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Is seasonal eating the key to winter health?

Nutritionist Sophie Lester chats about whether seasonal eating can support your health and immune system this winter. 

Dark mornings, dark nights and freezing temperatures – yep, winter has definitely arrived and just to add the icing to the Christmas cake, so has the influx of colds, the flu and mood swings.

For most people this time of the year is spent getting ready for the festivities and planning for the New Year and unfortunately, thinking about our health is often an afterthought. During the winter months, not only are we more susceptible to colds and the flu, but we can also experience a case of the ‘winter blues’. This increased feeling of ‘bleh’, brought on by the change in weather is characterised by dips in mood, energy and can end up with us staying inside eating our way through the chocolate box we bought for the in-laws… But never fear, there are things we can do to help ourselves enjoy the festivities whilst also feeling our best!

Eating for winter health

Ensuring you have a varied and balanced diet is key to supporting your immune system – don’t worry, I’m not going to tell you to put the mince pies down! Instead, I am going to discuss the advantages that seasonal foods can provide this winter.  

While no food alone can “boost” your immune system, poor nutrition, such as an inadequate quantity and variety of fruit and vegetables, can have a negative effect on your body’s ability to fight viral infections such as colds [1]. Eating a surplus of fruit and vegetables, along with a balanced diet (and no, I don’t mean a mince pie in each hand), can offer you all of the nutrients you need to stay healthy this winter. 
 

Winter

So, what fruit and vegetables are available in the UK at this time of year? 

 

Apples

Apples are an excellent source of fibre. The fibre in apples is a soluble type of fibre called pectin. Not only is fibre a superb way to feel ‘fuller for longer’ and therefore reduce snacking throughout the day, but this soluble type of fibre may also offer extra benefits. Soluble pectin fibre can actively lower cholesterol in your blood [2] – if you want to boost the quantity of fibre in your apples, eat them unpeeled. 

Beetroots

Beetroots are a rich source of nitrates. Nitrates are beneficial chemicals which scientists have proposed to trigger vasodilation (a fancy scientific word which means they relax our arteries). This leads to a reduction in blood pressure. One study by the British Heart Foundation found that patients with high blood pressure who drank a 250 ml glass of beetroot juice every day reduced their blood pressure significantly! [3] An excellent reason to have a glass of the pink stuff (we mean beetroot juice… not rosé wine).

Brussels sprouts

Brussels sprouts are an excellent source of beneficial chemical compounds called glucosinolates. These compounds are responsible for the bitter taste of sprouts and are thought to be a plant defence mechanism – to stop us eating them! Mmmm … When eaten by us, glucosinolates have a protective effect on our bodies. An increasing number of scientists have found that glucosinolates are potentially anti-carcinogenic (they may protect us from cancer) [7]. Although more research is needed to confirm this - you have no excuse for not eating yours! 

Squash and pumpkins

Squash and pumpkins are brightly coloured in orange, red and yellow tones because they naturally contain a compound called carotenoids. Our bodies can transform plant-based carotenoids into Vitamin A, which supports immune function, eyesight and our reproductive system. If you want to maximise the quantity of carotenoids in your squash, we suggest roasting them. When boiling, the carotenoids escape out of the vegetable into the water… and down the drain. Along with roasting, try eating yours with olive oil which can enhance your body’s ability to absorb carotenoids [8]. 

You can test your body’s Vitamin A levels using our Medichecks Vitamin A (Retinol) Blood Test.

Mushrooms

Mushrooms are an excellent source of Vitamin D. To get an extra boost of Vitamin D from your mushrooms, try placing yours on the windowsill on a sunny day. No, we have not lost the plot (!) - like us humans, mushrooms can produce Vitamin D in their skins [9], so this is a genius way to get more Vitamin D in your diet. A high number of adults in the UK are deficient in Vitamin D [10]. So we are recommended to take a 10 ug daily supplement throughout the winter months.

You can test your own Vitamin D levels using our Medichecks Vitamin D (25 OH) Blood Test

The advantages of seasonal eating

•    Seasonal fruits and vegetables can offer you fresher food, and therefore tastier food, at this time of year. 
•    Buying seasonal foods in the UK often means supporting local farms and businesses, and therefore helps our economy. 
•    Seasonal food may cost less money to buy in the supermarket, as they use fewer resources to produce and store. 
•    Eating seasonally, whether the food is grown in the UK or abroad, can reduce greenhouse gas emissions because less energy (such as heat) is invested into growing the food [4].

What about eating out of season?

Though seasonal produce is an excellent choice for freshness, flavour, and supporting local businesses, we should not be afraid to continue eating non-seasonal fruit and vegetables. Non-seasonal fruit and vegetables, which have been frozen, tinned or stored, still count as 1 of your 5 a day. What’s more, you’d be surprised to hear that many nutrients, such as Vitamin C, can be really well preserved over time. 

In fact, one study found that the Vitamin C content in frozen peas was higher than in fresh! [11]. So, it could be argued that it would be much better to have your peas and eat them – whether they are in season or not.

In addition, storing fruit and vegetables are an excellent way to combat food waste and therefore contributes to helping the environment. In our UK households, it is estimated that we throw away 4.5 million tonnes of edible food waste a year [12], so we all must do our little bit to help where we can.

How about preserving seasonal foods?

You may even want to try fruits and vegetables which have been preserved to last longer than their season – this way, you will have an adequate supply of vegetables all year round. You could even try preserving some seasonal foods yourself - by the way, homemade pickles make excellent Christmas presents (hint, hint).

One way to preserve foods is through fermentation. Some fermented foods offer extra health benefits because they contain probiotics. Probiotics are a source of ‘friendly bacteria’ which can beneficially affect our health by improving the balance and function of the gut bacteria [5].

There has been increasing attention around the role of a healthy gut in maintaining a healthy immune system. Probiotics are thought to have a positive effect on our immune system* [6] and some studies have even shown that eating probiotics can make colds last for a shorter length of time! [5]. Probiotics have no major health claims yet, but it is an exciting area of ongoing research, so keep your eyes (and pickled onions) peeled…

Some examples of preserved fermented foods with potential probiotic benefits include:
Yoghurt: an excellent source of friendly bacteria, look for ‘live cultures’ on the packet
Kimchi: a Korean side dish flavoured with spices and chilli
Sauerkraut: a European dish made from shredded cabbage
Kombucha tea: a slightly fizzy, sweetened tea drink thought to originate in Asia

*If you have a health condition which means your immune system does not function properly, you may be at risk when taking a probiotic so should seek a doctor’s advice.

Take care this winter.

To summarise, it is important to take care of our physical and mental health during the winter months as we are particularly susceptible to colds, the flu and feeling down. By supporting our bodies from the inside, with a diet full of fruits and vegetables, we can improve our health, wellness and our relationship with the planet.

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References

[1] Calder, P.C., Carr, A.C., Gombart, A.F. and Eggersdorfer, M., 2020. Optimal nutritional status for a well-functioning immune system is an important factor to protect against viral infections. Nutrients12(4), p.1181.

[2] Brouns, F., Theuwissen, E., Adam, A., Bell, M., Berger, A. and Mensink, R.P., 2012. Cholesterol-lowering properties of different pectin types in mildly hyper-cholesterolemic men and women. European journal of clinical nutrition66(5), pp.591-599.

[3] Kapil, V., Khambata, R.S., Robertson, A., Caulfield, M.J. and Ahluwalia, A., 2015. Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study. Hypertension65(2), pp.320-327.

[4] Macdiarmid, J.I., 2014. Seasonality and dietary requirements: will eating seasonal food contribute to health and environmental sustainability?. Proceedings of the Nutrition Society73(3), pp.368-375.

[5] https://www.bda.uk.com/resource/probiotics.html

[6] Galdeano, C.M., Cazorla, S.I., Dumit, J.M.L., Vélez, E. and Perdigón, G., 2019. Beneficial effects of probiotic consumption on the immune system. Annals of Nutrition and Metabolism74(2), pp.115-124.

[7] Traka, M. and Mithen, R., 2009. Glucosinolates, isothiocyanates and human health. Phytochemistry Reviews, 8(1), pp.269-282.

[8] Arranz, S., Martínez-Huélamo, M., Vallverdu-Queralt, A., Valderas-Martinez, P., Illán, M., Sacanella, E., Escribano, E., Estruch, R. and Lamuela-Raventos, R.M., 2015. Influence of olive oil on carotenoid absorption from tomato juice and effects on postprandial lipemia. Food chemistry168, pp.203-210.

[9] Phillips, K.M. and Rasor, A.S., 2013. A nutritionally meaningful increase in vitamin D in retail mushrooms is attainable by exposure to sunlight prior to consumption. Journal of Nutrition & Food Sciences, 3(6), p.1.

[10] Davies, J.H. and Shaw, N.J., 2011. Preventable but no strategy: vitamin D deficiency in the UK.

[11] Bouzari, A., Holstege, D. and Barrett, D.M., 2015. Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage. Journal of agricultural and food chemistry63(3), pp.957-962.

[12] https://wrap.org.uk/sites/files/wrap/Progress_against_Courtauld_2025_targ