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Too much Earl Grey causes problems

Summary

As reported in the journal Lancet, large quantities of tea flavoured with bergamot essence (as in Earl Grey tea) can cause health problems. It may bring on muscle cramps, involuntary twitches, burning or prickling feelings, and blurred vision. A man aged 44 years reported muscle cramps to his doctor. He had consumed up to four litres of black tea daily for 25 years and had recently switched to Earl Grey tea, believing it would be less harmful to his stomach. Within a week, he developed muscle cramps and other unusual symptoms, including a feeling of pressure in his eyes. He also had blurred vision, particularly in darkness. After five months, the patient switched from Earl Grey back to pure black tea and his symptoms completely disappeared within a week. They remained absent when he stopped drinking all tea for a week. He also found they did not recur as long as he consumed no more than one litre of Earl Grey tea daily. Essence of bergamot oil is used to flavour Earl Grey tea. The side effects observed in this man can be explained by one of its components bergapten.
Finsterer J. Lancet 359:1484, 27 Apr 2002

Case report details

As reported in the journal Lancet, even tea can cause health problems if flavoured with bergamot essence (Earl Grey tea) and consumed in large quantities. It may induce muscle cramps, involuntary twitches (fasciculations), burning or prickling feelings (paraesthesias), and blurred vision. A man aged 44 years went to his doctor with muscle cramps. He had consumed up to four litres of black tea daily for 25 years and had recently switched to Earl Grey tea, believing it would be less harmful to his stomach. Within a week, he developed muscle cramps in his right foot. Over the next few weeks they had spread to his left foot, right calf and towards his hands. Other symptoms included involuntary twitches of the right adductor pollicis and gastrocnemius muscles, burning or prickling in the end regions of all limbs, and a feeling of pressure in his eyes. This was associated with blurred vision, particularly in darkness. Appropriate tests excluded motor neurone disease, polyneuropathy, myopathy, neuromyotonia, stiff-man syndrome and Machado-Joseph disease. After five months, the patient switched from Earl Grey to pure black tea and his symptoms completely disappeared within a week. They remained absent when he stopped drinking all tea for a week. He also found they did not recur as long as he consumed no more than one litre of Earl Grey daily. Essence of bergamot oil is used to flavour Earl Grey tea. Bergamot oil contains bergapten (5-methoxypsoralen), bergamottin (5-geranyloxypsoralen), and citropten (5,7-dimethoxycoumarin). It is a well known UVA-induced photosensitiser (making the skin abnormally sensitive to sunlight), has a toxic effect on the liver and can also cause contact allergy. The side effects observed in this case can be explained by bergapten, which has effects on electrical conduction in membranes of peripheral nerves (it is a largely selective axolemmal potassium channel blocker and reduces potassium permeability at the nodes of Ranvier). The resulting hyperexcitability of the nerve axon membrane and timing alterations of nerve potassium currents can cause the twitching and muscle cramps.
Finsterer J. Lancet 359:1484, 27 Apr 2002

Originally posted week beginning 13 May 2002

Disclaimer

This is a summary article from MedALERT, a clinical journal review service written by Kathleen Nash. Originally selected to inform General Practitioners, knowledgeable New Zealand health consumers may also find this article useful. This information is intended solely for New Zealand residents and is of a general nature only and no person should act in reliance on any statement contained in the information provided and at all times should obtain specific advice from a health professional. All rights reserved. © UBM Medica (NZ) Ltd. This publication is copyright.

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