A few years ago anti-oxidants burst into the headlines being touted as the new essential anti-aging, and cancer wonder molecule. Now, you can’t seem to buy a moisturiser without a label on it proudly stating it “contains anti-oxidants” but what exactly are anti-oxidants, and are they really the wonder compound they are made out to be?
What are anti-oxidants?
Anti-oxidants are compounds that inhibit oxidation. Oxidation occurs in all living cells, and has been recognised as a major contributing factor contributing in human diseases like inflammation and cancer.
Oxidation is a chemical reaction which leads to the release of reactive oxygen species (ROS) . At low levels reactive oxygen species can act as cell signalling messengers, but at high levels they can cause cellular stress. This is because reactive oxygen species can interact with and damage important components of our cells- like DNA, and proteins, which can lead to cancer-causing mutations (1). UV light from the sun can increase the generation of ROS in cells, and as such has been shown to have a significant role in the aging of skin (2).
The idea that ROS-driven stress is a major contributor to cancer, inflammation and skin aging has led to a huge interest in the use of anti-oxidants for the prevention of oxidative damage. The potential protective properties of anti-oxidants has led to them being promoted in diets (think blueberries, goji berries…), and now skin care- but do they do as much good as is claimed?
Anti-oxidants in the diet
There are many foods that you have probably heard to include in your diets due to their high antioxidant activity: Blueberries, red kidney beans, strawberries. spinach, broccoli, carrots, cocoa… the list goes on! These foods get their anti-oxidant activities from compounds they contain called phytochemicals – such as vitamin C, Vitamin E, Carotenoids, and polyphenols.
Dietary intake of antioxidants has been pretty well studied, however a lot of the research has been done in vitro (i.e. on single human cells), or in animal models such as mice and rats. The in-vitro and animal studies that have been done show very promising data which strongly suggest that many phytochemicals can enhance animal health, decrease inflammation, and even stop progression of cancer (in-depth review of polyphenols and oxidative stress) . However, only a very limited number of studies have actually looked at the impact of dietary antioxidants on humans- and this is the critical thing (in depth review about human-based studies of dietary antioxidants).
Although in vitro models, and animal models do give a good initial insight into the effect of a compound, these models are very different from humans. In vitro models are normally made up of single cell, or sometimes mixed cell models, for dietary studies gut epithelial cells are commonly used. This quite simply does not reflect the complexity of the human gut. In comparison, animal models do show a more ‘whole body’ like system and effect, however often absorption rates can be very different between animal models and humans. This can mean, for example, that dosages have to be significantly increased in humans to see a similar effect- and this extreme high level may not actually be good for us. In fact, supplements available on the market containing extremely high levels of antioxidants (like 1000mg of vitamin C, or 5000mg of Green tea) can be detrimental to our health. Just recently a man who had been taking highly concentrated green tea supplements ended up in hospital with liver damage.
Also, a lot of these studies are based on the intake of a single antioxidant, a high dosage of a flavonoid, or a polyphenol- and therefore the effects may not be the same as though achieved via eating a food such as a berry which contains multiple different antioxidants.
Finally, there have been studies suggesting there may be a maximum level of antioxidants that your body can have. Studies have shown that upon consumption of a food containing high levels of antioxidants, you will get a sharp rise in the antioxidants in the blood, but the ‘excess’ antioxidants are quickly removed from the blood by your body to get back to normal levels. A fairly recent episode of BBC’s “Trust Me I’m a Doctor” did a mini experiment looking at this- you can find the data and explanation here. This may mean that you won’t actually get any benefit from consuming super high levels of antioxidants, as your body will just act to remove them…
What does this mean for you? Absolutely eat a varied diet full of veggies and fruits they are super good for your overall health, but maybe be wary of buying into any new foods being touted as the next “high-antioxidant” must have.
Antioxidants and skincare
More recently, antioxidants have started appearing a lot more on labels of skin care products- from face masks and moisturisers to foundations- all promoting the benefits of antioxidants for anti-aging.
Once again I would take these claims with a pinch of salt…. A lot of skin care companies will be using either in vitro experiments, or animal models (if any) to look at the effects of anti-oxidants on skin health. As I discussed above, this isn’t really applicable to humans (have a look at my previous blog article: Skin care secrets for some more in-depth information about this). Human skin is designed to be a barrier- which means not a lot gets through it. As such, you may need to use a cream with very high levels of an anti-oxidant to actually get absorption and a functional concentration. Also, a lot of these anti-oxidants are inherently unstable, and require specialist matrices not to mention, protection from light to continue to have an activity- so realistically how good is a anti-oxidant containing foundation which been open for 4 months going to be?
As with dietary anti-oxidants, there is a lot of very promising data coming out about the skin-health promoting effects of anti-oxidants, however there is still a lot of work for scientists to conduct to truly understand how these anti-oxidants are working, concentrations that we should be applying, and best storage methods.
There is ever such a lot of exciting data coming out about anti-oxidants in relation to human health, however there is also quite a bit of bad-science surrounding anti-oxidants and a lot of over-hype as well. My takeaway message is eat a balanced diet, use skincare you love (USE SPF- this is the best protection against skin aging out there!!) and don’t always fall for the hype.
Reading: Here are a few articles + books which you may like to look at 🙂
The angry chef: bad science and the truth about healthy eating
The cancer research science blog has a great series of blogs all about antioxidants read the first one here, and the lack of evidence supporting health benefits of vitamin supplements to cancer by Ed Yong here.