Public concern around Thai tea’s vibrant hue has intensified after the Thailand Consumers Council revealed in March 2025 that many popular Thai tea products contain high levels of Sunset Yellow FCF. As more parents become aware of what’s in their children’s drinks, questions are being raised about the potential behavioural and health effects of synthetic food dyes.
A peer-reviewed study published in The Lancet is particularly relevant. This randomised, double-blinded, placebo-controlled trial investigated the impact of two additive mixtures — including Sunset Yellow FCF (or E110 in Europe) — on children’s behaviour. Conducted on a general community sample of three-year-olds and eight or nine-year-olds, the study examined whether artificial food colourings and preservatives could influence hyperactivity levels. Its findings offer useful insight for parents and educators concerned about attention, restlessness, and behavioural regulation.
Key findings from the study include:
- Study Design: The trial involved 153 3-year-old and 144 8/9-year-old children, each randomly assigned to receive a drink containing one of two artificial additive mixtures or a placebo (free from additives). The study was carried out over six weeks, with behavioural assessments conducted by parents, teachers, and trained observers.
- Additive Mixtures: Both mixtures tested included Sunset Yellow FCF (E110), along with other common food dyes and sodium benzoate (a preservative). The study did not isolate the impact of individual additives, but measured the effect of the mixtures as a whole.
- Behavioural Outcomes: The results indicated a significant increase in hyperactivity among children who consumed the additive mixtures compared to those who received the placebo. This was observed in both age groups, though the effect size varied. In particular, parents and teachers of 8/9-year-olds reported noticeable increases in impulsivity and attention difficulties during the weeks when additives were consumed.
- Conclusion from Researchers: The authors concluded that artificial food colourings and sodium benzoate preservative — even in the general population of children without diagnosed behavioural conditions — may have a measurable impact on hyperactivity. They suggested that these findings indicate artificial additives can increase hyperactive behaviour in children, and recommended that further consideration be given to the use of such additives in children’s diets.
What This Means for Families
While the research does not focus on Thai tea specifically, it raises timely questions for families whose children may consume beverages or snacks containing similar synthetic colourings. Products containing Sunset Yellow FCF and other additives may appear harmless, but could influence attention and behaviour — especially in younger children. For parents seeking to support focus, learning, and emotional regulation at home, it may be worth paying closer attention to food labels, limiting artificial additives, and opting for naturally coloured or additive-free alternatives where possible.
As with many areas of nutrition and health, moderation and informed choices are key. Understanding the research can help families navigate what’s best for their children.
For more detailed information on this research, read the full study here.
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