Anthony Glock, Junior Physiologist at AXA Health

Winter nutrition

30 November 2020

Winter is approaching and with it comes nasty colds and flus and, for some, the ‘winter blues’. AXA Health Junior Physiologist Anthony Glock explains how we can use nutrition to reduce our risks of catching colds and preventing the winter blues from getting the better of us. 

Immune system

Most of us link the winter months to cold weather and the desire to stay warm. The flu virus, among others, thrives in this lower temperature and consequently increases our risk of getting ill. While we can’t eliminate colds altogether, we can provide our bodies with the right nutrients to ensure our immune system is operating at its best.

There are numerous vitamins and minerals that can assist in boosting our immune system, such as vitamins A, C, D & E, zinc, iron and selenium. While consuming adequate amounts of these vitamins and minerals is essential for a healthy immune system, there are ways in which our immune system can be weakened. This includes alcohol consumption, lack of sleep and, in some extreme cases, exercising too often and at too high an intensity (more common in ultra-endurance athletes). We can help prevent exercise weakening our immune system by ensuring we are properly fuelled beforehand and by allowing our bodies to recover in between bouts of exercise. Eating plenty of carbohydrates before and after, along with adequate protein, can help fuel the body and aid recovery. Striving for plenty of fruits and vegetables will offer an abundance of antioxidants to further assist this process.

Mood

Many people dislike the winter and often experience a dampened mood during this time when compared with summer. For some, it can lead to depression, otherwise known as Seasonal Affective Disorder (SAD), where the symptoms are experienced in a seasonal pattern. It appears that the lower light levels associated with winter, due to the shorter days, could be affecting our serotonin levels and, therefore, our mood. Serotonin is a chemical in the body that is produced from an amino acid (tryptophan) and, when released in the body, often contributes to feeling of happiness. Coinciding with this, reduced light exposure can affect our food choices by making us crave more sugary treats, as they have the ability to lower amino acid levels in the brain, allowing the precursor to serotonin, (tryptophan) to be picked up. While we may crave sugary treats, such as chocolate, we can boost our serotonin levels with complex carbohydrates such as whole grain foods and sweet potato. They will be kinder on our waistline and are much more nutrient-dense with vitamins, minerals and fibre.

There is some research that links antioxidant intake to decreased tryptophan breakdown. When less tryptophan is being broken down, a greater abundance is available in the brain to be used to create serotonin. We can also get tryptophan from our diets; however, due to competition with other amino acids in the brain, we can’t significantly increase tryptophan levels with dietary tryptophan. While we can’t increase serotonin levels from eating tryptophan-high foods, it is recommended to still eat adequate amounts of protein, to ensure tryptophan is available for the brain.

Evidence suggests that vitamin D, which is made by the body after exposure to sunlight on the skin, can play a role in serotonin production. This comes down to the effects it has on melatonin; after exposure to sunlight, there is an inhibitory effect on melatonin receptors to melatonin. Less binding on these receptors leads to an increase in serotonin levels and a potential boost in mood. Other nutrients such as magnesium and omega 3 have shown positive effects on symptoms of depression. This highlights the importance of eating a healthy balanced diet has, not just on our physical health but the protective role it can play in our mental health as well.

Bone health

During the winter months, we get a limited amount of sunlight exposure meaning that many of us won’t get enough vitamin D. Vitamin D plays a role in serotonin production and our immune systems, but it also plays a pivotal role in our bone health. Vitamin D is required for calcium to effectively used to support our bones. It is difficult during the winter to get adequate amounts of vitamin D from the sun, which can lead to our bones becoming weaker unless we seek alternative sources. In fact, research has shown that our bone density can decrease between 0.3-0.9% a year if we don’t get enough vitamin D. This can be problematic as we get older for it can lead to osteoporosis and increase our risk of fractures from falls. The risk of falls increases over the winter months due to the weather conditions as rain and ice can make surfaces very slippery.

It is important therefore to increase our vitamin D intake. Luckily, we can achieve this through our food as well as sunlight exposure. There are a range of vitamin D fortified products such as cereals and milk alternatives, but we can also find vitamin D naturally in oily fish like salmon and sardines. If due to dietary restrictions you can’t consume those foods you can look at supplementing with vitamin D however, always consult with a GP prior to taking any supplementation to work out what is best for you.

Vitamin & mineral sources

All of the following minerals and vitamins play an important role in supporting our immune function. Use the list below to see how you can boost your intake through different foods.

Vitamin A: Spinach, carrots, sweet potatoes, eggs, oily fish, liver, mango, red peppers etc.

Vitamin C: Oranges, orange juice, peppers, strawberries, blackcurrants, broccoli, potatoes and Brussel sprouts.

Vitamin D: Sunlight (main source), oily fish, red meat, liver, egg yolks and fortified foods such as spreads and cereals.

Vitamin E: Plant oils (soya, corn and olive oil), nuts, seeds and wheatgerm.

Antioxidants: Grapes, blueberries, red berries, nuts, dark green vegetables like spinach, sweet potatoes, beans and fish.

Calcium: Milk, cheese, other dairy foods, broccoli, cabbage, soya beans, tofu, nuts, fish (if bones are eaten e.g. Sardines and pilchards), fortified milks and breads.

Iron: Liver, meat, beans, nuts, dried fruits, wholegrains, most dark green veg such as watercress and kale.

Magnesium: Green leafy veg like spinach, nuts, brown rice, bread (wholegrain), fish, meat and dairy foods.

Omega 3: Mackerel, salmon, herring, oysters, sardines, anchovies, flaxseeds, chia seeds and walnuts.

Selenium: Brazil nuts, fish, meat and eggs.

Tryptophan: Salmon, poultry, eggs, spinach, seeds, nuts and soy products.

Zinc: Meat, shellfish, dairy foods, bread and cereal products.

It’s important to stay warm during the winter, but also to continue with healthy eating habits to ensure your immune system, mood and bone health is functioning optimally.

References

Barr, T. et al. Opposing effects of alcohol on the immune system. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 65, pp. 242-251. (2016)

Christensen, L. The effect of food intake on mood. Clinical Nutrition, 20, pp.161-166. (2001)

Getz, L. Winter Nutrition — Healthy Eating Offers Good Protection During the Chilly Season. Todaysdietitian.com. (2009). Accessed 26 Sep. 2019.

Hahn, I. et al. Does outdoor work during the winter season protect against depression and mood difficulties?. Scandinavian Journal of Work, Environment & Health, 37(5), pp.446-449. (2011)

Lambert, G. et al. Effect of sunlight and season on serotonin turnover in the brain. The Lancet, 360(9348), pp.1840-1842. (2002).

Lansdowne, A. and Provost, S. Vitamin D 3 enhances mood in healthy subjects during winter. Psychopharmacology, 135(4), pp.319-323. (1998).

Null, G. et al. Nutrition and Lifestyle Intervention on Mood and Neurological Disorders. Journal of Evidence-Based Complementary & Alternative Medicine, 22(1), pp.68-74. (2016).

Partonen, T. Vitamin D and serotonin in winter. Medical Hypotheses, 51(3), pp.267-268. (1998).

Strasser, B. et al. Mood, food, and cognition. Current Opinion in Clinical Nutrition and Metabolic Care, 19(1), pp.55-61. (2016).

Wurtman, R. and Wurtman, J. Carbohydrate craving, obesity and brain serotonin. Appetite, 7, pp.99-103. (1986).

www.nhs.co.uk 

Got a health question?

We’re here to help you take care of your health - whenever you need us, wherever you are, whether you're an AXA Health member or not.

Our Ask the Expert service allows you to ask our team of friendly and experienced nurses, midwives, counsellors and pharmacists about any health topic. So if there's something on your mind, why not get in touch now.