Vitamin C is necessary for our immune health. Below I discuss steps that you can take for yourself to maintain a healthy, balanced immune system. We don’t want an immune system that over-reacts and turns on your body or one that doesn’t react enough.

We place demands on our immune systems all the time and for the most part we are completely unaware of the tasks it is undertaking to protect us from pathogens such as bacteria, viruses and fungi. So in order for that to continue being the case, we need to provide our bodies with the best internal and external environments we can.

Supporting Immune Function

The immune system is highly complex. There are, however, some basic nutrients that have been shown to support its function.

Vitamin C is one of these. I will discuss what it is; why it is important; where we can source it from and how we can optimise the amount of vitamin C we can absorb. It is important to remember that we are what we absorb and not just what we eat.

The environment in the body needs to be functioning well to ensure that the nutrients we take in go to the cells, tissues and organs that need them. We also need to avoid foods like sugars that use up the nutrients in the body without providing any of their own.

What is vitamin C?

Vitamin C is also called ascorbic acid and is a water soluble vitamin. It cannot be made in the body and this is why we need to ensure that we get enough from the food that we eat. It also isn’t possible to store vitamin C in the body because it is water soluble and excreted easily in the urine. In order to maintain adequate amounts of the vitamin, it is better to spread your intake throughout the day and preferably include foods containing vitamin C in your daily diet.

Why is it needed?

The benefits of vitamin C to protect against bone, cartilage and tooth loss along with protecting against muscle wastage have been known for many years. It is also needed for collagen formation and wound healing; it helps us to absorb minerals such iron and calcium and it is essential for assisting with the functioning of the immune system. 

Vitamin C provides various roles in promoting immune function. Firstly, it protects the epithelial barriers in the body from the external environment (1). Epithelial barriers are found in the skin, the digestive tract as well as the nose, mouth, throat and the respiratory pathways including the lungs.

It also enhances the action of white blood cells in their defence against foreign invaders as well as removing dead cells from the body to reduce tissue damage (1).  

Powerful Antioxidant

Vitamin C acts as an antioxidant by donating electrons to unstable atoms or free radicals (1). Free radicals can be produced as a by-product of normal processes in the body such as breathing, liver and immune functions and exercise. They can alter the structure of proteins, fats and DNA in the body leading to disease (2). Viruses can also generate free radicals in the body. If these processes remain unchecked, the damage can grow and spread causing harmful inflammation.

If you think about how apples go brown when you cut them open and leave the flesh to come into contact with the air. You can slow down the browning process by squeezing lemon juice over the fruit. This works because the ascorbic acid (Vitamin C) in the lemon juice reacts with the oxygen in the air before the enzymes on the surface of the apple get a chance to react with it. The same goes for mopping up free radicals in the body by making sure you eat foods rich in antioxidants.

When we are looking for foods that are high in vitamin C, it is important to remember that we need to eat whole foods because we benefit from the addition of the other vitamins, minerals and fibre contained in these foods as all the components work synergistically together to give us the maximum health benefits.

So what can deplete vitamin C in the body?

A high level of sugar in the diet can lead to lower levels of vitamin C being allowed in to cells. This is because glucose and vitamin C share the same transporters to get into cells (3). If your diet is high in sugar, vitamin C will have to compete with glucose at the transporter sites.

Smoking also depletes vitamin C levels in the body (4).

How do we preserve vitamin C?  

The way we buy, store and prepare food can also affect the amounts of vitamin C we get from our food. So if we are not careful, Vitamin C can be depleted from our food before we can get a chance to eat it.

There are plenty of fruits and vegetables that contain vitamin C and ideally you want to include a good diversity of both in your diet. Heat damages vitamin C, so it is a good idea to consume fruit and raw vegetables when you can.

Cooking, storing and preparing Food

When you are cooking, use a steamer to lightly cook your vegetables. If you use as little heat and cook them for a shorter period of time you will preserve more vitamin C (5). Cutting fruit and vegetables depletes vitamin C, so only do this just before you want to eat them.

The same goes for storing them. The longer they are stored, the more of the vitamin is lost. Try to do a few shops when you are buying fresh produce. If this isn’t possible, then frozen fruit and vegetables are an excellent way of getting the maximum amount of nutrients from your food as they are often frozen directly after picking which preserves their freshness.   

Foods rich in vitamin C

Broccoli, Brussels sprouts, kale, peppers, chilli peppers, strawberries, lemons, oranges, kiwis, blackcurrants, parsley, thyme.


(1) Carr, A.C. & Maggini, S. (2017) Vitamin C and immune function. Nutrients, 9 (11).

(2) Lobo, V., Patil, A., Phatak, A. & Chandra, N. (2010) Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy Reviews, 4 (8), pp.118–126.

(3) Santosh, H.N. & David, C.M. (2017) Role of ascorbic acid in diabetes mellitus: A comprehensive review. Pathology & Surgery, 4 (1), pp.1–3.

(4) Schectman, G., Byrd, J.C. & Gruchow, H.W. (1989) The influence of smoking on vitamin C status in adults. American Journal of Public Health, 79 (2), pp.158–162.

(5) Yuan, G.F., Sun, B., Yuan, J. & Wang, Q.M. (2009) Effects of different cooking methods on health-promoting compounds of broccoli. Journal of Zhejiang University: Science B, 10 (8), pp.580–588.

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