Viruses cause colds and throat infections, exposure to cold doesn't. If they did, Inuits, Icelanders and Ladakhis would be struggling with a stuffed nose and niggling cough the whole year through.
While some people argue that cold weather increases your susceptibility to infection, the sudden rise in coughing and sniffling around you in the winter months has more to do with increased time spent indoors in contact with people who are contagious and can pass on the infection.
Some researchers argue that cold weather lowers the body's ability to fight infection. A Welsh study, reported in the journal Family Practice, reported that acute chilling of the feet- study participants were asked to sit with their feet dunked in cold water for 20 minutes- caused 10% participants to develop symptoms of a common cold. All of them didn't.
The study concluded that only people who carry a latent virus develop a cold because when the body is chilled, the blood vessels in the nose and throat constrict, lowering the supply of infection-fighting white blood cells. As white blood cell levels fall, so does the body's defence against viruses, including those from the rhinovirus and coronavirus families that cause an infection in the nasal passages, sinuses and upper throat.
If there is risk from cold weather at all, it is only for people who exercise in extreme cold- temperatures 5°C and under - as the combined stress of cold and exhaustion amplifies immunodeppression because of circulatory and metabolic changes.
Compared with the young, people over 65 years are far more likely to catch infections such as cough and colds, flu, chest infections and pneumonia. The severity of infections is also a lot worse. The increased risk in older adults is likely to be because of a fall in T cells, a type of infection-fighting white blood cells because of the thymus atrophying with age and producing fewer T cells.
Stressful situations- both physical and psychosocial- also compromise immune response at a cellular level. Psychological stress affects the immune system by disrupting communication between the nervous, endocrine (hormonal) and immune systems. Animal studies have shown that stressful situations delay the production of antibodies in mice infected with an influenza virus and suppressed the activity of T cells in animals inoculated with herpes simplex virus.
So, there is no need to worry about exposure to moderate cold making you sick. But this does not mean you shouldn't dress warm in winters. As in any other weather, dress for comfort without worrying about compromising your immunity.
But there several things you can do to give yourself an immune boost. Apart from lowering the risk of health disorders such as heart disease, stroke, diabetes, osteoporosis and certain cancers, moderate-intensity exercise lowers your vulnerability to harmful bacteria and viruses. This happens in many ways.
Include superfoods in your diet to stay fit this winter (Photo: Shutterstock)
Physical activity rids the lungs of airborne bacteria and viruses that are linked to common upper respiratory tract infections. Exercise boosts the production of macrophagus, the cells that fight bacteria along with T cells. It increases blood flow that helps circulate white blood cells that fight infection, while simultaneously lowering the secretion of stress-related hormones such as cortisol that suppress immune function.
Begin by chalking out some sort of exercise plan. Moderate exercise -100 steps per minute, or 3,000 steps in 30 minutes five times a week- will prompt your immune system run like clockwork.
Once you've got an exercise plan, re-examine your diet- are you eating healthy? Not likely.
Most people eat on the run and do not get enough proteins found in meats and legumes, B-complex vitamins found in yeast, liver, red meats, cereals and nuts, and anti-oxidant rich fresh fruits and vegetables. Eating out too much also results in having poor quality fats from baked and fried foods. The only way to compensate is by eating healthy at home.
Drink plenty of water and warm liquids. Since people don't feel thirsty in the winter months, dehydration is fairly common in dry, cold weather, which can dry the mucosal lining inside the nose and throat and raise risk of infections. Dehydration also makes the blood thicker, putting pressure on the heart.
Add to that the zero loss of salt through sweating and you are at risk of increases blood pressure, a heart attack risk factor. People on hypertension drugs must consult their doctor to discuss whether they need to change the mediation dosage and must remember to take blood-thinners such as aspirin to reduce blood viscosity.
Superfoods that boost immunity
Yoghurt: Natural probiotics found in yoghurt maintains gut health by restoring the balance of beneficial bacteria that optimise nutrient absorption and boost T cells production. Supplements, such as probiotic yoghurt or fermented drink, also work.
Serving: One bowl a day of yoghurt or one dose of fermented milk a day
Mutton, poultry, pork: Meats have B-complex vitamins and zinc, which is needed to develop white blood cells that fight invading bacteria and viruses. Vegetarians should get their zinc supply from lentils and legumes, such as soyabeans, peas and lima beans. Meats are also a loaded with iron- vegetarian sources are green, leafy vegetables, lentils and kidney beans - needed to fight infection. Since zinc may limit the absorption of iron, increase consumption of iron-rich foods so the one nutrient doesn't nullify the benefits of the other.
Legumes, shellfish and red meat (if you have healthy cholesterol) at least twice a week, or poultry thrice a week
Vitamins A and C: Vitamin A is found in all foods coloured red, orange and yellow, such as mangoes, papaya, pumpkin, carrots and sweet potatoes. Its deficiency leads to damage in the mucosal linings of the respiratory, gastrointestinal and genitourinary tracts, which are the body's first defense against bacteria and viruses. Vitamin C, a well-established immunity booster, is found in citrus fruits such as lemons, oranges and mangoes.
A small mango or papaya and a glass of fresh lime a day.
Fish and shellfish: Selenium, found in shellfish such as oysters, lobsters, crabs, and clams, helps white blood cells produce a protein- called cytokines - that helps clear flu viruses out of the body. Fish oils have omega-3 fats, which lower inflammation and protect the respiratory tract and lungs from infections. Vegetarians should replace fish with nuts, seeds and safflower (kardi), sunflower, mustard and soya oils.
Fish or shellfish twice a week (unless you're pregnant or planning to be), 8-10 mixed nuts a day.
Garlic: Garlic contains allicin, ajoene and thiosulfinates, which are compounds that fight bacterial, viral and fungal infection, with one British study reporting that it lowers risk of viral infection by two-thirds! Garlic also protects against colorectal and stomach cancers.
Two crushed garlic a day (add to cooked food or if you hate the smell, take supplements)