A nutritionist's advice for a stronger immune system
In the midst of the biggest pandemic of our lifetime, looking after our health has never been so important. While we are all hearing lots about how to reduce the spread of Covid-19, there is little being said about how we can support our immune systems should we, or someone we love, contract the virus.
So let's jump into it and find out more about how you can strengthen your immune system and give your body the best chance at fighting back from any infection.
How does the Immune system work?
Our immune system is built to help defend the body when it comes into contact with an illness such as bacteria or viruses. Made up of hundreds of different biochemical processes, it protects the body from harmful substances, germs, and cell changes that could make you sick.
In short, there are two main parts of the immune system: the innate response and the adaptive response. The innate response is our first line of defence. It reacts to an invader by trying to remove it from the body and it’s this that can make us feel feverish or snotty.
The adaptive response is the more specific response that can ensure long term protection against diseases like measles by using memory cells to kill certain pathogens. Again, made up of hundreds of reactions all dependant on each other.
Can you boost the immune system?
When you envision just how complicated the immune system really is, it’s hard to believe that a singular food, or slight change in behaviour could influence its whole functioning. And you’re not wrong there…
In fact, we can’t simply ‘boost’ the immune system – it’s not a case of take this now and it’ll boost it tomorrow. Which is why none of these tips below are body hacks or quick fixes, they’re all to be taken into account alongside a long term, healthy diet and lifestyle.
Ways to support the immune system
That said, there are ways to ensure the immune system has what it needs to be able to function optimally. Making sure you’re not deficient in certain vitamins and minerals is a great place to start. Here are the top players you need to pay close attention to…
Vitamin A
Vitamin A plays a major role in the protection and maintenance of our epithelial and mucus tissues – our body’s first line of defence against pathogen invasion. In other words, it helps to maintain the health of skin cells, the respiratory tract and intestines[1].
One way it does this is by helping to promote mucin secretion. This improves the immune response within the lung tissues by helping the body remove inhaled particles of pathogens from the lungs, thus reducing the risk of respiratory tract infections[2].
Being a potent antioxidant, vitamin A helps decrease the levels of pro-inflammatory molecules that could weaken the immune system response. Vitamin A also plays a fundamental role within immune cells such as B and T cells, helping to make antibodies which neutralise the pathogens that enter our body when infected with a virus[3].
Pre-formed vitamin A (retinol) exists only in animal products. However, beta carotene, found in food sources can be converted into vitamin A (for sources, see below). For beta carotene to be efficiently converted into vitamin A, its best eaten with a fat source, this is because it is a fat soluble vitamin (same with vitamin D)[4].
Recommended daily amount: for true vitamin A (retinol) consume 700–900 mcg, don’t exceed the upper daily limit of 3,000 mcg. For beta carotene aim for 6 - 15mg daily, no upper limit.
Food sources of beta carotene: yellow and orange foods like pumpkin, carrots, sweet potato, butternut squash, peppers, mangoes. Other sources include kale, spinach, dandelion greens, cabbage, swiss chard.
Vitamin C
Vitamin C or ascorbic acid is a water soluble vitamin that has been used for decades in supporting a healthy immune system. Being a potent antioxidant, vitamin C helps protect the body from oxidative stress - the process by which harmful free radicals circulate within the body, interfering with our immune system.
Vitamin C also plays a key role within helping to kill viruses and preventing pathogen replication. In fact, most cells within the immune system rely on vitamin C to function properly with the most important ones being phagocytes and t-cells.
Supplementing with vitamin C has been shown to reduce the duration and severity of upper respiratory tract infections, including the common cold[5][6].
Retrospective vitamin C studies have proved so promising that high doses taken intravenously, have been given to Covid-19 patients in China in a clinical trial. The results of this study however, won’t be ready until Sept 2020 but it could prove a promising, natural treatment in helping corona virus patients recover quicker from symptoms.
As it is a water soluble vitamin, your body will not store it, it’s therefore important that you consume it on a daily basis. Luckily, vitamin C is abundant in a broad range of fruits and vegetables.
Daily recommended amount: aim for a minimum of 200mg daily from food.
Food sources: Kiwi, bell peppers, oranges, citrus fruit, grapefruit, broccoli.
Vitamin D
More commonly known for its role in teeth and bone health, Vitamin D is actually one of the most important vitamins when it comes to helping the immune system fight off influenza. So much so that most doctors and nutritionists are recommending supplementing during this COVID-19 outbreak to help protect against the virus.
Also known as the sunshine vitamin, vitamin D is produced naturally when our bodies are exposed to sunlight. The correlation between high vitamin D levels in the summer and lower rates of cold and flu describes why it is referred to in the medical world as a seasonal stimulus. This also sheds some hope on fatal cases being less harsh as we head into the eye of the storm in the warmer months.
So how does it work? Studies are still researching the exact mechanisms but it’s been found that vitamin D receptors are present on immune cells which help regulate both the innate and acquired immune response - in particular within respiratory tract infections[7].
A recent, randomised, double blind, placebo controlled trial found vitamin D supplementation to reduce the odds of developing a respiratory infection by approximately 42%. This study also found that it was the daily supplementation that had the biggest effect on prevention of cold and flu, rather than larger doses taken on a single or monthly basis. Meaning regular, daily supplementation is recommended[8].
Despite playing such a crucial role within the immune system, vitamin D is actually one of the most common deficiencies in the world. The poor visibility of sunlight within the northern hemisphere has a huge part to place in this, which is why it is recommended by health professionals including the NHS that everyone should take a supplement in the months Sept-April.
Recommended daily amount: 1000–4000 IU should be enough to ensure optimal blood levels in most people, or as directed by your doctor.
It is recommended to have vitamin D3 with vitamin K2 to aid absorption.
Sources: 10-15 mins of skin exposure to sunlight or a vitamin D3 supplement. Note that some people have trouble converting vitamin D from sunlight, I would recommend testing your vitamin D levels to be sure.
Zinc
Zinc is a key mineral which is essential making enzymes, enzymes fundamental to the immune system. It is also involved in white blood cell response to infection. Because of this, people who are deficient in zinc are more susceptible to cold, flu, and other viruses.
Supplementing with zinc may be beneficial for those who are already sick. A 2019 study on 64 hospitalised children, all with respiratory tract infections found that taking 30 mg of zinc per day decreased the total duration of infection and the duration of the hospital stay by an average of 2 days[9]
Daily recommended amount: aim for 10-15mg per day.
Food sources: Hemp seeds, tofu, wholegrains, cashews, dark chocolate and chickpeas or a supplement.
Selenium
Selenium is another potent antioxidant which helps lower oxidative stress in your body, which reduces inflammation and enhances immunity. Selenium has shown to be essential for the immune system by being protective against certain pathogens.[10]
Daily recommended amount: 75 mcg/day for men and 60 mcg/day for women
Food sources: Brazil nuts, brown rice, oatmeal, lentils, barley. Just one serving of brazil nuts a few times a week will make up your recommended amount of Selenium.
Other ways to protect the immune system
Prioritise gut health
The gut plays a major role in the immune function, so much so that 75-80% of the body's immune cells are actually found within the gut. It is also here where micronutrients such as the vitamin and minerals mentioned earlier are broken down and absorbed by the body, further aiding the immune system function. It’s therefore super important to make sure our gut microbiome is healthy. The best way to do this is through the diet - more specifically by eating insoluble fibre or probiotic foods, such as kefir, kimchi, kombucha and sauerkraut.
Another, tasty and more convenient way to consume probiotics would be through a supplement such as thrive which contains 10 billion probiotics in each scoop.
Reduce stress
Stress releases the hormone cortisol which can turn off cells within the immune system causing your immune response to be lowered. It can be a bit of a vicious circle as the more you stress, the weaker your immune system will be, causing yet more stress.
Try taking time out of your day to carry out relaxation exercises such as breathwork, meditation or exercise. Instead of switching on your phone and watching the news to see yet more hysteria. I would recommend doing a 10-20 minute meditation, if you’re not familiar or comfortable with meditating, use an app like headspace, calm or a guided video from YouTube - this will go a long way for helping to reduce your stress levels.
Sleep
Sleep is so important, and even more so when fighting off a virus. During sleep, your body regulates cytokines – the protein that helps fight infection and inflammation. It’s also a critical time in which your body recovers from the day. You should always aim to get around 7-8hrs per night.
If you’re suffering from disrupted or deprived sleep taking naps throughout the day can help. One study from the Sleep Foundation found that taking two naps that are no longer than 30 minutes each —one in the morning and one in the afternoon could help decrease stress and offset the negative effects that sleep deprivation has on the immune system.
Stay informed but don’t get bogged down.
This can be easier said than done but there is a lot of scaremongering out there which can worsen our panic and cause anxiety from the unknown. Instead, try to funnel your energy in more positive ways by using this as an opportunity to learn a new skill, spend time with the family or re-evaluate what is important to you. Remember that it is only temporary, we will get through this and we will come through the other side stronger than ever.
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References:
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6162863/
[2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3776272/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3471201/
[4] https://www.ncbi.nlm.nih.gov/pubmed/24899156
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707683/
[6] https://www.ncbi.nlm.nih.gov/pubmed/29099763
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
[8] https://www.bmj.com/content/356/bmj.i6583
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548996/
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288282/