Beta-Glucans and the Dual Role of Prolactin: a detective story

Beta-Glucans and the Dual Role of Prolactin: a detective story

Beta-Glucans and the Dual Role of Prolactin: a detective story

Intro

A handful of our valued lactogenic foods—oats, barley, brewer’s and nutritional yeast, seaweed and medicinal mushrooms—are blessed by a molecule called beta-glucan.

It might seem obvious that beta-glucan increases the milk-making hormone prolactin as well as bringing about changes in a mother’s physiology that promote good lactation. Yet, a clear mechanism of action eluded us for decades. In fact we were told it was impossible.

That is because we only thought about beta-glucan as food and about prolactin as a hormone. Beta-glucan is more than food, and prolactin is more than a hormone.

To prepare for this article, I did a dive into disparate studies. I believe that especially for lactation consultants and for curious mothers, what I learned in the process will excite you. It is truly a detective story.

If you need help remembering terms from biology, this intro will get you started.

Beta-Glucans are a long-chained sugar molecule. Because they are not digestible—our digestive enzymes and intestinal flora cannot break them down for absorption—they remain in the intestine, thickening and softening the stool for easier “going.”

Beta-Glucans molecules are called a polysaccharide. Poly here means many, and saccharide means sugar. They are called viscous because they are gel-forming. Think of how gloppy oatmeal gets when you cook it: it’s the gel-like polysaccharides in oats that quell out and make the glop.

A cell-receptor is a place on a cell’s outer membrane that is perfectly formed to lock in a specific particle. Here, the Dectin-1 receptor locks in beta-glucans fragments.

Tissues are specific cells that work together to form organs or parts of the body that do specific things: muscle tissue, bone tissue, glandular tissue, and so on. In this article, I mention pituitary gland tissue, the gland in the brain that produces prolactin, and mammary gland tissue, the tissue in the breasts that secretes milk.

The immune system is a complex set of cells that work together to fight off disease. The endocrine system is a complex set of hormones that work together to coordinate everything from how we use energy from food to how we orgasm or lactate. There’s also a system that involves neurotransmitters such as serotonin and dopamine.

Although we think of these systems as separate entities, they are not. In this article we’ll learn about an overlap between the immune system and the endocrine system. We’ll discover that prolactin is both a hormone and an immune cell. And we’ll learn that beta-glucan from food acts like a vaccine, training the immune system to react more quickly to pathogens.

Macrophages are the big polar bear of the immune system. They eat up any particle that looks like a threat to the body. They can travel into and throughout the various tissues of the body, and what they eat also travels throughout the body with them. They excrete their crush fragments into the extracellular matrix, a system of gel-like polymers and proteins that surrounds and supports all the tissues of the body.

In 1989, researchers from France placed swine’s pituitary tissue in a petri dish and let it swim in an extract of beta-glucans from oats and barley. Within 2 hours, the pituitary tissue secreted quantities of prolactin, the milk-making hormone.[1]

To those of us looking for answers, this outcome was exciting. It seemed to resolve the question whether eating barley or oats actually raised levels of prolactin and breast milk production or if women were simply imagining this result.

A second study by the same researchers injected beta-glucans into the bloodstream of ewes and cows, resulting in greater secretion of prolactin and improved milk production.[2] And a US-Germany study from 2004 confirmed that beta-glucans, in direct contact with the pituitary gland, increase prolactin.[3]

Sadly, in spite of these results, our hopes for a causal relationship between beta-glucans and milk production were dashed. That’s because beta-glucans are an insoluble fiber that is not digested and absorbed into the body. While in a petri dish or if injected directly into the bloodstream, this molecule increased prolactin, when eaten as food, beta-glucans were not absorbed into the body and thus could not reach the pituitary and increase prolactin. Alas!

Until science discovered how beta-glucans were absorbed into the body it would rule them out as a substance that increases milk supply.

Beta-Glucans form a bridge between the immune and the endocrine systems

Researchers conducted the above studies from the 1980s to the early 2000s. Since that time, researchers did discover at least one way that beta-glucans can escape from the intestine: they hitchhike a ride via large immune cells called macrophages.

Let’s look at what happens.

Because beta-glucans resemble fungi, the macrophages in the intestine believe they are a pathogen. They therefore attack and “neutralize” the beta-glucan.

Macrophages are garbage collectors. With their enormous size, they surround and engulf pathogens, fungi, cancer cells, microbes, cellular debris, and whatever else appears to be a threat. Then the macrophages, much like garbage trucks, crush what they have collected into tiny pieces. 

Macrophages can pass back and forth through the intestinal wall. Anything that a macrophage eats while in the intestine will be carried out of the intestine and into the body. So you see, there is in fact a way for beta-glucans to get into the interior of the body: as crushed fragments in the belly of a macrophage.

When a mother eats food that contains beta-glucan, her macrophages first engulf the beta-glucan and then crush it into tiny fragments.

The macrophages then carry the beta-glucan fragments to the interior of the body.

When they die (and about a billion are born and die each day), they release all their fragments into what is called the extracellular matrix.

Now the beta-glucan fragments, floating around freely, can attach to other immune cells. To do this, they use a cell receptor called Dectin-1.

Remember that name: Dectin-1 receptor

This turns out to be a good thing. Remember: beta-glucans have a molecular structure that is similar to fungi as well as other pathogens. That is why, when they attach to Dectin-1 receptors, they actually educate and train the immune cells to react more quickly and fight off pathogens, including cancers and upper respiratory diseases.[4]

SIDE-NOTE: Tissues within the mammary glands, the uterus, pancreas, and fat pads also produce prolactin. And depending on the context, prolactin will function as a hormone or as an immune cell.

The Pituitary has Dectin-1 receptors!

In 2014, Iranian researchers, studying beta-glucans and pituitary tissue in vitro, were able to identify Dectin-1 receptors on the prolactin-producing cells of the pituitary.[5]

They determined that beta-glucans, attaching to these Dectin-1 receptors, triggered prolactin production and also increased the intensity of prolactin production.

Trumpet sounds please! 

Summary

So now we know how beta-glucan escapes from the intestine. We know that beta-glucans have a beneficial effect on the immune system. We understand that the pituitary is part of the immune system, and that when beta-glucans lock into Dectin-1 receptors on the pituitary, prolactin is released in its capacity as an immune cell.

But is the story really over? 

I have to wonder if other tissues in the body also produce prolactin when beta-glucans are around. What about fat-pads, and tissue in the mammary glands?

I do not know the answer, but researchers from China, studying sprouted barley grains, a beta-glucan rich food for lactation, stated that they saw increased prolactin expression in mammary gland tissue in response to beta-glucans.[6]

Yes, they found prolactin was expressed from tissues in the mammary gland, in response to a beta-glucan rich food. My detective hat is on again… stay tuned.

 

Pectin

Pectin, like beta-glucan, is tested in animals [7] and also in vitro on pituitary tissue. Researchers have shown pectin to increase prolactin. [8]

But while we do not yet know how pectin increases prolactin, we do know that beta-glucan and pectin have much in common.[9]

  • Both pectin and beta-glucan are immunomodulatory: they improve immune responses.
  • Both are non-digestible fibers, and are viscous (gel-like) polysaccharides.

Studies on viscous polysaccharides have established their profound value for metabolic health: they reduce insulin spikes and allow for better blood sugar balance.

See my article on the dance of hormones in the postpartum, and my article on the conditions in which diet can help support lactation, for more information on these subjects. 

Some Thoughts

Traditional postpartum diets are often rich in beta-glucans (barley, oats, seaweed, mushrooms, yeast) and in pectin (seaweed, greens, some fruit). These foods are prepared by the family for the mother, who is urged to eat them throughout the day, every day, for weeks and even months on end.

We can help mothers learn how to use lactogenic foods in their daily fare. Indeed, oats, oatmeal and oat-cookies are sources of beta-glucans and are the lactogenic food of choice by Western women. We can expand this range.

Consider the dual stimulation: suckling at the breast produces prolactin in its role as a hormone, and beta-glucan activates prolactin in its role as an immune cell. Most likely, beta-glucans stimulate tissues beyond the pituitary to produce prolactin.

Looking at how women have eaten beta-glucans after childbirth, most likely for thousands of years, perhaps there is a lesson for us here about the potential benefits of a lactogenic diet in a world where lactation is ever more difficult. 

Afterword

While this article concentrates on beta-glucans and pectin, many other lactogenic grains, vegetables, fruit, and herbs are especially rich in viscous polysaccharides and have unique ways of supporting lactation.

We have a lot still to learn.

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References

[1] Sepehri H, Renard C, Houdebine L-M. β-Glucan and Pectin Derivatives Stimulate Prolactin Secretion from Hypophysis In Vitro. Proceedings of the Society for Experimental Biology and Medicine. 1990;194(3):193-197. doi:10.3181/00379727-194-43077  

[2] Sawadogo L, Sepehri H, Houdebine LM. Mise en évidence d’un facteur stimulant la sécrétion de prolactine et de l’hormone de croissance dans les drèches de brasserie [Evidence for a stimulating factor of prolactin and growth hormone secretion present in brewery draff]. Reprod Nutr Dev. 1989;29(2):139-46. French. PMID: 2502999. 

[3] Breuel, K. F., Kougias, P., Rice, P. J., Wei, D., De Ponti, K., Wang, J., … & Williams, D. L. (2004). Anterior pituitary cells express pattern recognition receptors for fungal glucans: implications for neuroendocrine immune involvement in response to fungal infections. Neuroimmunomodulation11(1), 1-9. 

[4] Moerings, B. G., de Graaff, P., Furber, M., Witkamp, R. F., Debets, R., Mes, J. J., van Bergenhenegouwen, J., & Govers, C. (2020). Continuous Exposure to Non-Soluble β-Glucans Induces Trained Immunity in M-CSF-Differentiated Macrophages. Frontiers in Immunology. https://doi.org/10.3389/fimmu.2021.672796 

[5] Shaerzadeh, F., Sepehri, H., & Delphi, L. (2022). Stimulation of Prolactin Synthesis by β-Glucan via Dectin-1 Receptors in GH3/B6 Cells. Journal of Mathematics9(4). 

[6] Zhang, Z., Wei, Q., Zeng, Y., Jia, X., Su, H., Lin, W., … & Wang, Q. (2021). Effect of Hordei Fructus Germinatus on differential gene expression in the prolactin signaling pathway in the mammary gland of lactating rats. Journal of Ethnopharmacology, 268, 113589. 

[7] Sawadogo, L., Houdebine, L. M., Thibault, J. F., Rouau, X., & Ollivier-Bousquet, M. (1988). Effect of pectic substances on prolactin and growth hormone secretion in the ewe and on the induction of casein synthesis in the rat. Reproduction Nutrition Développement28(2A), 293-301.

[8] Sepehri H, Renard C, Houdebine L-M. β-Glucan and Pectin Derivatives Stimulate Prolactin Secretion from Hypophysis In Vitro. Proceedings of the Society for Experimental Biology and Medicine. 1990;194(3):193-197. doi:10.3181/00379727-194-43077 

[9] Sawagado, L., & Houdebine, L. M. (1988, January). Identification of the lactogenic compound present in beer. In Annales de biologie clinique (Vol. 46, No. 2, pp. 129-134).