Across the UK and Ireland in recent years, there has been an increase in kids becoming seriously ill soon after drinking sugar-free slushies. A new study has pointed the finger at glycerol, a compound that’s used as a sugar substitute and, until now, has been considered safe.
Glycerol is a versatile compound widely used in the food, personal care, medical, and pharmaceutical industries. In food and drinks, it’s often used as a thickener, preservative, and sugar substitute. In 2017, the European Food Safety Authority (EFSA) re-evaluated the safety of glycerol as a food additive – given the designation E 422 – finding that it had “low acute toxicity.”
However, a recent study led by the Birmingham Women’s and Children’s NHS Foundation Trust has examined the cases of 21 children from across the UK and Ireland who, between 2009 and 2024, became seriously unwell soon after drinking sugar-free slushies containing glycerol.
“Slush ice drinks are popular, brightly colored soft drinks, designed to appeal to children and young people," said the researchers. “Slush ice drink ingredients vary, but the majority available in the UK and Ireland are marketed as ‘no added sugar’ or ‘sugar free’.
“Varieties which are sugar free or have no added sugar contain glycerol (E 422; also referred to as glycerin) in order to maintain the slush effect,” they continued. “The patients reported here all presented shortly after consuming slush ice drinks containing glycerol.”
Information about sex was available for 18 of the 21 patients: 54% were male and 44% female. The average age of patients when they presented to an emergency department for treatment was three and a half but ranged from two to almost seven. Information about the onset of symptoms was available for 15 patients: 93% became unwell within an hour of ingesting a slushie.
Of the 17 patients for whom information about their level of consciousness was available, 94% presented with an acute decrease in consciousness. One child had a tonic-clonic seizure, which causes stiffening of the body and rhythmical jerking. Twenty children (95%) presented with low blood glucose levels or hypoglycemia; with severe hypoglycemia seen in 65% of them. The median blood glucose was 1.2 mmol/L (21.6 mg/dL), where the lower range of normal is 3.9 mmol/L (70 mg/dL).
Ninety-four percent of patients had metabolic acidosis on presentation, a condition in which the blood becomes too acidic due to an accumulation of acid. Normally, the body maintains blood pH within a tight range – around 7.35 to 7.45 – but in the present study, the patients’ median pH at presentation was 7.21. In addition, almost all patients (95%) had elevated lactate levels and 12 of 16 children had low potassium levels. From this constellation of symptoms, the researchers determined that the children had glycerol intoxication syndrome (GIS).
“GIS is not well defined; very few cases have been reported in the literature and the specific pathophysiology remains unknown,” said the researchers. “Episodes in adults were triggered by rapid and large doses of glycerol intake with or without catabolism, and characterized by metabolic acidosis and lethargy, which may progress to coma and seizures.”
Catabolism refers to the process by which the body breaks down molecules to release energy. When catabolism is seen in the context of glycerol intoxication, it suggests that the body is in ‘emergency mode,’ breaking down too much too quickly, which contributes to the dangerous buildup of acid.
“Although slush drinks have been around for some time, there are no published medical reports regarding this associated GIS,” the researchers said. “A cause of the recent apparent surge in cases may be the reduced sugar content of these drinks, secondary to two main factors: first, public health and parental concerns about high sugar ingestion, and second, the introduction of a ‘sugar tax’ on high sugar containing drinks in Ireland and the UK in 2018 and 2019, respectively.”
All of the children responded quickly to initial treatment and correction of their hypoglycemia. They were discharged after being advised to avoid slushies. Twenty children followed this advice and had no further hypoglycemic episodes. One, however, drank another slushie a few years later (at age seven) and again rapidly developed hypoglycemic symptoms that progressed to vomiting and drowsiness. Their parents gave the child a glucose drink and called an ambulance. By the time it arrived, the child’s blood glucose had returned to normal, and their symptoms had started to resolve.
In light of the rise in UK cases, the Food Standards Agency (FSA) and Food Standards Scotland (FSS) issued new voluntary industry guidance on glycerol in slushies, advising that they not be sold to children four and younger, and that children under 10 should not be offered free refills as part of any promotion.
In discussing the present study’s findings, the researchers say that slushies offer no nutritional value and no health benefits and, therefore, the recommendations about their consumption need to be focused on safety.
“There is poor transparency around slush ice drink glycerol concentration; estimating a safe dose is therefore not easy,” the researchers in the present study said. “It is also likely that speed and dose of ingestion, along with other aspects such as whether the drink is consumed alongside a meal or during a fasting state, or consumed after high-intensity exercise, may be contributing factors.”
The TL; DR version? Go easy on the slushies – regardless of your age (but especially if you’re a kid).
The study was published in the journal Archives of Disease in Childhood.
Source: BMJ Group
