Women may have stronger immune systems than men, according to the US National Academy of Sciences, but we still get hit with an average of three colds a year. Defy those odds by building up your natural defenses.

Pop a probiotic

The buzz around gut-friendly probiotics just got a little louder. Not only do some of the microorganisms combat gastrointestinal woes, they can also influence your body's T cells – the crucial white blood cells that help power your immune system. According to recent research published in the journal Postgraduate Medicine, women who downed daily probiotics saw their T-cell count skyrocket, making them much less vulnerable to infections. Though you can score some of the healthful stuff in a variety of foods like yoghurt, miso and tempeh, you're better off taking a 60- to 90-milligram supplement every morning during cold season, says lead study researcher Dr Mira Baron.

Raise your D levels

Supernutrient vitamin D strengthens bones, fights inflammation, and boosts your mood. Turns out, it can also help slay infections. A study from the University of Colorado Denver School, US, found people with low D levels were 36 per cent more likely to catch respiratory ailments. Other current research shows that, when people with ample D do get sick, they may recover faster. "Vitamin D helps your body produce a protein called cathelicidin that fights bacteria and viruses," says Dr Carlos Camargo, an associate professor of medicine at Harvard Medical School, US. Because it's nearly impossible to get enough D from food – even if you regularly nosh on salmon and dairy products – it's best to invest in 1000 IU supplements. Take two a day in the winter months, when the sun's rays aren't as strong. (Soaking up natural sunlight prompts the body to make its own vitamin D. However, experts caution against too much D-producing sun exposure because it can lead to a heightened risk of skin cancer.)

Get pampered

Regular 20-minute, moderate-pressure rubdowns decrease the body's level of cortisol, a stress hormone that can take a toll on your immune system, says Dr Tiffany Field, director of the Touch Research Institute at the University of Miami School of Medicine in the US.

"Massage stimulates your nervous system to slow the production of cortisol," she explains. "And by lowering cortisol, you're increasing your immune response." No time to squeeze in a spa appointment? Lie face up on the floor with a foam roller positioned perpendicularly under your back and slowly roll over it in an up-and-down motion.

Cut some kilojoules

Even slightly overweight people who slashed their energy intake by just 10 per cent ended up with heartier T cells, according to the Journal of Gerontology, possibly because a little extra weight can prompt the body to release a certain immune-suppressing hormone-like compound. Stash a pack of sugar-free gum in your bag and reach for a piece when you crave a mid-afternoon snack, says dietitian Sharon Zarabi. Or swap your regular latte for plain green tea; you'll not only save hundreds of kilojoules but also ward off infection. (The brew is brimming with antioxidants called catechins, which may have serious immune-aiding abilities.) Or, when you're lagging, take a 10-minute walk – even if it's just around the house – instead of reaching for a sugary pick-me-up.

Clock in face time
Surprise: all of your friends come with benefits. People with the most types of relationships – everything from close friends to neighbours – have a greater resistance to infectious diseases, according to the journal Health Psychology. Conversely, that same research shows that loners' immune systems suffer. "Lonely people often have high stress levels, which can have a negative effect on the immune system," says psychologist Dr Sheldon Cohen. The exact number of friends you need to help you stay cold-free is unclear, but don't let that stop you: set a goal of making one new connection a month, whether it's at the office, the gym or the coffee shop.