Not Common Knowledge: The Largest Immune Organ

Monday, July 9th, 2018

Although many consumers understand the basics of the immune system—such as how one catches a cold—most are not aware that the largest immune organ in our body is the gastrointestinal tract. By Shali S.

We rarely consider the function and functionality of our immune systems until there’s a bump in the road. This calls to mind Aldous Huxley’s (arguably) most renowned saying: Most human beings have an almost infinite capacity for taking things for granted—this is, unfortunately, true in the case of our immune systems. We undervalue our immune health despite its profound impact on our longevity.

As Dr Jill Cline, author of The Immune System notes: “The benefits of good immune health go beyond protection from infections and often the immune system is undervalued until a problem occurs. Immune health or the lack thereof, has profound metabolic consequences and new research indicates that it can affect several body systems including cognition, allergic response, gut health and longevity.”

Most people understand the immune system as the first barrier of defence against external infections—in other words, it performs the function of fighting off infectious bacteria before it takes root in the host. While our immune systems are able to prevent active infections most of the time, once in a while, pathogens are able to get past the aforementioned barrier of defence, causing our immune systems to take action against these pathogens through physical responses: common symptoms include fever, flu and other inflammatory responses.


Not Common Knowledge: The Largest Immune Organ

Although many consumers understand the basics of the immune system—such as how one catches a cold—most are not aware that the largest immune organ in our body is the gastrointestinal tract. According to Dr Cline, the GI tract contains 70 percent of all immune cells. She notes: “…vast numbers of bacteria inoculate the gastrointestinal (GI) tract shortly after birth and play an integral part in normal immune system development. The GI tract utilises all three primary body defences: physical barriers, innate immunity and adaptive immunity.”

Physical Barriers: physical barriers on the surface of the body play a significant role in slowing or blocking microbial invasion.

Considering that the human gut is the largest immune organ, the most effective way to support and boost the immune system would be through effective nutrition. The foods we consume not only affect growth and development in the long run, they also contribute to the microorganisms living in the GI tract—microbiota—which play a vital role in regulating nutrient absorption of the intestinal cells. In other words, we are what our microbiota eat!

There are several ways to achieve a healthy microbiome naturally, two of which are linked to the consumption of pro and prebiotics. Probiotics are types of ‘living’ friendly bacteria similar to those that inhabit the digestive tract. Sources of probiotics are cultured foods, like yogurt, kefir, sauerkraut and kimchi. Prebiotics are ‘non-living’ food ingredients that reach the large intestine unaffected by digestion, and ‘feed’ the good bacteria in the gut, helping them grow and flourish. Good sources of prebiotics include bananas, honey, onions and leeks.


A Surprising Source Of Probiotics In Asian Nutrition: Tempeh

Although originally an Indonesian ingredient, tempeh has been a part of Southeast Asian cuisine for decades. But little do consumers know that this one humble ingredient is rich in probiotics, protein, fibre, B vitamins and many more naturally-occurring minerals that help gut microbiota flourish. The proteins found in tempeh also have high biological value—in other words, they are complete proteins with essential amino acids—and help to increase good cholesterol.

Tempeh also restores the balance of intestinal flora in the digestive tract and helps to prevent bloating and diarrhoea, as well as eliminates any harmful bacteria in the gut. According to research from the Journal of the American Dietetics Association, consuming foods with probiotics regularly—like tempeh—helps to boost the immune system by maintaining the status quo of the gut.


We Are What Our Microbiota Eat

Many millennial consumers are turning to traditional eats, like tempeh and other fermented foods, to maintain optimal gut health. It is important to keep in mind that although it is tempting to purchase additional supplements to help maintain a healthy gut, nutrition is the fundamental way in which our largest immune organ, our gut, can remain a healthy microbiome.


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