Vitamin A, Leaky Gut and The Immune System

vitamin a leaky gut intestinal permeability immune system

The interplay between intestinal permeability and different disease states is a major interest of mine. Naturopaths, Herbalists and wisdom traditions including, among others, Ayurveda and Chinese Medicine have known that the different body systems influence and affect each other in intricate ways.

Science is finally catching up to this thinking and many traditional healing concepts are being ‘proven’ in the scientific research.

Today we will be exploring the impact that vitamin A has on leaky gut and the immune system.

This article is part of a long exploration into the world of leaky gut and associated diseases. Further reading would include these articles.

 

A Quick Vitamin A Primer

First off what is vitamin A.

It is a fat soluble vitamin that influences a whole range of different body processes including among others

  • Cell differentiation
  • Growth factors
  • Immune function

The most important function in relation to this article is vitamin A’s function in supporting the mucous membrane in the digestive tract (1).

Vitamin A comes in a few different varieties. Beta carotene, also known as provitamin A and retinol, known as preformed vitamin A. The carotenoids are potent antioxidants but are less active than retinol (2).

Beta carotene can be converted into a retinoid form. The conversion rate is hotly debated and quite hard to pin down to a number. An interesting point here is that in vitamin A deficiency the conversion from beta carotene to active vitamin A is upregulated. More is converted.   

Retinol, and retinoic acid, are considered the physiologically active form of vitamin A. They have profound effects on the body and influence cell differentiation, development and immune function.

Retinol, and only retinol, makes up the light absorbing units in the retina of the eye. It is required for vision (3).

 

Theories on Intestinal Permeability and Disease States  

In the past we have covered the connection between different disease states and leaky gut.

Leaky gut has been associated with the progression of different autoimmune disease. A quick summary would take into account three specific factors outlined in this paper.

  1. The genetic susceptibility to an autoimmune disease. This is where many people stop. You might think that having the genes for a particular autoimmune disease is a sure thing. There are a number of other factors that need to present
  2. The trigger. The idea here is that something needs to actually set off the autoimmune progression. This is referred to as an ‘antigen’. Many times it can be bacterial, fungal or viral. Sometimes it may be an undigested food antigen setting off the immune system.
  3. Finally the environmental agent (the trigger) needs to be able to interact, and set off, the immune system. I like to think about it like a chemistry reaction. There needs to be contact between the antigen and the immune system for a reaction to happen.

In this theory leaky gut is required.

In a healthy functioning system the gut barrier keeps these antigens inside the gut. When permeability increases the immune system interacts with these antigens setting off an overactive response (5).

 

Vitamin A, Leaky Gut and Disease Progression

A recently published review dives deep into vitamin A and leaky gut. Today we will be picking out some important points to discuss.

First off intestinal epithelial cells, forming the gut barrier, is covered by a mucous layer. This layer is crucial for the healthy functioning of the gut. It traps invading microbes preventing inflammation. There are also antimicrobial peptides found in this mucous layer again helping to defend and protect the underlying tissue.

Retinol has been shown to have be inversely correlated with intestinal permeability (7).

Translation – lower serum retinol was associated with increased leaky gut.

The study looked at 30 children’s serum vitamin A. They also tested their intestinal permeability with a lactulose/mannitol test. They found low vitamin A in the children that had high mannitol in their urine, indicating leaky gut.

Now this isn’t concrete data. We need more information to come to solid conclusions.

Another study compared difference in immune function and intestinal permeability in children with suspected low vitamin A. While the intestinal permeability did not change between the group receiving high dose vitamin A therapy and the placebo group there was a significant decrease in parasitic infections, notably Giardia (8).

The conclusion here was that vitamin A supports immune function and defence to Giardia. I would assume we can extend that to other parasitic infections like Blastocystis and Dientamoeba fragilis.

Back to the review.

Vitamin A may improve leaky gut in a number of ways. Much of this is still being worked out. Some is in-vitro (aka test tube) data and some is animal studies. We can’t draw any strong conclusions from this evidence but it does point us in the right direction.

  • Vitamin A has been shown to improve the tight junctions which control what passes from the gut lumen into the body.
  • Vitamin A has an intricate relationship with the gut microbiota. Together they influence the immune function by regulating the B-cell response.
  • Certain gut flora produce acetate, a short chain fatty acid. This in turn pushes B-cells to become IgA producing cells (a top defender in the gut ecosystem). Vitamin A is needed as a signal to make this process happen.
  • Influenced by vitamin A the gut flora can promote a more tolerant immune response by upregulating T regulatory cells. I like to think of these T regulatory cells as the dampener on an overactive immune system.

So we are left with the question as to how vitamin A improves leaky gut? Is it directly through influencing the cellular structures that heal and seal the gut wall or is it by interacting with the beneficial microbes that make up our gut microbiome?

The answer is probably both.

In the words of the authors of the review ‘It is likely that RA exerts protective effects against a leaky gut and, subsequently, autoimmune pathologies through both direct and indirect mechanisms.’

 

Where Do We Find Vitamin A – Food Sources

This article we are focusing on improving leaky gut and maintaining the gut barrier. As such there is a main focus on the active form of vitamin A. Different forms are found in the foods below (9).

Preformed vitamin A is commonly found in certain animal foods including

  • Liver
  • Eggs
  • Fish

Beta-carotene is found in a number of plant foods, but remember it still has to be converted into the active form to function on the gut wall.

  • Carrots
  • Spinach
  • Broccoli
  • Parsely
  • Sweet potatoes
  • Apricots
  • Peaches

 

References and Resources

  1. Vitamin A : nutrition, side effects, and supplements
  2. Vitamin A, carotenoids, and retinoids.
  3. Meeting the Vitamin A Requirement: The Efficacy and Importance of 𝛽-Carotene in Animal Species
  4. Alterations in intestinal permeability.
  5. Alterations in intestinal permeability.
  6. Retinoic Acid, Leaky Gut, and Autoimmune Diseases.
  7. Retinol and Retinol-Binding Protein: Gut Integrity and Circulating Immunoglobulins
  8. Effects of vitamin A supplementation on intestinal barrier function, growth, total parasitic, and specific Giardia spp infections in Brazilian children: a prospective randomized, double-blind, placebo-controlled trial.
  9. Meeting the Vitamin A Requirement: The Efficacy and Importance of 𝛽-Carotene in Animal Species

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