5 Natural Ingredients You Should Eat to Boost Immune Function

5 Natural Ingredients You Should Eat to Boost Immune Function

Over the past 18 months, we have all become far more aware of our physical health. We are now well-versed in the art of social distancing, hand sanitizing, and mask-wearing. We’re more in tune with our bodies than ever before, instinctively knowing what feels normal and checking that we’re virus-free at the slightest sign of a cough. But when it comes to maintaining a robust immune system, do you know what to eat?  

Let’s look at five of the best natural ingredients to consume for a stronger immune system and better overall health.  


What can I eat to boost my immune system?

1. Vitamin C

Vitamin C is a potent antioxidant. Studies show that, when taken daily, vitamin C helps fight inflammation, protects against infection, and decreases the duration and severity of the illness. In other words, vitamin C can help protect us against colds and the flu, and when we do catch something, it can reduce the uncomfortable symptoms of a cold and help us recover more quickly.

Vitamin C-rich foods include:

  • Bell peppers

  • Potatoes

  • Bok choi, broccoli, brussels sprouts, cabbage, and similar members of the Brassicaceae family

  • Strawberries and blackcurrants

If you are concerned that you don’t get enough dietary vitamin C, I recommend taking at least 500 milligrams of vitamin C a day. If you live a high-stress lifestyle, generally don’t eat much fresh produce, or are exposed to situations that make you susceptible to infection, you should take at least 1,000 milligrams daily.

The good thing about vitamin C is that it's a water-soluble vitamin, so if you ingest “too much”, you just urinate it out. There are some cases reported where there's an increased incidence of kidney stones from over-intake of vitamin C, but that's typically somewhere around 10,000 milligrams.

 2. Zinc

Zinc is also a potent antioxidant shown to decrease the incidence, severity, and duration of the common cold and flu. I advise all my patients to take a minimum of ten milligrams of zinc daily, although 20 is optimal for immune support. The more zinc you have, the more added immune support you have. The side effect of zinc is that it could cause nausea if taken in excess. That's why you want to find a supplement that has just the right amount and won’t cause the side effect of nausea.

 3. Vitamin D

Alongside being important for good bone health, vitamin D has also been shown to be important for the immune system. Studies show that when patients have a vitamin D deficiency, they are more likely to catch a virus. 

We often refer to vitamin D as the sunshine vitamin, and that is because it’s the only nutrient our bodies produce when we are exposed to sunlight. There is a theory that the flu season is more common during the fall and winter time because of the shorter days. The shorter days come with decreased sunlight exposure, resulting in lower vitamin D levels. That element may be part of the reason why the flu season is during the shorter days of the year.

You can find naturally-occurring vitamin D in the following foods:

  • Mushrooms

  • Soy milk 

  • Fish, such as salmon, sardines, tuna, and herring

  • Egg yolks

4. Probiotics

Probiotics are important for a strong immune system because we now understand that our gut health is an integral part of the immune system. 70% of our immunity comes from our gut and the lifestyle that we live, whether that involves processed foods, high stress, and sleep deprivation, or a whole foods diet and plenty of rest.

All of these things can come together and affect the environment of the gut and can either help or disrupt the microbiome. A healthy microbiome is necessary for a healthy immune system and taking probiotics is one way to ensure adequate immunity and gut health.

5. Curcumin & Other Plant Flavonoids

Curcumin is a root associated with decreased viral infection, in both severity and duration. It has powerful anti-inflammatory properties which helps to ease inflammation caused by infection, as well as several other health issues down the line. Plant flavonoids, as well as curcumin, elderberry, and echinacea are used as part of ancient Chinese medicine. They have been used for centuries to decrease the incidence, duration, and severity of a viral infection.

Plant flavonoids can be found in almost all fruits and vegetables, grains, roots, tea, and wine. Quercetin, rutin, elderberry, echinacea, and hesperidin are all plant flavonoids. Plant flavonoids have been shown to have anticarcinogenic properties, promoting good overall physical health and a stronger immune system.


In a world where health anxiety is something most people have experienced at some point over the course of the pandemic, the best remedy is high-level of self-care. While it’s difficult to fight viral infections with medications, we can give our immune system the tools to keep the many viruses and bacteria we come into contact with at bay. Thankfully, a change in diet is one of the easiest ways to reduce your risk of catching a cold or the flu.  

While it’s almost impossible to never catch a cold, there are certainly ways we can protect ourselves against the common cold and flu. A healthy diet containing the ingredients discussed above can reduce our chances of falling ill with the flu as well as reducing the severity of the symptoms we experience.


Dr. Nancy Rahnama, MD, ABOM, ABIM, is a medical doctor board certified by both the American Board of Obesity Medicine and the American Board of Internal Medicine. Her specialty is Clinical Nutrition, that is, the use of nutrition by a medical doctor to diagnose and treat disease. Dr. Rahnama has helped thousands of people achieve their goals of weight loss, gut health, improved mood and sleep, and managing chronic disease.