One of the main reasons for age-related diseases such as dementia, cardiovascular diseases or cancer is oxidative stress levels in cells. Oxidative stress is caused when reactive oxidants enter a cell. These molecules carry too many oxygen atoms and are eager to get rid of them. When one of these oxygen atoms reacts with one of the protein atoms within a cell, it can change and damage the protein.
Pollutants such as cigarette smoke help build those damaging oxidants - but it's also created within the human body through tissue respiration. There are about a dozen different oxidants, the most common ones being ozone (O3) or free radicals (instable oxygen molecules). Even hydrogen peroxide (H2O2) which is - in its liquid form - often part of cosmetics, disinfection or bleaching agents, is an oxidant.
Until now, scientists have thought that antioxidants can prevent oxidants from causing any damage within a cell. Vitamins C, E, or beta-carotene (provitamin A) would essentially help dismantling the oxidant.
Vitamin pills don't do the trick
Most doctors would agree it's a good idea to include these vitamins as part of a healthy diet. But pills containing the antioxidants rarely do the trick. They are unable to help in the fight against aging processes.
"Even some very good, long term studies were unable to show a positive effect," says Isabell Keller of the German Society for Nutrition (DGE). "Quite the contrary, results have shown that there is a higher risk of developing cancer" with these pills.
A biochemist from Heidelberg was able to shed more light on the complicated issue of oxidants. Tobias Dick, researcher at the German Cancer Research Center, found that cells can produce their own anti-oxidants - glutathione - which fight off oxidants.
Cells fight back
Glutathione reacts with those oxidants - the cell then isolates the product. And over time, the cell is able to slowly dismantle it.
"We used to think that the more glutathione has oxidized in a cell, the more oxidative stress it produces," says Dick. "But we've noticed that this correlation is incorrect."
Cells are much more resistant and robust when it comes to oxidative stress than scientists had previously assumed.
Dick spotted a carrier that is responsible for disposing the oxidized glutathione. That's how he noticed that the cell had previously isolated this oxidized glutathione. The researcher hopes he will be able to manipulate this transportation process to make cells more resistant - or less resistant when it comes to cancer cells - against oxidative stress.
Even though cells can produce their own antioxidants, you should still consume antioxidants via fruit and vegetables.
"The positive effect of fruit and vegetables has been proven," nutritionist Keller says. In addition to vitamins they provide other healthy substances, too.
Keller recommends eating five portions of fruit and vegetable every day - that's 400 grams (14 ounces) of vegetables and 250 grams (9 ounces) of fruit for an adult.
"If you follow these guidelines, you won't need any supplements," Keller says.
There are, however, some exceptions to the rule when supplements do actually help.
It's not about antioxidants though.
Iodized and fluorinated salt can prevent a deficit in these two important minerals.
"Pregnant women and women who want to become pregnant should take supplements containing folic acid," Keller says. Folic acid can help reduce the risk of a baby developing defects in its nerve system. Vitamins K and D are also important for a baby's development - and a vitamin D supplement is also good for adults in winter when there is not enough sunlight for the body to create its own.