But if you don't want to spend a winter sniffing and piling on the pounds, now is the time to take charge. While colds and flu are more common during cold weather, it's not the weather itself that causes the infections, it's the fact that the cold weather drives everyone inside.
This increases person-to- person contact, which in turn spreads the winter lurgies, bringing everything from sore throats, swollen glands, aching muscles, cold and hot flushes to constantly blocked noses.
Cold weather also makes people less active, so it is harder to get motivated for exercise. This weakens the immune system and makes the body even more susceptible to illness.
So now is the time to get started on your winter health preparations. Do it now and you might just make it through to next spring with nothing worse than a dry cleaning bill for your winter coat.
KNOWLEDGE IS POWER . . . so know your immune system
Making your body stronger is the key to fighting off winter bugs, so it's crucial to understand the way we fight disease and infection.
Our immune system is different from other systems in our bodies in that it is not a group of physical structures but a complex matrix of interactions involving many different organs.
These include structures and substances, such as white blood cells, bone marrow and lymphatic vessels, which all need to work together to protect the body from disease and infection.
If any part of this process breaks down, it can have a significant impact on our wellbeing.
The good news is that there are many things we can do to protect our health, including improving our diets, exercising regularly and cutting down on stress.
EAT YOUR WAY TO HEALTH . . . and give your immune system the ultimate boost
Poor nutrition is the number one cause of poor immunity. Although your immune system is invisible, its billions of cells are made only from food. Deficiencies of even one nutrient can profoundly reduce the strength of your immune system.
So the way we eat affects how easily we are able to function. For example, when your blood is full of sugar after eating sweets, there's less room for immunity-boosting cells.
This can leave you 50 per cent more vulnerable to infection for up to five hours.
So what should we eat? Well, three balanced meals a day combining carbohydrates, protein and vegetables is crucial, as is avoiding comfort foods made from refined carbohydrates which reduce our immunity levels.
Vitamin C is probably the single most important vitamin for the immune system, as it's essential for the production of lymphocytes which help develop the body's own antibodies. Citrus fruits are all rich in vitamin C and, appropriately for this time of year, so are squash, pumpkin and broccoli.
You can roast pumpkin and squash in the oven, with a little olive oil or steam lightly. I love broccoli steamed then tossed in chill flakes and Tamari sauce.
Then there's vitamin E. This interacts with vitamin A and C, and acts as a scavenger, destroying free radicals, which are bad for the body. Foods rich in vitamin E are all nuts and seeds, eggs, wholegrains such as oats, rye and brown rice. Zinc boosts the immune system and promotes wound healing. Soups, fresh fruit and vegetables such as avocados which contain lots of vitamin E, are good sources of zinc, as well as potatoes, parsnips, carrots and turnips. Up your garlic levels.
It has anti-viral, anti-bacterial, anti-fungal and anti-oxidant properties.
Omega oils increase the activity of phagocytes, the white blood cells that eat up bacteria, so try to include oily fish such as herring and salmon in your diet.
Hot foods such as chilli peppers, hot mustard, radishes, pepper, onions, and garlic contain substances called "mucolytics" (similar to over-the-counter expectorant cough syrups) that liquefy thick mucus that accumulates in the sinuses and breathing passages. So don't hold back on the chilli.
Quality protein - such as that found in free-range eggs, oily fish and seafood, game or meat from grass-fed livestock - provides materials needed for making immune cells. It's also rich in zinc. If you're vegetarian, eat plenty of eggs, nuts and seeds as a substitute. Don't forget to stock up on vitamin D - found in oily fish, butter, eggs and milk.
Vitamin D is being increasingly recognised as a major player in immune function.
DRINK UP . . . and flush away those bugs
Support your immune system by avoiding fizzy drinks and drinking more and more water - even when the temperature drops.
It's really important to drink lots of water to help keep the mucus membranes in your nose hydrated, as they're your first line of defence against infection and if they get too dry they're a much less effective barrier against infection.
If cold water isn't your thing, try it hot with slices of fresh lemon - or opt for herbal teas instead.
SUPPLEMENT IT . . . and get a helping hand
It's also possible to get additional help thanks to herbal remedies which protect against winter colds and flu. Organic echinacea tincture strengthens the immune system by increasing the number of white blood cells, and helps the body fight off colds and flu. A daily supplement of vitamin C also works wonders.
If you are worried you are not getting enough nutrients, you can also supplement your diet with Omega oils, a good multivitamin and mineral tablet from a vitamin company such as Solgar, Viridian or Higher Nature. Take in extra vitamin C - 1000mg per day - with bioflavonoids if you feel a cold coming on.
• Nell Nelson is a TV presenter and a BANT qualified nutritional therapist, based in Edinburgh. For an appointment with Nell telephone 07766-155 673 or visit www.nellnelsonnutrition.com.