The Immune Miracle – Chapter 5 – Eating for Immunity

Dr. Shawn Talbott (Ph.D., CNS, LDN, FACSM, FACN, FAIS) has gone from triathlon struggler to gut-brain guru! With a Ph.D. in Nutritional Biochemistry, he's on a mission to boost everyday human performance through the power of natural solutions and the gut-brain axis.

The Immune Miracle

The all-natural approach for better health, increased energy, & improved mood.

Shawn M. Talbott, PhD, CNS, LDN, FACSM, FAIS, FACN


Chapter 5

Eating for Immunity

The first thing to keep in mind when it comes to supporting the immune system with lifestyle interventions such as diet, exercise, stress management, and dietary supplements, is that they’re ALL important in their own specific way. You can’t neglect one and expect the others to “pick up the slack” or expect a supplement to “make up” for a poor diet. That said, dietary supplements can be an easy, safe, and effective way to help your immune system “get an edge” when you’re under stress or find your systems depleted or run down.

When it comes to dietary supplements, we need to also consider that there is a huge difference between chronic supplementation (to support the immune system on a regular basis) and acute supplementation (to bolster immune system activity to battle an existing infection). For example, the popular immuno-stimulant herb echinacea appears to be quite effective (when standardized for the right compounds) in stimulating immune system activity to battle a new infection – but it is not recommended for prolonged or continuous use, due to concerns over cellular toxicity. Likewise, vitamin C and zinc would be appropriate at low doses for chronic “protection”; whereas, higher levels are effective on a short-term basis for direct activity against invading pathogens.

You might remember from the Introduction of The Immune Miracle, that the primary key to bolstering immunity is, of course, to protect our bodies from infection in the first place. The last chapter (Chapter 4) gave an introduction to the concept of immune system priming. The next chapter (Chapter 6) goes into even more detail about how to most effectively prime our immune system function for optimal health and wellness. Some of the supplements covered in this chapter help to maintain normal immune system function, while others actively promote or stimulate immune function above normal levels. The latter approach is one that should not be undertaken lightly, and then only for a short period of time, because as indicated in earlier sections, a chronically stimulated immune system can be just as bad as a chronically suppressed immune system: both can lead to myriad health problems.

When it comes to protection (or prevention), we’re primarily talking about strengthening the immune system. It is always a good idea to keep your immune system “humming” throughout the year (not just when cold and flu season comes rumbling into town). The sections that follow provide a number of points to consider for supporting immunity, including nutrition, exercise, rest, fluid intake, and exposure to pathogens.

Exposure to pathogens

Viruses cause colds and flu; bacteria can cause all sorts of unpleasant effects (gastrointestinal cramps, fever, diarrhea, etc.). Probably the most effective way to reduce your exposure to any pathogens is to wash your hands as frequently as possible. One of the primary ways that viruses and bacteria are transferred between people is through “secondary contact” – someone with the “bug” touches something, like a handrail or doorknob; then, you touch the same object and pick up the “bug” there. Frequent hand washing can reduce the chance that you’ll transfer those pathogens from your hand to your eyes or nose, where they’ll enter and begin to infect your body.

Fluid intake

Why is it that our mothers and grandmothers always made us drink more fluids when a cold came on? Mostly, it’s because your body needs that extra fluid to “flush out” the infection – via several routes, including increased mucous production. With the more severe influenza infections, dehydration can result from fluid lost from vomiting and diarrhea; so, be sure to replace all losses plus drink a bit extra for good measure.


Regular physical activity is a vital part of maintaining optimal immune function: those who exercise at a moderate level at least a couple of times each week are far less likely to get sick compared to sedentary individuals. On the other hand, be aware that extremes of exercise – whether extremely intense or extremely long in duration (such as marathons or triathlons) – have been associated with reduced immune protection and increased risk of infection (primarily in competitive athletes).


When it comes to optimal nutrition, any significant nutrient deficiency can impair functioning of the immune system. As such, it is always wise to include a complete multivitamin supplement as part of your total immune system support. In a multivitamin, be sure to look for one that supplies at least the recommended daily allowance (RDA) levels for the nutrients listed below. Many popular products contain some of them; so, check the labels and add additional amounts as needed to reach the suggested intake. To round out your nutrient armory, consider adding additional amounts of key amino acids such as N-acetyl-cysteine (1-2 grams per day) or glutamine (1-5 grams per day) – both of which have been linked to elevated immune system responses. Finally, there are a number of immune-stimulating herbs and herbal blends available,  the most effective of which seem to be echinacea, goldenseal, and astragalus.

Immune-friendly Nutrients

Nutrient Daily Value (Adults) Optimal Intake for Immune Support
Vitamin A 5,000 IU 5,000 IU with at least 50% derived from beta-carotene (women who are pregnant, or who may become pregnant should NOT exceed the RDA for pre-formed vitamin A unless directed to do so by a personal physician)
Vitamin C 60 mg 250 – 1,000mg
Vitamin E 30 IU 30 IU from natural mixed sources including both tocopherols and tocotrienols
Vitamin D 600 IU 1,000 – 2,000 IU
Mixed Carotenoids 5-6 mg 5 – 50 mg
Iron 18 mg 18 mg
Selenium 62 mcg 100 – 200 mcg
Zinc 15 mg 15 – 45 mg


Astragalus has been used as an herbal “tonic” for centuries in Traditional Chinese Medicine (TCM) and in Native American folk medicine. As a tonic, astragalus is used primarily as a “prevention” herb throughout the cold and flu season – a different usage than the more popular echinacea, which is best used for early stage treatment as soon as you feel a cold or flu coming on. Research studies have shown that astragalus can help fight bacteria and viruses by enhancing various aspects of the body’s normal immune response, i.e. enhanced function of specific immune system cells such as T cells, lymphocytes, and neutrophils. In TCM, astragalus is often combined with other “tonic” herbs such as ginseng, cordyceps, or ashwagandha, to keep the immune system “humming” during periods of high stress; each of these appear to be somewhat effective in increasing energy levels and (possibly) enhancing the immune-stimulating effects of astragalus.

Echinacea is the “King” of the immune function herbs (with over 300 scientific studies attesting to its immune enhancing effects). It is important to note that the primary use of echinacea is in the acute (short-term) treatment of the common cold – NOT for prolonged use (past a few weeks) as general immune system support. Also, echinacea is generally not recommended for use by individuals with autoimmune disorders (such as multiple sclerosis or rheumatoid arthritis) due to its immune stimulating properties. The best use of echinacea is immediate consumption following acute exposure to an infected individual (meaning that as soon as Aunt Mary coughs on you, you should reach for the echinacea capsules).

Goldenseal is a popular herbal remedy for immune system stimulation, due to its high content of berberine. Because of the “endangered” status of goldenseal, however, many consumers (and supplement manufacturers) are turning to other berberine-containing herbs such as barberry and Oregon grape, which also appear to be quite effective alternatives for immune system support. Berberine has been shown to block the adherence of various infectious bacteria (such as streptococci) to the body’s respiratory linings. However, berberine-containing herbs are known to cause uterine contractions, so they should be avoided during pregnancy.

A number of mushrooms are used in TCM to support immune system strength. Among the more popular are Shiitake, Maitake and Reishi – all of which contain various polysaccharide and amino acid components that may help stimulate immune cell activity and get the immune system “ready” to do battle with invading pathogens. Although they are not completely understood, current theory suggests that the complex polysaccharides and small protein structures present in herbs such as astragalus and in mushrooms act as immuno-modulators, because of similarities between these compounds and the cellular surfaces of pathogenic bacteria (though the herbs lack the infectivity that pathogens have).

Nettle leaf is an herbal treatment used for symptoms of hay fever and other mild allergic conditions. It may act as a gentle antihistamine, helping to alleviate sneezing, nasal congestion, and itchy, watery eyes without many of the common side effects of synthetic antihistamines (nervousness, insomnia, drowsiness).

Probiotics, which are also called “beneficial bacteria”, are quite effective for supporting immune function. The most popular varieties used in dietary supplements, Lactobacillus acidophilus and Bifidobacteria bifidum, have been shown in hundreds of studies to “boost” immune function via their effects on increasing white blood cell numbers, activity, and effectiveness. Used in conjunction with pre-biotics (indigestible carbohydrates that “feed” the growth of friendly bacteria in the intestines) such as fructo-oligosaccharides (FOS), probiotic organisms can displace certain pathogenic microbes in the intestines to help prevent disease. Typical dosage recommendations are in the 2-4 billion organisms/day range. Be careful to select a product that is fresh and has been transported and stored under proper conditions (refrigeration is best).

Vitamin C is the perennial immune-booster and cold-fighter. Despite the exaggerated old wives’ tale of vitamin C preventing the common cold, it is clear that regular consumption of higher than RDA amounts of vitamin C (500mg to 2 grams daily) can help reduce the duration and severity of colds. In fact, clinical studies now suggest that about 1 gram of vitamin C consumed on a regular basis throughout the cold and flu season can reduce cold incidence by about 20% and cold duration by almost 40%. Vitamin C can also act as a natural antihistamine to help open up congested airways. In some people, however, high doses (500mg or more) can produce mild diarrhea or gas, so you may need to experiment to find the most effective dose for you (reduce intake until symptoms disappear).

Often used in conjunction with vitamin C are a wide variety of bioflavonoids, such as quercetin, rutin, hesperidin, and a number of  catechins and polyphenols found in green tea, grape seed, and pine bark extracts. All possess powerful antioxidant functions that can both strengthen immune system cells and protect healthy body tissues from damage; some, such as quercetin, may also work as an antihistamine. Taken separately, or in combination in “mixed bioflavonoid” complexes, these phytochemical compounds can be taken at dosages of several hundred milligrams per day to help prevent infections and alleviate mild symptoms of colds, flu, and allergies such as hay fever.

Vitamin A is an effective immune system nutrient because it helps keep bacteria and viruses from penetrating the protective mucous membranes (mouth, nose, stomach, lungs) and gaining a foothold in the body. Since vitamin A is a fat-soluble vitamin, people on low-fat diets may be limiting their consumption of foods rich in vitamin A (liver and dairy) and should consider a supplement. For men and postmenopausal women, vitamin A is considered relatively safe up to 25,000 IU (7,500 mcg of “retinol equivalents” – or RE) per day, but it is best to avoid dietary supplements with more than 5,000 IU of “pre-formed” vitamin A in favor of supplements that provide at least half of their vitamin A content in the form of natural beta-carotene. In pregnant women, or in those who could become pregnant, less than 10,000 IU (3,000 mcg RE) per day is more prudent, as high-dose vitamin A is linked to birth defects and other damaging effects in the developing fetus. All women considering becoming pregnant should discuss vitamin supplementation with a personal physician – especially for vitamin A supplements. A safer alternative may be to consider a mixed-carotenoid supplement, because beta-carotene can be converted into vitamin A in the body, but only at levels which the body requires.

Selenium is a building block of the body’s key antioxidant enzymes, glutathione peroxidase (GPx). GPx is also thought to play a key role in helping immune system cells protect us from invading viruses and bacteria. Selenium has shown positive results as an important immune system nutrient in studies of cancer (some forms of which may be caused by viruses), AIDS, and chronic fatigue syndrome. When combined with zinc, these two nutrients provide a boost to general immunity. Since few Americans get the recommended amounts of either selenium or zinc from their diets, a dietary supplement may be needed – especially during the cold and flu season. To achieve intake levels associated with enhanced immunity, consider a supplement providing selenium (200mcg/day) and zinc (15-30mg/day) together.

Zinc lozenges have become one of the most popular natural approaches to treating the common cold, and there is actually some good scientific evidence to support their use. Zinc lozenges appear to reduce cold symptoms, such as sore throats, hoarseness, and coughing – and may even be able to shorten the duration of colds by a full day or so. Like vitamin C, zinc is an essential nutrient for optimal functioning of the immune system; both offer significant antiviral activity when consumed at elevated levels for a short period of time. It appears, however, that some forms of zinc lozenges may be more effective than other forms, due to the total amount of ionized zinc that the lozenge actually releases into the mouth and throat. At least one study has shown that lozenges containing zinc gluconate plus citric acid, sorbitol, or mannitol may not deliver high enough levels of ionized zinc; whereas, lozenges which contained glycine (an amino acid) appeared to deliver a higher quantity of ionized zinc.

Vitamin D is a fat-soluble vitamin that acts as a steroid hormone (the body can make its own vitamin D from cholesterol in the skin after being triggered by the sun’s UVB rays). Thus, factors such as sun exposure, use of sunscreen, geographic location, gender, age, race, and others will influence a person’s vitamin D status. Vitamin D, as a steroid hormone, influences virtually every tissue system in the body, including our bones, intestines, pancreas, brains, muscles, cardiovascular system, and cell growth cycles (which are related to cancer risk). In addition to the long list of biological functions of vitamin D listed above, vitamin D also acts as an immune system modulator – preventing excessive expression of inflammatory cytokines and increasing the “oxidative burst” potential of macrophages. Vitamin D dramatically stimulates the expression of potent anti-microbial peptides which exist in neutrophils, monocytes, and NK cells – as well as in the epithelial lining of the respiratory tract where peptides play a role in protecting the lung from function.

According to research published in the New England Journal of Medicine (2007), most of us (as many as 1 billion people worldwide) have a vitamin D deficiency. Some of the most common risk factors for vitamin D deficiency include:

  • Living at Northern latitudes (anywhere above San Francisco or Philadelphia or London – no vitamin D is made in the skin at a latitude of 52-degrees-N from October to March, because the atmospheric ozone filters out the UVB rays of the sun)
  • Failure to get at least 15 minutes of direct sun exposure daily
  • Being dark-skinned or African-American
  • Being elderly (those over 50 make only 25% of the vitamin D of a 20-year-old)
  • Being overweight.

A “normal” range of vitamin D in the blood is 30-74mg/mL – and an “optimal” level suggested by most research is 50-70mg/dL (for protection from heart disease and cancer). Being in full sun for 15-30min in the summer will produce approximately 20,000IU of vitamin D, which is released into the circulation within 48 hours (assuming person is light-skinned, non-elderly, and of normal body weight).

Vitamin D reduces cell proliferation and increases cell differentiations. It also slows the growth of new blood vessels and reduces inflammation – each of which can reduce the risk for certain cancers. In numerous studies, higher intakes of vitamin D and higher vitamin D status have been linked with reduced rates of cancer. A study from Creighton University showed a 77% reduction in cancer diagnoses (with 1,100IU/day of vitamin D in postmenopausal women). Another, the Health Professionals Follow-up Study (HPFS), showed a reduction by half in colon cancer rates  when comparing the subjects with the highest to the lowest vitamin D concentrations.

Scientific evidence also suggests that vitamin D deficiency is responsible for immune-related conditions including autism and asthma. For example, the seasonal vitamin D deficiency that spikes during the winter months (when sun exposure is reduced) has been associated with immune system dysfunction, including autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes, rheumatoid arthritis, and autoimmune thyroid disease. Many scientists have even suggested that the vitamin D deficiency in the winter months may be the seasonal trigger for influenza outbreaks around the world.

Flu epidemics rear their heads in the winter (when vitamin D levels are low) and retreat in the summer (when vitamin D levels are higher); this is despite the fact that influenza viruses are found in the population year-round (but epidemics do not “break out” until vitamin D levels fall). Vitamin D levels are lowest (in the Northern hemisphere) from November through May (7 months) and highest (enough to prevent flu outbreaks) in from June through October (5 months).

Why Vitamin D Supplements Are Needed

Only a very few foods are a good source of vitamin D, including fortified dairy products and breakfast cereals, fatty fish, beef liver (too high in vitamin A for vitamin D to be absorbed), and egg yolks. Cod liver oil is also a good source of vitamin D, but also tends to contain too much vitamin A, which can interfere with the absorption and activity of vitamin D in the body. Researchers from Creighton University have estimated that 3,000IU/day of vitamin D (total intake including food and supplement sources) is required to assure that 97% of Americans will achieve desired blood levels of 35ng/mL.

The two forms of vitamin D found in dietary supplements are D2 (ergocalciferol) and D3 (cholecalciferol). D3 is the preferred form because it is chemically equal to the form of vitamin D produced by the body, and is 2-3 times more effective than the D2 form at raising blood levels of vitamin D. A daily dose of 2,000IU of vitamin D3 would be expected to raise blood levels by 20mg/mL – which is about the amount of “deficiency” that the average person might expect to have (especially during the winter months in a Northern-latitude city in the USA).


About the Author

Exercise physiologist (MS, UMass Amherst) and Nutritional Biochemist (PhD, Rutgers) who studies how lifestyle influences our biochemistry, psychology and behavior - which kind of makes me a "Psycho-Nutritionist"?!?!

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