Foods for Immune Function
Our immune systems are very complex, and are being constantly barraged by stimuli from within our bodies and from the outside world. The state of our immune system is directly impacted by our emotions, stress levels, restful and adequate sleep, lifestyle, exercise and diet.
To keep our immune system running at its optimum requires a healthy diet:
- Regular meals
- A diet rich in whole, natural foods which include fruits, vegetables, whole grains, seeds, beans and nuts
- Low in “bad” fats and refined sugars
- Contains adequate, but not excessive, amounts of protein (as a guide, a portion of protein per meal is about the size of the palm of your hand)
- 6-8 glasses of water a day
A strong immune system also requires us to manage our stress levels so you could also include the following:
- 8 hours sleep a night
- Daily deep breathing and relaxation exercises
- Regular programme of aerobic exercise and 5-10 mins of stretching
- Taking time to play/be creative/laugh and enjoying the company of family and friends
- Being outside in the fresh air, connecting with nature, getting some sun on your skin
Did you know that?
Sugar is one of the components most damaging to our immune system. It can depress the ability of white blood cells to protect your body from invaders and also can affect vitamin C being transported into the body’s tissues. The effects of this can last for up to 5 hours after ingesting sugar.
Vitamin A helps to defend our mucosal surfaces and their secretions, so is very important for our gut health and lung health and the health of our eyes and nose. Vitamin A stimulates and enhances numerous immune processes, including our antibody response.
Vitamin A rich foods include organic full fat dairy, liver and eggs. Carotine (which our body converts to vitamin A) is from orange coloured foods, so carrots, tomatoes, mango, apricot, pumpkin, melon, sweet potato and squash
Carotene rich vegetables enhance immune function as they enhance the function of our white blood cells. These foods include: Highly coloured vegetables, such as dark greens, yellow and orange squash/pumpkin, carrots, sweet potatoes, red peppers, tomatoes.
Try: Butternut squash soup – this recipe has lots of goodies for supporting immune function and you can make extra and freeze portions for when you feel poorly https://www.bbc.co.uk/food/recipes/roasted_butternut_squash_10281
Vitamin C (ascorbic acid) is known to be antiviral and antibacterial and helps improve our resistance to infections. Our levels can be quickly depleted during the stress of an infection as well as in chronic disease. Vitamin C is lost in water and destroyed by light and heat, so eat some RAW veg and fruit daily.
- Berries (blueberries, strawberries, blackberries, cherries, raspberries, blackcurrants, cranberries) are all a good source of vitamin C and flavonoids. When not in season I recommend buying bags of frozen (there is usually something in the freezer section in the supermarket called something like a fruits of the forest berry mix which you can defrost in small portions and add to smoothies or stir into your bircher muesli )
- Apples – an apple a day keeps the doctor away! They contain vitamin C, potassium and flavonoids such as quercetin. They also help your gut bacteria (which play a role in your immune function too) as they are rich in the fibre pectin. They are best raw with the skin. The sourer the variety the more likely it is to have more health supporting flavonoids as opposed to the modern sweet varieties.
- Broccoli and Cabbage-family vegetables contain vitamin C and so that is why you should only lightly steam them or try and have some raw (eg in coleslaw).
Broccoli, Brussel sprouts, cabbage, cauliflower, collards, kale, mustard greens
- Citrus fruits are also a good source of vitamin C, as is kiwi fruit.
Aim to have 2 portions of fruit a day. Easiest way is to snack on an apple and add berries into your breakfast. Whole fruits are much better than juices (avoid shop bought juices and smoothies, no matter how healthy they market themselves to be they are full of sugar)
Vitamin D keeps the immune system in check. Deficiency has been shown to increase the risk of upper respiratory tract infections. The most active form of this vitamin is vitamin D3, or calcitriol. Plant based foods provides us with vitamin D2, or ergocalciferol.
Sources are as follows:
- Dairy products (full fat or fortified) and eggs, fish, liver. Also mushrooms, when exposed to light, can provide a source of D2 but this is only 30% as effective as D3.
- Fortified foods such as non-dairy milk alternatives – NB you need to check if it is still vegan if that is why you are having non-dairy.
- Sunlight – 5-30 mins exposure at least 2 x week between 10am and 3pm to the face, arms, legs or back without sunscreen between April to October. People with dark skin need to spend longer in the sun to produce the same amount of vitamin D as someone with very light skin. You cannot make vitamin D sitting indoors at a sunny window, as UVB rays can’t get through the glass.
Aim to: get outside for 15 minutes a day should the sun decide to shine…
Try this: have an omelette for lunch packed with vegetables and some delicious herbs such as chives. https://www.bbcgoodfood.com/recipes/fridge-omelette
Low levels of Zinc in the diet may decrease resistance to infections. Zinc has been found in studies to inhibit the replication of some viruses and to reduce the risk and severity of common infections such as the common cold. Zinc is extremely rich in oysters. It is also rich in pumpkin seeds, ginger root and pecans – generally seeds, nuts, legumes and wholegrains contain zinc in good amounts.
Use ginger root liberally…add it into cooking, it’s delicious in soups. You can grate it into a mug and add a slice of lemon and hot (not boiling) water for a delicious lemon and ginger tea.
Selenium is essential for efficient and effective operation of many aspects of the immune system. It protects our immune cells (neutrophils) and allows other immune cells (lymphocytes) to proliferate.
Whole grains (such as brown rice, oats, wheat germ/bran, and barley), fish, meat and eggs are the richest sources of selenium, and eating just two Brazil nuts will provide a good source of selenium a day (you don’t need more than this). Garlic and Swiss chard are also relatively high in selenium. So, by eating a couple of Brazil nuts a day and eating a varied diet of whole grains, fish, turkey, eggs and occasional red meat you are on the road to ensuring adequate levels.
Nuts and seeds – Hopefully now you can see why I bang on about including them in your diet? They are rich in zinc, selenium, vitamin E, essential fats (Brazil, almond, walnut, pumpkin seeds).
Try this: Just use a couple of old (clean) jam jars or kilner jars and keep some nuts in one and seeds in the other and then keep them somewhere you will see them on your kitchen counter so you remember to add them to your breakfast, sprinkle into salads or stir through some brown rice with your dinner.
So, basically to look after your immune system:
Eat a wholefood diet rich in vegetables, apples, berries, nuts, seeds, whole grains and pulses (and a small amount of good quality meat and animal products if you aren’t vegetarian/vegan)
Walk outside in the sunshine and whatever way you find effective to decompress from stress, do this daily.
Finally… Get some sleep!
- Sleep enhances immune defence and has a role in the proper functioning of the immune system
- Lack of sleep can make us more prone to catching colds and ‘flu.
Try to: Establish a good sleep routine, don’t watch the news at 10pm if you are an anxious person, switch off your social media feeds and any news based television at 9pm and take yourself off for a bath, a read of a favourite book or anything you find relaxing and calming. The news will still be there in the morning and us all watching it late at night and feeling worried and anxious doesn’t change things.
The main resource for this fact sheet is:
Murray & Pizzorno (2005) The Encyclopaedia of Healing Foods. London, Piatkus. If you have more than a passing interest in nutrition I highly recommend this book as a resource.