Healthy through the winter - How to strengthen your immune system

When it gets wet and cold outside, the number of infections rises sharply. There are many reasons for this, but fortunately there are also many ways to strengthen the immune system and thus make the body's own defenses fit for the winter.

The corona pandemic is currently showing once again that infections really feel at home and spread in leaps and bounds when the year draws to a close, when flip-flops and summer dresses are swapped for winter boots and thick coats. But what is this actually due to?

The influence of the seasons

First of all, it is important to note that the pathogens that cause flu and flu-like infections (we'll get to the difference in a moment) are in "summer sleep". However, the environmental conditions and living habits of people are different. On the one hand, there is the mostly dry and, above all, warm air, which is anything but an ideal habitat for pathogens. In addition, life in the warm months takes place much more outdoors, which on the one hand strengthens the immune system, but on the other hand also makes it more difficult for pathogens to spread.

In this context, the results of a study from 2015 are exciting, in which researchers found that a good 5,000 of the almost 23,000 genes in the human body are active differently in summer and winter. This provided genetic evidence for the apparent changes in our immune system over the year. For our latitudes, it was shown that such genes, which primarily serve the defense against infections, are more active in summer than in winter. Vitamin D in particular plays an important role in this. Since the hours of sunlight are fewer in winter and life takes place more indoors, many people have a vitamin D deficiency. Together with cold temperatures, this weakens the immune system.

Those who take vitamin D regularly also need vitamin K2. Vitamin D3 controls the absorption of calcium, while vitamin K2 ensures that this calcium reaches where it is needed in the body - i.e. the bones. At the same time, it prevents calcification - the storage of calcium in places where it is not wanted.

The combination of vitamin D3 and K2 thus works more effectively and is even better absorbed by the body! We use the highest quality raw material on the market for vitamin K2 (Micro-encapsulated all-trans vitamin K2 (MK-7) from Kappa Bioscience). The most stable form of K2 has the highest bioavailability and thus develops the most lasting effect.

Not to be confused: flu and flu-like infection

In autumn and winter, our immune defenses are weaker than in spring and summer and therefore more susceptible to the very pathogens that transmit flu-like infections and the "real" flu (influenza).

Flu-like infections are infections that can be triggered by a whole range of different viruses and are characterized by flu-like symptoms. They are also commonly referred to as the common cold, although it should be emphasized that the cause of a cold is always a pathogen. Cold can facilitate transmission, but alone does not cause an infection. The course of the infection can vary greatly. If the pathogen meets a strong immune system, it is quite possible that no or only a few symptoms appear. If the immune system is weak, however, an influenza infection can bring with it a wide range of symptoms such as a scratchy throat, cough, cold, sore throat, headache, aching limbs and fever, and can last for up to two weeks. The additional weakening of the immune system makes it even more susceptible to other pathogens, especially bacteria. Since influenza infections are spread by a variety of pathogens, vaccination is not possible. In normal cases, however, a cold can be easily treated with rest, plenty of fluids and minerals, and possibly over-the-counter medicines.

The "real" flu is spread by influenza viruses. As with the common cold, it is spread primarily by droplet infection, and many people infected with influenza remain asymptomatic. However, if symptoms do occur, they are usually much more severe and persistent than with a cold. Above all, the sometimes high fever is extremely dangerous for the body, which is why risk groups such as people with weakened immune systems, the elderly or pregnant women are usually advised to have a flu vaccination.

Keeping the immune system fit

The best protection against infections of all kinds (including SARS-CoV-2) is a strong immune system. The good thing about this is that there are a whole range of ways in which the body's own defenses can be strengthened.

The first of these is regular exercise. The reason for this is that the body of athletes is used to eliminating potentially harmful cells in the body through physical activity, this also succeeds much faster and more effectively with pathogens of all kinds. Moderate endurance training is ideal here, but strength training also has a positive effect on the immune system. The type of exercise is less important than the intensity. During intense physical exertion, the immune cells in the body multiply particularly quickly, but are subsequently broken down, so that at the end of the training there are even fewer immune cells than before. This is known as the open-window effect. Sustained excessive training with insufficient regeneration also puts a strain on the central nervous system and can thus further weaken the immune system. Load control therefore plays a decisive role.

Sufficient sleep is particularly important in this respect. Researchers at the University of Tübingen were able to show that after just three hours without sleep, the ability of the body's own T cells (defense cells) is reduced. In other words, if you get enough restful sleep, you strengthen your immune system. In this respect, the cold temperatures actually benefit us: at cool room temperatures (16 to 18 degrees Celsius are ideal for the bedroom), we generally sleep much better than at high summer temperatures.

Even though these summer temperatures may be more of an invitation to leave the house, it is also advisable to shift your sporting activities outside at least once in a while, although there are hardly any alternatives at the moment anyway. Because as our grandparents already knew: Fresh air is healthy! The reasons for this are again manifold. On the one hand, natural daylight helps to keep the body clock, which has a positive effect on sleep quality. Furthermore, exercise in the great outdoors has been proven to reduce stress and thus also improve physical regeneration. Fresh air also has a positive effect on our psyche. Daylight helps us to prevent vitamin D deficiency, but it is above all the respiratory tract that benefits from fresh air. Dry heated air is actually poison for our mucous membranes, which dry out as a result, making it easier for germs to spread. That's why it's also important to heat and ventilate properly in closed rooms: regular intermittent airing and plants help to improve the quality of the air in the room. The room temperature should also not drop too much, otherwise there is a risk of mold growth.

A healthy and balanced diet is at least as important as regular exercise and fresh air. Because the immune system can only work well if our body is sufficiently supplied with the right nutrients. As a rule, five portions of fruit or vegetables a day are recommended. However, most Germans do not achieve this recommendation. The result is deficiencies in one or more micronutrients. Most micronutrients can be supplied in sufficient quantities through the diet. For this, however, the diet must be varied and diverse. Below is an overview of the most important micronutrients for the immune system and essential natural sources:

Micronutrient	Natural sources
Vitamin A	Leafy vegetables, peppers, carrots, dairy products, liver
Vitamin B12	Meat, dairy products, fish
Vitamin B6	meat, potatoes, whole grain products
Vitamin B2 (riboflavin)	Meat, dairy products, whole grain products
Vitamin C	Bell peppers, citrus fruits, berries
Vitamin D	Fatty fish such as herring, egg yolk, liver, mushrooms
Vitamin E	Nuts, vegetable oils
Carotenoids	Tomatoes, carrots, peppers
Citrus bioflavonoids	Citrus fruits
Folic acid	Whole grain products, asparagus, green leafy vegetables
Copper	Whole grain products, nuts, legumes, cocoa
Niacin	Fish, meat, dairy products
Selenium	meat, fish, nuts, mushrooms
Zinc	fish, meat, dairy products
Iron	Meat, fish, eggs, cereals, nuts, legumes

The micronutrients can of course also be supplemented if a sufficient supply through the diet is not possible or only with difficulty. This can be particularly useful for athletes, since the increased physical stress also increases the need for micronutrients. In addition, care should be taken to ensure a sufficient protein intake. Single amino acids such as glutamine can also help to improve regeneration and thus support the immune system.

Furthermore, it is advisable to limit or completely avoid the intake of stimulants such as alcohol and nicotine, as these massively weaken the immune system.

Pay attention to hygiene

Those who strengthen their immune system through regular exercise, sufficient fresh air, plenty of sleep and a healthy diet will have to deal with flu-like infections or a "real" flu much less frequently. For Covid-19, too, the available studies indicate that people with a well-trained immune system are much more likely to remain symptom-free. However, this is not a free pass. It is therefore immensely important to observe key hygiene rules, i.e. above all to wash and/or disinfect one's hands regularly. Then pathogens hardly stand a chance!