Nutritionist Rob Hobson shares his advice on using your diet to support your immune system, including how to prepare these immune-boosting foods for optimum flavour.
🕒 6 min read
The immune system helps to protect the body against disease. There are two ways in which the immune system does this: innate and acquired immunity.
Innate immunity is programmed into us all, while acquired immunity is the second line of defence and develops over our lifetime.
Importantly, diet can play a role in how the immune system functions – and it is clear from the research that people with a poor diet are more susceptible to ill health.
Diet and immunity
If you're trying to boost a weak immune system, studies have shown that numerous foods are particularly beneficial.
This member of the allium family has long been regarded for its anti-viral, anti-microbial, and anti-bacterial properties that may help to protect against coughs and colds.
The active ingredient in garlic is allicin, together with other sulphur compounds that act as powerful antioxidants. These compounds have been shown to enhance the disease-fighting response to some types of white blood cells in the body when encountering viruses.
Garlic can be added to any dish but adding it to roasted vegetables brings out the sweetness. Roast in the skin then squeeze out the flesh and combine with lemon juice and olive oil to dress the vegetables.
Mushrooms and garlic both have benefits for the immune system.
Ginger is well-researched for its protective effect on immunity. It contains compounds, including gingerol, which have powerful anti-inflammatory and antioxidant properties.
One study published in the journal Advanced Pharmaceutical Bulletin looked at a group of adults with type 2 diabetes and found that after taking 2g of powdered ginger daily, they had significantly reduced levels of specific inflammatory markers in the body, including C-reactive protein (CRP).
Ginger can be used to spice up curries and stir-fries but also works well in juices and smoothies. Powdered ginger also works well when brewed in a tea with lemon juice and hot water.
This bright spice contains an active ingredient called curcumin, responsible for its yellow colour.
Curcumin is a polyphenol that acts as an antioxidant in the body while also inhibiting a protein and enzyme that promote inflammation.
Curcumin's anti-inflammatory properties result from its ability to modulate cells within the immune system, such as T cells, macrophages, and natural killer cells.
Several studies have also found turmeric to be more effective than ibuprofen for post-surgical pain and swelling.
Curcumin is not easily absorbed, but this can be enhanced when eaten with fat or black pepper.
You can add turmeric to lots of dishes, especially one-pot meals such as curries or soups. Turmeric can also be added to scrambled egg or salad dressings.
Another idea is to add turmeric to nut milks along with other spices, as a chai tea.
Read more: Turmeric for immunity
Health writer Karen Evennett explores all the ways this golden spice can brighten up your immune system.
Like other dark green leafy vegetables, broccoli is a good source of vitamins and minerals. Many of these are excellent vitamins for the immune system, including zinc, iron, vitamin C and an array of B vitamins.
Other compounds found in green vegetables, such as beta carotene, also help to support the immune system, as do sulphur-containing compounds such as sulforaphane.
Broccoli is not just a side dish. Raw broccoli is great with dips and is delicious when griddled with chilli and garlic. You can also add a little broccoli to juices and smoothies.
Nuts contain a good source of the mineral selenium, which is lacking in the diet of many people; according to the National Diet and Nutrition Survey, 36 per cent of adults do not eat enough.
Dietary selenium, mainly through its incorporation into selenoproteins, plays a vital role in inflammation and immunity. Adequate levels of selenium are essential for initiating immunity but they are also involved in regulating excessive immune responses and chronic inflammation.
Almonds are a very nutritious snack but to add flavour, try coating them in soy sauce and honey, then baking. You can also make your own almond milk by blitzing almonds with water in a blender.
Almonds are a delicious, versatile and easy addition to your diet.
Vitamin D is now recognised as a potent modulator of the immune system. The vitamin D receptor is expressed in several immune cells, including monocytes, macrophages, and activated T cells.
Oily fish are one of the few foods to contain a natural source of vitamin D (think salmon and trout). During the winter months, we need to rely on a supplement.
Fatty fish also contain omega 3 fatty acids, which are well understood to help reduce inflammation in the body. These essential fatty acids also help immune cells respond more quickly in the body.
Try coating salmon in marinades or spice mixes, then baking. Raw salmon can also be finely cubed then marinaded with lemon juice, chilli and coriander as a ceviche or tartare.
Berries are rich in vitamin C. This vitamin contributes to the immune system's normal functioning and may benefit people at high risk of colds due to frequent exposure — for example, children who attend group childcare during the winter.
Interestingly, a 2013 review of 29 randomised trials with more than 11,000 participants showed that among highly active people (such as marathon runners, skiers, and Army troops doing heavy exercise in subarctic conditions) taking at least 200 mg of vitamin C every day appeared to cut the risk of getting a cold in half.
For the general population, taking daily vitamin C did not reduce the risk of getting a cold, but taking at least 200mg of vitamin C per day did appear to reduce the duration of cold symptoms by an average of 8 per cent in adults and 14 per cent in children, translating to about one less day of illness.
Berries are great added to salads.
To save on waste, berries past their best before date can also be frozen and used to make smoothies or fruit compotes, served with yoghurt or ice cream.
Shiitake mushrooms have traditionally been known as the 'medicinal' mushroom in many Asian countries for their perceived health benefits.
Research has suggested that these mushrooms' compounds may help stimulate the immune system. This is thanks to beta-glucans, which are naturally occurring polysaccharides in a plant's cell walls, such as mushrooms and seaweed.
Studies show that they can modulate the immune system and increase its defences by activating the complement system (which helps the ability of antibodies to clear pathogens from the body) by enhancing the function of macrophages and natural killer cells – two immune cells that fight foreign bodies.
The active ingredient Shiitake mushrooms is Lentinan, a beta-glucan unique to this variety of mushrooms. Lentinan has been shown to stimulate the activity of white blood cells, increase the production of interferon (a natural antiviral agent) and increase the activity of antioxidant enzymes.
Mushrooms can be used in many dishes and are a good substitute for meat when finely chopped and used to make burgers or sauces such as Bolognese. Add lentils to add protein and fibre.
Shiitake mushrooms can be bought dried (which work great as stock) and fresh, which can be added to many dishes, including stir-fries, risottos, casseroles, or simply sautéed and served on top of toast.
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