by Yuye Shuai

Preface

Raspberry leaf tea is a traditional herbal remedy. Today it is mostly thought of as a woman’s herb, especially for promoting a healthy pregnancy. Its use dates back to ancient Greece, Rome, China and India, where it was used extensively as a treatment for wounds and diarrhoea. However, these applications of raspberry leaf originate from traditional lore and rigorous clinical evidence for its safety and efficacy is still required.

Introduction

Raspberry (Rubus idaeus L., Rosaceae), is native to Europe and northern Asia, but usually cultivated in other temperate regions. The leaves are used medicinally. Raspberry is a common fruit in Japan, Korea, Europe and the United States. It is widely distributed in northeast China, but only as a wild plant and rarely appearing in the market for consumption.

R. idaeus  is a perennial which bear biennial stems (“canes”) from a perennial root system, and the branches of the plant have barbed thorns. The fruit of raspberry is produced in summer or early autumn but cannot be termed as berries in botanical terminology as it is actually an aggregate of numerous drupelets around a central core. Normally, the fruit is red, edible, and sweet but tart flavoured. The leaves of the raspberry plant taste astringent and odourless and are the medicinal part of the whole plant (the botanical drug). The raspberry leaf (RL) can be brewed into a tea, which has been used for centuries for facilitating childbirth (Wren, Williamson and Evans, 1988).

In traditional European medicine, it is reported that drinking raspberry leaf tea during pregnancy can make it easier to give birth. Therefore, it has been called ‘pregnant woman’s herbal tea’ or ‘woman’s tonic’. It is generally believed that RL contributes to the health of muscles of the uterus and pelvis, the nutritional value of breast milk, and the secretion of breast milk. However, the tea also has the effect of stimulating the uterus, hence pregnant woman who intend to use RL tea during pregnancy should consult a physician first. In particular, the consumption of tea should be limited to the earlier stages of pregnancy.

Biological diversity of the genus

 Rubus is one of over a hundred genera in the family Rosaceae, and 250 species of Rubus and many hundreds of microspecies have been established worldwide, among which R. ideaus is cultivated in most temperature countries (Patel, Rojas-Vera and Dacke, 2004).  R. strigosus (American Red Raspberry) is closely related to the European raspberry (R. idaeus) and has also been classified as the variety Rubus idaeus subsp. strigosus (Michx.) Focke (Patel, Rojas-Vera and Dacke, 2004). Generally, red-fruited, cultivated raspberries are R. idaeus or horticultural hybrids of R. idaeus and R. strigosus.  

Main Chemical Compounds

A great variety of metabolites have been identified in RL. The presence of tannins (include ellagitannins, gallotannins) and flavonoids (including kaempferol, quercetin, hyperoside) act as antioxidants so as to protect cells in the body from damage. In addition, raspberry leaves are loaded with nutrition and vitamins, including magnesium, zinc, iron and vitamin C, which can contribute to antioxidant properties. Other constituents comprise phenolic acids (include caffeic acid, chlorogenic acid, p-coumaric acid), tocopherol (TCP) and various alcohol, aldehyde, terpenoids (www.EMA.europa.eu, 2013; Williamson, Driver & Baxter, 2013). However, currently there are no in vitro studies that provide significant evidence regarding which chemical compound of RL could be responsible for the relaxant effects on the uterus.

Traditional uses of Raspberry Leaf

The leaves of R. idaeus have been used as ‘natural remedies’ in various countries to treat conditions like diabetes, stomatitis and inflammation. For this purpose RL has been available in a variety of pharmaceutical forms, such as infusion, eye lotion and mouthwash. Astringent, stimulant, tonic and slightly alterative effects are important for its popular medical use.

The best-known effect of raspberry leaf is to facilitate labour as it is believed capable to tone the uterine muscles. Therefore, RL is considered useful for the relief of menstrual cramps. (Edwards, Da Costa Rocha, Williamson & Heinrich, 2015). The British Herbal Pharmacopoeia (BHP) describes RL as an ‘astringent and partus preparator’ (preparing for birth) (British herbal pharmacopoeia, 1990). With regard to when to use RL tea during pregnancy, consuming it in the last 2 or 3 months of pregnancy could strengthen the uterus prior to giving birth, and the usage in the first months of pregnancy could help to prevent miscarriage as well as to reduce morning sickness (Rjwhelan.co.nz, 2011). Other recommendations of applying RL include drinking RL tea during the menstrual cycle to alleviate cramps.

In the ‘King American Dispensatory’ of 1905, it is described that a decoction of the leaves of raspberry with cream can alleviate nausea and vomiting. The addition of aromatics was also noted to be useful in diarrhoea, cholera mortus (deadly cholera) and cholera infantum (children’s colera) (King, Felter and Lloyd, 1905). The usage of RL for diarrhoea is also recorded in the British Herbal Pharmacopoeia (BHP), together with indications for stomatitis, tonsillitis and conjunctivitis (British Herbal Pharmacopoeia, 1979). An infusion of RL could be used to treat diarrhoea. The infusion taken cold may be a reliable remedy for extreme laxity of the bowels. According to the literature, the infusion alone, or as a component, is able to produce immediate relief in stomach and bowels complaints. It is also noted especially useful for relaxed conditions of intestines of children (King, Felter and Lloyd, 1905; Botanical.com, 2019). In the light of the BHP, a dose of 4-8 grams dried leaves, 4-8ml liquid extract (1:1 in 25% alcohol), or by infusion three times daily is recommended. It may also be combined well with other herbs, such as agrimony for diarrhoea, sage as a mouthwash or gargle, and eyebright as an eye lotion (British herbal pharmacopoeia, 1979). What’s more, RL could also produce significant success in constipation when combined with Mountain Flax (Henriettes-herb.com, 2019).

RL as an eyewash or a mouthwash can be utilized when there is inflammation or infection present or when there are sores that are slow to heal. In folk medicine, the RL gargle could be made by boiling one ounce of the herb in 1½ pints of water down to one pint, and then filter after it is cooled (Henriettes-herb.com, 2019). Using it frequently is good for sore throat and mouth.

Raspberry leaf tea in Pregnancy

In modern society, raspberry leaf tea is mostly referred to as a woman’s herb and is a popular traditional remedy. In a study with 600 Norwegian pregnant woman 5.7% reporting using it (Nordeng, 2011). It is considered by some herbalists and midwives to be a good way of preparing for labour and birth due to its potential benefits in toning woman’s uterus. This include strengthening the uterus wall so as to speed up labour or just to help it progress at a steady pace. Frequently, it may also be used to alleviate morning sickness during the early stage of pregnancy, ease the pain of labour, or help to reduce the risk of bleeding after labour.

However, some midwives and doctors advise against taking anything that may interfere with labour, especially when there is a lack of evidence that raspberry leaf tea works. The truth is that currently available scientific evidence is insufficient to support the use of raspberry leaf in terms of facilitating childbirth or during pregnancy and breastfeeding (Boltonft.nhs.uk, 2019).

Scientific evidence for Raspberry Leaf

Preclinical evidence

It has been shown in vitro experiments that raspberry leaf extracts also have a relaxant effect in guinea-pig ileum (Rojas-Vera, Patel and Dacke, 2002). Langhammer and Nilsen reported in 2014 that raspberry leaf could help to reduce paracetamol-induced hepatotoxicity, but no animal or clinical studies are carried out yet (Langhammer and Nilsen, 2014).

Clinical evidence – Use in pregnancy and birth

In 1999, a retrospective study found that first-stage labour of pregnant woman who used raspberry leaf take was shorter compared to a control group (Parsons, Simpson and Ponton, 1999). Simpson et al. in 2001 found that a raspberry group spent shorter time in the second stage of labour compared to the placebo group and a few more women required forceps or vacuum-assisted birth in the placebo group (Simpson, 2001). Nevertheless, the results from both studies above are not statistically significant. In 2010, Jing Zheng et al. failed to find the direct effect from raspberry leaf to uterine contractility (Jing Zheng et al., 2010). In 2013, it is summarized by the EMA that results from studies on raspberry leaf to support the traditional indication are limited in terms of gestation and pregnancy (EMA.europa.eu, 2013).

Safety of Raspberry Leaf

Similar to other herbal teas, it is advisable to use raspberry leaf in moderation due to the presence of multiple chemicals in the tea and their unknown working mechanisms in the body. In 2009, it was reported for the first time that raspberry leaf may have long-term consequences for the health of the offspring, raising concerns about the safety of raspberry leaf for use during pregnancy (Johnson et al., 2009). In the same year, another preclinical study in rats showed precocious puberty and their offsprings possessed an increased risk in growth restriction (Holst, Haavik and Nordeng, 2009). In 2013, the EMA summarized that the use of raspberry leaf is not recommended for pregnant woman (except under medical supervision), children and adolescents under 18 years old, and should be avoided during lactation or long-term use (Ema.europa.eu, 2013). Cheang et al. in 2016 reported the hypoglycemic effects of raspberry leaf, which means woman with gestational diabetes mellitus (GDM) should be cautioned about its use (Cheang et al., 2016). It is recorded that the side effects of raspberry leaf tea include nausea, loose stools and Braxton Hicks contractions, some of which are likely to be those symptoms normally found in pregnancy (Boltonft.nhs.uk, 2019; Ema.europa.eu, 2013).

Conclusion

The use of raspberry leaf has a long tradition of use. Although a large number of active compounds have been identified, the safety has not established thoroughly due to limited clinical evidence. Despite the wide use of raspberry leaf, no clinical trials could be found to support the traditional indications like dysmenorrhea and diarrhoea (EMA.europa.eu, 2013). The pharmacological data on raspberry leaf does not conflict with its traditional application, but clinical trials or other evidence to corroborate the use of raspberry leaves to treat any traditional indications are rather sparse. Even with regards to the popular use for relaxing uterine muscles, there is currently no clinical data pointing to potential active metabolites in the plant. Therefore, more research is needed in terms of the unknown mechanisms and active ingredients.

However, in traditional medicine, the astringent characteristic of raspberry leaf makes it a suitable treatment for a variety of indications, including diarrhoea, pregnancy and inflammation. Additionally, medicinal uses to facilitate childbirth has a century-long tradition. As a supplement or some other form raspberry leaf has been formulated for various uses. For example, mouth wash for stomatitis, eye lotion for conjunctivitis and infusions for diarrhoea. In conclusion, raspberry leaf tea is a relatively safe herbal tea if taken under a midwife’s or physician’s supervision, and few adverse effects are reported, but the safety is of primary importance. Since it could affect the most vulnerable of all humans unborn children and infants as well as their mothers the uncontrolled use cannot be endorsed from a pharmaceutical or medical perspective

Disclaimer

In this essay we do not to advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and not be considered as a recommendation or an endorsement of any particular medical or health treatment. The use of any such product should be based on the appropriate advice of a healthcare professional or based on the information available in the patient information leaflets (i.e. for THR products).  

References

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