askST: What are the long-term effects of consuming the unapproved additive in Chun Cui He milk tea?

A reader asked what the adverse long-term effects, if any, are of consuming the non-permitted additive contained in Chun Cui He milk tea drink. The drink has been recalled by the Agri-Food and Veterinary Authority because it contains L-theanine, a non-permitted food additive. L-theanine, an amino acid found naturally in tea plants and fungi, is said to have calming properties. Mind&Body editor Ng Wan Ching replies:

L-theanine is believed to help relieve stress by inducing a relaxing effect without drowsiness and may also have some benefits for the immune system, said doctors.

But, information regarding adverse reactions to L-theanine alone (versus combined with caffeine, as in tea) is lacking. Clinical trials used small numbers of participants and the reporting on adverse events was poor, said Dr Timothy Tan, resident physician at the 24 Hour Emergency at Raffles Hospital.

One study among elderly participants recorded a higher number of reported headaches among those receiving four doses of L-theanine at 250mg per dose.

In 2006, a study found no consistent, statistically significant treatment-related adverse effects in rats fed high doses of L-theanine for 13 weeks. The areas studied included behaviour, body weight, food consumption and efficiency, blood and urine analysis.

Large studies in humans have not been undertaken.

There are no reports of clinical toxicity from daily tea consumption. Adverse reactions recorded in human studies using tea extracts include headache, dizziness, and GI symptoms, said Dr Michael Wong, deputy medical director at Raffles Medical.

An increased incidence of renal tubule adenomas in a small number of female rats given high dosages (400mg/kg body weight per day) was attributed to genetic predisposition.

These are a form of kidney tumour that is generally benign or non-cancerous but carry the potential to become adenocarcinomas which are malignant, said Dr Wong.

There is no consistent and statistical evidence on long-term consumption of L-theanine as there are very limited studies done on this food component and some have small sample sizes which are not able to yield significant results, said Dr Tan.

However, there are other factors that need to be considered for long-term consumption of high sugar content drinks which may lead to other metabolic problem such as obesity and diabetes, he added.

More askST stories here.