Rev up your immune system
Matthew Kadey, MSc, RD
Red, watery eyes; sneezing; coughing attacks; runny nose; headache; sore throat; fatigue
Red, watery eyes; sneezing; coughing attacks; runny nose; headache; sore throat; fatigue. A cold or flu is about as lovable as endless rain. Thing is, winter doesn’t have to mean enduring miserable sleepless nights with a stuffed-up nose if you feed your body what it needs to keep viruses at bay.
In addition to proper nutrition, it’s essential to maintain good hygiene and a regular exercise regimen. Someone sneeze on you in the elevator? Hit the kitchen to keep the tissue box at arm’s length. Quick, boost your immunity this cold and flu season with these powerful immune-boosting foods and recipes.
Increase your intake of vitamin D with nutrient-rich salmon. A 100 g serving contains up to 1000 IU, four times as much as farmed salmon.
Although most Australians get enough vitamin D through incidental daily sun exposure, for those living in southern states or who don’t often venture outdoors, many experts recommend at least 1000 IU of vitamin D each day during the winter through food and supplementation. What’s more, researchers reported astaxanthin, the pigment that gives salmon its pink colour, can also increase T-cell activity, enhancing immune response.
According to the findings of a study involving almost 19,000 subjects in the Archives of Internal Medicine (2009), people with the lowest average levels of vitamin D were 36 per cent more likely to develop an upper respiratory infection than those with higher levels of the sunshine vitamin. Individuals with lung diseases, such as asthma or emphysema, were particularly susceptible to respiratory infections due to vitamin D deficiency.
Other vitamin D sources: sardines, mackerel, milk, fortified dairy alternatives, egg yolk
This orange-fleshed tuber has strikingly high amounts of beta carotene. In the body, beta carotene is converted to vitamin A, which promotes a healthy immune system by increasing production of white blood cells that seek out and destroy foreign bacteria and viruses.
Beta carotene also acts as an antioxidant to help knock out free radicals, those nefarious cell-attacking compounds that can weaken your defences.
Other beta carotene sources: kale, carrots, pumpkin, butternut squash, rockmelon, apricots
The isolated germ from the wheat kernel is packed with zinc. This mineral is vital for the development and normal functioning of cells such as neutrophils involved in the immune response to germs that lead to colds and flu. A study in the Journal of Infectious Diseases (2008) reported that subjects with the common cold who were administered zinc experienced reduced duration and severity of symptoms.
Wheatgerm also contains an abundance of selenium, an antioxidant that may enhance immune T-cell functioning.
Add wheatgerm to smoothies, oatmeal and baked goods.
Other zinc sources: oysters, crab, cocoa powder, yoghurt, beans, cashews, pumpkin seeds, game meats, lamb
Japanese matcha is produced when steamed young green tea leaves are ground into a fine powder. Because the whole leaf is consumed, it delivers a huge dose of polyphenol catechin compounds including epigallocatechin gallate (or less of a mouthful, EGCG).
Studies suggest tea polyphenols can help halt the replication of the influenza virus and rev up T-cells, the first line of defence against nasty microbes.
To make matcha, place a teaspoon in a small bowl, pour simmering water over top and whisk briskly. You can also add it to smoothies, baked goods and whipped creams.
Other catechin sources: white tea, oolong tea, green tea, beans, apricots, apples
If you regularly like to work up a sweat, make sure to pack plenty of apples in your gym bag. Researchers from the University of South Carolina reported that stressful exercise can increase susceptibility to upper respiratory tract infections, but quercetin, a potent antioxidant present in apples, was found to lessen the risk. Leave the peeler in the drawer, as almost all the quercetin in an apple is found in the peel.
Other quercetin sources: red onions, tea, parsley, red wine, capers, olive oil, dark berries
Beneficial critters such as those present in yoghurt have been scientifically found to help reduce the incidence, severity and duration of symptoms associated with the common cold. Dutch scientists reported the immune-enhancing effects of probiotics may be due to activation of certain genes in the walls of our intestines.
A study in the Journal of Nutrition (2010) reported that whey, a protein found in dairy products, can stimulate immune cells into action. On top of fending off the sniffles, a robust immune system also helps maintain digestive and skin health as well as improve your mood.
Purchase plain yoghurt to get fewer kilojoules and less added sugar than you do from fruit-flavoured versions.
Other probiotic sources: tempeh, sauerkraut, kefir, kimchi, miso
If you’re going to load up on yoghurt this flu season, make sure to grab a handful of almonds as well. A type of fibre in the skin of almonds may improve digestion and boost immunity by acting as a prebiotic and thereby a food source for good bacteria in the digestive tract, researchers at the Institute of Food Research in the UK report.
Almonds are also sky-high in vitamin E, a fat-soluble antioxidant that improves functioning of immune cells.
Other vitamin E sources: olive oil, wheatgerm, hazelnuts, avocados, sunflower seeds, peanut butter
Mushrooms can give the immune system a hand in attacking foreign invaders, according to a study reported in the Journal of Nutrition (2008). Surprisingly, lowbrow white button mushrooms were found to have a bigger impact on revving up the immune system than much-lauded and more expensive exotic varieties such as shiitake, oyster and maitake.
These fabulous fungi contain a polysaccharide fibre called beta-glucan that is thought to be behind many of the immune-boosting benefits of mushrooms.
Other beta-glucan sources: oats, barley, yeast
Researching vitamin D
A 2010 study published in the Journal of Infectious Diseases found that subjects given a daily vitamin D supplement over a six-month period were less likely to take sick days from work than those who were given placebos.
Scientists believe vitamin D is involved in the production of a protein found in cells that plays a role in immunity. Danish researchers discovered vitamin D is necessary to rev up T-cells, the immune system’s virus-killing cells.