seasonal eating for optimal immune function
At the end of summer when that first nip is in the air, it marks the start of cold and flu season.
During our lifetime we experience an average of 200 colds – that’s 5 years of coughs, congestion, headaches and sore throats. These are generally the result of viral infection of the upper respiratory tract. The common cold is usually harmless although it might not feel that way at the time. The most common cold-causing culprits are the rhinovirus family of which there are around 160 different cold-causing ‘serotypes’ making it possible to have several colds one after another. Viruses change how they ‘look’ to your immune system frequently through mutations in their genetic code. This allows them to evade any prior immunity we might have formed and means our immune system has its work cut out. It also explains why we tend to get repeated coughs and colds throughout our lives.
While the immune system is always active, it has seasonal variations
It’s not just infections that are more common in winter
Although you can catch a cold in any season, Rhinoviruses prefer cooler climes. This explains in part why viral coughs and colds are more prevalent in winter. Studies show that the immune system is stronger during the summer. In addition, Lower infection-fighting UV light in the dark winter months combined with cold-induced changes to the nasal immune system contributes to increased winter susceptibility. Cooler weather drives people close together indoors without opening windows for ventilation - perfect conditions for germs to spread. Lack of sunlight leads to a drop in our vitamin D levels - another key factor in the immune system’s infection defence.
It’s not only those seasonal runny noses that we all seem to suffer more in winter, Winter darkness can leave us waking feeling groggy, tired and demotivated. A host of health conditions including heart attacks and strokes and even depression are all more common in winter, while people tend to be healthier in the summer.
There is now empirical evidence supporting the common belief that seasonal changes in infections and other health conditions are also down to seasonal changes in our immune system. Evolution has equipped animals with innate timing mechanisms - internal “clocks” - that synchronize our physiology to reflect the varying challenges that recur during the different seasons. Irrespective of how good your immune system is, it is not constant across the seasons.
For example, studies have shown that the levels of certain immune cells in the blood, such as lymphocytes, neutrophils and natural killer cells, vary throughout the year. Additionally, the levels of certain inflammatory molecules, such as cytokines and C-Reactive Protein (CRP), have also been shown to fluctuate seasonally.
These changes are primarily attributed to the varying activity of genes in our immune cells responding to environmental cues. Primarily the length of day and to a lesser extent air temperature and humidity. Some genes become more active in the summer months, while others became more active in the winter. For example, one gene involved in the body's anti-inflammation response is increased during the summer, while some involved in inflammation are increased in the winter when there is an increased chance of viral infection so the threshold required to trigger an immune response is lower. The human immune system will adapt to different seasonal variations with more pronounced differences between winter and summer as you move further from the equator.
In addition to daylight, there may also be other factors that influence the seasonality of the immune response including changes in sleep patterns, stress levels, vitamin D levels and social behaviours but these are, by-in-large much more minor contributors.
It is important to note that while the immune system may exhibit seasonal variation, it is still active year-round and can respond to infections and other challenges at any time. Additionally, other factors, such as age, genetics, and underlying health conditions, can also influence the immune response.
Eat seasonally to support your body’s needs.
Have you noticed that you crave different foods at different times of the year? There is something fundamentally human about following the ebbs and flow of the seasons through our daily recipes and rituals. Seasonal eating is the practice of consuming foods that are in season during a particular time of year. This means eating foods that are grown and harvested locally, rather than relying on imported produce that may have been shipped from far away. There are many benefits to seasonal eating, both for our immune health and for the environment.
Seasonality for health & much more
The natural cycle of produce is perfectly designed to support our health. For example, cold weather brings a desire to eat warming hearty foods seasoned with spices each with unique flavours and antimicrobial qualities that not only reflect their natural growing season but meet the specific nutritional demands of our immune system when infection risk is higher. And in the heat of summer, juicy fruits like berries bursting with antioxidants that also offer a refreshing treat on a sunny day. Our local environment has our immune systems’ nutritional needs covered with the unique qualities of seasonal produce. Building a lifestyle around seasonal foods can facilitate the body's natural needs. But there are other benefits too.
Better nutrition, flavour and variety
Seasonal foods are often fresher and more nutrient-dense than out-of-season produce. When fruits and vegetables are grown in season, they are able to ripen naturally and fully develop their flavour and nutritional profile. On the other hand, when produce is grown out of season and transported long distances, it may be picked before it has fully ripened, and may lose some of its nutritional value during transit. Eating seasonally also means you are more likely to eat the freshest produce and consume it at the time it was ripened – this is now known to preserve its phytonutrient properties.
Seasonal eating can have a significant impact on diet diversity by promoting the consumption of a wider range of fruits and vegetables. When we eat with the seasons, we are more likely to try new and different types of produce that may not be available year-round. Eating seasonally also encourages us to experiment with new recipes and cooking techniques. When we have a variety of seasonal produce at our disposal, we may be more motivated to try new recipes or experiment with different cooking methods to make the most of what is available. By increasing diet diversity through seasonal eating, we can improve our overall nutrient intake and support a healthy gut microbiome.
Community, cost and sustainability
Eating seasonally creates a sense of community, is more like to come from smaller-scale producers and benefits the local economy. It can be a great way to build community and connect with others who share your values. Joining a community-supported agriculture group or shopping at a local farmers' market can help you meet local growers and learn more about where your food comes from. Recently we took membership with the local farm My Little Farm which is a place to not only be involved in growing and harvesting seasonal food but also to connect with others and create a community of people who have shared values.
Seasonal foods are often cheaper than out-of-season produce since they are in abundance during their peak harvest time. This can help you save money on groceries, and also support local farmers and markets. Eating seasonally also has environmental benefits. When we consume foods that are grown locally and in season, we reduce our carbon footprint by decreasing the distance that food needs to travel to get to our plates. This can help to reduce greenhouse gas emissions and support local agriculture but is also known to improve the nutrient quality of produce.
When food is grown outside of its season or natural environment it needs a lot more human assistance in form of pesticides, to grow and look appealing to us. By choosing local and seasonal food, you are also more likely to get produce grown with minimal artificial support! And although there might not be much difference between the vitamin and mineral content, produce grown without pesticides can have up to 100 times more phytonutrients.
TOP TIPS TO SASS UP YOUR SEASON:
Think food first – focus on phytonutrient-rich meals before pill-popping vitamins & minerals.
Shop small & shop local – up your intake of seasonal produce by looking for local growers and farmers markets.
Economy and environment – when foods are in season, the price can go down. It’s also environmentally friendly.
Get creative – Eating seasonally forces you to cook more and challenges your creativity; google a new recipe, or come up with a dish
Herbs and spices – an excellent way to increase diversity and variety in your meals is to add seasonal herbs and spices. They often pack a huge phytonutrient punch too.