How to Enhance Your Immune System Naturally (Diet and Supplements)

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Nature gives us many natural ways to boost our immune system and protect us against viruses and bacterial infections, which can lead to poor health. When we are young we can fight off infections easily, but as we get older, the immune system ages and it becomes a little harder to shrug them off as easily as we did in our youth.

Below are a few of the best ways to enhance your immune system with foods and supplements!

1. Beta-glucans

Beta glucans are derived from yeast and also oats. Oat beta-glucans is mildly effective at increasing immunity, as shown in one study where they demonstrated that in humans, oat beta-glucan was able to offset the negative effects of exercise stress [2].

“Exercise stress was associated with a 28% increase in morbidity (P = 0.036) and 18% increase in mortality (P = 0.15). Ingestion of ObetaG before infection prevented this increase in morbidity (P = 0.048) and mortality (P = 0.05)”

The immune system modulating effects of beta-glucans has been known for a couple of decades. When you ingest the beta-glucan from yeast, the glucan molecules are unaffected by the acid of your stomach and pass through unchanged.

Once they are absorbed into the blood they are taken up by phagocytes which digest them, and then over a period of days they are slowly released, and there the beta-glucan molecules attach to the receptors on the surface of immune cells called macrophages.

This causes a cascade of effects on your immune system, which basically makes the immune system stay on high alert and ready to attack any foreign invaders.

There are several effects of ingesting beta-glucans:

* Increasing the production of cytokines

* Increasing the activity of NK cells

* Increasing populations of macrophages

* Increasing the number of dendritic cells

* Increasing the number of T cells

2. Tea polyphenols

Catechins that are found in green tea and white tea have antiviral, antibacterial, and antifungal properties. EGCG is able to work in many different ways to both boosts the immune system and also block viral replication to prevent infection.

There is plenty of evidence that green tea is able to protect against both colds and flu. So perhaps this winter, you may want to sip on some green tea all day!

One of the ways green tea is able to work is by altering the protein coating around the virus and also blocking enzyme activity.

One study in a Japanese care home, they reported that influenza was reduced by over 90% if green tea was gargled every day. But the sample size was very small and therefore the study should be replicated.

Green tea is a very safe beverage and with plenty of other benefits, even if it doesn’t offer complete protection against influenza infections.

Other benefits from green tea include:

  • Kills many types of bacteria.
  • Can inhibit biofilm formation and make bacteria more susceptible to killing by the immune system and antibiotics.
  • Can reverse antibiotic resistance according to some studies.
  • Decrease inflammation associated with infections.

For the best results, you should try to find matcha green tea. This type of green tea has the most EGCG and L-theanine content

3. Vitamin D

Researchers are beginning to understand the effects of vitamin D on the immune system and how it can protect us against infections.

According to research, vitamin D is able to make the immune system smarter, so it can better identify between foreign invader and self. It also helps boost natural peptides which our innate immune system uses to puncture hole in a bacterium and viruses to kill them.

When we have enough vitamin D in our system, we are better able to fight off colds and flu. It’s recommended that optimal levels of 25(OH)D3 are above 32 ng.  For every 1000 IU of vitamin D you get, whether it be from supplements or the sun, you will raise your levels of 25(OH)D3 by about 10 ng.

Check out my article here on vitamin D supplements and also my article on the best vitamin D foods.

4. Lactoferrin

Lactoferrin protects the body by binding to iron so that the bacteria cannot use it. In breast milk, there is a lot of lactoferrin and this is one of the reasons why babies who are breastfed have better immune systems.

Lactoferrin coats anywhere that germs can gain entry into the body, such as the nose, eyes, and sex organs. Therefore, taking lactoferrin supplements is thought to be beneficial in protecting against infections.

5. Ginger

Ginger is a very well known spice and healthy herb for things like nausea and sickness. Ginger is able to prevent sickness and nausea and act as a natural antiemetic.

Some doctors instruct women to use it while pregnant and have morning sickness. Other uses include travel sickness, general nausea, indigestion, and acid reflux disease. Although ginger has many benefits for the digestive system, it appears to be ineffective when used postoperatively.

Ginger is also a good natural antiviral, antibacterial, and also acts as a powerful anti-inflammatory. You can read more on ginger supplements and their benefits here and here.

6. D Mannose

UTI infections are usually caused by E. coli, which also happens to be the bacteria that D mannose is most effective against. When you consume D mannose (which is found in small amounts in cranberry juice), it’s not absorbed by the body and the majority of it ends up in the urine.

Once you flush out your bladder, the E. coli detaches from the bladder wall because it has a higher affinity for the D mannose within the urine. The best thing about this cure is that there is no chance for resistance and it will clear any antibiotic-resistant bacteria.

Unfortunately, for that unlucky 10% of bladder infections which isn’t caused by E.coli, you will have to take antibiotics.

Check out how to use D mannose for a UTI.

7. Manuka Honey

Manuka Honey has powerful healing properties and it’s completely natural. Studies have shown that it has the ability to kill resistant bacteria that antibiotics aren’t able to work against.

Not only is it a great anti-inflammatory but it also helps kills MRSA infections and other pathogens. Consuming Manuka honey is good for the throat and digestive system. One use of manuka honey is killing H. pylori.

8. Garlic

Garlic has been known for a very long time to be a good natural antibacterial and antiviral. The compound responsible for this is called allicin and is produced after you crush the garlic clove.

If you consume lots of garlic, it will boost your immune system and also directly inhibit viruses and bacteria. In fact, one study conducted in the UK showed that garlic is able to reduce the number of sick days with a cold significantly, as well as reduce symptoms and prevent reinfection.

Check out the ways you can use garlic for a sore throat and which are the best garlic supplements.

9. AHCC 

If there was one supplement that I would recommend to most people it would be AHCC. This supplement is one of the most researched supplements to fight infections and cancer. The only downside is that it can be quite expensive relative to regular beta glucan supplements.

AHCC is used primarily in Asia, but more recently it’s becoming popular in the west. It has hundreds of scientific studies to back up its beneficial effects and there are clinically tested AHCC supplements available for regular consumers.

Check out some of the main benefits and side effects of taking AHCC.

10. Nasal Irrigation with a Neti Pot

Sounds disgusting, right? A recent study was published showing that kids who used products that spray water up the nose such as sterimar help ward of infections.

Sterimar contains water and sea salt at the right concentrations similar to that of the human body. Due to the osmotic effect of salt, you will want to have the right concentration so that it doesn’t cause irritation and bleeding inside the nose.

Interestingly, sea salt actually helps kill bacteria by this method, as well as increasing the action of cilia – which is tiny hairs in your nose that remove particles and keep mucus moving.

When these stop working or are paralyzed by things like cigarette smoke, you can be more susceptible to issues like colds and sinusitis.

11. Red Wine

There was a study on the BBC news website a few years back showing that red wine stops common colds. This is probably due to the resveratrol found in red wine.

“Rather than directly attacking the flu virus itself, resveratrol seems to block host-cell functions that are essential for viral replication, says the report by Anna T. Palamara and colleagues at the University of Rome. They write that the substance holds promise as a possible weapon against flu.”

I’m not much of a wine drinker myself. In fact, I stay away from alcohol generally. But for those who do like a drink, choose red wine!

For those who don’t like a drink, you can try taking resveratrol supplements instead.

12. Broccoli

Broccoli can restore a suppressed immune and also transiently stimulates immune function. The effect is quite dramatic and in-vivo studies show that it stimulates various immune system components to augment the host’s defense against cancer, viral, bacterial, and fungal infections.

One of the main compounds that are created from eating broccoli is called Diindolylmethane and it has very interesting effects!

Diindolylmethane (DIM) Immune Modulating Properties Include:

Stimulation of Interferon-γ Sensitivity by Increasing IFN-γ Receptors.
Stimulation of Interferon-γ, G-CSF, IL-6 and IL-12 Production.
Synergy with Interferon-γ in Expression of the MHC-I Complex.

Find out more about DIM Supplements.

Calorie restriction and immunity in humans

We all die of something, whether it is a heart attack, stroke, cancer, or some other problem.  And high up on the list is death from infections. So in that case, we need to find better ways to protect ourselves from becoming sick.

Usually, viral or bacterial infections can be fatal to many of the elderly because their immune systems are weak. It’s one of the many concerns people have about doing calorie restriction.

CR tends to lower the number of white blood cells that protect us against infections, and therefore this might be our biggest concern.

Based on some of the evidence in animal models where infections such as influenza and bacterial infections are given to mice, CR can have different effects on the survival of these animals.

It appears to depend on the degree of restriction and how much fat reserves the animals have. Once the animal reaches a critical body weight, it is not able to recover from the infection and then dies (see the attached graph which illustrates this point).

During the time symptoms come on there is a marked decrease in appetite and the resources go into fighting the infection. Fever, as well as an increase in metabolic rate, will cause the animal to expend more energy than normal.

As you can tell in the graph, the body weight of both groups decline, but only the ad libitum fed animals are able to maintain enough of their reserves to stay alive and recover.

“Young and aged mice can lose up to 35% of their body weight and recover from infection, which suggests a critical weight indicative of sufficient energy reserves to recover from infection.”

In humans, the critical body weight in which there is a threat to life is a BMI of 13 in males and 11 in Females.

In the study by Dr. Luigi Fontana at Washington University in St Louis, he has shown that the average BMI for people practicing long-term calorie restriction is 19.6, which is above the recommended normal BMI between 18.5-25.

This might give more than enough body fat reserves to survive an infection if such a weight is maintained. However, under more severe CR where a person has a BMI of less than 16, this could pose a significant risk to health and life.

Antibiotics would be very useful in helping ensure that CR does work in humans and that life-extending effect of CR is not prevented by excess mortality due to infectious disease.

If CR does retard the aging process in humans but the risk of death from infectious remains higher, then this might negate any potential lifespan extension that could be gained from lifelong calorie restriction.

Although antibiotics are currently becoming less effective because of the overuse and misuse of antibiotics, newer generations of antibiotics are expected to become available within the next 10 years.

In contrast to the animal evidence which suggests that CR might predispose humans to infections, there is little human evidence to back this up.

So far the work on CR and its effect on immunity in humans haven’t been looked at in enough detail to give a clear answer on the matter.

Recently there was a study that showed those who have been on short-term calorie restriction have improved T cell function, which is crucial against viral infections.

In rhesus monkeys, which are closer to humans biologically and genetically, there have been reports showing that calorie restriction is able to slow down the aging of their immune system.

Anecdotal reports from people who are practicing calorie restriction seem to indicate that there are fewer infections or absence of infections since starting calorie restriction.

However, this might not be because of the calorie restriction itself but might be an effect of the foods that are consumed on the diet. Plant foods contain many compounds that have found to be beneficial in killing bacteria, viruses, and fungi.

Flavonoids, polyphenols, catechins, lactoferrin, fatty acids like omega 3, and beta glucans, are all generally consumed in far greater amounts in a typical calorie restriction diet.

The combination of these compounds might have a synergistic effect in not only attenuating the decrease in immune system capability to deal with the infection but also directly inhibit infections.


[1] Barry W. Ritz and Elizabeth M. Gardner. Malnutrition and Energy Restriction Differentially Affect Viral Immunity

[2] Davis JM, Murphy EA, Brown AS, Carmichael MD, Ghaffar A, Mayer EP. Effects of oat beta-glucan on innate immunity and infection after exercise stress.

[3] Messaoudi, J. Warner, M. Fischer, B. Park, B. Hill, J. Mattison, M. A. Lane, G. S. Roth, D. K. Ingram, L. J. Picker, D. C. Douek, M. Mori, and J. Nikolich-Zugich. Delay of T cell senescence by caloric restriction in aged long-lived nonhuman primates. Proc Natl Acad Sci U S A 103 (51):19448-19453, 2006.

[4] Ahmed T, Das SK, Golden JK, Saltzman E, Roberts SB, Meydani SN. Calorie restriction enhances T-cell-mediated immune response in adult overweight men and women. J Gerontol A Biol Sci Med Sci. 2009 Nov;64(11):1107-13. Epub 2009 Jul 28.

[5] Synergistic effect of nonspecific immunostimulation and antibiotics in experimental peritonitis.[

[6]Supplementation with active hexose correlated compound increases survival following infectious challenge in mice.

[7] Active hexose correlated compound (AHCC) enhances resistance to infection in a mouse model of surgical wound infection.

[8] Prophylactic efficacy of a basidiomycetes preparation AHCC against lethal opportunistic infections in mice

[9] Antiviral Res. 2005 Nov;68(2):66-74. Epub 2005 Aug 9 Antiviral effect of catechins in green tea on influenza virus

[10] Rowe CA, Nantz MP, Bukowski JF, Percival SS.

A specific formulation of Camellia sinensis prevents cold and flu symptoms and enhances gamma, delta T cell function: a randomized, double-blind, placebo-controlled study.

[11] Ziv OREN, Jeffrey C. LERMAN*, Gudmundur H. GUDMUNDSSON†, Birgitta AGERBERTH‡ and Yechiel SHAI Structure and organization of the human antimicrobial peptide LL-37 in phospholipid membranes: relevance to the molecular basis for its non-cell-selective activity

[12] Is honey the answer to the MRSA crisis–name_page.html

Reviewed and updated: February 2019.

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  • Matt, this is a nice post with a variety of potential strategies for maintaining good health. Regarding the 100% mortality for the energy restricted mice, it is well known that CR reduces the white cell count. Most people who practice a sufficient degree of CR have low white blood cell counts. This may contribute to not being able to cope well with infections, and it may be advisable to keep sufficient body reserves by not letting the BMI fall below 17.5 which is considered the threshold of anorexia.

  • Hi Matt,

    Thanks very much for posting that reconstructed figure on the time course of body weight in immune response to & survival of flu — I had missed it, and it’s exceptionally important!


  • Hey Matt,
    That was a very interesting entry to read. As someone with a bmi around 16.7 and currently practicing CR, it seems the best way to avoid the infection related mortality would be to make sure you consume enough calories while sick even if you don’t feel hungry. If someone was so sick they could not keep food down, that would seem to be a cause for major concern.

  • “it seems the best way to avoid the infection related mortality would be to make sure you consume enough calories while sick even if you don’t feel hungry. If someone was so sick they could not keep food down, that would seem to be a cause for major concern.”

    Yes thats what I do! Except when I am nauseaus but I seldomly am.

    Oh and my dad had to take vitamin D for these blisters he kept getting on his lips, and it cured it 🙂

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