The most dangerous threat to your immune system may not be what you think it is. This threat isn’t some flesh eating contagion or some vindictive virus seeking to destroy all humankind. In fact, this threat to your immune system is one of the most easily modifiable lifestyle risk factors, meaning you can control whether it becomes a dangerous threat or not.
What is this malicious menace that threatens your ever vital immune system? And how in the world can you be in control of it? Simple. That which can become a dangerous threat to your immune system is a low fiber diet. Yep, not eating your fiber is killing you. But how can that be? Sure we hear that we need to eat fiber to stay regular, blah, blah, blah. So what does that have to do with you immune system. Plenty!
Let’s begin with what exactly the immune system is and what it does.
The immune system is our defense against external pathogens such as bacteria, viruses, etc., and possible harmful internal components such as malignant and autoreactive cells. Furthermore our immune system can be broken down into two parts, the innate (born with) and the adaptive (acquired over our lifetimes). As part of our immune system we have a mucosal defense system that is ever so cleverly placed in areas where those external invaders like to get into our bodies, i.e. respiratory, urinary, reproductive, and intestinal tracts. As part of that mucosal defense is the associated lymphoid tissue. Lymphoid tissue, in general, is the cells and organs that make up the lymphatic system, such as white blood cells (leukocytes), bone marrow, the thymus, spleen, and lymph nodes. Specifically in the gut, there is lymphoid tissue referred to as gut-associated lymphoid tissue (GALT) which works in the immune system to protect the body from invasion in the gut.
So you are probably thinking, great, I now know what my immune system is, but why are talking about fiber? To understand that, let’s now take a gander at our friend fiber.
There are two main types of fiber, soluble and insoluble. Both types of fiber are undigested and not absorbed into the bloodstream. They aren’t used for energy, but instead all arrive in the colon unchanged. Almost all plant food sources have some portion of each.
Insoluble fiber doesn’t dissolve in water, nor is it fermented or broken down by our gut bacteria. But because it holds onto to a lot of water, it delivers a larger, softer stool. So you can see this would be useful for those suffering from constipation.
Now soluble fiber is just that. It’s soluble and forms a gel when mixed with liquid. Soluble fiber actually attracts water and can help decrease diarrhea in some cases, such as for those suffering from IBS. Unlike insoluble fiber, the soluble fiber can be broken down and fermented by gut bacteria.
So in a nutshell that’s what fiber is, however, there is actually a third realm in the fiber world called Resistant Starch (RS). The term “resistant” refers to this starch’s ability to resist digestion, unlike most other starches. Instead, it passes to the large intestine where it produces the same effects of soluble and insoluble fibers, and does not spike insulin levels as do some other starches. And because nothing is ever simple, RS comes in four different types.
Here is a breakdown of what those types of RS are, examples included:
RS Type 1: Starch is physically inaccessible, bound within the fibrous cell walls of plants.
RS Type 2: Starch with a high amylose content, which is indigestible in its raw state. Cooking these foods causes changes in the starch making it digestible to us, and removing the resistant starch.
- Green (unripe) bananas
RS Type 3: Aka retrograde RS because it forms after RS Type 1 or Type 2 is cooked and then cooled. These cooked and cooled foods can be reheated at low temperatures, less than 130°F, and still maintain the benefits of RS. Heating at higher temperatures will convert the starch back into a form that is digestible to us rather than feeding our gut bacteria.
- Cooked and cooled parboiled rice
- Cooked and cooled potatoes
- Cooked and cooled properly prepared (soaked or sprouted) legumes
RS Type 4: This is a synthetic form of RS that is not recommended.
- Hi-maize resistant starch
The lovely thing about RS, as you may have picked up from reading above, is that it works to feed our gut bacteria. Not only does it feed our gut bacteria, it actually selectively feeds the good bacteria, stimulating their growth. When the good bacteria feed on the RS they produce short chain fatty acids (SCFA) via the fermentation process. The most noteworthy SCFA it produces are acetate, butyrate, and propionate, with butyrate being of most importance. The reason butyrate is so essential is that it is the preferred energy source of the cells lining the colon, plus is helps increase metabolism, decrease inflammation, and improve stress resistance. As a bonus, RS appears to increase butyrate production more than other soluble fibers and improves insulin resistance and drops blood glucose levels after meals. Nice!
Ok, so you know what the immune system is doing and what the low down on fiber is. So how in the world can a low fiber diet be the most dangerous threat to your immune system? Well let’s continue on with how fiber and the immune system interact, shall we?
First, we mentioned that butyrate lessens inflammation. Because it has a knack for doing that it actually improves the integrity of our gut because it reduces intestinal permeability and therefore keeps toxins in the gut and out of the bloodstream. Plus any SCFA that aren’t used up by the cells in the colon enter our bloodstream, mosey on to the liver, which helps spread them all through the body allowing them to exert additional anti-inflammatory goodness. One more nice thing RS does for us? It protects us from DNA damage and increases apoptosis of not so nice cancerous or pre-cancerous cells. Thanks RS.
Another way fiber benefits our immune system is that soluble fiber increases the secretion of the protein interleukin-4 from our cells. Interleukin-4 helps stimulate our body’s T-cells. This is important because T-Cells control nearly all aspects of the adaptive immune response. T-cells can search for foreign invaders, directly kill infected cells, destroy cancer cells, activate and help other immune cells that make antibodies, and they never forget previous invaders.
So you can see getting enough fiber in your diet has many benefits that boost your immunity, lower inflammation, and helps keep cancer at bay. To feed your body and your gut bacteria the fiber they need, it’s best to get it from whole food sources, mainly fruits and vegetables. Now these vegetables can be fresh, frozen, or canned (as long as no other ingredients are added to them). This will give your gut flora a good dose of prebiotics, the undigested fiber, to feed them and carry on the fermentation process and get some amazing SCFA. You can also get your fiber through fruits and vegetables that have been already been fermented. Eating fermented foods like kimchi and sauerkraut not only give you fiber, but also helps populate your gut with beneficial bacteria improving your immune system and overall health even more. Another way to get a dose of fiber in prebiotic form, due to the fiber called pectin it contains, as well as a good dose of probiotics, is be consuming raw, unfiltered apple cider vinegar. Raw, unfiltered apple cider vinegar’s ability to provide both prebiotics and probiotics make it a special food called a synbiotic.
Other fiber you may have seen in processed food is called functional fibers. Functional fibers are non-digestible carbohydrates that have been isolated or extracted from a natural plant or animal source, or have been manufactured or synthesized.
- Psyllium husks
- Chitin from crustacean shells
- Resistant dextrins
Functional fibers are often added to foods to bulk up the fiber content to fool consumers into thinking these are high fiber foods and are “healthy”. In reality these fibers may be doing more harm than good. Excess insoluble fiber can bind to minerals such as zinc, magnesium, calcium, and iron, preventing their absorption. Some soluble fibers such as pectin and guar (when taken in large excessive amounts) may inhibit pancreatic enzyme activity and protein digestion in the gut, leading to an anti-nutritive effect. So while you do need fiber, excessive, processed fiber may be hurting you more than helping you. So stick with whole food plant sources of fiber and know your body will receive the right amounts of fiber to keep your gut and immune system in tiptop shape.
A question you may now have is, how much fiber to I need each day? Recommendations for fiber intake are 38 grams of fiber for men and 25 grams for women per day. However, the average person only gets 15 grams each day. Uh, not good.To get enough fiber each day, eat a lot of fruits and vegetables. Mix and match them, make amazing, bountiful salads and veggie loaded frittatas, chow down on some cooked and cooled potatoes and green bananas, and don’t forget to load up on the sauerkraut. Just get your fiber! Your immune system will thank you!
So to avoid the most dangerous threat to your immune system all you have to do is:
Eat fiber in these forms:
- Fresh, frozen, or canned fruits and vegetables (with no other added ingredients)
- Fermented fruits and vegetables
- Raw, unfiltered apple cider vinegar
Avoid processed and synthesized fiber (functional fiber)
There you have it. Simplicity at its finest. Eat your fruits and veggies and your body’s immune system will no longer have to endure the threat of a low fiber diet. It’s all up to you! Let’s not wait any longer…get to munching on those fruits and veggies ASAP!
Cardiff University. 2009. Tcells.org. T-cell Modulation Group. Beginners Guide to T cells. http://www.tcells.org/beginners/tcells/
Kresser, C. February 17, 2012. ChrisKresser.com. Myths and Truths About Fiber. https://chriskresser.com/myths-and-truths-about-fiber/
Nett, A. August 14, 2014. ChrisKresser.com. How Resistant Starch Will Help to Make You Healthier and Thinner. https://chriskresser.com/how-resistant-starch-will-help-to-make-you-healthier-and-thinner/
Schley, P., et al. March 1, 2007. British Journal of Medicine. Cambridge Univeraity Press. The immune-enhancing effects of dietary fibres and prebiotics. V: 87. I: s2. Pages: 221-230. https://www.cambridge.org
Yunsheng, M., et al. April 2006. The American Journal of Clinical Nutrition. Association between dietary fiber and serum C-reactive protein. V: 83 (4). Pages: 760-766. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1456807/