Dr Des Corrigan takes a festive look at what we consume at Christmas time
Over the years, I have used Christmas as a theme for my December article by writing about the healthy and the not so-healthy effects of the many plants we use in our celebrations, be they as foods, flavourings, decorations or gifts. This year I thought I would review some updated information about several of those ‘Christmassy’ plants.
The spice plant that most evokes Christmas for me is cinnamon. That characteristic smell as it is weighed out and then stirred into the cake and pudding is a source of endless memories. While I adore its taste in cakes and pastries, I draw the line, however, at the whole concept of the cinnamon latte. With all due respect to the global chains that promote such an abomination, I say “thanks but no thanks”.
Medicinally, cinnamon bark is seen by the European Medicines Agency (EMA) as a traditional herbal medicinal product for treating the symptoms of mild spasmodic complaints such as bloating and flatulence, and, secondly, in cases of mild diarrhoea.
Whatever about the latter, I suspect that the need for the former indication might feature prominently at this time of over-indulgence. I have mentioned previously that the EMA may be behind the times when it comes to cinnamon as there is a significant body of research into its value as a supplement in type 2 diabetes. A 2024 systematic review in Phytotherapy Research updated information on the effect of cinnamon supplementation on glycaemic control for type 2 diabetics. A meta-analysis of 24 randomised controlled trials (RCTs) found that there was a statistically significant reduction in fasting blood sugar and in the homeostatic model assessment for insulin resistance, compared to controls. HbA1c levels were significantly reduced by Chinese cinnamon (cassia bark) at doses above 3g per day whereas Sri Lankan cinnamon was less active. The overall conclusion was that there was potential for cinnamon as an adjunct to existing therapy.
Another key ingredient in Christmas baking is dried fruit – or, more accurately, dried grapes in the form of sultanas, raisins, and currants. Grapes, especially the red ones, are rich in antioxidant polyphenols called anthocyanins. As a result, much has been made over the years about the health benefits of red wine made from those grapes. In addition to the anthocyanins, the skin of grapes (both fresh and dried) is particularly rich in a chemical called resveratrol. This is known to have a spectrum of biological activities including antioxidant, anti-inflammatory, anti-hyperlipidaemic, anti-tumour, anti-angiogenic, anti-aging, neuroprotective, and cardioprotective effects. While animal studies suggest an effect on hypertension, a 2019 meta-analysis of 17 RCTs published in reviews in Food Science and Nutrition, found no significant reduction in blood pressure after taking resveratrol.
An umbrella review of the numerous separate meta-analyses of resveratrol supplementation in patients with type 2 diabetes, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD) appeared in the American Journal of Clinical Nutrition in 2021. The authors identified 11 meta-analyses involving patients with diabetes, 17 with patients with metabolic syndrome and 10 covering patients with NAFLD. While some benefit was seen on BP, lipid profile, and glycaemic control, the magnitude of the effect was deemed “trivial”. Only in the case of HbA1c levels was the effect judged to be clinically favourable. The authors concluded that current evidence does not support supplementation with resveratrol for cardiometabolic risk factors in patients with those conditions. A 2024 review in Phytotherapy Research found that 86 per cent of the 51 meta-analyses involving resveratrol were of low methodological quality. It seems to me that this substance is another example of a highly pharmacologically active plant chemical in search of a clinical condition to treat.
I have a similar feeling about the active phytochemical from what is probably the most maligned of all the Christmas plants, namely the humble brussels sprout. It, or rather its characteristic component, has huge potential clinically, but this is not yet fully evidence-based. In common with all the other members of the cabbage family (Brassicas) it contains sulforaphane, although broccoli has the highest concentration. According to a 2024 review in Phytotherapy Research, several commercial formulations of sulforaphane are currently in clinical trials in patients with lung, breast, head and neck, and prostate cancer. The review refers to “some encouraging” results but notes that many of the RCTs have yet to be completed. The International Journal of Molecular Sciences reported in 2023 on the positive in vitro and in vivo effects of sulforaphane found during studies of prostate cancer progression. One RCT reported no effect on the disease, although a second used a soup from a variety of broccoli with a high level of the precursor of sulforaphane called glucoraphanin (a sort of pro-drug) given weekly to prostate cancer sufferers over a period of 12 months. Compared to ordinary broccoli, consuming the glucoraphanin-rich soup reduced the risk of disease progression. A systematic review this year in Phytomedicine noted that sulforaphane enhances antioxidant activity, suppresses inflammation, and inhibits apoptosis. These may be good reasons to eat sprouts and other Brassicas but I am not sure that the Christmas dinner table is the most appropriate forum to extol their virtues.
In addition to the anthocyanins, the skin of grapes (both fresh and dried) is particularly rich in a chemical called resveratrol
While sprouts may provoke strong reactions, my final choice is in no way controversial, in fact for many it would not be Christmas without those preparations from Theobroma cacao that we call chocolate. A systematic review and meta-analysis of RCTs of the effect of chocolate on cognitive function in healthy adults appeared earlier this year in Phytotherapy Research. Results from the seven trials showed that chocolate significantly reduced executive function time. Language and executive function were raised by a factor of six. Short-term effects were seen in younger adults and cognitive function was slightly improved in postmenopausal women. The effects were attributed to the chronic intake of flavanols found in dark chocolate, in particular. So, if you think that reaching for the nearest box of chocolates is the antidote to the post-Christmas dinner dulling of your mental capacity, can I suggest that you start your chocolate intake well in advance of the day itself, rather than relying on a short- term boost.
Whether you will be, like me, working off the Christmas calories by means of a postprandial snooze or if you throw yourself whole heartedly into after-dinner board games and entertainment, I wish you and your families a Happy Christmas and a peaceful New Year
Dr Des Corrigan, Best Contribution in Pharmacy Award (winner), GSK Medical Media Awards 2014, is an Adjunct Associate Professor at the School of Pharmacy and Pharmaceutical Sciences at TCD where he was previously Director and won the Lifetime Achievement Award at the 2009 Pharmacist Awards. He was chair of the Government’s National Advisory Committee on Drugs from 2000 to 2011, having previously chaired the Scientific and Risk Assessment Committees at the EU’s Drugs Agency in Lisbon. He chaired the Advisory Subcommittee on Herbal Medicines and was a member of the Advisory Committee on Human Medicines at the HPRA from 2007 to 2024. He has been a National Expert on Committee 13B (Phytochemistry) at the European Pharmacopoeia in Strasbourg and served on the editorial boards of a number of scientific journals on herbal medicine.
