Gut Health Series, Part 3: The Gut-Immune Connection

It’s that time of year again. Cold and flu season is upon us, and the desperate search for an immune boost has begun. Let’s face it: no one actually enjoys being sick, and many can’t afford to take the time off work. Fortunately, there’s only one place you need to look for answers to boosting immunity: your gut!

Up to 80% of your immune system is located in the gut. The intestines contain the largest mass of lymphoid tissue in the entire body. This tissue stores immune cells, such as B cells, T cells, and natural killer cells, that recognize and defend against viruses, bacteria, and parasites. Because our intestines are inside our bodies, most people don’t realize that they form a protective barrier between our bloodstream and the outside world. What’s inside your gut often comes from outside your body- from the food you eat, the air you breathe, and the water you drink. This barrier is an important part of the immune system, providing the first line of defense against anything dangerous you happen to breathe in or swallow.

The intestines may seem small, but their total surface could cover an entire tennis court. There are over 500 different species of bacteria contained in the human intestines. That’s around 3 pounds of bacteria! Some of these bacteria are beneficial for our health, while others can be harmful. This ratio between “good” and “bad” bacteria is one of the most important factors in immunity. The beneficial bacteria in the gut protect us in all kinds of ways. They regulate inflammation and produce substances that kill off infectious bacteria, such as E.Coli and Salmonella, that can make us sick. They also compete with bad bacteria for food and space. When good bacteria take over, there’s nothing left for bad bacteria to thrive! Finally, beneficial bacteria “talk” to epithelial cells that line the gut, helping keep the protective barrier strong and healthy.

What happens when the gut barrier breaks down?

A healthy gut regulates which particles pass through this barrier into the rest of the body. There are small “gates” between cells of the barrier that allow digested food to pass through, while keeping undigested food and harmful substances inside for further digestion and elimination. When this barrier breaks down, a condition known as leaky gut, proteins and bacteria can “leak out” into the bloodstream and trigger an immune response. Large proteins and bacteria are meant to stay in the intestines. When they escape and enter the bloodstream, your immune system fails to recognize them and treats them like a foreign invader. One of the immune system’s main roles is maintaining balance between reaction (recognizing something as harmful and launching an attack) and tolerance (recognizing something as harmless and ignoring it). With leaky gut, the immune system becomes overwhelmed, loses its tolerance, and reacts to all kinds of unnecessary things. This lowers overall defenses as the immune system is too exhausted to fight off bacteria and viruses, leading to higher rates of colds, flus, and other infections.

Leaky gut can also increase food sensitivities, which further lower immune function. For example, you eat a piece of cheese and dairy proteins slip through the intestinal barrier, triggering an immune reaction. The immune system is now primed to react every time you eat this food. The more time and energy it spends attacking food, the less it has to fight off things that are actually harmful.

What causes leaky gut?

As discussed in Part 2 of this series (the gut-thyroid connection), there are many factors that can compromise digestive health. Antibiotics, NSAIDs, birth control pills, chronic stress, and poor diet are the most common. These create inflammation in the gut and can also signal the “gates” in the barrier to open up and spill large proteins into the blood. Even factors during birth and infancy can impact gut health. Children born through c-sections have been shown to have lower levels of beneficial bacteria. Breastfeeding is also an important factor because it colonizes a newborn baby’s gut with healthy bacteria from the mother.

How can I tell if I have leaky gut?

Not surprisingly, many of the symptoms associated with leaky gut are the same signs that point to a weak immune system. Common symptoms include:

  • Frequent colds or flus
  • Fatigue
  • Headaches
  • Joint pain
  • Skin breakouts or rashes
  • Recurrent sinus, ear, and/or skin infections
  • Digestive problems, such as cramping, nausea, frequent gas/bloating, heartburn, diarrhea, and constipation

What can I do to improve my gut and immune health?

Fortunately, there are many ways to help heal leaky gut and reintroduce healthy bacteria! Try these simple steps below to help improve your gut and get your immune system back on track:

Try an elimination diet. An elimination diet removes the most common food sensitivities, including gluten, dairy, eggs, corn, and soy. These foods can cause inflammation that worsen leaky gut and decrease immune function (remember, if your immune system is busy fighting foods, it doesn’t have much time for anything else). Avoiding foods for a period of 3 months, then adding them back in one at a time can help determine individual sensitivities.

Incorporate gut-friendly foods and supplements. L-glutamine, aloe, licorice, and zinc carnosine are popular supplements to help restore the intestinal lining. Fermented foods, such as kombucha and fermented vegetables, are free from major allergens and help increase healthy bacteria in the gut.

Avoid overuse of antibiotics. While antibiotics can be lifesaving, they are also overprescribed. Colds and flus are often viral and antibiotics kill bacteria, not viruses. They are often prescribed on a “try it and see” basis- if the infection is bacterial, they may work. If it’s viral, they’ll be ineffective and will wipe out good bacteria, further compromising your immune system.

Skip the antibacterial products. We’ve been taught to Lysol our homes and slather ourselves in hand sanitizer during cold and flu season. These products, like antibiotics, wipe out healthy bacteria and may even increase antibiotic resistant bacteria (these strains can be harmful and may not respond to antibiotics). Studies have shown that regular soap and water are just as effective at reducing bacterial levels on hands as antibacterial soaps without the associated risks!

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