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Leslie Beck's Food for Thought

Boost your immunity with these flu fighters Add to ...

With kids back in school, flu season is top of mind for many parents. Resurgent H1N1 virus, seasonal influenza and the common cold are expected to bring sneezing, coughing, aches and chills.

While you can't prevent these viruses from making their fall appearance, a healthy diet can bolster your immune system making it better prepared to respond. The right nutrients and certain supplements may also help ease cold and flu symptoms.

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Flu season starts in October and lasts until April and colds typically occur between September and May. It's no coincidence we get sick more often during the fall and winter. Cooler temperatures keep us indoors where we're more likely to come into prolonged contact with others who are infected.

Vitamin D is thought to play a role in seasonal flu. The nutrient increases the body's production of proteins that destroy viruses, including influenza. Given that vitamin D is synthesized in our skin on exposure to sunlight, low blood levels of the vitamin in the winter months may make us more susceptible to getting the flu. Canadian researchers are currently investigating vitamin D for swine flu protection.

Your first defence against colds and flu is good personal hygiene. Frequent and thorough hand washing, covering your mouth when coughing or sneezing, and cleaning surfaces that you touch with germ-killing disinfectant will help protect you, your family and your co-workers from infection-causing germs.

Adequate sleep also helps guard against infection. Sleep deprivation disrupts immune function and increases levels of proteins in the body associated with inflammation. Aim for seven to eight hours of sleep each night; children and teenagers need nine to 10 hours.

A healthy immune system also needs regular exercise. Studies show that physically active people get fewer colds each year than do their sedentary peers. But don't overdo it. Intense workouts or prolonged endurance exercise steps up the production of stress hormones, which can hinder the body's ability to fight infection. Aim to get 30 to 60 minutes of light to moderate activity most days of the week.

When it comes to nutrition, a healthy diet that includes protein and plenty of fruit and vegetables will help build a strong immune system. While no single food or supplement is guaranteed to keep winter viruses away, studies suggest the following strategies may help.

Vitamin C

Although this nutrient promotes the body's production of immune compounds, there's little evidence that taking vitamin C can prevent colds and flu in average folks. However, in individuals under physical stress (such as marathon runners), supplementing with vitamin C cuts the risk of developing a cold in half.

Vitamin C does seem to lessen cold symptoms in adults and kids. A review of 30 studies involving 11,350 participants concluded that vitamin C reduced the duration of colds.

To reduce cold symptoms, 2,000 milligrams of vitamin C a day, taken in divided doses, appears to be most effective. Children, people under physical stress and those with low dietary intakes of vitamin C tend to respond best to this vitamin.

High doses of vitamin C may increase the risk of oxalate kidney stones. People with a history of kidney stones should restrict their intake to 100 milligrams a day.

Vitamin D

The advice for Canadian adults to take a vitamin D supplement in fall and winter to help reduce cancer risk may also protect from the flu by enhancing the body's immune system.

Take 1,000 IU (international units) of vitamin D each day throughout the fall and winter. Older adults, people with dark skin, those who don't go outdoors often and those who wear clothing that covers most of their skin should take the supplement year-round.

Children should supplement with 400 IU a day.

Zinc

This mineral is vital to a healthy immune system. Foods rich in zinc include oysters, seafood, red meat, poultry, yogurt, wheat bran, wheat germ, whole grains and enriched breakfast cereals. Your diet and a multivitamin and mineral supplement will provide all the zinc you need to stay healthy.

Zinc lozenges can reduce the duration of cold symptoms. Compared to cold sufferers taking placebo pills, those taking zinc gluconate or zinc acetate lozenges experienced faster recovery from coughing, sore throat, runny nose and headache.

Echinacea

This herb enhances the body's production of white blood cells that fight infection. The most recent review of 16 randomized trials concluded that the majority of studies report a positive effect, most notably when supplements of Echinacea purpurea (Eastern purple coneflower or Purple coneflower) were used.

Echinacea should be taken until symptoms are relieved and then continued two to three times daily for one week.

Ginseng

A special extract of North American ginseng, sold as COLD-fX (Afexa Life Sciences Inc.), can help treat colds and flu. A 2008 study of 323 healthy adults who had suffered at least two colds the previous year, found that compared to those taking a placebo, people who took COLD-fX were 26 per cent less likely to get a cold. Among those who did get colds, half were less likely to catch a second one.

The recommended does is 200 milligrams, twice daily, during cold and flu season. While COLD-fX shows promise for healthy adults, it has not been tested in children or the elderly.

Probiotics

These "friendly" strains of bacteria added to yogurt and sold as supplements are thought to stimulate the immune system. In adults, taking a daily supplement containing lactobacilli and bifidobacteria has been shown to reduce the severity and duration of colds and flu.

Probiotics may also be useful in preventing colds and flu in children. A study published last month in Pediatrics found that healthy children, aged 3 to 5, who took probiotics during the fall and winter suffered significantly less fever, coughs, antibiotic use and missed school days.

To supplement, buy a product that contains 1 billion to 10 billion live cells per dose (capsule). Choose a probiotic supplement that contains both lactobacilli and bifidobacteria strains. Children's products are available on the market; these usually contain one-quarter to one-half of the adult dose.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.

Follow on Twitter: @lesliebeckrd

 

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