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Nutrition and immunity

In her weekly column, Bradford West Gwillimbury licensed nutritionist Nonie De Long talks about the proper nutrition for a good immune system
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Dear Nutritionist,

I’ve read your column a lot over the past year. I really look forward to it but I have a hard time understanding how nutrition can affect so much. For example, when this whole COVID thing hit last year you wrote that it impacts immunity. I remember because there were some heated responses to the idea. My question is this: do you really think nutrition affects immunity? If so, tell us how exactly. I, for one, don’t understand it and would like to.

Thank you,
Janet

Dear Janet,

Thank you for reading regularly and for the challenging question. Ok, challenge accepted! Let’s talk about the thing nobody in public health is talking about during this public health threat: our immune systems! Let’s talk about how they work and what on earth that has to do with nutrition. But this is a complex question, so I’m going to address it in two parts. Today we’ll talk about the immune system and implications for immunity and next week we’ll unpack theories in immunology.

Innate Immunity
You may be surprised to learn that the human immune system has many branches. One set of these is often referred to as innate immunity. This type of immunity is indiscriminate. It is simply a system set up to keep offending pathogens locked out or, to take them down fast if they get in. Let’s explore this more.

Our first line of defense is actually our skin. It provides a physical barrier to limit what is able to get into the body. Let’s think of this as our shield. It’s hard to penetrate because the cells are so tight and it’s also oily and acidic to help protect against pathogens. Once the skin is broken, the healthy body responds immediately to marshall help to the site of breach. That is how scabs and swelling happen in an area where the skin has been punctured or cut or scratched.

Potential pathogens may try to enter via other openings instead of our skin, so we also have mucous membranes. The nasal passageways and bronchi of the lungs house mucus to trap and stop potential pathogens as they enter. This is part of the reason nose breathing is so important for optimal health. As we all know, mucous production is ramped up when the body thinks there has been a breach of its defenses.

These passageways also have a structure called cilia. These are tiny hair-like molecules that work to sweep unwanted debris that have been trapped out of the lungs and nasal opening. In addition, muscles and innate reflexes that cause us to cough and sneeze also help us to expel germs from the airways. (I just sneezed as I wrote that. My immune system is doing its job)!

Our ears similarly have their own excretions to trap potential pathogens, and there are cilia in the ear canals to sweep these pathogens out. The eyes have lash lined lids to protect them, as well as tears that wash away debris that may enter. The vaginal canal in women has an acid pH and microbiome that protects it from pathogens. The ureters and colon also have their own unique mucous membranes to protect them from invaders, as well.

Bacteria and viruses and parasites can also enter via the mouth. So, much like the exterior of the body, the digestive tract from top to bottom is lined with a skin membrane to keep potential toxins or pathogens out. If something bad does get in through the mouth and the nose doesn’t detect it, we have a very strong acid produced by the lining of the stomach to kill the offender when it arrives. The immediate reaction of the stomach to something that is profoundly unwholesome is to retch it out. Or quickly expel it. But sometimes it is just killed by the stomach acid.

Further down, the intestines have a mucous membrane and cilia, much like the lungs, with tight junctions to keep potential harms out and sweep the digested food along. These tight junctions help the healthy gut membrane to be highly selective in what it lets through.

We also have a plethora of bacteria (more than we have human cells) to help break down and absorb foods, synthesize vitamins, signal hormones, and inform the immune and nervous systems. Science on the role of the gut biome in immunity is still being unpacked to understand how we can harness it.

If, by chance, anything gets past these, we have an inflammatory response, run by mast cells that live in our connective tissues. They essentially roam around looking for suspicious activity to respond to. When they do find potential invaders (usually identified by proteins) they create histamine. This, in turn, makes blood cells more permeable to get blood into the area, complete with white blood cells to fight infection.

This is what happens in an allergic reaction. We will get redness, heat, swelling, itching, and increased mucus production. The reason why antihistamines are effective is because they block the histamine response that signals the other responses. The problem with this approach, however, is that the body will continue to signal louder and louder when there is an underlying problem like a repeat offender and silencing one signal will result in another popping up. Think of a biological whack-a-mole situation. You take antihistamines like mad and your allergies suddenly stop but now you have a new, deeper symptom like IBS instead. Yes, dear reader, they are connected.

In the inflammatory response there are some white blood cells that can actually chase and envelope offending pathogens. Others just kill the pathogen and die. When these collect we get pus. And yet others protect our organs not only from outside invaders but also rogue cells inside. There are even cells called natural killer cells that, well, just naturally kill unhealthy cells via an enzyme. They seek out damaged cells in our bodies - so for example when an invader has infected one of our cells - and secrete an enzyme that dissolves the invader’s membrane.

We also have specialized cells on the surfaces of our bodies, both inside and out, that watch for invaders then eat them and take that information back to the spleen and lymph nodes to inform the immune system about what to watch for.

This is only the innate immune system! We still have the acquired branch of the immune system to discuss.

Acquired Immunity
The acquired immune system is more highly evolved. It has to learn about pathogens we are exposed to and store information on them to figure out how to target them with our defenses. Once this part of our immune system encounters a virus it stores that information forever, often as antibodies. Think of these as tags. Whenever we are exposed to that offender henceforth, the healthy body knows what to do to take it down promptly. This applies to new strains of the same virus, as well.

The acquired immunity starts to develop as soon as we are born. The more pathogens we are exposed to, the more informed and stronger this immune system becomes. Once an offender is tagged, special cells mount different responses including swarming the offender so it can’t move and killing it. This acquired immunity can even be passed to us via mother’s milk and is only one of the advantages of breastfeeding for a healthy baby.

Acquired immunity can be further divided into responses for when cells are infected and when infection is just in the body fluids. The first is called a cell mediated response and it includes cells that signal for help and others that signal to be destroyed. The second is the humoral response, as bodily fluids were historically called the humors. This response regulates antibody production. It gets more specialized than this, but now you have the basic understanding! All this is to say, your body has some very very specialized cells with very specialized functions and various arms of its immune system.

Now we will now discuss how nutrition impacts these.

Immunity and Nutrition
How do you imagine cells are made? We are born with them, yes, but over time they die and are replaced. Some die within days and others over weeks or months. Different cells have different lifespans. When they are replaced, the quality of that cell is determined by the quality of the nutrients available to it at that time. If we have only consumed subpar foods with low nutritional quality, guess what kind of cell membrane and cell mitochondria we are going to make? Guess how those cells will function?

This begs the question, how do we acquire nutrients? Well, we do this through our diet, through bacteria in our guts that synthesize vitamins, and through sunshine on the surface of our skin. Next week we will address the bacteria in our intestines. This week let us look at the other two.

Sunshine
Yes, sunshine impacts immunity profoundly. Vitamin D is a very important nutritional factor in immunity, as it plays a role in regulating our cells and our genes. You can read scientific papers aplenty on this, but a great overview can be found here. You can view a list of articles on the other roles of vitamin D in good health here.

The sun gives us vitamin D, and it can NOT be produced when we wear sunscreen. In Canada we are also limited because we have so many months when exposure to the elements is unrealistic. In addition, those with darker skin tones have to get more sun exposure to make the same amount of vitamin D. As such, most of us are deficient on blood tests. Thus, most nutritionists and doctors now recommend supplementing with vitamin D3 for optimal immune function. Doctors like Dr. Mark Hyman, who specialize in functional medicine, recommend supplementing with between 200IU and 600IU daily. And that is in the U.S. where the seasons may not be as harsh. I know some practitioners who recommend more. The best bet is to get a test from your doctor to help direct your dose. The optimal range is considered between 40-70 ng/mL. Testing or professional guidance is helpful because vitamin D is fat soluble and is stored in the body. It’s best to know exactly what you’re doing.

In addition to D, antioxidants like vitamin C are very important in immune function. Antioxidants prevent or delay cell damage by invaders. They strengthen our immunity to attack from outsiders. Vitamin C deficiency is linked to higher rate of infections and impaired immunity. Humans are one of the only mammals that don’t make vitamin C endogenously. As such, we need to get it from our diets.

Vitamin C is best used in combination with a bioflavonoid like quercetin or taken alongside it, as this is how it’s packaged in nature. Since vitamin C is water soluble, the worst that happens when you get too much is you get loose stools. If you back off with your dose, that subsides. Quercetin is naturally present in the white pith in oranges and peppers, alongside the vitamin C in the food. We don’t typically eat this, so taking a supplement is helpful.

It’s not widely known, but melatonin is another very potent antioxidant that is protective for the immune system. You can read more about it’s unique role in immunity here. This is a lesser known application of melatonin, but it’s important, as it’s one of the only antioxidants that gets into the mitochondria of our cells. And it’s recycled to have more impact. As we use more artificial light at night I see a greater need for melatonin clinically.

I also want to talk about zinc. Zinc is essential in immune function, as you can read here and here. Those deficient in zinc demonstrate more susceptibility to various pathogens, as cited in one of the papers above. Zinc can be supplemented orally, because it’s hard to get enough from our diet. Oysters are the richest source. How many of us eat fresh oysters often? We also need to remember, copper displaces zinc, so copper piping and birth control pills or IUD devices can deplete our zinc stores. Vegetarians are often very deficient in zinc. I prefer the picolinate form for absorption in my clients. To read more on zinc imbalances and supplementation from an expert in functional medicine, go here.

Let me put this all into perspective. If you have low stomach acid because you’ve taken a PPI or are above a certain age (declines as we age) or because of NSAID use that damaged the stomach lining or because you just have a tendency to weak stomach acid via your genes - you aren’t going to extract zinc (or B12) from your foods. You are going to be deficient and more susceptible to various pathogens, according to the research above and copious other sources.

One telltale sign of low zinc is a loss of smell and appetite. When zinc stores are brought back up to a good level, the sense of smell returns.

If you don’t eat fruits and veggies you will not be getting much vitamin C and quercetin. There are few other mammalian species that don’t make vitamin C endogenously. One is guinea pigs. If they don’t get vitamin C drops in their water they die within a short period of time. Die. Other species make it innately so that they have enough. But not humans. So what we eat determines our level of vitamin C unless we supplement. This is one supplement I believe everyone should take. That was the belief of Linus Pauling, perhaps one of the most intelligent and humanitarian scientists to have lived, and still the only person to have won two unshared nobel prizes.

I’ve already explained how we are likely almost all deficient in vitamin D by the end of winter here in the North. So supplementing with vitamin D3 is a very common recommendation for the public here. Good old sunshine can do the job, too.

These are just a few ways nutrition impacts our immunity. Next week we will continue this and explore the gut biome and its role in immunity.

Thank you for writing in, Janet. I hope this answers your question and gives you actionable help to boost your own immune system naturally. As always, if readers have their own health questions, I welcome them. Just send me an email at [email protected]. Readers can sign up for my free newsletter at hopenotdope.ca to stay abreast of health news and upcoming events. Thanks for reading!

Namaste!
Nonie Nutritionista