How Can You Strengthen Your Immune System?
Our immune systems do a great job of protecting us against germs that cause infections (pathogens) as well as fighting off any infections that do take hold and make us sick. But how they work is far from simple to understand.
The human immune system is made from an intricate network of organs, cells and other tissues, all interconnected and working together to form a defence against pathogens and even cancers (thanks to the way it can kill tumours). And since they are so complex, no two immune systems are exactly alike.
Two important components of your immune system are your bone marrow – which makes your blood cells (including immune cells) – and your thymus, a gland found at the front of your windpipe, above the heart. Some of the immune cells produced by bone marrow migrate to the thymus, where they multiply and ‘learn’ how to recognise the difference between normal healthy cells and invading pathogens such as viruses, bacteria and parasites.
These particular immune cells are called T cells, which belong to a group of cells called lymphocytes (white blood cells). But there are many more different immune cells in the human immune system, each of which has a job to do whenever a pathogen triggers the immune system into action.
Another important part of the immune system is the lymphatic system, which is made up of a network of vessels and tissues including hundreds of little glands called lymph nodes. These have a range of important functions in the immune response, one of which is to ‘teach’ T cells how to recognise and destroy pathogens.
You can find out more about what the immune system is made up of and how it works by reading Understanding how the immune system works.
If your immune system isn’t as strong as it should be you may get sick more often than you should. A weakened immune response can cause recurrent and potentially severe infections that can become quite serious very quickly including bronchitis, ear infections, sinus infections, skin infections and pneumonia. These are all possible signs of immune suppression, which can be treated medically.
But if your immune system is only slightly depressed, leading to more infections but not unusually severe symptoms, what can you do? Are there any lifestyle changes you could make that would help your immune system become stronger?
The truth is there’s still a lot we don’t know about the complexity of immunity, how it responds to pathogens and whether or we can reinforce an immune system that’s performing slightly below par by non-medical means. But the good news is an increasing number of researchers are starting to pay more attention to the immune system and how lifestyle factors may influence it.
Natural health practitioners, meanwhile, argue that your lifestyle can certainly have an effect on your immunity. Take diet, for instance. We know good nutrition is important for our cells to function properly, so it’s reasonable to think that this includes the cells that are part of the immune system too.
What Foods Make Your Immune System Stronger?
We all know someone who eats hardly anything but junk food yet rarely catches a cold or takes a day off sick. But this doesn’t mean that, for the rest of us, what we eat doesn’t have an important influence on our immune health.
Indeed, poor nutrition and malnutrition are widely understood to be harmful to immune function, so having a balanced diet is important if you want strong resistance to infections and other illnesses.
According to Public Health England’s Eatwell Guide, a healthy balanced diet includes at least five portions of a variety of fruit and vegetables every day, starchy foods such as potatoes, bread, rice and pasta (starchy foods should make up about a third of your food intake), some dairy foods (or dairy alternatives), some protein (beans, pulses, fish, eggs, meat etc) and small amounts of unsaturated oils, spreads and other foods high in fat, salt and sugar.
Studies that examine the effects of nutrition on the human immune system are still relatively few in number. However, some have uncovered immune system benefits in certain foods.
Berries and Dark Chocolate
Blueberries – along with other red and purple berries – are rich in antioxidant plant compounds called flavonoids, specifically a type of flavonoid called anthocyanidins. In one study, researchers discovered people who eat foods rich in flavonoids are 33 per cent less likely to get upper respiratory tract infections – or colds – than those who don’t eat many flavonoid foods (i).
Flavonoids are found in many fruits and vegetables, and are responsible for their rich, vivid colours. In general, the brighter the colour, the richer a food is in flavonoids. Examples include peppers, plums, grapes, strawberries, onions, Brussels sprouts, spinach, kale and citrus fruit. You can also get your flavonoids from red wine, tea and dark chocolate.
Oranges, Eggs and Oily Fish
As well as providing flavonoids, oranges are a good source of vitamin C. According to researchers, vitamin C improves the function of some of the components of the human immune system (ii), including some lymphocytes and natural killer cells.
Like flavonoids, vitamin C is found in a wide range of fruits and vegetables, including red peppers, kiwifruit, broccoli and even potatoes. Meanwhile oranges – as well as other orange and yellow fruits and vegetables – also contain vitamin A, which alongside vitamin D is believed to be important for a number of immune processes (iii).
Vitamin A is found in fortified foods (such as breakfast cereals), eggs and cod liver oil. You can also get it from foods that contain a plant compound called beta-carotene, since beta-carotene is converted in the body to vitamin A. Foods rich in beta-carotene include orange and yellow fruit and veg as well as most dark green, leafy veg.
Vitamin D has sparked other researchers’ interest in its role in immunity too, with experts suggesting it has clear benefits for immune health (iv).
Foods containing vitamin D include fortified foods as well as oily fish (including salmon, fresh tuna, sardines, herring and mackerel), egg yolks, red meat and liver. However, for many people the main source of vitamin D is exposure to sunlight (our bodies create vitamin D when our skin is exposed to the sun). This means that, if you spend time outdoors during the spring and summer, you may be getting all the vitamin D you need at that time of year.
However, the NHS recommends everyone should consider taking a daily supplement containing 10mcg vitamin D during the autumn and winter. It suggests you should consider taking a supplement during the spring and summer too if you spend a lot of time indoors or if you usually wear clothes that cover up most of your skin when you’re outside (v).
Beans, Nuts and Oysters
If you want to keep your immune system functioning at its best, it’s also a good idea to make sure your diet includes a good supply of zinc. Found in cells throughout the body, zinc is needed to keep your immune system healthy. Indeed, according to the UK National Institutes of Health Office of Dietary Supplements, older people and children in developing countries who have low levels of zinc may have a higher risk of getting pneumonia and other infections (vi).
You can get zinc from a variety of foods, with oysters providing the highest amounts (red meat, seafood, poultry and fortified foods contain good amounts of zinc, plus you can also find it in beans, nuts, seeds, dairy foods, eggs and whole grains).
Does Exercise Help Your Immune System?
Exercise boosts health in a number of ways. It can help you to keep a healthy weight as well as maintain good bone health. It can also reduce your risk of major illnesses such as heart disease, stroke, type 2 diabetes and cancer, and even reduce your risk of early death by up to 30 per cent (vii).
But can staying physically fit help keep your immune system healthy too?
According to the US National Library of Medicine, it isn’t known exactly if or how exercise increases your immunity to certain illnesses (viii). Some of the theories as to why it may work – though none has been proven – include:
Exercise affects cells in your immune system (lymphocytes) as well as antibodies, helping them to circulate through your bloodstream more quickly and therefore detect pathogens (disease-causing germs) faster.
Being physically active could help flush pathogens out of your lungs and airways, reducing your likelihood of getting a cold, flu or other illness.
Exercise increases your body temperature, albeit briefly, but even this temporary increase may help the body fight infection more effectively.
Exercise also reduces your production of stress hormones, high levels of which may increase your risk of illness.
On the other hand, could too much exercise be bad for your immunity? This idea has been prevalent since research from the 1980s discovered marathon runners had symptoms of infections in the days and weeks after their race.
More recently, however, experts have found endurance sports may actually be good for the body’s ability to fight off illness (ix). The researchers – from Bath University – found while exercises do cause changes in immune cells, these changes do not dampen the immune system. Rather the immune system is boosted after exercise, they claim.
How Much Exercise Should You Do?
The NHS suggests the following for adults aged 19 - 64 (x):
At least 150 minutes of moderate activity a week or 75 minutes of vigorous activity a week.
Being physically active every day.
Doing strengthening activities that work all the major muscles on two days of the week.
Spending less time sitting and breaking up long period of inactivity.
Recommendations for the over-65s are the same, except that it’s advised you do activities that improve your balance and flexibility as well as your strength on at least two days of the week.
Examples of moderate activity include brisk walking, gentle cycling, dancing, hiking, rollerblading, water aerobics, pushing a lawn mower and playing doubles tennis. Vigorous activity, on the other hand, includes jogging or running, cycling at speed or on hills, skipping, martial arts, sports such as football, rugby, netball and hockey, and walking up stairs.
For more information on exercising and staying fit, take a look at our library of sports articles.
More Ways to Maintain Your Immunity
Besides eating healthily and taking regular exercise, there are a few more things you can do that may be useful:
Smoking can be harmful to your health in many ways, including impairing your immune system. Researchers believe it may affect important immune system cells such as T cells and B cells, as well as natural killer cells and other cells called macrophages (xi). Smoking has also been linked with autoimmune health – which is when the immune system attacks healthy body tissues – and may play a part in the development of autoimmune conditions such as rheumatoid arthritis and psoriasis (xii).
There’s lots of help available if you want to quit smoking. For instance, you can buy nicotine replacement therapy (NRT) products that help with nicotine withdrawal symptoms such as cravings. These include patches, gum, lozenges and inhalators.
Drink in Moderation
After the emergence of the virus that causes Covid-19 symptoms, the World Health Organization advised that access to alcohol should be restricted during lockdown. One of the reasons, it says, is that alcohol compromises the body’s immune system – making it especially important for people to cut down during the pandemic (xiii).
Indeed, health experts have long been aware of a link between drinking alcohol and immune-related health issues such as susceptibility to infections, as well as slower recovery from infection. They also believe the ways in which alcohol affects the immune system are complex – this includes the way it affects the structure and integrity of the gastrointestinal system (xiv).
To keep the health risks from alcohol to a low level it’s safest not to drink more than 14 units a week on a regular basis. If you regularly drink that much, try to spread your drinking evenly over three or more days.
Get Plenty of Sleep
If you want to keep your immune system healthy, try to avoid having too many late nights. Getting a good night’s sleep is thought to be important, especially during times when your defences are low and when there are lots of infections in the environment (during winter, for instance, when cold and flu bugs are widespread).
According to the US-based National Sleep Foundation, if you don’t get the amount of sleep your body needs, your immune system makes fewer cells called cytokines, which are proteins that help some other immune cells communicate with each other (xv). This, it says, may be because cytokines are produced and released while you sleep.
Most adults need between six and nine hours of sleep a night, says the NHS (xvi). If you sometimes find it difficult to get the right amount of good-quality sleep, take a look at the tips in our guide to sleep and insomnia.
Practise Good Hand Hygiene
Most of us learned a lot about good hygiene during the coronavirus pandemic, but it’s important to keep up those hygiene standards outside pandemic times too if you want to avoid getting sick. Even if you eat well, sleep well, exercise regularly, stop smoking and cut down on alcohol, all of that good work can be undone if you fail to wash your hands at key times.
Whether during a pandemic or cold and flu season, or indeed at all times, it’s a good idea to get into the habit of washing your hands or using hand sanitiser containing at least 60 per cent alcohol...
Before, during and after preparing food
Before and after looking after someone who has diarrhoea or vomiting
Before and after treating a cut or wound
After using the toilet
After changing a baby’s nappy
After blowing your nose, coughing or sneezing
After touching an animal, animal feed or animal waste
After handling pet food or pet treats
After touching rubbish or using a rubbish bin
Make sure you lather up your hands for at least 20 seconds, then rinse them under clean running water and dry thoroughly using a clean towel or air dryer (if you’re using hand sanitiser apply a generous amount and rub your hands together for at least 20 seconds).
Many experts, including those from Harvard Medical School, believe chronic stress suppresses the immune system and increases your susceptibility to colds and other infections (xvii). If you’re feeling tense, try to do something that relaxes you. Even sitting quietly for five minutes and focusing on your breathing can be helpful. It may also help you get a better night’s sleep if you practise relaxation before bedtime.
Find out more about stress and how to manage it by reading our guide to stress symptoms and signs.
Natural Immune System Support
Eating healthily is important if you want to keep your immune system in top condition. But we all know isn’t possible to have a perfect diet 100 per cent of the time. When this happens to you, one thing you could do to keep your immune system healthy is to take a good-quality multivitamin and mineral supplement. Your multi should contain good levels of all the usual vitamins and minerals, including vitamins A, C and E, and zinc (alternatively you could consider taking these in single supplements).
You may also want to try one of the following:
A popular medicinal herb, echinacea is used to relieve the symptoms of the common cold and influenza-type infections, based on traditional use only. There is also some evidence that various forms and species of echinacea may reduce cold symptoms and help you get over a cold faster (xviii). One study also suggests taking echinacea as a long-term preventative may reduce the number of colds you catch (xvix).
Elderberries – which grow on the Sambucus tree – have a long traditional use for the relief of colds and flu. One study investigating the effect of an elderberry extract found it reduced flu symptoms by three to four days, and that it might also be beneficial for the immune system by increasing the production of immune cells called cytokines (xx).
The millions of micro-organisms and bacteria that live in your digestive system are thought to play a key role in immune response, as well as your overall health and fitness. Indeed, experts believe around 80 per cent of immune tissue is found within the digestive tract (xxi).
Acidophilus and other types of live bacteria are thought to help boost the immune system and reduce the risk of viral infections, with some studies suggesting they may help prevent and relieve symptoms of colds and other infections (xxii). One study also suggests taking certain types of live bacteria may shorten the length of a cold by almost two days as well as reduce the severity of symptoms (xxiii).
Food sources of live bacteria include yoghurt, kefir, sauerkraut, miso and tempeh, but nutritional supplements that contain live bacteria are also popular.
A mineral that’s essential for many processes in the body – including the regulation of muscle and nerve function, blood sugar levels and blood pressure – magnesium also plays an important role in the immune system. In older people, for instance, a magnesium imbalance or deficiency may play a part in immune dysfunction and increase susceptibility to age-related diseases (xxiv).
Many of us may not be eating enough magnesium, but you can easily get more of it by taking a good-quality magnesium supplement. To increase the magnesium in your diet, try eating more whole foods such as brown rice, nuts, pulses and green vegetables.
Natural compounds called polysaccharides that are found in baker’s yeast, grains such as oats, barley, rye and wheat, as well as some mushrooms (shiitake, for instance) and seaweed, beta glucans (or β -glucans) are increasingly thought to be important for immune health.
While they may not be as well known as some other nutritional compounds, researchers have been interested in beta glucans since the 1960s. Several studies have shown that beta glucans have various effects on the human immune system, including protecting against infection and stimulating the immune system to respond to pathogens (xxv).
Researchers have found that, among their various actions, they trigger and enhance the function of immune cells including macrophages, neutrophils, monocytes, natural killer cells and dendritic cells (xxvi). A review of studies into beta glucans has also concluded that they appear to be effective at enhancing immune function and reducing susceptibility to infection and cancer (xviix).
Beta glucans may even help reduce the symptoms of common cold infections, with experts investigating firefighters finding that those taking beta glucans had 23 per cent fewer colds than those taking a placebo (xxviii).
To find out more about keeping your immune system strong, visit our section on immunity. Meanwhile for lots more information on a wide range of health topics visit our pharmacy health library.
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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.
Christine Morgan has been a freelance health and wellbeing journalist for almost 20 years, having written for numerous publications including the Daily Mirror, S Magazine, Top Sante, Healthy, Woman & Home, Zest, Allergy, Healthy Times and Pregnancy & Birth; she has also edited several titles such as Women’ Health, Shine’s Real Health & Beauty and All About Health.