Red Raspberry Leaf (Rubus idaeus): Myths & Facts, Safety & Efficacy, Mechanism of Action
Red raspberry leaf tea is perhaps the best-known herbal medicine used in pregnancy. It has a long
tradition of use in both Europe and North America. Many women have heard it is “good for you” and so they drink it.
Did your mom drink it when she was pregnant? Mine did. It is an excellent choice of herbal ally during pregnancy. Considering how useful it is, and how popular, I think it should be better understood.
MYTH: Red raspberry leaf induces labor.
NOT TRUE! NOT TRUE!
Fact: Red raspberry leaf is safe and useful throughout pregnancy, especially in the second and third trimesters. It does not induce labor.
This misunderstanding stems from the fact that Rubus ideaus is used to prepare for labor. The herb is a wonderfully effective uterine tonic, meaning it has a toning, strengthening, and nourishing effect on the tissue and function of female reproductive tract (Hoffman, 2003).
Via its mineral content (especially calcium) and various polypeptides, it enhances the ability of the uterus to contract when labor begins, and can make labor more efficient.
The herb affects smooth muscles, meaning it has gentle action beyond the uterus in the smooth muscles lining the digestive tract. As a herb for digestion, it is most often used when stool is loose, but can also be part of a formula to address constipation.
Red raspberry leaf is also rich in tannins, lending it a whole other realm of actions. Tannins astringe,
or pull together tissue. Think of the feeling of black tea – also rich in tannins – in your mouth. It is a little bit drying, but also toning & tightening, making it great for skin and mucous membranes. Tannins are a good fit when there is excess fluid, as in diarrhea or certain kinds of gut inflammation, and can also be used to address bleeding. Indeed, a red raspberry leaf mouthwash is used for bleeding gums. Further down in the body, Rubus idaeus tea is used for postpartum uterine bleeding as well as bleeding in the gastrointestinal tract.
Red raspberry leaf plays a role in supporting fertility as well, as it is thought to help thicken the uterine lining (Gilbert, 2015).
Uterine Tonic (also tones pelvic floor); Partus preparator; Astringent; Nutritive
Pregnancy; Fertility; Painful periods; Diarrhea; Constipation (mild); Decreasing excess bleeding (eg postpartum, but also gastrointestinal, as a mouthwash for bleeding gums)
Note: some references list Red Raspberry leaf as a galactagogue, aka promoter of lactation, but this is not a primary action of the herb, and for most folks, not the best herb for this action. The herb is also listed as a nausea treatment in pregnancy, but clinically, nausea would not be my reason to choose Rubus ideaus. The herb may also lower blood sugar if it is elevated, but, again, this is not a primary action of the herb.
What is a partus preparator?
An herbal combination used traditionally to help someone prepare to give birth, usually taken in the last 4-6 weeks of pregnancy. The combination is designed to tonify the uterus, encouraging efficient contractions, as well as being mildly soothing and astringent. While the herbs used vary considerably, common choices include Red Raspberry Leaf, Blue Cohosh, Black Cohosh, Partridge Berry, Cotton Root and Spikenard.
Blue Cohosh in particular does not have a good safety profile. There have been case reports of infants with bleeding in the brain or heart attacks (Romm, 2010) – and this herb should be used only with the advice of a trained herbal clinician.
In fact, modern herbal medicine practitioners are now divided as to the efficacy or necessity of a partus preparator formula, and may prefer to select specific herbs to meet the needs of the individual pregnant client. Many practitioners will use homeopathics and acupuncture rather than a partus preparator formula.
Constituents of Red Raspberry Leaf
Flavonoids, tannins (8-14 %), polypeptides, minerals (eg calcium, iron, phophorus).
Some sources reference an alkaloid, fragrine, but recent research has not confirmed its presence.
Most commonly taken as a tea: 1 tsp to 2 tbsp per cup, steeped 10 min to overnight depending on desired action. (Longer steeping will result in a stronger medicinal action, as well as higher mineral content). 1-4 cups per day.
Studies have found efficacy with certain extracts in tablet form as well.
Tincture: 2-4 ml (1:5 in 40% alcohol), 3 times per day.
Check out this Pregnancy Tonic Tea featuring Red Raspberry & Nettle Leaves.
Or become a kitchen herbalist with this fancy/simple Red Raspberry Leaf Vinegar.
I will refer below only studies on pregnant women, leaving out studies on rats, guinea pigs, cats, rabbits, and isolated uterine muscle as these do not replicate the complex physiology of a pregnant human drinking a herbal infusion.
It is worth noting that from the studies on isolated uterine muscle, red raspberry leaf appears to have a tonic effect – that is, it increases tone of relaxed smooth muscle, and induces relaxation where muscle tone is already high (Mills & Bone, 2005; Mills, Duguoa et al 2006). It is also noteworthy that Rubus ideaus has an apparent relaxing effect on the muscle of the small intestine (specifically the ileum), at least in Guinea pigs (Rojas-Vera J1, Patel AV, Dacke CG, 2002).
Although nearly two thirds of US midwives report prescribing Red Raspberry leaf to their clients (McFarlin et al 1999), and many, many women self prescribe the tea, there have been relatively few human studies.
One randomized controlled trial of 192 women with low-risk single pregnancies compared red raspberry leaf tablets (2 x 1.2 g per day) to placebo from 32 weeks gestation onwards. There were no adverse effects for either mothers or babies.
Those who took the herbal tablets had a shorter second stage of labor, as well as lower rates of forceps delivery (Simpson et al, 2001).
Another study involving 108 women (57 in treatment group, 51 in control group) confirmed that the herb is safe. They also noted lower rates of pre and post-term gestation – meaning fewer babies were born too early or late – as well as less likelihood of obstetric interventions, including caesarian section, and vacuum or forceps delivery (Parsons et al 1999).
Safety & Concerns
Considered safe in pregnancy and while breast-feeding.
Due to the high tannin content, the herb may interfere with absorption of iron and other minerals, similar to black tea. So, take supplemental iron at a different time than you drink your tea. Note that the herb itself contains iron along with other minerals. In balance as they occur in nature, this mineral content is considered well-absorbed.
Boon, Heather & Smith, Michael. 2004. The Complete Natural Medicine Guide to the 50 Most Common Medicinal Herbs. Toronto, ON: Robert Rose, Inc.
Gilbert, Cyndi. 2015. The Essential Guide to Women’s Herbal Medicine. Toronto, ON: Robert Rose, Inc.
Gladstar, Rosemary. 1993. Herbal Healing for Women. New York, NY: Simon & Schuster, Inc.
Hoffmann, David. 2003. Medical Herbalism: The Science & Practice of Herbal Medicine. Rochester, VT: Healing Arts Press, a division of Inner Traditions International.
McFarlin B, Gibson M, O’Rear J, Harman P. 1999. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J Nurse Midwifery, 44:205-216.
Mills, Simon & Bone, Kerry. 2005. The Essential Guide to Herbal Safety. St Louis, MO: Elsevier – Churchill Livingstone.
Mills, Edward, Dugoa, Jean-Jacques, Perri, Dan, Koren, Gideon. 2006. Herbal Medicines in Pregnancy & Lactation: An Evidence-Based Approach. London & New York: Taylor & Francis Group.
Romm, Aviva. 2010. Botanical Medicine for Women’s Health. St Louis, MO: Elsevier – Churchill Livingstone.
Simpson M, Parsons M, Greenwood J, Wade K. 2001. Raspberry leaf in pregnancy: its safety and efficacy in labor. J Midwifery Women’s Health, 46:51-59.
Weed, Susun. 1986. Wise Woman Herbal for the Childbearing Year. Woodstock, NY: Ash Tree Publishing.
Wood, Matthew. 2009. The Earthwise Herbal: A Complete Guide to New World Medicinal Plants. Berkeley, CA: North Atlantic Books.