With more than 9,000 confirmed cases of swine flu in the UK and experts estimating that the number could rise dramatically in the autumn, this is a good question. It is likely that a weakened immune system could make you more susceptible to a virus, and that eating well can give your body the best chance of fighting back.

As Dr Nick Phin, who is head of pandemic flu planning at the Health Protection Agency, explains: “A person who is malnourished is likely to be more susceptible to infections and for most people, a healthy and nutritionally balanced diet will be an important factor in helping to maintain a healthy immune system.”

Obviously, advice on reducing your chances of catching the virus includes catching your sneezes in a tissue, placing it quickly in the bin and washing your hands and surfaces regularly to kill the virus and help to prevent it getting into your body in the first place. But if it does get in, what you eat may help to optimise the strength of the membranes in your ears, nose and throat to form an internal physical barrier against invading organisms.

Protein-rich meat, chicken, eggs and fish, milk, dairy foods, pulse vegetables, nuts, seeds and soya-based foods all supply vital nourishment for the epithelial cells in these membranes. Three average-sized servings a day of any of these are important to maintain the integrity of these “barrier” tissues.

Tucking into plenty of bright orange and dark green fruits and vegetables such as carrots and pumpkins, apricots, mangoes, spinach and cabbage, meanwhile, will keep levels of vitamin A, another nutrient that is needed for strong respiratory membranes, topped up.

If the virus does penetrate these physical barriers, it is the job of an army of white blood cells to try to engulf and eat viral invaders. Vitamin C appears to be especially important in playing a role in mobilising bug-eating macrophage cells, as well as having its own specific anti-viral properties.

Given that we cannot store this nutrient in our bodies, ensuring that some vitamin C-rich foods are on the menu each day is important. This can be anything from peppers and spinach to citrus fruits, berries or frozen peas. Even canned fruit provides some, as do orange and grapefruit juices.

Other internal immune system bug-beaters include “T-cells”. The mineral zinc is crucial for the formation of these antibodies, with even a mild deficiency being linked to more frequent colds and flu. The good thing is that impaired immune responses can be restored to normal by having sufficient zinc in your diet.

You can find zinc in beef, eggs and seafood, especially crab, oysters and sardines. Wholegrain foods and pumpkin seeds are pretty good too, although zinc from these is less easily absorbed than the zinc in animal protein.

With around 40 per cent of women in the UK getting less iron in their diets than the recommended daily amount, this is the other mineral that could do with some special attention. Iron deficiency, with or without anaemia, leads to a wide range of defects in immune-system function, some of which could lay you more open to the swine flu virus.

Iron can be found in similar foods to those mentioned above as being good for zinc. However, if you know that you are not getting these regularly, then a daily multivitamin and mineral supplement containing 100 per cent of the recommended amount (14.8mg) is a sound immune-system booster.

Quick ways to keep the doctor away

The super nutrient “allicin”, formed when raw garlic is crushed or chewed, appears to help to block the ability of viruses to invade and damage tissues. If you can bear it, chewing a raw clove a day may help your immunity.

Research from the University of North Carolina suggests that a general protection against influenza viruses is offered by the mineral selenium. Three Brazil nuts a day will meet your daily needs.

Medical herbalists suggest that the following can boost immunity against ordinary seasonal flu: two echinacea tablets two or three times a day, plus a 300mg tablet of extract of St Johns Wort three times a day, and a cup of herbal tea made from equal parts of 10g mint, 10g elderflower and 10g yarrow. Such doses should be supervised by a qualified herbal practitioner found via phytotherapists.org or nimh.org.uk

If you have a nutrition question, e-mail amanda.ursell@thetimes.co.uk