Foods that Boost the Immune System? The 4 Greatest Nutrition Myths

agrumi e frutta fresca

Our immune system is built to fight viruses, bacteria, and fungi, which can cause infections. A strong immune system is important to keep us from getting sick. But does taking vitamin C supplements as a preventative measure really make a difference? 

A woman lying in bed being sick with medicine

We take a close look at 4 common myths: 

Myth #1: “Vitamin C protects us from the common cold” 

Getting enough vitamin C (ascorbic acid) is important for keeping our immune system in fighting form. The Mayo Clinic recommends 65 to 90 mg per day. 

Foods rich in vitamin C are: 

  • Bell peppers (140 mg per 100 g)
  • Brussels sprouts (110 mg per 100 g)
  • Broccoli (95 mg per 100 g)
  • Citrus fruit (50 mg per 100 g)

Lemons and oranges

We often read that increasing the intake of vitamin C during cold season can protect us. This has actually not been scientifically proven. However, taking >200 mg can shorten the duration of a cold.(1) But you don’t have to take supplements to consume this amount. A healthy diet rich in fruits and vegetables will provide a sufficient amount. Since vitamin C is water soluble, vegetables and fruits should be washed thoroughly, but quickly, and veggies should be gently steamed to avoid losing their nutritional value.


For a long time, people believed that if endurance athletes like marathon runners took vitamin C preventatively, it would aid recovery and keep them from getting sick. This has since been disproven. Supplements with high doses of vitamin C should only be taken with caution or even avoided before a race,(2) because it can have a damaging effect on muscle endurance. 

Myth #2: “Cow’s milk causes mucus production” 

Many people don’t drink cow’s milk when they have a cold, cough, or sore throat, because they believe that it increases mucus production and slows the healing process. Is that true? In fact, there is no scientific proof of this. 

A glass of cow milk

An Australian study looked at two groups: one drank cow’s milk and the other drank soy milk.(3) Participants showed a significant increase in three reactions: a white coating on the tongue, increased urge to swallow, and thickened mucus, which made swallowing difficult. However, these increased equally in both groups. The fact is that the coating that develops in the mouth and throat comes from milk fat, which is present in both cow and soy milk. This is often perceived as phlegm. 

You still want to give up cow’s milk? We’ve compiled a list of the best non-dairy milks.

Myth #3: “Honey strengthens your immune system” 

Tea with honey is a common folk remedy for colds. But does this natural sweetener really strengthen the immune system? Can it prevent or soothe a sore throat? An Israeli study looked at the effect of honey on nighttime coughing and problems sleeping due to upper respiratory infections in a cohort of 300 children (aged 1 to 5). 200 of the children were given 10 g of honey before bed. The remaining 100 were given a date extract as a placebo, which had a similar consistency and color. 

a glass of honey

According to statements from the parents, the honey seemed to improve the symptoms. Coughing was reduced in both frequency and severity. Why? Honey has anti-inflammatory, anti-bacterial, and antiseptic qualities. It doesn’t cure a sore throat or strengthen the immune system, but it can ease the symptoms.


Children should not be given any honey in their first year. Raw honey can contain the bacteria clostridium botulinum, which can cause infant botulism. This type of food poisoning may lead to paralysis of breathing and swallowing muscles and can be fatal.

Myth #4: “Bacteria is Bad for Your Health”

When we think about bacteria, most of us think of diseases and infections. Our body does carry “bad” bacteria, but we also have tons of healthy bacteria living inside us. The human gut is home to an enormous number of “good” bacteria (around 1.5 kg). These microorganisms that live in the digestive tract of humans are known as the human microbiome or gut flora. They play a critical role in keeping us healthy and affect how strong our immune system is. The microbiome helps develop the intestinal barrier and immune functions of the gut, which are necessary for a healthy immune system. A dysbiosis can lead to immune disorders such as asthma, multiple sclerosis, and rheumatoid arthritis. 

Did you know…

…antibiotics can cause severe damage to the intestinal flora? However, the microbiome of a healthy adult recovers quickly after completing the cycle of treatment.

Healthy gut bacteria are essential for a strong immune system. Curious how you can support the microbiome with a healthy diet? Foods high in fiber as well as pre- and probiotics have a positive effect on the health of your gut.  

A glas of fermented veggies

These include:

  • yogurt
  • kefir
  • sour milk
  • fermented vegetables (sauerkraut, kimchi)
  • kombucha
  • legumes
  • artichokes 
  • asparagus
  • onion

Regularly incorporate these foods into your diet to keep your gut happy. 

Curious what else you can do to help your body fight infections? These seven superfoods boost your immune system if you eat them regularly. 


Julia Denner Julia is a dietician and sports nutritionist. Before she began her position as Communications Specialist at Runtastic, she spent several years working as a dietician in the surgical department at Vienna General Hospital. Julia is passionate about inspiring others to eat a healthy, balanced diet. View all posts by Julia Denner