The benefits of seasonal eating

This article was written by one of our regular contributors; medical student with a BSc in human nutrition + MSc in clinical and public health nutrition – Rebecca Fox.

What is seasonal eating?

Seasonal eating involves consuming produce at a time of the year when it becomes naturally ready to harvest. Different types of fruits and vegetables have their own set of conditions for ideal growth, and differ depending on where you are in the world. For example, in the UK this would mean tucking into a juicy apple in September or cutting up crisp asparagus in June. 

Being able to eat seasonally seems straightforward, but has been made more complex by our increasingly globalised food system. For this reason, the UK Department of Environment, Food and Rural Affairs has come up with a nice definition of seasonality based on where the food was grown vs where it was consumed [1]:

I) Local Seasonality: Refers to foods that are both produced and consumed locally.

II) Global Seasonality: Food that is produced in season in one part of the world, but consumed in another. 

Why is it good to eat things that are in season?

Eating seasonally is beneficial both for both our health and the environment. 

Health Benefits

In terms of health benefits,  it has been shown that the nutrient content of fruits and vegetables varies according to season, climate and level of ripeness. However, it has been shown that produce is more nutrient-rich right after being harvested. For example, turnips have been shown to have the highest antioxidant and vitamin content in autumn — when they’re most ripe [2] , whereas the antimicrobial and antioxidant content of rosemary, seems to be the highest in the summer [3].

When many fruits and veg are picked in other parts of the world and shipped to their destination (i.e. your local supermarket), they end up sitting in storage for a while as a result. Storage conditions, including temperature (refrigeration/freezing), light levels and time stored may affect antioxidant and other nutrient levels in fruits and veg [4].  For example, antioxidant levels in cruciferous vegetables such as broccoli, cabbage, and brussels sprouts  have been shown to be reduced by 7-46% after being stored for just 1 week at 1℃ [5]. Similarly, the antioxidant content of cherries tends to decrease with storage at cool temperatures [6]. 

Environmental Impact

Environmentally speaking, growing, transporting and selling produce contributes a sizable carbon footprint. Greenhouse gases are produced in many stages of the growing, processing, distribution and retail aspects of food production- accounting for around 20-30% of total greenhouse gas emissions in the UK [7]. However, studies have shown that carbon emissions related to globally seasonal foods aren’t necessarily higher than locally grown produce. Take tomatoes for example. Tomatoes are only able to grow in the UK during the spring/summer months outdoors. Since we all love to have fresh tomatoes year-round, some of them would need to be grown indoors in big commercial greenhouses when the weather cools down. However, these commercial greenhouses require a lot of energy to maintain and therefore have a higher carbon footprint than transporting tomatoes from countries like Spain where the climate is conducive to growing tomatoes in the UK off-season [8]. The same goes for apples grown in New Zealand vs the UK. It turns out that importing apples from New Zealand right after they’re picked (i.e. during the UK winter) may have a lower environmental impact than storing them locally for long periods of time in refrigeration units [12].

Now, that’s not to say that shipping produce doesn’t contribute any greenhouse gases. Bananas imported from Ecuador and consumed in Europe, for example, have an estimated carbon footprint of 1.28 tonnes of CO2 per tonne of bananas [9]. To put that into perspective, that’s the equivalent amount of energy it would take to drive an average car 5,177 kM.  

Essentially, it seems that produce both grown outside during their natural growing season without any additional energy (greenhouses, lamps etc.) and consumed in the same region have the lowest environmental impact [10]. So, the way to eat sustainably is to consume produce that is grown close-to-home using natural sunlight. 

It’s also important to remember that sustainable eating is complex and impacted by many different factors, and seasonal eating is just one part of this. In the grand scheme of things, our fruit and vegetable intake has a smaller environmental foot-print than consuming a lot of animal-based products and other factors beyond food like car and airplane use.  

Something to Think About

Globalisation has allowed us all to try a tremendous variety of nutrient-rich fruits and vegetables from around the world, giving us all a bit more choice when it comes to our 5-a-day. In a perfect world, it would be wonderful if everyone was able to grow, sell, and consume the same variety of produce grown in-season and close-to-home. Many areas of the world, though, have climates that are not necessarily conducive to growing the variety of fruit and vegetables we have all become accustomed to (avocados in Northern Canada anyone?).  As well, in the UK, the National Diet and Nutrition Survey indicates that only 31% of adults and 9% of children meet their recommended 5-a-day intake for fruits and vegetables [11]. So, since the UK climate allows a limited variety of produce production, consuming fruits and vegetables that are only local and seasonal may reduce the number of choices available, and may impact people’s nutritional intake.

However, that’s not to say that small efforts aren’t worthwhile. We can all do our part to try to eat as seasonally, and locally as possible within our means. Consuming frozen and tinned fruit and vegetables is another way of including a bigger variety of plants in your diet, as these can be stored for a long period of time and consumed out of season. 

How do I eat more seasonally?

There are a number of different ways we can try to eat more seasonally:

→ Gardening: try growing your own fruit or veg in your own allotment! Check out our other piece to get some ideas on how to start

→ Shop at farmers markets

→ Be aware of what foods are in season, and choose these most of the time. There are a number of great resources available to let you know what produce is in season for your region and it’s well-worth a google (also check out our season guide – linked below!).

What Foods are in Season?

Take a look at our our guide to seasonal eating below for some tips on which fruits and veg are in season!

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References

1. Stelmach-Mardas M, Kleiser C, Uzhova I, Peñalvo JL, La Torre G, Palys W, Lojko D, Nimptsch K, Suwalska A, Linseisen J, Saulle R. Seasonality of food groups and total energy intake: a systematic review and meta-analysis. European journal of clinical nutrition. 2016 Jun;70(6):700-8.
2. Aires A, Fernandes C, Carvalho R, Bennett RN, Saavedra MJ, Rosa EA. Seasonal effects on bioactive compounds and antioxidant capacity of six economically important Brassica vegetables. Molecules. 2011 Aug;16(8):6816-32.
3. Lemos MF, Lemos MF, Pacheco HP, Endringer DC, Scherer R. Seasonality modifies rosemary’s composition and biological activity. Industrial Crops and Products. 2015 Aug 1;70:41-7.
4. Tiwari U, Cummins E. Factors influencing levels of phytochemicals in selected fruit and vegetables during pre-and post-harvest food processing operations. Food Research International. 2013 Mar 1;50(2):497-506.
5. DuPont MS, Mondin Z, Williamson G, Price KR. Effect of variety, processing, and storage on the flavonoid glycoside content and composition of lettuce and endive. Journal of agricultural and food chemistry. 2000 Sep 18;48(9):3957-64.
6. Gonçalves B, Landbo AK, Knudsen D, Silva AP, Moutinho-Pereira J, Rosa E, Meyer AS. Effect of ripeness and postharvest storage on the phenolic profiles of cherries (Prunus avium L.). Journal of Agricultural and Food Chemistry. 2004 Feb 11;52(3):523-30.
7. Garnett, T (2008) Cooking Up a Storm: Food, Greenhouse Gas Emissions and Our Changing Climate. Surrey: University of Surrey, Food Climate Research Network, Centre for Environmental Strategy
8. Edwards-Jones G. Symposium on ‘Food supply and quality in a climate-changed world’. Proceedings of the Nutrition Society.;69:582-91.
9. Roibás L, Elbehri A, Hospido A. Carbon footprint along the Ecuadorian banana supply chain: Methodological improvements and calculation tool. Journal of Cleaner Production. 2016 Jan 20;112:2441-51.
10. Macdiarmid JI. Seasonality and dietary requirements: will eating seasonal food contribute to health and environmental sustainability?. Proceedings of the Nutrition Society. 2014 Aug;73(3):368-75.
11. Bates, B, Lennox, A, Prentice, A et al. (2011) National Diet and Nutrition Survey: Headline Results from Years 1, 2 and 3 (Combined) of the Rolling Programme 2008/09–2010/11. London: Department of Health
12. Edwards-Jones G. Does eating local food reduce the environmental impact of food production and enhance consumer health?. Proceedings of the Nutrition Society. 2010 Nov;69(4):582-91.