The Immune System – A Primer

Intricate, complex, amazing: That’s the human immune system.

Standing guard throughout every part of our bodies, it protects us from the hordes of germs, fungi, and viruses that threaten to (literally) tear us apart.

In fact, when we eat, our immune systems get into the act from the very first moment we pop the food into our mouths.

Bet you didn’t know that your saliva contains powerful antimicrobials like lysozyme, alpha-amylase, and lactoferrin!

And these antimicrobials are only the basic, front line defense. Any germs, that sneak past, will confront a much more formidable barrier: our stomach’s hydrochloric acid.

Corrosive enough to remove the rust from steel, hydrochloric acid will pulverize most invaders in our stomach before they reach our intestines.

If our stomach acids lose the battle, we also have proteins and chemical compounds further down the digestive chain that can sense and fight any harmful bacteria that may have made it past.

Finally, our own personal bacterial population (those probiotics you hear so much about) help prevent harmful bacteria from entering our bloodstream or taking root in our small intestine and colon.

The foods we eat affect these bacteria and the complex compounds they release.

Nutrient-dense, fiber-rich whole foods tend to promote a healthy bacterial balance, where as a diet rich in processed foods, fats and sugars can lead to dysbiosis — otherwise known as microbial imbalance.

That’s why a balanced whole foods diet is your best insurance against all kinds of viruses and infections.

In fact, our GI tract comprises of over 70% of our immune system! 

Eating and immunity

If your diet is lousy, you’ll get sick more often than someone who eats a healthier diet.

Viruses and bacterial infections will hit you harder and keep you out for longer. Meanwhile, eating poorly while you are sick, will only make you sicker.

Good nutrition allows our bodies to respond to germy invaders quickly and efficiently.

And in order to function well, the cells of our immune system need plenty of vitamins, minerals, amino acids, and essential fatty acids.

Prebiotics and probiotics

Prebiotics and probiotics deserve special mention for helping to prevent illness. Both are essential for gut health. And gut health is essential to immunity.

Prebiotics (a.k.a. food for bacteria) help nourish our good microbial friends. Usually this is some form of semi-digestible fiber that our bacteria can chow down on, and/or that helps move food through the GI tract.

And probiotics (the bacteria themselves) have been shown to help us recover faster, when we get sick.

That’s why all of us should ensure that our systems are well colonized by these friendly critters.

The best whole food sources of prebiotics are:

• Vegetables: asparagus, garlic, Jerusalem artichokes, leeks, and onions

• Carbs: barley, beans, oats, quinoa, rye, wheat, potatoes, and yams

• Fruit: apples, bananas, berries, citrus, kiwi

• Fats: flax seeds and chia seeds

And the best whole food sources of probiotics are:

• Dairy: yogurt, cheese, and kefir with live and active cultures

• Fermented vegetables: pickles, sauerkraut, kimchi

• Fermented soy: miso, tempeh

• Miscellaneous: soy sauce, wine

Getting probiotics from food

If you’re healthy, aim for 1-2 servings of probiotic-rich foods each day. If you’re hoping to prevent or alleviate a medical problem, you may need to increase the dose.

Getting prebiotics from food

If you’re healthy, aim for 2-3 servings of prebiotic-rich foods each day.

To eat or not to eat: That is the question  

While a whole-foods diet, rich in prebiotics and probiotics, will go a long way towards protecting you from viruses and bacterial infections, even the healthiest diet can’t ward off every invader. And if you do get sick, of course you’ll want to recover faster.

Should you feed a cold and starve a fever, as the famous adage recommends?

One small study did find that eating helps combat a cold virus. And fasting allows the body to fight fever-related infections.

But the study is far from conclusive. Especially when the reasons for its findings remain unclear.

What we do know is that moderate calorie restriction can:

• improve cell-mediated immunity and

• offset chemotherapy-induced and aging-related changes in immune function by helping to replenish stem cells.

On the other hand, during periods of very low food intake:

• our defenses against specific pathogens are lower, and

• the immune system is suppressed.

In the most severe cases, the malnutrition-infection cycle can ultimately lead to kwashiorkor (a severe type of malnutrition).

Sounds like a bit of a toss-up, doesn’t it?

Appetite and illness

With something to be said theoretically both for eating and fasting while sick, practically speaking, it’s best to rely on your own body’s signals.

In fact, when it comes right down to it, our own appetite cues probably give us the clearest picture of what we should eat (or avoid eating) when we get sick.

For example, very few of us want to eat when we’re hit by influenza or by gastroenteritis.

That’s because flu-like bugs and bacterial infections lead to higher levels of circulating TNF-alpha (an inflammatory cytokine), which promotes appetite suppression.

Maybe this is the body’s way of guarding its resources? After all, digestion takes a fair amount of energy — energy that may be better used to fight off invaders when we’re sick.

It’s an interesting possibility, but at this point it’s pure speculation.

The role of inflammation

We do know that behavioral and metabolic factors can influence immunity. Signalling mechanisms that control energy metabolism and immune function seem to be intertwined.

For example, our hunger hormone, ghrelin, may inhibit the creation of pro-inflammatory compounds.

And this can be a good thing or a bad thing — depending on circumstances.

How so? Well, inflammation helps us fight off invading pathogens. But too much inflammation will make our symptoms worse.

For example, a fever will increase metabolism as well as body temperature. This in turn improves the body’s chances of fighting off a bug — speeding it through the system.

At the same time, a fever can also dehydrate us, which makes it harder to move a pathogen through the body and out.

Meanwhile, infection itself can increase our body’s nutrient needs, especially for fluid, protein, and several micro and trace nutrients.

Moreover, specific nutrients can affect immune function. A particular nutrient might be a source of fuel for an immune system cell, or it might influence other tissues that regulate overall immune function.

All in all, we’re talking about a very complex set of relationships. No wonder scientists have yet to get to the bottom of it all.

That said, considering that colds often result from viral infections, and fevers often result from bacterial infections, the advice to eat when you have a cold and fast when you have a fever does rest on some plausible biological arguments, which is why, in cases of mild or moderate illness, it’s worth a try.

Especially if your own appetite agrees.

Whole foods and immunity

Let’s say you get sick despite all the precautions — and your appetite doesn’t entirely disappear. Are there any particular foods that could hasten recovery?

As a matter of fact, there are.

A few examples:

• Garlic. Acts as an antibiotic, and has consistently been found to lessen the severity of colds and other infections.

• Chicken soup. Commonly touted as a food for colds, chicken soup actually works! It provides fluids and electrolytes, is warm and soothing, and may also contain anti-inflammatory properties that decrease cold symptoms. You have to use real chicken soup though — the kind you make from simmering a chicken carcass — rather than stuff from a can or package.

• Green tea. Boosts the production of B cell antibodies, helping us rid ourselves of invading pathogens.

• Honey. Has antibacterial and antimicrobial properties, and is an effective cough suppressant. In one study it was as effective as a cough-suppressing drug. A few teaspoons in a cup of green tea is all you need. (Plus, you’ll get the benefits of green tea at the same time.)

Supplements

In general we use whole foods to improve our immunity. But under certain circumstances, you might want to supplement.

Nutrients that can support immunity and that are generally well tolerated, include:

• Vitamin C supplements

• Zinc

• Elderberry extract

• Ginseng

Quercetin may also assist in immune function (1,000 mg a day for 3 weeks). It’s found in onions, apples, red wine, broccoli, tea.

Beta-glucan (found in oats) might help immunity.

Stevia might enhance white blood cell activity.

Selenium also appears to play a role in infection and changes in viral virulence (but be mindful of excessive supplementation).

Consuming foods rich in vitamin E (such as nuts, olive oil or avocadoes) may also help. This may enhance T cell function. And might lead to less influenza and fewer respiratory infections.

What you can do right now

To prevent getting sick:

• avoid over or under exercising

• avoid over or under eating

• maintain a healthy body weight

• wash your hands

• get enough sleep, consistently

• manage stress

• eat plenty of nutrient-dense foods

• feed your healthy bacteria

For some, periodic fasting might also be useful.

Also, consider supplementing vitamin D, probiotics, and a wide-spectrum food-based vitamin/mineral supplement.

But recognize that if you’re not eating a balanced, whole food diet, supplementing with probiotics won’t do a lot of good. An isolated supplement can’t fix a broken diet. Address your diet first.

If you’re already feeling sick:

• drink lots of fluids (especially water and green tea)

• rest and recover

• focus on immune-boosting foods

• supplement with pre and probiotics

• use immune-boosting supplements

And above all, listen to your body cues.

If you’re hungry, eat. If not, don’t.

If you’re hungry, eat. If not, don’t.

In the end, no matter how well you manage your nutrition, exercise, sleep, and stress, you will get sick sometimes. We all do.

Don’t be a hero and pretend you’re not sick. Instead, take the steps outlined here to get back on your feet as quickly as possible.