Infertility is an emotional topic for anyone who has experienced it. In many cases, infertility cultivates a desperation to find anything that may help with successful embryo implantation, and a quick google search produces millions of herbal remedies that claim to either help, or hinder, your dreams of pregnancy. This article examines two nutrients, quercetin and bromelain, both of which have been implicated for their role in pregnancy or infertility for different reasons. We examine the scientific evidence behind these health claims.
Quercetin is a bioflavanoid that occurs naturally in many plant foods and drinks, especially red wine, tea, and onions. (1, 2) It possesses high levels of antioxidants and has an array of purported health benefits, including beneficial effects on cardiovascular disease, cancer, metabolic syndrome, and oral health. (1) These beneficial health claims have led to an increase in the rise of people taking quercetin as a supplement, but there is some evidence to suggest that quercetin may effect fertility, and caution should be taken by people of reproductive age. (1)
Quercetin is a xenoestrogen, a sub-category of the endocrine disruptor group that have estrogen-like effects. (1) This means quercetin supplementation may affect estrogen-dependent processes involved in reproduction. (1)
Animal studies have shown that supplementation with quercetin has interesting effects on female fertility. (1) In one study, younger female mice receiving a quercetin supplement experienced an increase in litter size, but these litters were more spaced out and there was an overall reduction in litters born. (1) In contrast, older female mice supplemented with quercetin experienced a decline in litter size. Another study in rats receiving a quercetin supplement noted an increased gestational duration, 10% reduction in pregnancy success rate, and an increase in litter size. (3) Importantly, the quantity of quercetin given as a supplement in both these studies was low-dose, and was relevant to human dietary consumption. (1) The mice study concludes that their data supports the further investigation of the negative effects of quercetin supplementation on women of reproductive age, to assess whether the negatives outweigh the positive health benefits for humans.
Studies on the effect of quercetin on male fertility are notably contradictory, with one study finding that quercetin may be used to treat male infertility (4). Another study found that quercetin improved sperm motility, viability, and serum total testosterone in diabetic rats. (5) A more recent study of healthy male mice, however, found that the pro-oxidant effects of quercetin can be held responsible for decreasing sperm motility and concentration. (2) This same study also found that quercetin had the ability to disturb endocrine function and therefore effect Sertoli cell function and structure. (2)
If you do a quick google search of ‘bromelain and fertility’ or ‘bromelain and implantation’ you are bombarded with articles advocating for the use of bromelain to help with successful implantation, but does science back this claim? Not exactly…but this doesn’t mean there isn’t some potential truth to it!
Bromelain is a substance found in pineapples, particularly in the stem. (6) It contains a variety of substances such as proteinases, peroxidises, phosphatises, protease inhibitors and organically bound calcium, and exhibits an assortment of pharmacological effects. (6) Some of the reported health benefits of bromelain include decreasing malignant cell growth and thrombus formation, possessing anti-inflammatory properties, controlling diarrhoea, and helping with dermatological and skin debridement. (6) There is however, a notable lack of peer-reviewed research on the beneficial effect of bromelain on implantation. This does not necessarily mean that bromelain won’t help with embryo implantation, but rather, that there needs to be further research done to substantiate the rather large claims that have been made.
So, where do these claims come from? There are two main reasons that bromelain has been suggested as a beneficial supplement for successful embryo implantation; for its blood thinning properties, and its anti-inflammatory properties. (6)
Blood thinners, such as aspirin, are commonly prescribed for women undergoing IVF because of their anti-inflammatory, vasodilatory, antiplatelet aggregation properties. (7) This explains the potential perceived benefit of a more natural alternative such as bromelain, especially because many women prefer not to consume drugs during the pre-conception and conception period. It should be noted though that the level of aspirin typically prescribed is a low dose, and it is not fully understood what effect unmeasured consumption of bromelain in the diet might do for embryo implantation. (7)
The response of the immune system has been shown to be key to a successful implantation and continued pregnancy. (8) Although, paradoxically, research has shown that successful implantation occurs more readily when the uterus has suffered some ‘trauma’ (e.g. a uterine biopsy in the IVF process), the inflammatory response that follows is also one of the biggest threats to the survival of the embryo. (8) A very swift anti-inflammatory reaction following implantation is needed to suppress the mother’s immune response so that her body does not reject the embryo as a foreign ‘parasite’. (8) This is why bromelain, with its anti-inflammatory properties, have been touted as a potential aid in successful pregnancies.
It is important to note that there are also potential detrimental effects of consuming bromelain for a successful implantation and pregnancy, especially if you are already on blood thinning medication. So, although a moderate amount of bromelain, eaten as a part of your daily fruit intake in the form of pineapple, is probably going to be ok, steer clear of bromelain supplements unless you’ve been advised otherwise by a health professional.
This blog was written by Clare Carrick @loopnutrition as part of her 2020 internship with Wholefood Healing.
1. Beazley KE, Nurminskaya M. Effects of dietary quercetin on female fertility in mice: implication of transglutaminase 2. Reproduction, Fertility and Development. 2016 Jun 8;28(7):974-81.
2. Ranawat P, Kaushik G, Saikia UN, Pathak CM, Khanduja KL. Quercetin impairs the reproductive potential of male mice. Andrologia. 2013 Feb;45(1):56-65.
3. Johnson JR, Makaji E, Ho S, Xiong B, Crankshaw DJ, Holloway AC. Effect of maternal raspberry leaf consumption in rats on pregnancy outcome and the fertility of the female offspring. Reproductive Sciences. 2009 Jun;16(6):605-9.
4. Taepongsorat L, Tangpraprutgul P, Kitana N, Malaivijitnond D (2008) Stimulating effects of quercetin on sperm quality and reproductive organs in adult male rats. Asian J Androl 10:249–258.
5. Khaki A, Fathiazad F, Nouri M, Khaki A, Maleki NA, Khamnei HJ, Ahmadi P (2010) Beneficial effects of quercetin on sperm parameters in streptozotocin-induced diabetic male rats. Phytother Res 24:1285–1291.
6. Tochi BN, Wang Z, Xu SY, Zhang W. Therapeutic application of pineapple protease (bromelain): a review. Pakistan journal of nutrition. 2008;7(4):513-20.
7. Fabozzi G, Giannini A, Piscitelli VP, Colicchia A. Adjuvants Therapies for Women Undergoing IVF: Is There Any Evidence of their Safety and Efficacy? An Updated Mini-Review. Obstet Gynecol Int J. 2017;7(4):00254.
8. Pennisi, E. (2018). Tamed immune reaction aids pregnancy. Science, 359(6373), 260–260. doi:10.1126/science.359.6373.260