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Red Raspberry Leaf Tea—Simple Beverage or Uterus Superfood?

Red raspberry leaf tea is an ancient tonic—pregnant women as early as the 6th century drank the stuff. It is still a popular herbal supplement for pregnancy today, with claimed benefits ranging from it’s ability to strengthen the uterus and help prepare the body for birth to directly stimulating labor (in one survey, more than half of American midwives  said they recommended raspberry leaf to naturally induce).

During my pregnancies, even though I’m a bit of a skeptic, I loved the promise of a magical uterine strengthening elixir as much as the next pregnant gal. Naturally, I ventured into the wilds of internet claims to suss out these potential benefits and I found that the claims varied widely:  

From the very direct— “It strengthens the uterus and pelvic muscles which leads to shorter and easier labors.

To the anecdotal— “…my sister’s sister took it and had a 5 hour labor! Then two pushes and out!

To the seemingly scientific— “It has been shown to concentrate the effects of contractions to make them more effective.

But is there actually scientific evidence and biological reasoning behind these claims? Time for digging…

Claim 1: Red raspberry leaf tea induces labor and/or shortens time in labor

Kinda… maybe… maybe not….

First, I have to point out that the scientific study of the raspberry leaf is weak (at best). In 2009, a team of researchers tried to dig up every possible research study they could and only found a handful of studies testing the herbal remedy [1].  Six of those studies tested the effects of red raspberry leaf in a lab, with non-human or petri dish subjects (discussed below). Five studies took place in the clinic and actually considered humans with working human uteruses. Since that 2009 publication, only a few more studies (mostly in the lab) have trickled out. 

(Note: finding only a few studies is not for lack of trying—the authors in the research round-up stretched so far as to include an obscure paper from 1941 that only included three women!)

The five clinical studies, looking at the safety and efficacy of red raspberry leaf use in pregnant humans, did not show any strong beneficial (or harmful) effects.

Some studies showed a shorter first or second stage of labor…  but only by a few minutes. Only one study showed that it shortened the length of pregnancy… but only by a couple of days. Maybe that counts as inducing labor?

Weak evidence, yes. BUT, if shaving a few minutes off your labor and a few days off your pregnancy sound appealing (and I do not blame you if it does), there you go!

Claim 2: Red raspberry leaf tea strengthens the uterus and/or stimulates contractions

Yes… and no.

Overall, the laboratory studies show that raspberry leaf can facilitate more rhythmic contractions in uterine tissue. And rhythmic contractions are important for labor progress. However, some studies showed that the red raspberry leaf’s effects worked through toning and some showed that it worked through relaxing. Clearly, those two things are in direct conflict and are a scientific red flag, a reminder to take these studies with a grain of salt.

This red flag mainly calls into question study design. The laboratory studies use rodent uterine tissue and some of those rodents (mostly rats) are already dead long before the tissue is harvested and tested. Then, with their long dead or newly dead subjects, the researchers stick the isolated tissue into a petri dish and douse it in red raspberry leaf extract. This study design is not exactly equivalent to you drinking a cup of tea with your intact human uterus inside your human body housing a human baby.

Another lab study published after the review also directly tested how red raspberry leaf extract might stimulate uterine contractions in rodent uterine muscle, comparing pregnant to non-pregnant rats with some more promising results[2]. When rats were not pregnant, direct application of the extract to uterine tissue had no effect on uterine contractility. However, when the researchers tested a pregnant rat’s uterus, the muscle’s contraction response to raspberry leaf rivaled that of oxytocin.  Oxytocin, as you may know, is the main hormone in charge of stimulating the uterus to contract.

 

Keep in mind, these studies are not studying you. They are studying a rodent uterus. Peeled into exposed muscle layers. Sitting in a petri dish. Doused in red raspberry leaf extract.

Not exactly a cup of tea.

 

Then the researchers went one step further and asked: does red raspberry leaf play the role of oxytocin’s little helper?  Unfortunately, they had a crazy small study (six subjects!) and their results split right down the middle: half of the test subjects showed that oxytocin-induced contractions were strengthened with red raspberry leaf; the other half showed strengthening followed by immediate blockade of contractions.  Not so helpful.

Building on that confusing finding, a more recent study looked closer at how exactly raspberry leaf works at the muscular level. In that study, the researchers doused rodent uterine muscle in increasing doses of raspberry leaf extract and found increasing responses of contraction activity. The response was similar to giving the muscle a classic stimulant. The effects of the extract in combination with different stimulants and relaxants also showed signs that red raspberry leaf contains a compound that might block a natural muscle relaxer. This action would enhance the ability of raspberry leaf to facilitate contractions [3].

So, yes, red raspberry leaf tea may have biological properties that stimulate the uterine muscle to contract. BUT, keep in mind, these studies are not studying you. They are studying a rodent uterus. Peeled into exposed muscle layers. Sitting in a petri dish. Doused in extract.  

Not exactly a cup of tea.

red raspberry leaf tea

But, is there a downside to drinking red raspberry leaf tea during pregnancy?

Well, fortunately, there were mostly no adverse effects noted. BUT, even one of the clinical researchers, a midwife who openly admitted to drinking copious amounts of red raspberry leaf tea during her pregnancies stated:

“After very well, term pregnancies, easy labours and births and two very healthy children, I am grateful that I knew about raspberry leaf. I would, however, discourage its use, until further studies can demonstrate its safety and efficacy.”

Michele Simpson, midwife

With that said, the only study I could find that suggested a downside showed some potentially scary trans-generational effects[4].  That’s right, drinking raspberry leaf tea while pregnant may affect your baby and your baby’s baby.  The babies of the mother rats used in the study showed signs of early puberty and the babies’ babies showed higher rates of growth restriction.

Before you get too freaked out about harming your baby’s baby, keep in mind that this study also requires the take it with a grain of salt advice.  Just like the studies showing the benefits, this study also has some serious design flaws.  In this study, mother rats were fed raspberry leaf extract every day from conception to weaning.  Think about this in human use case terms— these rats were consuming raspberry leaf extract throughout the entire pregnancy. Are you? Most importantly, developmental effects that occur at the level of the baby’s baby need to happen very early in pregnancy, when the ovaries are developing. Are you drinking it that early?

Again, just like sussing out the benefits, more studies are also needed about the potential risks of red raspberry leaf consumption during pregnancy[5].

Conclusion?

Despite what the internet might have you believing, the jury is still out on the benefits of red raspberry leaf tea. In the words of one scientific buzzkill:

“The fact that the product has been in traditional use for decades does not constitute evidence”.

L. Holst and colleagues

Basically, there are simply not enough good, quality, human-based studies to back up the claims that red raspberry leaf tea is a pregnancy super juice. 

With that said, in honor of full disclosure, I must admit that I kept a a steaming pot of “Mother to Be Tea” next to me for pretty much the entire third trimester of my second pregnancy. I can’t say that the tea helped get my daughter out of my body any quicker (she was born 11 days after her due date) but my labor was short (less than six hours) so… maybe it worked?

REFERENCES

[1] Holst L, Haavik S, Nordeng H. Raspberry leaf – Should it be recommended to pregnant women? Complementary Therapies in Clinical Practice. 2009. pp. 204–208.

[2] Zheng J, Pistilli MJ, Holloway AC, Crankshaw DJ. The Effects of Commercial Preparations of Red Raspberry Leaf on the Contractility of the Rat’s Uterus In Vitro. Reproductive Sciences. 2010. pp. 494–501.

[3] Olson AE, DeGolier TF. Research Article: Contractile activity ofRubus idaeusextract on isolated mouse uterine strips. BIOS. 2016. pp. 39–47.

[4] Johnson JR, Makaji E, Ho S, Boya Xiong, Crankshaw DJ, Holloway AC. Effect of maternal raspberry leaf consumption in rats on pregnancy outcome and the fertility of the female offspring. Reprod Sci. 2009;16: 605–609.

[5] Simpson M, Parsons M, Greenwood J, Wade K. Raspberry leaf in pregnancy: its safety and efficacy in labor. J Midwifery Womens Health. 2001;46: 51–59.

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Molly Dickens, PhD

About Molly

Molly has her PhD in Physiology and spent over a decade as an academic research scientist slightly obsessed with the colliding worlds of brain science, hormones, stress and the reproductive system. Nowadays she heads up Content and Community at Bloomlife and edits Preg U. Science is still her jam and she can't help but continue to dive into the research world to find interesting bits about pregnancy and parenting.

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