Sugar and Artificial Sweeteners: What the Evidence Says for Young Children

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When choosing juice or snacks for a child, you will eventually face the question: sugar or artificial sweetener? Both have something cited against them — "sugar causes cavities," "artificial sweeteners cause cancer." Each claim has some research behind it.

The actual state of the evidence is more layered than that binary. This article looks at the basis for the WHO's free-sugars recommendation, the safety evaluations for the major non-nutritive sweeteners, what the 2023 IARC classification of aspartame does and does not mean, and why the "sugar damages the brain" claim does not hold up well under examination. One specific note applies here: the evidence base for infants and toddlers is thinner than for adults on nearly every question in this area.

The WHO free-sugars recommendation — what it rests on

In 2015, the World Health Organization published its Guideline on Sugars Intake for Adults and Children, recommending that free-sugar intake be kept below 10% of total energy intake, with a conditional recommendation to reduce further to below 5% where possible [1].

in this framework means mono- and disaccharides added to foods and beverages by manufacturers, cooks, or consumers, plus sugars naturally present in honey, syrups, and fruit juices and concentrates. The lactose naturally present in breast milk and plain cow's milk is excluded.

The primary evidence base for this recommendation was a systematic review and meta-analysis by Te Morenga, Mallard, and Mann, which integrated randomized controlled trials and cohort studies [2]. In trials where participants were allowed to eat freely (ad libitum), reducing sugar consumption was associated with weight loss (mean 0.8 kg), while increasing it was associated with weight gain (mean 0.75 kg). Isocaloric trials — where overall energy intake was held constant — showed no effect on weight. The authors interpret this as evidence that the problem with free sugars is primarily their tendency to drive excess energy intake, not any direct metabolic effect of sugar per se [2].

The American Heart Association has gone further in its guidance for children specifically. In a 2017 scientific statement, the AHA recommended that children under two years old avoid all added sugars, and that children aged 2–18 consume no more than 25 g (roughly six teaspoons) of added sugar per day [3].

Non-nutritive sweeteners — established ADIs and what they cover

The major used in foods marketed to young children — aspartame, sucralose, and steviol glycosides (rebaudioside A from stevia) — all have established ADIs from JECFA, the Joint FAO/WHO Expert Committee on Food Additives:

Aspartame: 0–40 mg/kg body weight/day
Sucralose: 0–15 mg/kg body weight/day
Steviol glycosides (rebaudioside A): 0–4 mg/kg body weight/day

At typical dietary intake levels, neither adults nor young children would be expected to approach these thresholds. The structure of ADIs and how safety factors are incorporated is discussed in article 101.

An important qualification applies here, and it is worth stating directly: evidence on the effects of non-nutritive sweeteners on the gut microbiome and metabolism of infants and toddlers is substantially thinner than the evidence base for adults. Research in mice has suggested effects of non-nutritive sweeteners on [6], but human studies in infants and toddlers are very limited. This is a genuinely uncertain area. The ADIs provide a regulatory floor, but they do not answer every question about early-life exposure.

The 2023 IARC aspartame classification — not a safety reversal

In July 2023, IARC classified aspartame as Group 2B — "possibly carcinogenic to humans." In the same month, JECFA completed its 96th meeting and concluded that the existing ADI of 40 mg/kg body weight/day should be maintained, and that "the data evaluated indicated no sufficient reason to change the previously established ADI" [4].

These two statements appear to contradict each other. They do not. They are answers to different questions.

IARC's role is to evaluate the weight of evidence for whether a substance could cause cancer at all — the hazard identification question. Group 2B means the evidence is "limited": there are studies suggesting a possible association (the primary signal in the 2023 evaluation was a link with hepatocellular carcinoma), but the evidence does not yet meet the threshold for "probable" or "sufficient." JECFA's role is to assess whether exposure at actual consumption levels poses a health risk — the risk characterization question [4,5].

A useful comparison: Group 2B also includes aloe vera whole leaf extract and pickled vegetables. That neither of these features prominently in current cancer-risk conversations illustrates the distance between Group 2B classification and a practical health warning.

The 2023 episode was confusing primarily because two agencies with different mandates published assessments on the same substance in the same week. Read against their respective mandates, the assessments are compatible.

"Sugar harms the brain" — examining the claim

The claim circulates on social media that excessive sugar intake impairs brain development in young children. Looking at what the underlying research actually shows, the claim is more attenuated than its social-media form suggests.

Glucose is the brain's primary energy source. The specific concern in the research literature is not that glucose as such damages the brain but that high-sugar diets can cause rapid fluctuations in blood glucose, and that high-carbohydrate diets in animal models have been associated with effects on memory and learning. But the step from "rat data on high-sucrose diets" to "sugar directly damages the developing human brain" involves multiple inferential leaps that the available evidence does not support.

The established harms of excess sugar in young children run through different pathways: (the relationship between free-sugar exposure and carious lesions is well established and begins in infancy); excess energy intake and its effects on weight; and the displacement of nutrient-dense foods by low-nutrient-density, high-sugar alternatives. These are real concerns. "Sugar damages the brain" as a direct mechanism is not well supported by high-quality human evidence in this age group.

Putting it into practice

The practical summary for everyday food decisions:

The WHO and AHA recommendations focus on managing the quantity of free sugars — not on eliminating sugar — and the AHA specifically advises avoiding added sugars in children under two
Non-nutritive sweeteners have established ADIs, and typical intake is not expected to approach those thresholds even in young children
The 2023 IARC Group 2B classification of aspartame means evidence is limited, not that risk is confirmed; JECFA maintained the existing ADI in the same month
The primary documented harms of excess sugar in young children are dental caries and the energy-density / nutrient-displacement pathway — not direct neurological damage
The more productive frame than "sugar or sweetener?" is reducing the overall share of sweetened beverages and processed foods in the diet, in favor of dietary variety

Summary

The WHO's free-sugars recommendation rests on systematic evidence linking free-sugar intake to excess energy consumption and weight gain, and the AHA supports avoiding added sugars entirely in children under two. Non-nutritive sweeteners hold regulatory approval within defined ADIs, but evidence specific to infants and toddlers remains limited. The 2023 IARC aspartame classification (Group 2B) and JECFA's simultaneous maintenance of the existing ADI are not in conflict — they address different scientific questions. The "sugar damages the brain" claim lacks the high-quality human evidence that would support it as a direct mechanism; the real risks of excess sugar intake in young children are dental caries and dietary-quality displacement.

References

World Health Organization. Guideline: Sugars Intake for Adults and Children. Geneva: WHO; 2015. PMID: 25905159. https://www.who.int/publications/i/item/9789241549028
Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013;346:e7492. doi:10.1136/bmj.e7492. PMID: 23321486.
Vos MB, Kaar JL, Welsh JA, et al; American Heart Association Nutrition Committee of the Council on Lifestyle and Cardiometabolic Health. Added Sugars and Cardiovascular Disease Risk in Children: A Scientific Statement From the American Heart Association. Circulation. 2017;135(19):e1017–e1034. doi:10.1161/CIR.0000000000000439. PMID: 27550974.
World Health Organization / Food and Agriculture Organization of the United Nations. Summary of Evaluations Performed by the Joint FAO/WHO Expert Committee on Food Additives: Aspartame — JECFA 96th Meeting. Geneva: WHO; 2023. https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/en/
International Agency for Research on Cancer. Aspartame. IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Vol. 134. Lyon: IARC; 2023. https://www.iarc.who.int/featured-news/aspartame-hazard-and-risk-assessment-results-released
Suez J, Korem T, Zeevi D, et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 2014;514(7521):181–186. doi:10.1038/nature13793. PMID: 25231862.
Sylvetsky AC, Rother KI. Nonnutritive Sweeteners in Weight Management and Chronic Disease: A Review. Obesity. 2018;26(4):635–640. doi:10.1002/oby.22139. PMID: 29570245.