These four nutrients are essential, if you want to avoid colds, flus, and related infections

These four nutrients are essential, if you want to avoid colds, flus, and related infectionsDuring the winter period, many people catch a cold or are bed-ridden with a bout of the flu. They may consider this to be perfectly natural, but it is actually a sign of a weakened immune defense, and that makes them susceptible to contamination. What matters is to make sure to get plenty of vitamin D, vitamin C, selenium, and zinc, all of which are nutrients that have different functions in the immune system. Some nutrients are also needed in larger quantities to tackle a beginning infection, and it is important to act quickly in order to nip the infection in the bud.
In fact, it is vital for us to be nutritionally bolstered during the winter period, where otherwise harmless virus infections can lead to complications such as herpes, bronchitis, and pneumonia, if the immune system is unable to work full throttle.

Regular colds and influenza are the most common reason why people visit the doctor’s office during the winter period. The infections are caused by different types of virus that result in a variety of symptoms.

Colds are typically caused by rhino virus, and there are many different types. It is normally a harmless and brief infection with either a runny or blocked nose, sneezing, runny eyes, and slight pressure on the sinuses.

Influenza is caused by influenza virus A, B, or C, and there are several subtypes. The typical symptoms are like those experienced with a cold but people also have a high fever, shivering, muscle aches, headache, dry cough, and grave discomfort. Influenza is especially dangerous for older people and those with compromised immune systems, if it is accompanied by pneumonia.

Several factors can increase your risk of catching a cold or the flu, and we will address these factors in the following.

The time of year

Most cold and flu viruses occur during the winter period, which makes sense. First of all, we are not able to synthesize enough vitamin D from the sun, as it sits too low in the sky. Secondly, cold air can impair the body’s first-line immune defense in the nasal passage. And then there is the fact that rhino virus that causes colds reproduces quickly at lower temperatures in the nose. Finally, dry air dries out the mucosa in the nose, which makes the problem worse.


The immune system in children younger than six years of age is not yet fully developed. In other words, they still have not developed a natural immunity to the many different types of virus and bacteria. Ageing can also impair your immune system. For instance, older people have increasing difficulty with synthesizing vitamin D in their skin, producing coenzyme Q10, or taking up nutrients such as zinc (which is important for the immune system).

Impaired immunity

Lack of sleep, unhealthy diets, poisoning, stress, overtraining, top-level sports, chronic disease, and the use of different types of medicine all have the ability to weaken your immune defense.


Colds and flus are often passed on when people have hand-to-hand contact and transmit the infection to mucosa in their nose, mouth, or eyes. It can also happen after touching surfaces such as door handles or through droplet infection from sneezing or coughing. People who are together with many others in kindergartens, schools, large workplaces, or in filled busses, trains, airplanes, and other places with air condition, are also at increased risk. Ventilate the room, wash your hands frequently, and avoid touching your mouth, nose, and eyes with your hands, unless they are clean. Precautions like these can reduce your risk of becoming ill.

When infection leads to other complications

The immune defense consists of a set of proteins and white blood cells. The innate immune defense works like storm troops, while the adaptive immune defense develops after birth. The innate immune defense consists of different white blood cells and proteins that are able to take on most infectious germs. This goes unnoticed. In situations where the innate immune defense is unable to complete its tasks, it signals the adaptive immune defense for help. The adaptive system is the immune system’s special forces. T cells (in particular) combat the virus-infected cells, and the B cells produce antibodies. The process normally lasts for a week, and the unpleasant symptoms are a result of cytokines that are different signaling substances. In cases where we have had a similar virus infection earlier, our immune system has already made antibodies and built some kind of immunity. If it is a new virus, we still have no immunity.
The immune defense’s ability to fight germs and infections depends greatly on various nutrients that are important for the storm troops, for the immune system’s ability to communicate, and for the production of special forces and antibodies. If you lack a single nutrient, it may have fatal consequences.
Complications such as bronchitis, middle ear infection, and pneumonia typically occur when the immune defense is too weak. That way, bacteria from the natural microflora in our throat can spread to the middle ear or the lungs, where they are not normally found. These are called autoinfections because we infect ourselves.

The reason why we catch colds and flus again and again is that these different viruses can mutate and deceive the immune defense. Vaccines for preventing seasonal flu are only able to target a specific virus type, and the effect is limited. A strong and effective immune defense, on the other hand, can handle all types of virus and bacteria.

Vitamin D for long-term prevention

Vitamin D activates both the innate and the adaptive immune defense. We have in our respiratory tract a large number of white blood cells (macrophages) that depend on vitamin D in order to attack infectious germs. Vitamin D also boosts certain antibiotic peptides in the lungs. Scientists with The Faculty of Health and Medical Sciences at the University of Copenhagen have analyzed isolated T cells from human blood in laboratories and found that T cells need vitamin D to get started and to establish an army. However, if T cells have not taken up sufficient amounts of vitamin D from the blood, they cannot collaborate, attack, or develop immunity. The Danish discovery supports earlier findings and is published in the science journal Nature.
Lack of vitamin D is therefore one of the main reasons why we catch viruses during the winter period. It is not just because we don’t get enough vitamin D from sun exposure. It is also related to factors such as spending too much time indoors, growing older, having dark skin, using sun factor crème, being overweight, having type 2 diabetes, having kidney disease, having too much calcium in the blood, and using cholesterol-lowering medicine. Moreover, we need magnesium to activate vitamin D.

Important note

You are not likely to feel when you are running low on vitamin D, but your immune defense will know for sure. What is more, immune-boosting herbs like echinacea can never replace vitamin D.

How much vitamin D do we need during the winter period?

RI (reference intake) levels for vitamin D vary from country to country, but infants, older people and nursing home residents, dark-skinned individuals and people who wear veils are advised to take a vitamin D supplement. Recent studies also show that overweight individuals and diabetics have an increased need for the nutrient. Many experts claim that the actual need for vitamin D is much higher than the recommended intake levels and lies somewhere in the range between 30-100 micrograms. This amount is easy to synthesize on a sunny day during the summer period, but in the winter time we need a supplement, especially since our diet only contains a very limited amount of the nutrient.

Measuring blood levels of vitamin D

Vitamin D in the blood is measured as 25-hydroxy-vitamin D (or 25(OH)D). The official threshold value is 50 ng/ml, but many scientists claim that this is too little and say that as much as 60-100 ng/ml is needed for optimal disease prevention.

Vitamin C for the storm troops and the interferons

All white blood cells contain large quantities of vitamin C. The macrophages in our respiratory system, which constitute our first-line defense against airborne infections, also use quite a lot of vitamin C during their attacks. Furthermore, vitamin C is important for the production of interferons, which strengthen the communication between cells and prevent virus from replicating inside the cells.
Most animals are able to synthesize vitamin C from glucose (blood sugar). In the case of an infection, animals step up their production of vitamin C massively to strengthen their immune defense. Humans, however, do not have this ability and depend on vitamin C from dietary sources or from nutritional supplements. Some of the best sources of vitamin C are citrus fruits, red bell pepper, rosehips, broccoli, kiwi, and sweet potatoes. It is important to know that sugar interferes with the uptake of vitamin C in cells, and if you eat a lot of sugar, your need for vitamin C therefore goes up.
The reference intake (RI) level for vitamin C for adults is around 80-100 mg, but we probably need even more to boost our immunity. The first sign of a virus infection is typically a sore throat, and it is possible in many cases to stop the progression of the infection (within a few hours) with large quantities of non-acidic vitamin C (calcium ascorbate). That way, one can strengthen the immune system and emulate the effect that is seen in animals when they increase their endogenous production of vitamin C to combat infections.

Large quantities of vitamin C can soothe a cold and prevent pneumonia

Two controlled studies have found that 6-8 grams of vitamin C daily can shorten the duration of cold symptoms. Three controlled studies have demonstrated that vitamin C prevents pneumonia, which is a rather common complication that follows in the wake of a cold or the flu. In more complicated cases of influenza, doctors specialized in orthomolecular medicine have successfully administered even larger doses intravenously.
Daily ingestion of vitamin C in mega doses may, however, reduce the body’s levels of copper, which can impair immunity in those, who are already copper-deficient.

When studies fail to show an immune-boosting effect of vitamin C, it may be because of

  • Too small a dosage
  • Too late intervention
  • Too high sugar consumption
  • Diabetes and insulin resistance

Selenium deficiency impairs the immune defense

Even if we eat a healthy diet, nutrient depletion of the soil makes it difficult to get enough selenium, especially in Europe. This was demonstrated by Swizz scientists in a study not too long ago.
Selenium supports around 30 different selenoproteins that are important for energy turnover, immune defense, cancer prevention, and many other essential functions.
Since the 1970s, farmers have made a routine of giving their livestock selenium supplements to avoid a number of different diseases.

Selenium especially activates the T cells of the specific immune system

Selenoproteins are important for our innate and adaptive immune systems. Infections cause blood levels of the selenium to drop due to the increased need of white blood cells. In the late stages of an influenza infection, scientists have seen how levels of macrophages, T helper cells and T killer cells are lower in selenium-deficient mice compared with mice that have plenty of selenium.
An American study has shown that daily supplementation with 200 micrograms of selenium increases T killer cell activity by 118% and NK (natural killer) cell activity by 82%.

Selenium prevents different virus types from mutating

When humans are attacked repetitively by influenza, colds, and herpes, it is because the different virus types (known as RNA virus) are able to mutate. The different types of RNA virus alter their antigens, thereby deceiving the immune defense. The immune defense is therefore forced to start all over again. This is especially critical when the immune system is down, and selenium plays a vital role here.
Professor Melinda A. Beck from the University of North Carolina in the United States has published studies that show how selenium-depleted mice infected with influenza virus A show signs of increased mutation of the RNA viruses. That makes it more difficult for the mice to fight the influenza if you compare them to mice that are not selenium-deficient. The flu-ridden mice that were selenium-deficient also developed serious lung complications because of the virus, whereas the mice that had plenty of selenium only developed mild symptoms.

Selenium is very important for preventing influenza and other RNA viruses from mutating. It is hardly a coincidence that the new, dangerous influenza strains often originate from vast, selenium-depleted areas of China, Central Africa, and South-East Asia.

Selenium sources and supplements

Some of the best selenium sources are fish, organ meat, eggs, dairy products, and Brazil nuts. European agricultural crops are generally low in selenium. Research suggests that even if you eat fish and shellfish five times per week, it is difficult to get enough selenium. A good way to make sure to get enough selenium is to take a daily supplement of organic selenium yeast that contains a variety of different selenium types, just like you would get from eating a balanced diet with many selenium sources.

It takes 100 micrograms of selenium per day to saturate selenoprotein P

Selenoprotein P is used as a marker of selenium status in the blood. You need to consume around 100 micrograms of selenium daily to effectively saturate this selenoprotein, and that is around twice as much as you get by eating an average European diet.

Zinc deficiencies especially affect the T cells of the immune system

Lack of zinc increases the risk of virus infections and may cause them to drag out and become complicated.
Zinc supports over 300 different enzymes, many of which are relevant for the immune system. Zinc is important for the macrophages, granulocytes, and NK cells of the innate immune system and the T cells of the adaptive immune system.
A zinc deficiency is especially bad for the T helper cells that have a superior function in the immune defense. Because zinc is so vital for our T helper cells, having too little of the nutrient may weaken the immune defense and cause infections to drag out, or it may even cause the immune defense to overreact, which can lead to chronic inflammation.

Zinc sources and official recommendations

Some of the best sources are meat, shellfish, dairy products, nuts, kernels, and beans. Animal sources of zinc are easier for the body to absorb than plant sources. The average Danish diet only provides around 5 mg of zinc, which is half the recommended level (RI – or reference intake level).
The body’s absorption of zinc is impaired by e.g. sugar, birth control pills, inorganic iron supplements, and ageing. Even with a diet that contains enough zinc, it is possible to be deficient.

Short-term high-dosed zinc supplementation shortens the duration of cold

Zinc has become a popular remedy for preventing colds, and it may even help prevent respiratory infections in children. However, if you get enough zinc from your daily diet, a supplement of the nutrient will not necessarily make much of a difference.
Nonetheless, levels of zinc in the blood drop in connection with infections, because the white blood cells take up and use a lot of zinc when fighting virus and bacteria. For that reason, a team of scientists at the University of Helsinki in Finland wanted to take a closer look at how zinc supplements affect cold-ridden patients. The participants in the three Finnish studies that were included in the meta-analysis received 80-92 mg of zinc daily. This amount is way higher than the RI level. According to the results, these high-dosed zinc supplements were able to reduce the duration of the colds by 33 percent on average compared to placebo. The scientists underline that many commercially available zinc supplements contain too little zinc to make a difference. Moreover, a lot of supplements contain inorganic forms of zinc such as zinc sulfate or zinc oxide, which the body has difficulty with absorbing.
The supplements that were used in the Finnish meta-analysis contained organic zinc acetate. Another organic form of zinc, which has excellent bioavailability, is zinc gluconate.
Quite as expected, no serious adverse effects were observed in the three Finnish studies. However, it is generally advised not to take extremely high doses of zinc for longer periods, as this may eventually inhibit the body’s uptake of iron and copper.

Vitamin C, selenium, and zinc also work as antioxidants

When we contract an infection, the immune defense produces massive amounts of free radicals. Vitamin C, selenium, and zinc all have antioxidant functions. They are able to neutralize the free radicals and can prevent oxidative stress.


As shown, it is rather simple to strengthen and optimize the immune defense with sufficient amounts of vitamin D, vitamin C, selenium, and zinc. If you feel an infection coming on, it is a good idea to take large quantities of vitamin C. It may also be a good idea to take extra selenium and zinc for a brief period, as this can stall the infection or prevent it from dragging out and causing other complications. It is also vital to get plenty of sleep and to maintain good hand hygiene.

Important: Influenza vaccines only have a limited effect on healthy adults

For every 71 flu vaccines that are injected, only case of influenza is prevented. The vaccine does not have any effect on the number of sick days and days spent in hospital, according to a Cochrane Collaboration review of 90 different studies. The health authorities should therefore be more focused on the essential nutrients, on which the immune system depends particularly much.


Overview of the immune defense

Defense system Innate Adaptive


Storm troops and garbage collectors.

Special troops that develop immunity.
Develops after birth

Mechanical and biological Skin and mucosa.
Special compounds in their ”acute” phase Interferons
Complementary system
Direct destruction of cells NK cells
T cells: Mainly responsible for virus, fungus, and abnormal cells. B cells and antibodies: Mainly responsible for bacteria and toxins


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