May 21, 2009
Defensive action
A balanced diet, sufficient sleep, regular exercise and health supplements keep your immune system strong. POON CHIAN HUI reports
Keeping your body's natural defences in tip-top shape can go some way to shield you from viruses like Influenza A (H1N1).
Experts have said that a vaccine for this flu strain could take around six months to develop.
In the meantime, a robust immune system is needed to battle infection, said Dr Asok Kurup, a senior consultant at the department of infectious diseases at Singapore General Hospital.
'A good immune system will fight all types of infection, including all sorts of flu strains,' he said.
To grasp how important the immune system is,
Dr Kurup said that one must understand that pathogens are everywhere. This can clearly be seen in the case of a decomposing body where pathogens consume the flesh from outside in and inside out.
Hence, the immune system goes well beyond the common image of white blood cells clamping down on foreign cells; it is, in fact, a complex, multi-layered defence mechanism.
Physical barriers are the first line of defence. The skin keeps germs out of our bodies. Hair in the nose and the respiratory tract dispels dust and foreign particles. Mucus lining the digestive tract and other areas like the vagina prevents bacteria and viruses from settling in and entering the bloodstream.
If this first barrier is breached, a second group of protectors goes into action. A variety of white blood cells search for and destroy the foreign invaders by swallowing and breaking them down.
This immediate response is called the innate immune system function.
If pathogens manage to escape annihilation and start to reproduce in our bodies, the adaptive immune system kicks in.
Unlike the innate system, the adaptive system can recognise and remember foreign cells, thus enabling the body to develop resistance to diseases.
'Cells in the adaptive immune system have an immunological memory,' said Dr Kurup. 'Antibodies are also produced, so that a second infection will be prevented when the same bacteria or virus comes along.'
This is how vaccination works: a dead virus (in some vaccines, the virus can be alive, but weakened so as not to cause disease) is injected into the bloodstream to stimulate this response in the future.
However, this adaptive immune system is not
100 per cent foolproof. Even if we have been vaccinated or have had a particular type of infection before, we may get infected by the same bacteria or virus again.
Hence, we need to keep ourselves in the pink of health in order to give our immune system more bite.
Dr Kurup said: 'We should do the utmost to keep ourselves healthy, which ensures a strong immune system. Someone with a weak immune system may not be able to mount some of the responses needed to fight infections.'
A balanced diet
At the centre of a healthy immune system is a balanced diet.
"A balanced diet that includes a wide variety of foods will ensure an adequate intake of nutrients that may enhance the immune system,? said Ms Ong Fangyi, a dietitian at National University Hospital.
For starters, it pays to have adequate amounts of fruits and vegetables.
A recent study in the American Dietetic Society found that people who eat salads have higher levels of vitamins C, E, B6 and folic acid in their bloodstream - all contributing to a healthy immune system.
Fruits and vegetables also contain antioxidants, which get rid of unstable molecules called free radicals that can damage cells that drive the immune system.
One should eat different coloured fruits and vegetables to get a variety of antioxidants, said Ms Ong.
Also, add fermented milk products to the list - they contain beneficial bacteria that may help to promote a healthy immune system. Yogurt, for instance, contains live cultures.
Water is also important as it aids efficient removal of toxins from the body, Ms Ong added.
Regular exercise
Exercising regularly can strengthen immunity.
It helps to boost the production and circulation of immune cells, which are the frontline soldiers against bacteria and viruses, said Dr Ben Tan, head and senior consultant sports physician at Changi Sports Medicine Centre.
However, going overboard will drag your immune system down.
"Excessive exercise stresses the body and taxes the immune system," said Dr Tan. "Cortisol - a stress hormone that is released following prolonged, high-intensity exercise - suppresses the immune system."
Plus, the immune system will be made to channel its resources to repairing tissue damaged from excessive exercise at the expense of its defence function, he added.
The key here is to do regular, not sporadic, exercise. This is because the benefits which the immune system gains are not permanent, said Dr Tan.
"The immune system is enhanced immediately after exercise, but returns to its baseline within a few hours," he said. "Regular exercise, therefore, prolongs the positive changes."
Enough sleep
One must try to get enough sleep, said sleep specialist Kenny Pang, a ear, nose and throat consultant at Pacific Sleep Centre.
Sleep is essential for the body to recharge and repair tissues. It also reduces production of stress hormones, which otherwise will weaken the immune system.
Lack of sleep has been shown to weaken not only the immune system in general, but also the effects of flu vaccines.
A 2002 study on healthy young adults published in the Journal Of The American Medical Association, found that sleep-deprived individuals had less than half of the flu antibodies 10 days after the jab, compared to those who had sufficient rest.
Supplements
These are useful for people who are unable to have a balanced diet, said Dr Asok Kurup, a senior consultant at the department of infectious diseases at Singapore General Hospital.
Vegetarians, for example, may lack vitamin B12, which occurs naturally only in meat.
Supplements which people commonly take are multivitamins and specific nutrients like vitamin C and folic acid.
Those who opt for Traditional Chinese Medicine (TCM) can consider tonic herbs like cordyceps and wild ginseng.
'Cordyceps strengthen kidney and lung functions,' said TCM physician James Koh, owner of Pinnacle Acupuncture And Chinese Physician Clinic. 'In TCM theory, the kidney is the basis of our health as it removes toxins, while the respiratory system is often prone to virus attacks, like the flu.'
Wild ginseng - or pao shen in Mandarin - elevates chi, a natural energy that promotes proper bodily functions, said
Mr Koh, who added that tonics are best taken on a daily basis and not only when one is ill.
A sick person should take herbs like banlangen (Indigowoad root) and honeysuckle flower, which have anti-bacterial effects, he said.
However, it is important to exercise precaution when it comes to taking supplements, said Ms Ong Fangyi, a dietitian at National University Hospital.
'Certain nutrients can depress the immune system when taken in excessive amounts as a supplement,' said Ms Ong, citing zinc as an example. Hence, it is best to seek medical advice first, she added.
As for popular products like chicken essence, they do contain substances that may help in immune system function, she said. However, more studies are needed to verify their effectiveness.
Mr Sam Yap, an entrepreneur and founder of Cherie Hearts International, which has over 40 childcare centres here, believes in the benefits of supplements.
Children enrolled at the centres get a health supplement daily. 'Our kids take one tablespoon of cod liver oil every morning,' said Mr Yap.
The measure is also timely as Singapore is currently into one of the two peak periods for the hand-foot-mouth disease.
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