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Germs are all-around us, and within us too. It’s always been an important for your health to maintain a strong immune system, but even more so now with the coronavirus pandemic. Beyond social distancing and wearing masks, the last line of defence is our immune system, so we need to give put as much effort into boosting that as we do trying to prevent coming into contact with the virus to start with.
And it’s not just COVID-19 that the immune system defends us against – but a wide range of disease-causing organisms, called pathogens, such as other viruses, bacteria, fungus and parasites.
Given that whole books are written on the subject, and even those only start to scratch the surface, this is obviously a very simplified look at an amazingly complex system. If you want to discover more about how it works, Daniel M. Davis’ recent book The Beautiful Cure (link below) is well worth a read. If you just want a taster, before finding out how to improve it, then read on…
When a pathogen attacks the body, the body responds with a multitude of different process and immune cells. These are split between innate and adaptive immune systems, though they communicate with each other to coordinate their response to stop the infection.
The innate immune system is what we get naturally by birth and it acts as the body’s first lines of defence. Included in the definition of the innate immune system are physical barriers such as the skin that prevent the entry of foreign organisms into the body. These physical barriers also include mucus, tears, sweat and cilia that help to trap and remove infectious agents.
As well as these anatomical barriers, a range of white blood cells (including macrophages, neutrophils, and the brilliantly named natural killer cells) react to anything identified as foreign. The nearby blood vessels dilate and allow these phagocytes through to attack the intruders - this rush of cells to the infected area is what causes inflammation.
The innate immune system reacts fast and furiously, but in the same general way to everything, and isn’t enough to fight off severe infections.
This type of immunity is acquired by fighting against pathogens or through vaccination, hence often referred to as acquired immunity. The adaptive immune system is slow and involves B and T lymphocytic cells, produced in bone marrow and the thymus respectively.
The key component of the adaptive immune system is the antibody – a Y-shaped protein that attaches to antigens (targets on foreign bodies) at the V-end. The other end, called the C (“constant”) region, is the same no matter what antigen has been detected – and is the tag that other cells (such as T cells) use to identify targets for destruction.
Although slower to respond that the innate immune system cells, it is highly specific to each particular pathogen and therefore more effective in destroying it. Once human cells have been infected, it is also able to destroy our own cells to prevent further damage. Autoimmune disease occur when this process goes awry.
Even with such a complex immune system, we are still prone to infections and this susceptibility increases with age. As we get older, several physiological changes result in a weakened immune system. These include the bone marrow becoming inefficient in producing immune cells, and also the thymus gland shrinks (“thymic involution”) meaning less cells available to become T cells
Here’s what you need to know to support your immune system, so that it is in a better shape to save you from deadly infections
Like any other cell in the body, immune cells require a steady supply of nutrients, so a balanced diet with micronutrients increases the number of immune cells for defence.
The European Food Safety Authority suggests that vitamins and minerals could improve the functioning of the immune system. Although there is no single super nutrient which can improve immune response, a nutritious eating plate can build your immunity, for example:
Here’s some of the latest findings, as published in BMJ Nutrition, Prevention & Health(1) in May 2020.
Vitamin A is a strong antioxidant that improves gut barrier function and helps neutrophils ingest and kill pathogens (i.e. phagocytic activity).
Food sources: carrots, spinach, mangoes, sweet potatoes, broccoli, cantaloupe.
Vitamin B groups also improve the intestinal immune function by strengthening the gut barrier and phagocytic activity similar to vitamin A. A study revealed that a lack of vitamin B for 21 days resulted in impaired immune function.
Food sources: chickpeas, tuna fish, banana, kale, potato, chicken
Vitamin C plays a key role in the migration of immune cells to the site of infection. It also improves barrier protection by mediating collagen synthesis. Many studies report that this vitamin reduces the chance of infection. A meta-analysis identified that a significant risk of viral infections from the common cold to severe pneumonia exists in vitamin C deficient people.
Food sources: oranges, lemons, kiwi, strawberries, red and green peppers, broccoli, cabbage and cauliflower
Vitamin D alters the number of white blood cells known as T2 killer lymphocytes, which reduce the spread of bacteria and viruses. It has various immunoregulatory properties and is directly linked in immune defence. A study reported that people with low vitamin D status had a higher risk of respiratory infections.
Food sources: fatty fish, including canned fish like salmon and sardines; eggs, fortified milk, cheese, tofu and mushrooms. Vitamin D is also produced with exposure to the sun.
Zinc boosts white blood cells to invade foreign pathogens. It also has a wide range of other benefits like phagocytosis and improves antiviral response.
Food sources: beans, nuts, whole grains, dairy products
Copper promotes the production of interleukins (signalling molecules) and the proliferation of T cells. It helps in immune responses against bacterial and parasitic invasion.
Food sources: meat (particularly liver), oysters, green leafy vegetables, mushrooms
Selenium improves antibody production and natural killer cell activity. Deficiency of selenium increases the susceptibility of viral infections.
Food sources: eggs, seafood, nuts and seeds, poultry
Gut bacteria can help immune cells to identify harmful pathogens and to stimulate the release of cytokines (signalling proteins releases by immune cells) and antimicrobial agents, like bacteriocins, to destroy the microbes. Prebiotics are a food source for the friendly bacteria in your intestinal tract, boosting their support of the immune system. Probiotics are beneficial bacteria that can be obtained through regular intake of fermented foods (yoghurt, kimchi, kombucha and sourdough bread) or with supplements such as Yakult.
A 2017 trial found that children drinking 70 mL of fermented daily resulted in 20% fewer infectious diseases(2). If taking supplements, look for lactobacillus and bifidobacterium strains as they are considered to be safe and effective for long-term use.
Scientists call vaccines the real immune boosters. Vaccines are safe and effective, and trigger the activation of long-lived antibodies against weak or inactive parts of the pathogen.
The flu vaccine (commonly called the “flu jab”) is made available by the NHS every year to protect adults and children from seasonal flu (influenza). Many high-risk groups (e.g. over 65s, care home workers, people with an underlying disease) can the vaccine for free, but high street chemists also provide it to the general public.
The World Health Organization and EU identify the prevalent viral strains every year and accordingly make new vaccines which target the circulating variant of the virus. Its effectiveness varies each year, depending on how well the scientists predict which variant will be dominant.
One of the innumerable benefits of exercise is its ability to limit and delay the ageing of immune cells. Blood circulation can be improved with regular exercise which may contribute to active movement of immune cells to the infection site. Although a 2007 study concluded that moderate exercise may be better in its protective effect rather than repeated bouts of strenuous exercise(3).
Other studies suggest that regular physical activity reduces the occurrence of non-communicable diseases such as chronic inflammatory disorders, cancer as well as communicable diseases such as viral and bacterial infections(4).
Sleep and the immune system are interconnected and affect each other. Sleeplessness can slow down your immune function, and, the other way round, you can experience disturbed sleep when suffering from a viral infection. For example, many COVID patients report insomnia even after months of recovery.
The circadian rhythm is associated with the processes of both innate and adaptive immunity. Scientists have noticed cytokines rev up during night sleep, and also that T cells become stickier – a good thing, as that means they are better able to attach to infected cells.
A 2019 survey reported that 54% of people experience sleeplessness due to stress. Stress is also indirectly linked to proper immune response as stress hormones inhibit the stickiness of T cells – the opposite of what a good night’s sleep does. So not sleeping due to stress is a double-whammy for the immune system.
The American Academy of Sleep Medicine and the Sleep Research Society suggests a sleeping time of 7 hours or more for adults and 8-10 hours for teens to maintain optimal health(5).
Tips to improve your sleep:
So, as with all health goals, there is no superfood nor a super pill that can boost your immunity in a day or two. In reality, it is more of a consistent process which involves following a healthy lifestyle with a balanced diet, regular exercise, good sleep and supplements where needed.
1. Calder PC; Nutrition, immunity and COVID-19. BMJ Nutrition, Prevention & Health; 2020; DOI: 10.1136/bmjnph-2020-000085.
2. Corsello G et al; Preventive Effect of Cow's Milk Fermented with Lactobacillus paracasei CBA L74 on Common Infectious Diseases in Children: A Multicenter Randomized Controlled Trial. Nutrients; 27/6/17; 9(7); 69; DOI: 10.3390/nu9070669.
3. Brolinson PG et al; Exercise and the Immune system. Clinics in Sports Medicine; 26(3); 1/7/2007; DOI: 10.1016/j.csm.2007.04.011.
4. Campbell JP. Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan. Front Immunol; 16/4/2019; 9; 648; DOI: 10.3389/fimmu.2018.00648.
5. Watson NF et al; Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep; 1/6/2015; 38(6); 843-844. DOI: 10.5665/sleep.4716.
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European Union agency that provides independent scientific advice on risks associated with the food chain.
Specialized agency of the United Nations responsible for international public health
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