7 essential vitamins to stay healthy this winter

With a chill in the air and the nights drawing in, winter is almost upon us and with colds and flu inevitably on the increase, it is a good time to re-evaluate your diet to ensure you’re getting the vitamins you need to stay healthy.

There are more than 200 viruses known to cause the common cold, including 100 different rhinoviruses, respiratory syncytial virus (RSV), adenoviruses and four types of non-covid coronavirus, as well as influenza and parainfluenza. In addition, despite the vaccination rollout, covid is likely to peak again [1].

As well as the usual coughs and sneezes, stomach bugs such as norovirus also tend to peak in the winter when our immune system is lowered.

What can cause illness?

There are many factors that contribute to an increase in illness at this time of year, especially post-covid; we are once again spending more time indoors in close contact with others, colder temperatures and lower humidity mean viruses remain in the air for prolonged periods of time and reduced sunlight means we lose the decontaminating effects of ultraviolet rays, all influencing the rate of transmission.

People who suffer from allergies such as asthma or allergic rhinitis may also be at greater risk of illness due to their inflammatory nature leaving them more susceptible to more frequent or severe respiratory infections [2].

As part of the innate immune system, our metabolism is hugely important, it is responsible for supplying us with sufficient energy to fuel our immune cells and protect us from the invasion of potentially harmful microorganisms. Some viruses take advantage of our metabolism, high jacking our metabolic machinery in order to replicate and take over and compromised immune function leads to greater vulnerability to infection. Obesity for example has been shown to impair some immune functions such as the effectiveness of ‘natural killer’ NK cells – crucial in our first line of defence [3].

Even in the absence of allergy or disease, an unhealthy lifestyle can leave us more susceptible to illness, if we are not fuelling our bodies with the required nutrients or allowing enough time for rest and recuperation, we are simply not laying the groundwork needed for robust immune defences. Taking a closer look at our diet to ensure we’re giving our bodies the vitamins and minerals it needs for optimal immune function as well as addressing lifestyle factors such as stress levels and sleep quality will give us the best chance to stay healthy over the winter months.

What vitamins do I need to stay healthy?

Vitamin D

Enhances the immune response against various infections, in particular, upper respiratory infections such as colds, coughs and covid-19. It also works to modulate inflammation in the body, which is a common factor in disease.

In the UK 1 in 6 of us has ‘insufficient’ levels of vitamin D, with over 20% considered clinically deficient [4]. Vitamin D is produced in the skin in response to sunlight during the summer, however in the UK, due to our position on the earth, it is nearly impossible to get enough to sustain us year-round and it is a good idea to supplement.

Foods rich in Vitamin D

Oily, fatty fish such as salmon is the best source of the active form of vitamin D3, along with eggs. For vegetarians and vegans, mushrooms can provide a limited amount of vitamin D2, which is then converted into D3 in the body.

Vitamin C

Vitamin C has long been associated with strengthening the immune system and fighting coughs and colds – this is because it inhibits virus multiplication and improves immune cell function. It has been shown to influence resistance against bacteria and viruses, as well as reduce the severity and length of time we might feel unwell by 1-1.5 days [5]. The body cannot store vitamin C so aim to include multiple sources daily.

Foods rich in Vitamin C

Good sources of vitamin C include broccoli, leafy greens, peppers and citrus fruits.

Vitamin A

Vitamin A supports the immune response by strengthening the integrity of the mucosal lining of our digestive and respiratory tracts and has anti-inflammatory properties.

Several organs involved in the immune response, such as the thymus, which directs white blood cells are reliant on sufficient and regular intake of dietary vitamins and deficiency has been associated with reduced immune response and an increased risk of developing infections [6].

Foods rich in Vitamin A

Good sources of vitamin A include oily fish, eggs, dairy and liver, and its’ plant form beta-carotene in leafy greens, mango, butternut squash, pumpkins and carrots.

Omega 3

Omega 3 (along with omega 6) has important immune regulatory functions, comprised of EPA, DHA and ALA, it is involved in the production of protective immune markers [7]. In addition to this, omega 3 is our no.1 anti-inflammatory nutrient and helps to combat inflammation which is a hallmark and a common cause of ongoing illness or infection.

Food rich in Omega 3

oily fish such as wild salmon, mackerel and herring, vegetarians and vegans can get omega 3 from ground flaxseeds and their oil, as well as walnuts and hemp seeds. Algae-based supplements are another good option.

Zinc

Zinc is a consistent ingredient in immune-supporting supplements and for good reason, zinc can boost general immunity, inhibit the replication of various types of viruses and reduce the risk of respiratory infection. Zinc is crucial for the normal development and function of cells mediating innate immunity such as neutrophils, NK cells and macrophages [8].

Food rich in Zinc

Meat and seafood are the best dietary sources, along with beans, nuts, seeds, eggs and dairy.

Selenium

Selenium supports immunity and lung function by increasing the activity of the antioxidant glutathione. It supports the production of white blood cells and antibodies and is involved in initiating the immune response and regulating inflammation [9].

Food rich in Selenium

Seafood, meat, eggs and brazil nuts are all good sources of selenium.

Pre and probiotics

Supplementing with probiotics and prebiotics has been shown to be beneficial in both the prevention and management of low immunity.

Specifically, Lactobacillus rhamnosus GG [10] is protective against respiratory infections and can be consumed in fermented dairy products like yoghurt, kefir as well as kimchi, sauerkraut, tempeh and miso. Prebiotic fibres such as arabinogalactans are found in the cell walls of plants and can strengthen the immune system. Food sources include – carrots, radishes, pear, wheat, tomatoes, coconut and red wine [11].

What’s the best way to get your vitamins and minerals?

Good nutrition should always come first when it comes to optimising our health, however even when eating a mostly organic, whole-food diet, packed full of all the essentials – colourful fruit and vegetables, quality protein, fibre and healthy fat, it is increasingly challenging for most of us to achieve the recommended levels of micronutrients.

Today’s farming methods including the use of pesticides and chemicals which deplete our soil of key nutrients, hybridised crops and reduced soil quality all mean that fruit and vegetables in the UK contain around half the amount of key nutrients they did in 1940 [12].

In addition, food often travels a long way before arriving on our plates, further depleting the nutrient values.

Buying organic, and local, aiming to eat a diverse and varied diet, being mindful of cooking methods (which can reduce the nutrient content of some foods), supporting digestive health and supplementing can all increase our micronutrient status.

Some supplement companies offer whole food or food state vitamin and minerals which are grown or formulated from natural food sources, therefore, are easily identified, absorbed and utilised by the body.

It is common to find the same ingredients formulated in different ways such as tablets, effervescent tablets, capsules, liquids and sprays, which vary in terms of bioavailability, but the decision is often down to practicality rather than efficacy so choose a formulation that works for you.

Can I take too many vitamins?

Water-soluble vitamins such as vitamin C and B vitamins need to be consumed daily as they are not stored in the body and are quickly utilised and excreted, for this reason, it is difficult to take too much.

Fat-soluble vitamins, however, such as Vitamin A, D, E and K are absorbed and stored in fat tissues and the liver and can be toxic at high levels.

Summary

It’s important to ensure your diet is giving your body all the key nutrients it needs to support your immune system during the winter months when cold and flu viruses are more common in the general population. The best approach is to eat foods rich in the key vitamins you need, with the exception of vitamin D which is best taken as a supplement during the winter months.

Author: Becky Graham Nutritionist BA(Hons) Dip ION mBANT