What are antioxidants, and should we be supplementing them?

The word ‘antioxidants’ is thrown around quite frequently in relation to its health benefits. But what exactly are antioxidants and why are they so important? And how can we make sure we’re getting the right amount of them?

What are antioxidants and why should we care about them?

Antioxidants are compounds that neutralise ‘free radicals’; another term you may have heard of! Free radicals are atoms, molecules or ions that have an unpaired electron, making them highly reactive in the body. They are unwanted by-products of certain reactions, in part caused by factors such as smoking, pollution and UV light exposure. But interestingly, they are also the natural result of normal physiological processes in the body, such as certain reactions associated with our metabolism.

On their own, free radicals aren’t necessarily anything to worry about, but an accumulation of them can cause adverse chain reactions in the body such as inflammation. For example, free radicals can damage protein and even DNA, sometimes resulting in mutation which then grows at an abnormally fast speed, such as in instances of cancer. Another example is when free radicals ‘steal’ electrons from the cell walls of lipids, causing a chain reaction of ‘stealing’ across the cell wall and potentially contributing to diseases such as cardiovascular disease or arthritis.

This is where antioxidants can be beneficial. You can think of antioxidants as being very charitable; they donate electrons to free radicals, neutralising them. Once neutralised, the negative properties of free radicals are eradicated and the development of disease might be prevented.

How do we get antioxidants in our diets?

Antioxidants exist in many forms. One is vitamin E, which specifically can help to prevent free radical lipid cell wall damage. Vitamin E can be found in foods such as nuts, green vegetables and plant oils, and deficiency is relatively uncommon. The antioxidant properties of vitamin C allow for the ‘scavenging’ of free radicals, and also help to regenerate vitamin E once it has donated its electron to a free radical when neutralising it. Vitamin C deficiency is also uncommon, since it can be found in a wide range of fruit and vegetables. Another is beta-carotene, a precursor to vitamin A and another scavenger of free radicals. It is found in bright yellow, red and orange fruit and vegetables. Zinc helps to protect lipid cell walls from free radical damage, and is found in seafood, nuts, dairy and meat. There are also phytonutrients, non-nutrient compounds of which thousands of varieties exist. Once source is herbs, though we would likely need to eat unrealistic amounts of herbs in order to reap the benefits!

There is a lot of supporting evidence for the health benefits of dietary antioxidants specifically. Some studies point to reduced cancer risk, reduced body weight and lower blood pressure risk. And this list is by no means exhaustive!

What about antioxidant supplements?

When it comes to antioxidant supplements, it’s a bit more controversial. Some studies suggest similar benefits to those found in dietary antioxidants, such as a cross sectional study of over 4,700 elderly adults in which the use of a combined vitamin E and C supplement was found to be associated with reduced Alzheimer’s risk. However, other studies suggest a null (i.e. no effect) outcome or even a negative outcome of antioxidant supplementation. Concerningly, a systematic review of 78 randomised control trials found beta-carotene and vitamin E supplementation to significantly increase mortality risk. Another study found that vitamin C supplementation taken alongside cancer therapy in mice led to a reduction in the effectiveness of the therapy. Some theories as to why this occurs propose that the typically high doses of antioxidant supplements completely eliminate free radicals in the body and therefore our bodies’ natural defence mechanisms are interfered with, hindering them. Such high levels might also disrupt the highly complex network of antioxidant activity in our bodies, overall producing negative effects on our ability to deal with free radicals and inflammation.

What’s the verdict?

Although we can be pretty confident about dietary antioxidants, antioxidant supplementation requires more research before we can be more confidently understand its effects. In the meantime, antioxidant supplements should be approached with caution, especially considering supplements in general are not held up to the same scrutiny as medicines. As always, if you are concerned about antioxidants or any other aspect of your nutrition or health, please seek advice from a registered nutritionist, dietitian, or your GP.

References:

Prior, R.L. and Wu, X., 2013. Diet Antioxidant Capacity: Relationships to Oxidative Stress and Health. American Journal of Biomedical Sciences, 5(2).

Serafini, M., Bellocco, R., Wolk, A. and Ekström, A.M., 2002. Total antioxidant potential of fruit and vegetables and risk of gastric cancer. Gastroenterology, 123(4), pp.985-991.

Razquin, C., Martinez, J.A., Martinez-Gonzalez, M.A., Mitjavila, M.T., Estruch, R. and Marti, A., 2009. A 3 years follow-up of a Mediterranean diet rich in virgin olive oil is associated with high plasma antioxidant capacity and reduced body weight gain. European journal of clinical nutrition, 63(12), pp.1387-1393.

Farvid, M.S., Homayouni, F., Kashkalani, F., Shirzadeh, L., Valipour, G. and Farahnak, Z., 2013. The associations between oxygen radical absorbance capacity of dietary intake and hypertension in type 2 diabetic patients. Journal of human hypertension, 27(3), pp.164-168.

Zandi, P.P., Anthony, J.C., Khachaturian, A.S., Stone, S.V., Gustafson, D., Tschanz, J.T., Norton, M.C., Welsh-Bohmer, K.A. and Breitner, J.C., 2004. Reduced risk of Alzheimer disease in users of antioxidant vitamin supplements: the Cache County Study. Archives of neurology, 61(1), pp.82-88.

Bjelakovic, G., Nikolova, D. and Gluud, C., 2013. Antioxidant supplements to prevent mortality. Jama, 310(11), pp.1178-1179.

Heaney, M.L., Gardner, J.R., Karasavvas, N., Golde, D.W., Scheinberg, D.A., Smith, E.A. and O'Connor, O.A., 2008. Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer research, 68(19), pp.8031-8038.