Forget what you think you know about fighting off colds; vitamin C, echinacea and decongestants aren’t the best way to keep yourself fit and healthy through the winter, and in the case of decongestants may even do more harm than good. The science-backed approach is to look instead at some surprising alternative candidates for winter health: vitamin D, protein and wearing a hat - although maybe not for the reason you think.
Vitamin D, the sunshine vitamin: why you need it and where to get it
Deficiency in vitamin D has been linked to a number of health problems, not least of which is a weakened immune system. People with low vitamin D levels tend to have more sick days, catch more upper respiratory tract infections (such as colds, flu and COVID) and suffer more severe symptoms for longer than people with adequate vitamin D. It’s thought that vitamin D is crucial to the effective production and functioning of immune cells that fight pathogens (anything that invades the body and can cause disease e.g. allergens, viruses and bacteria), so it makes sense that when vitamin D is in short supply, your system as a whole is poorly equipped to deal with the invaders.
There are two main sources of vitamin D: your diet, and sunlight. When cholesterol in your skin is exposed to ultraviolet B (UVB) rays from the sun, it is converted into vitamin D. During the height of summer we will be producing plenty of vitamin D and storing any that we don’t use in the liver. Unfortunately, the low-intensity of the winter sun isn’t strong enough to stimulate the conversion of cholesterol so the majority of people will enter winter already vitamin D deficient. People with darker skin are also prone to low levels of vitamin D, as the melanin acts as a barrier and makes vitamin D synthesis from sunlight more difficult.
While getting outside as much as you can will give you many other benefits, at this time of year you will also need to increase you dietary intake of vitamin D rich foods . Food sources include:
- Oily fish (e.g. salmon, swordfish, tuna or sardines) and fish liver oils
- Egg yolks
- Milk and dairy products
- Tofu and some mushrooms (including portobello, shiitake, morel and button mushrooms)
- ‘Fortified’ foods with added vitamin D may help
Consider eating these foods as part of a meal with plenty of healthy fats as that will increase your absorption of their vitamin D. If you are in doubt, you should also have your levels checked with a simple blood test to find out if you could benefit from a vitamin D supplement.
Keep your nose warm
When heading out in the colder weather you will do well to heed your mother’s advice and wear a hat and scarf to keep you cosy. Make sure your nose stays warm. Inside your nasal cavity are your first defences against the viruses and bacteria that we breathe in. Billions of immune cells are primed to attack the next opportunistic invader. But they don’t like the cold. Reducing the temperature in your nose by just 5°C kills nearly half of your defenders. This leaves us with a greatly diminished resistance to invading air-borne viruses like the common cold, flu and COVID, and also to any pathogens already living in our airways, waiting for a window of opportunity to take hold.
Build a stronger immune defence with protein
Protein is often referred to as providing the ‘building blocks’ for our bodies as it is found in every single cell. Research has shown that a deficiency of protein (or its constituents, amino acids) negatively affects immune function and makes us more susceptible to infectious diseases.
So, if you want to stop viral infections like colds and flu in their tracks, you need to make sure that you are eating enough protein every day. Good sources of protein include:
Primary proteins- all meats, poultry, fish, eggs and dairy .
And secondary proteins (plant based) which need careful consideration to balance for a full protein profile.
- Legumes like beans and peas
- Nuts and seeds
Manage your blood glucose
While we can support our immune system by providing it with all the nutrients that it needs, we should also look to avoid causing it damage. A diet high in ultra-processed foods, refined carbohydrates and added sugars is associated with insulin resistance, elevated blood glucose and inflammation. In turn, these have been shown to interfere with several mechanisms in our immune system, leaving us more susceptible to infection and more severe symptoms.
The best thing you can do to defend against infection is maintain your health all year round, including making sure you get some level of exercise. But regular exercise can also help you mount a rapid response in the presence of a virus. When we exercise it stimulates white blood cell production to repair our muscles. White blood cells are also a key part of our immune response. So, if you are exercising regularly the production line of white blood cells will be already up and running. If you get an infection those cells may then be redirected to fighting that infection, without you having to wait for them to be made from scratch. It is also important that if you do v C’some down with cold and flu like symptoms and are poorly that stop exercising and that you don’t push yourself to keep exercising or you will be overstretching your immune system.