn’t support. And the purpose is lifting money from the pockets of vulnerable people.
And like the snake oils of old, the antioxidant potions have the potential to harm. Because many antioxidants turn pro-oxidant dependent on the circumstances or in higher concentrations. And some antioxidant reseach has reported a negative impact of supplementation (11)
So, if supplements and superfoods aren’t the answer, how do you get the antioxidants your need?
How to get the antioxidants you need
Plant foods are your best source of antioxidants. The evidence is strong – eating a variety of whole fruits, vegetables and grains protects against the scourge of ageing and disease. And the rich and varied antioxidants they contain contribute to the health benefits.
A plant based diet gives you the most antioxidants
Eat a wide variety of fruits and vegetables and you’ll cover most of the antioxidants. Add some grains, nuts, pulses and seeds and your good. And it doesn’t have to be complicated or expensive.
- eat as wide a variety of minimally processed plant food types as you can. Fruits, vegetables, nuts, seeds, grains, pulses and oils.
- include as broad a spectrum of brightly coloured fruit and vegetables as possible.
Eat (naturally) colourful food
Many antioxidants are the pigments that give the fruit and vegetables their colour. For example (12) :
- β-carotene – yellow and orange – e.g. sweet potatoes, carrots and dried apricots
- Lycopene – red – e.g. tomatoes
- anthocyanins – dark red, purple and blue – e.g. beetroot, purple berries, blueberries and red cabbage
- Lutein – green – e.g. leafy green vegetables like spinach, cabbage and kale
Yet just like a Picasso, the colours we see aren’t due to a single pigment, but a blend of pigments. And the deeper the colour, the more pigments contained. So, dark and brightly coloured fruits and vegetables contain more antioxidants.
Eat raw and cooked fruits and vegetables
Eating a mix of raw and cooked vegetables and fruits will increase the variety of antioxidants you absorb. Most cooking reduces the antioxidants, but in some cases, cooking increases the bioavailability. Mix it up!
Processing reduces the antioxidants
Processing and storage lower the concentration of most antioxidants in foods. Old fruits or overcooked vegetables have a faded colour. They’ve lost their antioxidant pigments. Most industrial processing and storage have a similar effect. Modern techniques are designed to keep the fresh look of fruits and vegetables. But their antioxidant content still drops.
Eat seasonally – (mostly)
Fruits and vegetables in season are cheaper, more nutritious and more environmentally friendly. And I’m a strong believer in low food miles. But here in Scotland, the winter seasonal vegetables are pretty monochrome. You need to add some unseasonal colour. Now, I’m not suggesting you eat fresh strawberries in December. But you need to eat some imported fruits and vegetables – And don’t ignore the frozen aisle.
Don’t peel fruit and vegetables.
OK – don’t peel all fruits and vegetables. But if the skin is edible, eat it. The antioxidants are far more concentrated in the skin than the flesh of fruits like apples and pears.
Expensive treats are just that
Yes – green tea, coffee, dark chocolate, turmeric and honey all contain some antioxidants. But eat them because you enjoy them. Not for the small
There’s no doubt antioxidants play a role in health. But the science doesn’t offer black and white health recommendations.
Marketers have hijacked the terms antioxidants, free radicals and oxidative stress. And they’re labels that sell products. Yet the reality is there’s little evidence to support their claims.
When it comes to antioxidants, your best approach is to eat the widest variety of unprocessed, plant-based foods you can. That way you’ll get the broadest possible range of antioxidants in your diet.
And if that advice sounds familiar, I make no apologies. It’s great, general healthy eating advice.
Hi, I’m Ralph – a nutritionist with over 25 years’ experience as a professional chef. I’m based in Edinburgh where I provide one-to-one nutrition coaching. If you’re not in Edinburgh I can help you online.