Washing your hands and keeping away from people who are ill are the most effective ways to stay well – but eating healthily, and thereby avoiding nutritional deficiencies, is another vital weapon in your immune health armoury. Tuck into these top foods, suggested by nutritionist Angela Dowden, to help give your immune system a boost.

Click or scroll through our gallery to find out what to eat to stay healthy at any time of year, as we count down to reveal the most immune system–boosting food of all.

Our selections and ranking are based on the nutritional profile and benefits of each food, with input from an expert nutritionist.

All nuts are nutritious – but grab a mixture of cashews, Brazil nuts and peanuts, and you’ll get particularly good levels of zinc, selenium, iron and vitamin B6. All of these vitamins and minerals play a key part in keeping your immune system healthy, helping you fight off infections and heal quickly.

You can get all the vitamin C you need from a healthy diet – and taking extra vitamin C in supplement form won’t stop you catching a cold. However, if you're already infected, research has shown that vitamin C might shorten symptoms by about 24 hours, as long as you consume at least 200mg daily.

A bowl of chicken soup may provide more than just comfort when you’re feeling unwell. Both chicken and turkey have lots of vitamin B6, which is important for a variety of bodily functions, including immune defence and creating red blood cells. Poultry is a good source of protein too, and it can be a healthy choice of lean meat.

Tuna is a protein that's rich in the antioxidant selenium, which is lacking from many people's diets. Studies have shown that a deficiency of this trace mineral may increase the severity of a flu virus. Research also suggests that selenium lowers the risk of heart disease, reduces the symptoms of asthma and boosts immunity in general.

Sardines can also do wonders for your immune system. Like tuna, they contain selenium – along with a smorgasbord of other nutrients, including vitamin B12, iron and vitamin D, all of which contribute to building the body's resilience to infections. Sardines are common in the Mediterranean diet, which is lauded for its health benefits.

In the past, it was thought that sugar suppresses the immune system – however, more recent studies suggest that glucose may help viral infections get better (but hamper recovery from bacterial ones). Either way, there’s no evidence that a modest amount of sugar is going to make you more susceptible to illness.

A 2018 study of children with a cough found that honey relieved symptoms better than diphenhydramine (an antihistamine cough suppressant). The British National Health Service (NHS) also recommends drinking hot lemon and honey to ease a cough – but not for children under 12 months. The sweetness of honey helps you produce more saliva, which lubricates your airways and eases cough symptoms. It's thought to reduce inflammation and break up mucus, too.

Polyphenols, the plant-based compounds found in many fruits and vegetables – including pomegranates – have several health benefits. Research has shown that consuming concentrated amounts of polyphenol antioxidants, such as those found in pomegranate juice, can soothe coughs and colds, helping to cut down the length of a cold by up to 40%.

Oats supply beta glucan, which, when given as a high-dose supplement, has been shown to prevent (and reduce the symptoms of) the common cold. A bowl of porridge won't stop full-on sniffles, but it will provide fibre and B vitamins, and it can also contribute to lower cholesterol levels.

Research suggests that eating garlic can help reduce your chances of catching the common cold. A freshly crushed garlic bulb is a good source of the health-boosting active ingredient allicin, which fights bacteria. If you're not a fan of the taste of garlic, you could always try garlic supplements instead.

A little cold-pressed rapeseed oil has all the heart-healthy monounsaturated fats found in extra-virgin olive oil, plus high levels of the antioxidant vitamin E, which helps support your immune system. Vitamin C regenerates vitamin E after it's done its job of protecting cells, so vitamin C–rich vegetables like peppers and leaves are the perfect foods to team with your oil.

It's not just green, red and orange foods that help your immune system – mushrooms are a decent source of selenium and B vitamins, too. Some supermarkets sell vitamin D–enriched mushrooms, which typically have 100 IU (2.5mcg) of vitamin D per 3.5oz (100g). That's a good chunk of the recommended daily intake – 600 IU (15mcg) – for those aged one to 70.

Adding a cooked carrot to your daily diet is a great way to boost health. Heat softens the carrot's cell walls, allowing more beta carotene – which helps the body produce vitamin A – to be absorbed. Just one carrot will supply enough beta carotene for your body to convert into just over the recommended daily intake of vitamin A. This is vital for your defences, as it helps to maintain the mucous passages that act as a barrier to viruses and bacteria.

If you don’t drink enough fluids, those all-important nasal passages can dry out and make infection more likely to take hold. Water doesn’t run the monopoly in terms of being able to hydrate, though – tea, coffee, soups and juices can all count, too. And don’t forget that foods with a high water content also help to hydrate you.

Foods high in the specific prebiotic fibres that nourish good gut bacteria include asparagus, onions, garlic, leeks and Jerusalem artichokes. Prebiotics can help stimulate the immune system by improving the balance between anti-inflammatory and inflammatory chemicals called cytokines.

Berries contain a range of phytochemicals, including anthocyanins, which can boost the health of good bacteria in the gut – which, in turn, benefits the immune system. Berries are also packed with vitamin C and other antioxidants that have been shown to help fight off respiratory infections and common colds.

Kefir provides a whole range of beneficial bacteria and yeasts, which together may help to make your immune system work more efficiently. Studies have shown that some kefir-specific microbes help to prime the immune system against bacterial infections. A product made the time-honoured way, with real kefir grains (cultures), is probably best.

Zinc helps the immune system work properly and aids in wound healing, while iron is also important for immune function. The best source of both? Lean red meat. That said, the World Cancer Research Fund recommends that we eat no more than 18oz (500g) cooked red meat per week. Nuts contain good amounts of these nutrients, too.

In a Tufts University study, consumers of wholegrains were shown to have increased levels of lachnospiraceae bacteria, which produce short-chain fatty acids needed for a healthy immune system. Those who consumed a wholegrain diet also had higher levels of T-cells – a type of white blood cell that wards off infection. Wholegrains are also packed with fibre, vitamins and minerals, and are said to lower the risk of heart disease.

Protein is made up of amino acids, chemical building blocks that support the body's immune system, helping with healing and recovery. The recommended daily intake of protein for adults is around 0.03oz (0.75g) per 2.2lb (1kg) of body weight in Australia and the UK, and ever-so-slightly more in Canada and the US. That's around 1.5oz (45g) for the average woman and 2oz (57g) for the average man. Protein-rich foods include seafood, lean meat, poultry, eggs, beans, peas, soya products (like tofu), nuts and seeds.

Did you know that just 6oz (175g) chopped red or green peppers will provide you with almost three times more vitamin C than an orange? Vitamin C is important for maintaining a healthy immune system, particularly during and after intensive physical activity (exercise fanatics, take note). Red peppers are also rich in vital vitamin A.

Another vegetable that packs more vitamin C than citrus fruit, kale is also a marvellous provider of vitamin A (from beta carotene) and other immunity-boosting antioxidants, including vitamin E. Compared to spinach, kale is the superior leafy green for your immune system, providing four times as much vitamin C and twice as much selenium. For maximum flavour, try it stir-fried with garlic, or add some to your morning smoothie.

As well as eating a balanced diet, it's important to have a healthy lifestyle. Quality sleep and plenty of exercise are two of the most important things to keep your immune system firing on all cylinders. A study published by the Sleep Research Society found that people who slept for six hours or less were four times more likely to catch a cold than people who slept for more than seven hours a night. Another study in the Korean Journal of Family Medicine showed that people who did regular, moderate-intensity exercise were 27% less likely to contract a cold than those who didn't exercise. So, combine your healthy diet with physical activity and a good night’s sleep for the best results.

Now find out how what you eat can affect your mood – and how to eat yourself happy

Last updated by Laura Ellis.