From the bark of cinchona tree to your glass, quinine is thought to have anti-arrhythmic properties because it’s able to slow electrical conduction in your heart, explains Dr Deborah Lee from Dr Fox Online Pharmacy. However, there’s more to quinine than being an ingredient in G&T, it’s also used as a drug.
“It can relax smooth muscle. Blood vessel walls are made of smooth muscle.
“If smooth muscle relaxes, blood pressure falls.”
And this isn’t the only way quinine could see your levels drop. The doctor said: “It has been shown to block anticholinergic receptors at the nerve-muscle junction.
“Other anticholinergic drugs are known to cause postural hypotension (a drop in blood pressure when moving from lying or sitting, to standing).”
However, she also noted that some studies haven’t shared such positive outlook on quinine and lower hypertension reading.
Others explain that while quinine might lower your levels, it needs to be administered intravenously.
She added: “Quinine is unlikely to lower blood pressure by any appreciable amount for the average healthy adult.
“However, if you are taking quinine tablets for night cramps and have a couple of gin and tonics a day, this small extra amount of quinine could be enough to cause an adverse event, for example, low blood pressure, or a cardiac arrhythmia [an irregular heartbeat].”
Sadly, those who are “healthy, fit” adults won’t get any blood pressure benefit from drinking tonic water.
Dr Lee explained: “The amount of quinine in tonic water is so low it is unlikely this will cause a significant fall in blood pressure.
“Tonic water is a very dilute solution of quinine. It contains 83mg of quinine per litre.
“If you are a fit, healthy adult, you are extremely unlikely to be able to drink enough tonic water for it to affect your blood pressure.”
But she also warned that certain people should think twice before having tonic water, including:
- Those who already suffer from cardiac arrhythmias
- Anyone prone to low blood sugars (type 2 diabetics on oral hypoglycaemic agents)
- Pregnant women
- Anyone with kidney or liver disease
- Anyone on medication such as blood thinners, antibiotics, antidepressants, antacids, digoxin, and statins.
“If you are on any cardiac drugs, always check with GP or pharmacist before you drink tonic water,” she concluded.