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Supplements to support immunity to respiratory diseases such as COVID-19

Supplements zur Unterstützung der Immunität gegenüber Erkrankungen der Atemwege wie COVID-19

We have noticed a lot of misinformation being spread recently about immune function and respiratory diseases such as COVID-19 and feel it is time to set the record straight. Respiratory diseases affect the nasal mucosa, airways or lungs and encompass a wide range of conditions from the common cold to pneumonia. The immune system is a complex network of cells, body tissues and organs that work together to protect your body on a daily basis from infections such as those mentioned above.

Scientific research shows that certain supplements can reduce the risk of infection and the severity of symptoms. In this article, we will discuss supplements that have been scientifically proven to safely support your immune system.

As always, it is advisable to consult a doctor before starting any supplement program if you have or suspect you have a medical condition or are taking any medication.

Fermented foods, probiotics and prebiotics can have anti-inflammatory and anti-pathogenic effects

Your digestive tract contains a rich community of healthy microbes that fight against outside invading pathogens and act as the body's first line of defense against infection. In addition, through a process called fermentation, they digest nutrients like fiber and other carbohydrates that you otherwise could not, resulting in the production of byproducts that play many important roles in the human body, ranging from protecting the gut to improving insulin sensitivity.

Recent research has found that your gut flora is a key component of a healthy immune system and your body's ability to fight viral and bacterial infections. Both probiotic supplements and fermented foods, which are a source of live bacteria, can significantly reduce your risk of infection by fighting pathogens in the gut and contributing to anti-inflammatory pathways throughout the body.

Certain strands of bacteria have stronger infection-protective and anti-inflammatory effects than others. Lactobacillus plantarum, Bifidobacterium lactis, Lactobacillus casei and Lactobacillus rhamnosus (also known as Lactobasciullus GG) are among the best "fighters" against viral infections in general and upper respiratory tract infections in particular (1, 2, 3, 4).

If you are considering using a probiotic supplement, then you should look for a product that contains at least one or two or more of the above-mentioned strands of probiotic bacteria.

Your diet can also be an important tool for supporting healthy gut flora. Fermented foods like kimchi, sauerkraut, miso and tempeh, as well as yogurt and kefir can directly add healthy bacteria to your gut, while prebiotic supplements and foods like beans and cruciferous vegetables can help these bacteria to better thrive in your gut.

Zinc can help make infections less severe

Zinc plays an important role in immune function as it is involved in the cell-mediated and humoral immune response - two types of immunity in which an immune response specific to a particular pathogen is generated. Low zinc levels or a zinc deficiency can therefore reduce the number of your immune cells available to fight pathogens that invade the body.

Following a review of 13 randomized, placebo-controlled trials on zinc and the common cold, researchers concluded that taking zinc within the first 24 hours of the first cold symptoms can reduce the duration of the cold and alleviate the symptoms of the illness (5).

Men need about 11 mg and women about 8 mg of zinc per day. Zinc is primarily found in red meat and seafood - especially oysters and molluscs. Zinc is also found in plant sources such as whole grains and pulses - albeit in smaller quantities. In addition, zinc from plant sources is less easily absorbed by the body than zinc from animal sources. Vegetarians and older people are at a higher risk of inadequate dietary zinc intake.

Although it is important to meet your daily zinc requirements, it is equally important not to overdo it with your zinc intake. The maximum amount of zinc you should consume per day is 40 mg. A higher intake can lead to copper deficiency and neurological problems (6, 20).

If you are struggling to meet your daily zinc requirements or are experiencing the first signs of a cold, it may be useful to take 25 mg of zinc per day. Zinc supplements are best taken on an empty stomach.

Vitamin C can support the immune system

You can't talk about immune function without mentioning vitamin C. Just like zinc, vitamin C is an essential micronutrient that must be obtained from the diet. Vitamin C plays an important role in immune function by acting as an antioxidant, improving immune cell function and supporting anti-inflammatory pathways in the body.

Vitamin C deficiency can lead to impaired immune function and increased susceptibility to infections. A study review (19) looked at hundreds of studies examining the role of vitamin C in immune function. The researchers concluded that supplementation with 100 to 200 mg of vitamin C per day can prevent respiratory infections.

Many supplements contain 1,000 mg of vitamin C per tablet or capsule. The bad news is that the absorption of vitamin C decreases with increasing intake. For example, at a high intake (around 1,200 mg) only 16% is absorbed, whereas at a low intake (< 20 mg) 98% is absorbed. As soon as you reach 1,000 mg, less than 50% of the vitamin C intake is excreted in the urine (20). For this reason, vitamin C is best taken in two to three smaller doses with meals.

Toxicity does not usually occur with vitamin C, but undesirable side effects can occur if the upper tolerated amount (2,000 mg per day) is exceeded over the long term (7).

Vitamin C is most abundant in fresh, whole foods such as pineapple, kiwi and broccoli. For this reason, it is not surprising that a lack of consumption of fresh foods, among other causes, has contributed to vitamin C deficiency being one of the leading nutrient deficiencies in the Western world (19).

As a water-soluble vitamin, vitamin C cannot be stored in the body. For this reason, it is important to consume foods rich in vitamin C every day to meet daily requirements.

Adequate vitamin C intake is essential for the proper functioning of the immune system. If you are concerned about not getting the necessary amount of vitamin C, you should consider taking two to three smaller servings (200 mg) of vitamin C daily.

Vitamin D supplementation can protect the upper respiratory tract

Studies show that people with optimal vitamin D levels are less susceptible to colds and other respiratory infections than those with low vitamin D levels. In a systemic randomized review (the gold standard of scientific research), vitamin D supplementation appeared to protect against acute respiratory infections such as the common cold. This was particularly true for people who were previously vitamin D deficient (8).

In addition, it was observed that the likelihood of developing upper respiratory tract infections was inversely proportional to the serum (blood) levels of vitamin D. In other words, this means that the likelihood of respiratory tract infection increases as your vitamin D levels decrease (9). Serum vitamin D levels should be above 32 ng/ml for optimal health.

The bottom line is that optimal vitamin D levels could protect you from respiratory infections. You should therefore aim for an intake of at least 1,000 IU of vitamin D per day, with many experts recommending significantly higher amounts in the range of 2,000 to 4,000 IU per day.

Natural food sources of vitamin D include cod liver oil, oily fish, mushrooms and egg yolks. However, apart from cod liver oil and natural sun exposure, the low levels of natural vitamin D in the diet mean that supplementation with vitamin D is the only way to achieve optimal levels.

Ginseng can relieve symptoms of upper respiratory tract infections in the elderly

Ginseng is a root with strong antioxidant effects that contribute to reduced inflammation, immune function support and other health benefits. Several studies have shown positive effects of ginseng on colds and respiratory infections.

In a systemic review that looked at several studies, researchers concluded that ginseng extract can reduce the duration of a cold (10). The same results were replicated in a randomized double-blind control study in which subjects were given ginseng extract for four months (11). Of particular relevance is that ginseng was able to reduce both the risk and duration of respiratory symptoms in older people by 48% and 55% respectively (12).

Ginseng could therefore be particularly helpful for older people. It works best when taken within a two-hour window around a meal. An optimal dosage is 2,000 mg of ginseng extract per day.

Garlic can activate genes associated with immune function and reduce the likelihood of disease

Garlic has been used by many different cultures in the past to fight infectious diseases due to its antimicrobial, antifungal and antiviral properties (13). Modern studies have shown that garlic can activate immune system genes and reduce both the severity and risk of colds.

In a randomized double-blind study, subjects were given a garlic supplement or a placebo over a 12-week period from November to February - the flu and cold season. The group that received garlic had fewer cases of illness and also recovered more quickly from colds than the placebo group (14).

In a similar study design, after 45 days of garlic supplementation, subjects showed significantly improved function of NK and T cells, both of which are involved in immune function, compared to the placebo group. After 90 days, the garlic group also had fewer cold symptoms, sick days and number of colds than the placebo group (15). Finally, another study found that adding garlic to meals activated genes associated with immune function (16).

You can either add garlic to your diet in its natural form, or use supplements that contain garlic extracts in concentrated form and also do not cause garlic odor. A good dosage is 500mg of garlic extract twice a day with breakfast and dinner.

The facts about elderberry and echinacea are not yet clear

Elderberry syrup has recently appeared in the spotlight as a natural way to support the immune system. The flowers and berries of the Sambucus nigra species have been most commonly studied and used in tea or syrup.

However, only a handful of small studies (about four) have been conducted to date. Although the results were positive - elderberry supplementation can reduce the duration and severity of upper respiratory symptoms - the amounts used varied from study to study (17).

In one study, for example, 300 mg of elderberry extract was used, while in another study 60 ml of elderberry syrup was used for five consecutive days. Sambucol, one of the most popular commercially available elderberry syrup products, contains just 3.8 mg of elderberry per 10 ml serving - and a full 8 grams of sugar. Even if taken several times a day, this would not be enough to reach the levels used in clinical trials.

And now something about echinacea. In a meta-analysis that looked at 24 randomized controlled trials, scientists concluded that echinacea could not be shown to have benefits in the treatment of the common cold.

Furthermore, in 2003, a study made headlines when scientists looked at 59 different echinacea supplements available on the market. They found that only 52% of the products tested contained the amounts of echinacea stated on the label and 19% contained no echinacea at all (18).

Due to the lack of studies on elderberry and the inconclusive results on echinacea, these two plant extracts cannot be recommended for treating colds or supporting the immune system at this time.

So which supplements can support the immune system?

Scientists who have studied the effectiveness of different supplements for fighting colds, flu, respiratory infections and other related symptoms are largely in agreement: taken daily, the following supplements are associated with a reduced risk of infection, reduced duration and reduced severity of symptoms, with each of these supplements having different unique properties that can support the immune system:

  • Probiotics
  • Zinc
  • Vitamin C
  • Vitamin D
  • ginseng
  • Garlic

We hope this summary will help you choose wisely and put you in the best position to protect yourself from contracting COVID-19 or other respiratory illnesses.


  1. 19747410 Consumption of a fermented dairy product containing the probiotic Lactobacillus casei DN-114001 reduces the duration of respiratory infections in the elderly in a randomized controlled trial.
  2. 20803023 Randomised, double-blind and placebo-controlled study using new probiotic lactobacilli for strengthening the body immune defence against viral infections.
  3. 23020819 Effect of Lactobacillus rhamnosus LGG® and Bifidobacterium animalis ssp. lactis BB-12® on health-related quality of life in college students affected by upper respiratory infections.
  4. 25927096 Probiotics for preventing acute upper respiratory tract infections.
  20. Groff. Advanced Nutrition and Human Metabolism. Australia: Wadsworth/Cengage Learning, 2009. print.


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