Otago University senior research fellow Margreet Vissers says fresh foods containing vitamins C and E and polyphenols help our bodies keep oxidative stress in check.
Vitamin E is found in vegetable oils, nuts, some grains and leafy green vegetables. Vitamin C is found in a wide range of fruit and vegetables, often alongside polyphenol antioxidants.
Polyphenolics are the coloured compounds in foods such as berries, grapes, plums and apples. They are also plentiful in cocoa, legumes and green plants, including broccoli, cabbage, celery and parsley. "It's the same old story. You have to eat your fruit and vegetables," say Dr Vissers, who is a member of Otago University's Free Radical Research Group.
The former Waitara woman says it's important to eat well to prevent problems like cancers, neurological diseases and heart disease.
"This is about disease prevention. What a lot of people do is think that once they get sick, now I should start eating well." Research shows that antioxidants do prevent cell damage from oxidative stress, but the jury is still out on whether a major increase in antioxidants will help after people become ill.
Dr Vissers' research interests are centred on cellular responses to stress, particularly from exposure to oxidants. Oxidative stress is the biological effects of oxygen toxicity, she says.
"Oxygen is a burning molecule. Our bodies use it to burn the sugar that we eat and that's how we get our energy by this controlled burning." In that process, oxygen is converted into water, but to get to that state, it goes through several reactive forms, generating what scientists call activated oxygen. Those forms include hydrogen peroxide, superoxide and hydroxyl radicals, which are all highly reactive forms of oxygen.
"If any of these reactive intermediates of oxygen escape from the compartment in which they are generated, then they are able to react with a whole lot of other biological molecules and you get kind of uncontrolled reactions and that's oxidative stress," Dr Vissers says.
The result is cell damage.
Antioxidants are there to prevent that damage.
"One, they can react with the oxidant like a protective barrier they act as a shield. Secondly, they can repair any of the damage done."
However, when there are more oxidants than antioxidants, things get out of balance.
"In our bodies, we have these recyclable antioxidant systems and as long as they're there to keep the oxygen under control, then everything's all right."
The oxidation process is part of the hazards of living with oxygen, Dr Vissers says.
"I sometimes describe this like the reaction of butter, which is pure fat, with air. If you leave butter out, it will go rancid because of the interaction with the air. It's oxygen that does that, and that's oxidative stress in the butter.
"The reason that happens is because the amount of reactive oxygen overcomes the antioxidant potential that there is in the butter."
Like butter, cell membranes are mostly made up of lipids (fats), which undergo a similar reaction to butter going rancid. Cell membranes have high concentrations of vitamin E, which is there to stop that. "But if that goes awry and the cell membrane lipids become oxidised, the cell will become leaky and that can cause cell death."
Oxidative stress can occur when people have high oxygen exposure. Inflammation and infections also cause problems because the immune system generates high concentrations of reactive oxidants. "They do that to kill bacteria. That's normally a controlled process, but if you have a massive infection or a long-term infection, the oxidative stress will become too great and you'll end up with damage.
"Another source of oxidative stress is through the action of some drugs that recycle oxygen and generate reactive oxidants. Sometimes we use those oxidative properties to help the drugs work and some anti-cancer drugs use this property as well."
But Dr Vissers says breathing in air and being exposed to the sun's UV rays causes oxidative stress. "Just having to live with such a reactive molecule is the biggest hazard, probably."
That's why it's so important to make sure that we get the vitamins and antioxidants to help our body's battle for balance. Vissers says there's a lot of interest in the DNA of the cell because this is where oxidative stress is more acute.
"You can induce long-term changes in the cell's genetic structure by introducing an oxidative stress and those changes go from generation to generation in the cells."
Those genetic changes also lead to cancer. "The evidence is very good that the better antioxidant system you have, the less likely you are to get cancer."
People imagine that if they eat foods high in antioxidants, then these compounds will flow through the bloodstream fighting oxidants. But Dr Vissers says research tells a different story. Some polyphenolics stimulate the cells to increase their own antioxidant production and enzyme systems. "So what you get from that food is your body saying: I need more of those enzymes. It's like a delayed sustained protection."
In the end, it all comes down to nutrition. "What we have learned from all this research is that we should do what our grandmothers told us - eat fruit and vegetables daily and make it fresh foods. Prepare your own food and minimise pre-made, pre-processed food."
And remember, the brighter, the better.
Freaky facts
1. Eating foods containing antioxidants helps our bodies fight illness. They help prevent cancer, improve vision and circulation, control inflammation and diabetes and generally help keep the effects of ageing in check.
2. The brain is extremely vulnerable to oxidative injury because of its high metabolic rate and elevated levels of polyunsaturated lipids, or fats. The latter are the target of lipid peroxidation. Consequently, antioxidant medications are commonly used to treat various forms of brain injury.
3. Antioxidants are being investigated as possible treatments for Alzheimer's and Parkinson's diseases. Research is also looking at how antioxidants may prevent noise-induced hearing loss.
4. Taking antioxidants as supplements is controversial and evidence of their effectiveness is unclear. They can be harmful for high-risk groups - the antioxidant beta carotene can increase lung cancer rates among smokers.
5. A free radical is one particular type of oxidant. "It describes a molecule that has an unpaired electron and is, therefore, called a radical, although not all are dangerous," says Otago University's Margreet Vissers.
No comments:
Post a Comment