The roots and rhizomes of Ginger (Zingiber officinale; Roscoe, Zingiberacae), have been used medicinally for thousands of years.  Originating from southern China and spreading to India and South East Asia, ginger is highly valued and throughout history has had huge economic importance throughout not only for making meals more interesting, but also for its medicinal properties. Dose-dependent antiviral activities of relevance against the current SARS-CoV-2 coronavirus for example, are of great interest at the present time^(1-4).

It is a component in a huge percentage of traditional herbal formulations, and like black pepper, became one of the most widely traded spices from Asia via the Silk Road and by sea during the Roman empire and beyond. Its reputation as an aphrodisiac, also made it sought after in Europe. Today it is cultivated in many tropical climates including throughout Asia and Africa, Brazil, Australia, the Caribbean and Polynesia. Many different local varieties and cultivars occur, depending on where it is grown. At least 140 other species are found in the Zingiber genus, some of which have become very invasive in some parts of the world.  

Like all medicinal plants, phytochemical and organoleptic (taste, smell, appearance) parameters of ginger vary depending on the source and post-harvest processing methods used⁽⁵⁾. Most known pharmacological properties are largely attributed to polyphenolic compounds known as gingerols in fresh ginger, which dehydrate to become shogaols in dry ginger.

More than 400 scientific papers a year are now being published on ginger’s potential therapeutic properties. Indications include conditions such as digestive upsets, infectious diseases, diabetes mellitus, obesity, inflammatory and degenerative joint conditions, pain and more⁽⁶⁾. This article will focus on digestive system applications.

Digestive Aid

Confucius is said to have written as far back as 500 B.C. that he was never without ginger when he ate, and the Greek physician Dioscorides wrote in his famous De Materia Medica of 77 A.D that ginger ‘warms and softens the stomach’⁽⁷⁾. Traditional and modern day uses include for ailments such as nausea and vomiting, constipation, belching, bloating, gastritis, epigastric discomfort, gastric ulcerations, and indigestion.

A recurrent feeling of early or prolonged fullness and sometimes pain in the upper digestive tract, known as functional dyspepsia, has been reported to improve following ginger intake⁽⁸⁾. This may relate to an accelerating effect on gastric emptying⁽⁹⁾.

A recent study using a newly developed animal model of IBS-D (the type of irritable bowel where diarrhoea is a predominant symptom), reported less diarrhoea and other benefits from ginger treatment. Oedema and inflammation in the colons of the IBS-D rats, was also reduced by ginger treatment⁽¹⁰⁾. While a clinical trial involving forty five irritable bowel syndrome (IBS) patients who took 1 or 2 grams of ginger a day failed to find significant benefits, IBS is a difficult and heterogenous condition to treat. Further human trials with greater participant numbers and possibly higher ginger doses, seem warranted⁽¹¹⁾.  

Diarrhoea and stomach upset are common adverse events of antibiotic usage, and ginger may be a useful adjunct, according to a recent study in rats. Reduced diarrhoea, improved diversity of the gut microbiotica and its faster recovery following antibiotic treatment, plus restoration of intestinal barrier function, was observed following ginger treatment⁽¹²⁾. Comparative effects to the drug sulfasalazine have been reported in a rat model of ulcerative colitis⁽¹³⁾. A trial involving forty six patients with mild to moderate ulcerative colitis who took ginger for 12 weeks, reported improvements in both disease severity scores and the quality of life⁽¹⁴⁾. Another human trial is planned⁽¹⁵⁾.

Evidence to date also suggests a useful protection against the development of peptic (gastric or duodenal) ulcers, by regular ginger ingestion⁽³⁸⁾.  Protective effects have been reported against aspirin ^{(16, 17, 18)}, indomethacin ⁽¹⁹⁾ and ethanol ^(20-23) induced gastric ulcers in rats. Administration of a steamed ginger extract for 14 days also had a marked protective effect against gastric mucosal damage⁽²⁴⁾. Protection against stress-induced ulcers, and inhibitory activity against Helicobacter pylori, the gut pathogen contributory to peptic ulcers, has also been reported^{(23, 25, 26)}. Human trials seem warranted.

Pharmacological actions contributory to ginger’s reputation as a good digestive system tonic, are multiple. They include a spasmolytic activity on smooth muscle^{(23, 24)}, antibacterial effects, and diverse anti-inflammatory properties. Many ginger constituents modulate cytokines, chemokines, cyclooxygenase-2, nitric oxide, nuclear factor-κB(NF-κB) and numerous other biochemical pathways involved in both acute and chronic inflammation^{(27, 28)}.

Nausea and vomiting

A recent meta-analysis incorporating 10 randomized trials and a total of 918 patients supported the efficacy of ginger in reducing the incidence of post-operative nausea and vomiting, although effects were not statistically significant compared to placebo⁽²⁷⁾. Underdosing of ginger, was suggested by the authors as accounting for this lack of statistical significance.

A Cochrane Review into the use of ginger products in women with nausea and vomiting in early pregnancy, concluded they may be helpful and three studies supported ginger over placebo⁽²⁸⁾.  Again however, the evidence of effectiveness was limited and not consistent, hardly surprising given the diversity in study design.  A more recent French review concluded that use of 1 gram of fresh ginger root per day for four days lead to a significant decrease in nausea and vomiting during early pregnancy, and did not reveal any risk for the mother or foetus⁽²⁹⁾. Personally though, I’ve always regarded the use of large ginger doses near to or during parturition as something that should probably be avoided, due to a theoretical inhibitory effect on prostaglandins involved in labour^{(30, 34)}.

A review of nine clinical trials published between 2012 and 2017, recently concluded that ginger may reduce chemotherapy-induced nausea in breast cancer patients⁽³⁵⁾. Other recent reviews however, while advocated ginger’s benefits as a cheap and accessible therapy, have failed to find statistical confirmation of its effectiveness in the management of nausea and vomiting in cancer patients^{(36, 37)}. Cumulatively however, they suggest that further research with stronger study designs, adequate sample sizes, standardized ginger products, and validated outcome measures to confirm efficacy and optimal dosing regimens, are needed.

Obesity management?

Ginger may also have potential uses in the management of obesity^(39-44). Several studies have reported weight lowering effects of ginger extract or powder in obese animal models. Korean researchers recently found that supplementation of the diet with 5% ginger significantly ameliorated the body weight gain, hyperglycaemia, hypercholesterolemia, and fatty liver produced as a result of a high fat diet, without altering food intake⁽⁴⁰⁾. Ginger also lessened adipocyte hypertrophy and reduced the inflammatory gene expression of adipocytes⁽⁴⁰⁾. Similar findings came from another recent study, where obesity preventive effects were accompanied by a healthy modulation of the gut microbiota, and elevation in levels of beneficial short-chain fatty acids (SCFAs)^{(41, 42)}.

Two clinical studies have taken place involving 12 weeks of ginger treatment in obese subjects, and while these have reported minor beneficial effects on weight loss and some metabolic features of obesity^{(44, 46)}, further and longer term clinical trials, are indicated.

Summary:

Ginger became famous and highly sought after because of its efficacy for a range of human health needs, not just as a tasty spice. While perhaps best known for its alleged anti-nausea effects, trials have produced somewhat mixed results, due in large part to the diversity of study designs, product types and doses used. Research in recent years is also increasingly supportive of its long reputation as a remedy for dyspepsia, peptic ulcers and inflammatory conditions of the digestive tract, although there is a need for further human clinical trials in these conditions.  Ginger’s utility as a gastroprotective and anti-inflammatory, and its ability to optimise many aspects of digestive function, certainly make it a spice to take an interest in.

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