When I was just entering the second trimester of pregnancy, I started experiencing very low blood pressure and accompanying fainting spells. While there’s no conclusive evidence to show that low blood pressure during pregnancy is dangerous for you or your baby , it can leave you feeling a bit tired and washed out. So I asked my obstetrician what I could do about it. I wasn’t entirely surprised when he ‘prescribed’ the unusual remedy of a piece of liquorice every morning and evening, having been advised something similar by a medical student when my low blood pressure prevented me from donating blood in university. But now I was pregnant – it was time to find out whether this liquorice thing really works, if so, how and (although recommended by my doctor) whether there were any concerns in pregnancy.
I was somewhat surprised to find out the answer to “Does Liquorice Raise Blood Pressure?” is yes! Far from being a quirky old wives’ tale, several studies have shown that the active ingredient, glycyrrhizin, works by mimicking some of the actions of the hormone cortisol [2,3]. Cortisol is commonly known for being released by your body when you are stressed, and most people will be familiar with the rise in blood pressure that accompanies this. That is roughly the same way in which liquorice works. However, the quantities needed to achieve this effect in a measurable way are only for the liquorice lovers – around 300mg of glycyrrhizin is required, meaning one to two 125g bags of liquorice every day! [2,3] (although an effect can be seen at lower doses).
I’m a fan of liquorice, so thought it no hardship to ‘endure’ a bag of liquorice a day to help boost my BP. But first, a quick check on pregnancy risks was in order. This time, I was shocked to find the conclusion that liquorice is clearly to be avoided during pregnancy. It turns out that the same effects that cause a rise in blood pressure also inhibit the placenta’s barrier to maternal cortisol. This can allow circulating stress hormone cortisol to reach the growing baby . Over sustained periods of time, this exposure to maternal glucocorticoids means the baby’s own hormonal ‘axis’ (the hypothalamic-pituitary-adrenal axis) is permanently re-programmed [5, 6]. This mechanism has been studied for the last two decades, and several studies focusing on liquorice in pregnancy have shown that babies born to moms who love a bag or two a day have a higher chance of pre-term birth and babies with higher BMIs, lower IQs, poorer memory, a higher likelihood of attention/hyperactivity disorders and aggression problems and experience early puberty [4, 6, 7, 8].
Most of us get told about avoiding runny eggs and undercooked meat when pregnant. It may not be a common dietary feature, but the evidence is even stronger for avoiding liquorice while pregnant – better to find another way to satisfy your sweet tooth!
 Zhang J, Klebanoff MA, (2001), “Low Blood Pressure During Pregnancy and Poor Perinatal Outcomes: An Obstetric Paradox”, American Journal of Epidemiology, Vol 153 (7), pp 642 – 646, https://doi.org/10.1093/aje/153.7.642
Hautaniemi EJ et al. (2017) “Voluntary liquorice ingestion increases blood pressure via increased volume load, elevated peripheral arterial resistance, and decreased aortic compliance.”, Scientific Reports (Nature), Vol 7(1): 1094 -7 doi: 10.1038/s41598-017-11468-7
 Sigurjonsdottir HA et al. (2001) “Liquorice-induced rise in blood pressure: a linear dose-response relationship.” Journal of Human Hypertension, Vol 15(8): 549 – 52.
 Raikkonen K et al. (2009) “Maternal licorice consumption and detrimental cognitive and psychiatric outcomes in children.” American Journal of Epidemiology, Vol 170 (9): 1137 – 46 . doi: 10.1093/aje/kwp272
 Raikkonen K et al. (2010) “Maternal prenatal licorice consumption alters hypothalamic-pituitary-adrenocortical axis function in children.” Psychoneuroendocrinology, Vol 35(10): 1587 – 93 doi: 10.1016/j.psyneuen.2010.04.010
 Reynolds RM, (2013) “Glucocorticoid excess and the developmental origins of disease: two decades of testing the hypothesis.” Psychoneuroendocrinology, Vol 38(1): 1 – 11
 Raikkonen K et al. (2017) “Maternal Licorice Consumption During Pregnancy and Pubertal, Cognitive and Psychiatric outcomes in children”, American Journal of Epidemiology, Vol 185 (5): 317 – 328 doi: 10.1093/aje/kww172
 Strangberg TE et al. (2001) “Birth outcome in relations to licorice consumption during pregnancy.”, American Journal of Epidemiology, Vol 153(11): 1085 – 8