Can Veg Boost Your Immune System?

Dr Glenys Jones

Glenys is a Registered Nutritionist (RNutr) specialising in nutrition and health communications. She is experienced in public health and sports nutrition, and has a degree in nutrition science, a Masters in sports physiology and a PhD in nutrition, health and performance. She is the Deputy Chief Executive and Communications Manager for the Association for Nutrition, which is the independent regulator for nutritionists recognised by the NHS, Public Health England, Wales and Scotland, plus many employers.

With the current Covid-19 pandemic, lots of us are concerned about our health and in particular our immunity. Unfortunately, there is lots of misinformation out there, so it is essential to have evidence-based facts, so that we can truly understand the role diet can have, and the important role veggies can play within this.

Can anything in my diet boost my immune system?

Let’s start with the facts – there are no foods or supplements that will boost our immune system, nor would we want them to, as an over-active immune system can be as equally risky as one that is suppressed. Nor will any food or supplement prevent us from contracting an infection, such as coronavirus, as this is a result of exposure. However what we can do is make sure that we have nourished our immune system, so that it is in the best condition possible for fighting off any infections we might pick up.

Following a healthy diet aids in the maintenance of a healthy immune system and helps to keep it in tip-top condition ready to tackle any infections.    

So how does the immune system work?

Our immune system is made up of two parts, innate and adaptive/acquired. Innate immunity provides our first line of defence and is designed to stop pathogens from getting into our bodies. This includes protective barriers such as our skin, stomach acid, sweat, tears and cells that attack foreign cells when they enter the body. Our innate immune system is non-specific and does not remember any previous infections.

Adaptive/Acquired immunity is the second-phase of our immune response and it has the ability to recognise a pathogen that we have previously been in contact with. Our body produces antibodies and an increase in immune cells. These are specific to the infection and this attacks and destroys the pathogen. It then adapts to remember the infection, providing a quicker and more efficient response to destroy the pathogen if it enters the body again.     

The importance of our diet

Having a diet which is rich in the nutrients that support immune cells to function efficiently enables our bodies to initiate an effective response against infections so these can be destroyed quickly and long-term inflammation can be avoided. Therefore it is beneficial to consume a varied diet, providing vitamins A, C, D, E, B2, B6, B12, Folate/Folic Acid, Iron, Selenium, Copper and Zinc. These nutrients work as antioxidants to protect healthy cells from damage, in the support of the growth and activity of immune cells, and/or in the production of antibodies. Vegetables, fruits, whole-grains and legumes are a good way of getting these nutrients into our body, as well as going outside to make vitamin D from sun exposure. These foods are also beneficial to the friendly bugs that live in our intestines, which can stimulate the activity of immune cells.

Adding fruits and vegetables into our diets?

Seasonal veggies are a tasty way of adding many of these nutrients into our diets. Whilst we get most of our vitamin D from exposing our skin to sunlight between March and September, we can also place mushrooms on the windowsill for an hour before we use them and they will use the sun’s light to naturally increase their vitamin D content.

Most of us are aware of the Government recommendation to consume at least five portions of a variety of fruits and vegetables each day, and adding even more veggies into our diets will be even more beneficial. Therefore try to increase your current daily intake by 1 or 2 portions and then when you have been able to maintain this, try to add in another portion until you are reaching around 5-7 portions every day, ideally with the majority being vegetables.

What is a Portion?

When adding fruits and vegetables to your weekly menu, it is worth remembering that unsweetened pure juices or smoothies can only count as one portion, as juicing/blending releases sugars, which can impact on your dental health. Therefore try to keep your intake of these to the 150ml portion size, which is the equivalent of a small glass.

For adults a portion of fruit or vegetables is 80g, except for dried fruit where due to the drying process a portion is 30g. Dried fruit should also be kept to meal times, so they are less likely to get stuck in between our teeth. Fruits and vegetables count whether they are fresh, frozen or tinned in either water with no added salt/sugar or fruit juice. Potatoes, yams and plantain do not count as a portion of vegetables, as they are classed as a starchy food and can be used to replace other starchy foods like pasta, rice or bread.

The portion size for children varies as they grow, but as a good rule of thumb a portion is the size that would fit in the palm of your child’s hand. Therefore for a toddler the size for fruit and vegetable portions is likely to be around 30-40g, 50-60g for primary school children, and 70-80g for secondary school children.

5 veggies that are good to include in our diets to support our immune system

  • Tomatoes provide a good source of vitamins A, C and E, plus a carotenoid called lycopene, which has also been associated with lowering the risk of heart disease and some types of cancer. This versatile veg is a great regular addition to our diets. (Portion = 1 medium or 7 cherry)
  • Carrots are a brilliant source of vitamin A, which our bodies make from the high levels of beta-carotene. A portion of cooked carrots provides adults with 200% of our daily intake of vitamin A. This helps to support and maintain healthy skin and cells lining our digestive tract, airways and urinary tract. Therefore aiding our bodies’ barriers to infections. (Portion = ½ medium or 3 tablespoons)
  • Onions provide us with vitamins A, B6, C, E, folate and iron.  Vitamin B6 is essential for the creation and action of the immune system’s cytokines and antibodies. Many reactions in our immune system are dependent on B6, therefore it is essential for the regulation of our immune response and adequate intakes are needed for optimal immune function. (Portion = 1 medium)
  • Peas are a good source of vitamin A, C, folate and iron, as well as being a good way of adding fibre and protein into the diet. Frozen peas are a great veg to keep in the freezer and can be quickly microwaved, steamed or boiled in just enough water to cover them - avoid using too much water, as this increases the amount of vitamin C lost during cooking. (Portion = 3 heaped tablespoons)
  • Broccoli provides the immune supporting vitamins A, C, E and folate, iron and selenium plus fibre. Folate is essential for the production and metabolism of DNA and RNA, which is needed for a healthy, functioning immune system. Whilst for many broccoli tastes sweet and is a veg particularly enjoyed by children, some find broccoli extremely bitter – this is genetic and is due to whether or not we have 2 alleles for a particular bitter receptor that means they are particularly sensitive to the bitter compounds (PTC) in broccoli and other cruciferous vegetables.  (Portion = 8 florets calabrese (regular) broccoli or 2 spears of tenderstem/ sprouting)

Including vegetables into our diets

We can use the increased time many of us currently spending at home as an opportunity to try out different recipes or add extra veggies into our current dishes. Let’s take Popeye’s favourite spinach as an example. It is a great source of vitamins A, C and Folate, and a good source of Iron and B2. We can enjoy this as an addition in the last few minutes of cooking a curry, added into pasta or soups or even on top of a pizza.  We can also try out some scrumptious spinach recipes such as spinach fritters, green mac and cheese, dal saag, pesto, spring veg stew, green veg Spanish tortilla, Mediterranean rolls, egg wraps, veg crumble, easy samosas or even a smoothie

If you have leftover spinach, you can also freeze this for future use. You just pop the leaves in a sieve or colander and pour boiling water over so that it wilts. You can then put the wilted spinach into ice cube trays and freeze these nutritious little blocks. You can also buy ready frozen spinach, which is great for having readily available in the freezer and reduces food waste, as you just grab out a block or two when needed.

TOP TIPS FOR SUPPORTING A HEALTHY IMMUNE SYSTEM

  1. EAT A VARIED & BALANCED DIET – if there is an inadequate intake of the nutrients our bodies need, the production and activity of both immune cells and antibodies can be impaired. Therefore eating a rainbow of fruit and veggies, whole-grains, legumes/pulses, lean protein and plenty of fluids (water, squash, tea, coffee – it all counts) is beneficial.
  2. DON’T SMOKE & LIMIT ALCOHOL – these substances can suppress and impair the activity of immune cells. Thus stopping smoking and limiting alcohol intake is advantageous.
  3. EXERCISE REGULARLY – being physically active not only benefits our physical health, but also our mental health. This help us to manage stress, which otherwise can result in the release of a hormone that suppresses our immune response.
  4. SLEEP WELL – aim for around 6-9 hours, as too little sleep can lower the amount of immune cells we have available to fight off infection. Try and keep to a routine if possible and stop using digital devices such as phones or tablets for at least an hour before bedtime, as the screen light can negatively impact on sleep.
  5. WASH HANDS REGULARLY – using warm water and soap for at least 20 seconds (or using sanitiser when out), especially after coughing, blowing your nose, before and after preparing/eating food and when coming in from outdoors. This physically removes bugs from our hands that could otherwise get inside the body, particularly if we touch our faces.
  6. KEEP YOUR DISTANCE – contracting an infection is down to exposure. Therefore maintaining social distancing reduces the risk of exposure to viruses such as coronavirus. Currently the recommendation is to keep 2 metres apart, or if this is not possible then to use precautions such as a face covering, not being face-to-face, washing hands and/or keeping interactions to a minimum, plus maintaining a distance apart of at least 1 metre.

About the author

Dr Glenys Jones

Glenys is a Registered Nutritionist (RNutr) specialising in nutrition and health communications. She is experienced in public health and sports nutrition, and has a degree in nutrition science, a Masters in sports physiology and a PhD in nutrition, health and performance. She is the Deputy Chief Executive and Communications Manager for the Association for Nutrition, which is the independent regulator for nutritionists recognised by the NHS, Public Health England, Wales and Scotland, plus many employers.

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