Taking vitamin E, C and other antioxidants can do more harm than good

4 December 2013

Research at the University of Oslo shows that taking antioxidant supplements, including vitamins C and E, can upset the body's inbuilt mechanism to handle stress and prevent damage to DNA. They have also found a key to quadrupling lifespan, at least in nematodes.

Hilde Nilsen and her research group at the Biotechnology Centre, University of Oslo studied a one millimetre-long nematode called Caenorhabditis elegans (C. elegans), which lives for only 25 days but has 20 000 genes, almost as many as humans. The DNA of C. elegans can easily be altered to increase its ability to repair DNA damage, or remove it altogether.

In C. elegans that do not have the ability to repair the damage, the researchers observed that they had a shorter lifespan, on average three days. These mutants do not, however, accumulate the DNA damage that would cause ageing, but paradoxically have less DNA damage. This happens because the nematode releases its own antioxidant defences — other repair proteins — to protect the DNA. They do, however, have less ability to respond to further stress.

It is thought that the purpose of the DNA repairs is to ensure production of healthy offspring, not necessarily to live as long as possible. Initiating a survival response that reinforces the antioxidant defences means that a lack of ability to repair the DNA has less impact than it would otherwise have on reproduction. To the species as a whole, it’s a small cost that some individuals will be less good at handling stress and have a shorter life.

"We have found several proteins that trigger this reprogramming. The process has the same effect as a reduction in caloric intake, which we know helps increase the lifespan in many species. In other words, there are two routes to a long life. When we stimulate both of these two routes in our nematode at the same time, we can quadruple its normal lifespan," Nilsen says.

"This is where I start worrying about the synthetic antioxidants. The cells in our body use this fragile balance to establish the best possible conditions for themselves, and it is specially adapted for each of us. When we take supplements of antioxidants, such as C and E vitamins, we may upset this balance."

"It sounds intuitively correct that intake of a substance that may prevent accumulation of damage would benefit us, and that’s why so many of us supplement our diet with vitamins. Our research results indicate that at the same time, we may also cause a lot of harm. The health authorities recommend that instead, we should seek to have an appropriate diet. I’m all in favour of that. It’s far safer for us to take our vitamins through the food that we eat, rather than through pills."

Further information

The Norwegian National Research Centre in Complementary and Alternative Medicine (NAFKAM) investigated the volume of dietary supplements consumed in Norway in 2012 and found:

  • in the previous year, 70% of the population had purchased dietary supplements;
  • in total, Norwegians spent nearly NOK3 billion on pills or beverages intended to supplement their diet;
  • many people use dietary supplements as elements of an alternative diet or in dosages that exceed the recommendations given in the instruction leaflet.


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