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Certain vitamins are crucial for the intestinal immune system

- and for the prevention of allergies and inflammation

Certain vitamins are crucial for the intestinal immune system Every day, the intestinal immune system has to defend itself against hordes of microbes and toxins. If it fails to function optimally, there is an increased risk of infections, allergies, and inflammatory diseases. More and more research reveals that essential nutrients help to control the intestinal immune defense. Also, new research shows how important a well-functioning immune system is for our digestion and health in general. This article takes a closer look at the vitamins that are known to be particularly important for the intestinal immune system. Another thing that is vital is to have adequate amounts of gastric juice.

The lion’s share of our immune defense is located in the intestines

All the things that we eat, drink, and swallow pass through our intestinal system, which, for the very same reason, is the part of the human body that is in most frequent and direct contact with pathogenic microorganisms such as virus, bacteria, fungi, and toxins. The intestinal system also harbors an enormous microflora that helps to ensure a well-functioning digestion. Certain bacteria and fungi may be harmful if they spread too much. This is why 80% of our immune cells and other vital defense compounds are located in the bowels.

The intestinal immune defense is highly specialized

The mucosa are equipped with a type of white blood cells called dendritic cells that represent the outposts of the immune defense. The dendritic cells fight the infectious germs and function as alarms by sending out signals (antigens) to the other white blood cells, preparing them for battle. In the lower part of the small intestine, we have some lymphoid tissues called Peyer’s patches that also house dendritic cells plus T and B cells that are more specialized.
B cells produce antibodies (IgA) that line the mucosa of the gastrointestinal tract and the airways. The IgA antibodies attach to infectious germs, kind of like a set of handcuffs, allowing other parts of the immune defense to take control of them.
The T helper cells (CD4) activate the T killer cells (CD8) that belong to the most aggressive kind of white blood cells. The T killer cells conduct a type of chemical warfare, blindly attacking in a way that causes inflammation and tissue damage, unless they are effectively controlled. This is where the regulatory T cells help to calm down the T killer cells, once the immune system has succeeded in battling an infection. A poorly controlled intestinal immune defense is associated with allergies (including food allergies), inflammation, and inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.

The balance between the T helper cells and regulatory T cells determines the force of an immune reaction

It is difficult to fight an infection with too few T helper cells. If there are too few regulatory T cells, on the other hand, autoimmune reactions such as Crohn’s disease, ulcerative colitis, and rheumatoid arthritis may occur, causing the immune system to damage certain tissues.

Vitamins are important for the intestinal defense system

Vitamins are essential nutrients that are primarily synthesized by different plants, bacteria, and fungi, but not by mammals such as humans. We get our vitamins from the food we eat. The vitamins are involved in various enzyme processes that have countless functions in the body. One of them is to support the immune system, including the intestinal defense mechanism, at which we will take a closer look.

Vitamin A

Vitamin A is important for the dendritic cells and helps the B vitamins in the Peyer’s patches produce IgA antibodies that line all mucosa. Vitamin A also controls the balance between the different T cells, which is highly important for a controlled immune response.
As mentioned earlier, the intestinal system has a huge microflora, and both vitamin A and vitamin D influence the communication between this microflora and the immune system. The body also needs zinc in order to utilize vitamin A.
A vitamin A deficiency or incomplete utilization of the nutrient may result in weak mucous membranes, which increases the risk of infectious diseases (including bowel infections and severe diarrhea in children caused by suboptimal functioning of the intestinal immune defense.

Real vitamin A is found in the liver of many animals, in egg yolks, and in fat-containing dairy products. Beta-carotene, a precursor of vitamin A, is found in yellow, green, and red vegetables such as carrots, spinach, red bell pepper, broccoli, melons, and corn. Alcohol, dysbioses, too little gastric juice, and insulin resistance may affect the uptake and conversion of beta-carotene into vitamin A

Folic acid (vitamin B9)

As soon as the regulatory T cells are activated, they consume generous amounts of folic acid. Mouse studies show that lack of dietary folic acid leads to a reduction of regulatory T cells in the intestines with an increased risk of inflammation. Folic acid is primarily found in liver, legumes, asparagus, sprouts, nuts, eggs, vegetables, fruit, and dairy products. Folic acid deficiencies are typically seen in people who eat unhealthily, consume too much alcohol and other stimulants, are pregnant, smoke, use birth control pills or have reached a ripe age.

Vitamin B2 (riboflavin)

Vitamin B2 is important for our energy turnover and for maintaining healthy mucosa. It is also involved in the energy turnover of white blood cells, also known as immune metabolism. When we get an infection, it is crucial that the white blood cells can reproduce quickly and strike a targeted counter attack, which requires rapid energy turnover inside the cells. Vitamin B2 is found in liver, whole-grain, eggs, legumes, almonds, nuts, vegetables, and dairy products. Lack of vitamin B2 is typically seen with imbalanced diets, alcohol and stimulant abuse, and the use of diuretics.

Vitamin D

The sun is our most important source of vitamin D. At our latitude, however, we can only synthesize vitamin D during the summer period where the sun sits sufficiently high in the sky to enable the process. Vitamin D is stored in the liver, but many people become deficient during the winter period, once their vitamin D stores have been depleted. Lack of sun exposure causes chronic deficiency. When the immune cells are affected by vitamin D, they release a peptide that has an antibiotic effect on a number of different microbes. Danish researchers have demonstrated that T killer cells that are assigned to fight bacteria, virus, and cancer cells cannot work without vitamin D. According to Professor Carsten Geisler from the University of Copenhagen, the T killer cells are every bit as dependent on vitamin D as a car is dependent on its battery in order to start.
Vitamin D also stimulates regulatory T cells and prevents the production of pro-inflammatory cytokines.
Vitamin D is therefore extremely important for an effective and properly controlled immune response.
Too little vitamin D is associated with an increased risk of infections and inflammatory bowel diseases like Crohn’s disease and ulcerative colitis, but also increases the risk of rheumatoid arthritis, and atopic dermatitis.
On the other hand, increasing evidence shows that high-dosage supplementation with vitamin D helps to prevent or ameliorate these conditions by strengthening the immune defense and inhibiting undesirable inflammatory processes.

Vitamin E (tocopherol)

Vitamin E is known as a powerful antioxidant that protects cells against free radicals. There are different forms of vitamin E such as alpha, beta, and delta-tocopherol. The different types of vitamin E work differently in the immune system. Alpha-tocopherol counteracts inflammation, while delta-tocopherol accelerates it.
We humans primarily get vitamin E from plant oils because the vitamin is synthesized in plants. Olive oil, sunflower seeds, and almonds are rich in alpha-tocopherol, while most other plants oils (including corn oil and margarine) contain more delta-tocopherol and less alpha-tocopherol.
Our dietary habits and choice of oils may affect vitamin E’s ability to control inflammation. Olive oil is a particularly rich source of anti-inflammatory alpha-tocopherol, but it is also a good source of omega-9 fatty acids. Unlike other plant oils with omega-6 fatty acids, olive oil does not promote inflammation.

Important to have enough stomach acid

Our stomach acid kills many bacteria, and its content of enzymes helps to break down protein. Nonetheless, many people, especially older people, have too little gastric juice. Ironically, they get the same symptoms as with too much gastric juice – for instance pain, acid reflux, and heartburn.
Too little gastric juice and the use of antacids impair the chemical defense mechanism and the digestion. People with too little stomach acid are often constipated. It is often possible to increase the production of stomach acid by taking strong B vitamins.


Koji Hosomi and Jun Kunisawa. The specific Roles of Vitamins in the Regulation of Immunosurveillance and Maintenance of Immunologic Homeostasis in the gut. Immune Network 2017

Pernille Lund: Immunforsvarets nye ABC. Forlaget Hovedland 2012

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