Genetic and environmental influences on free sugar and non-nutritive sweetener intake in toddlerhood and middle-childhood using data from the Gemini twin cohort: findings from the SWEET project

BACKGROUND: Exceeding recommended free sugar (FS) intake is linked to poorer metabolic health. Non-nutritive sweeteners (NNS) offer an alternative to FS, and emerging evidence suggests many children regularly consume them. Understanding the aetiology of variation in FS and NNS intake in childhood can inform population-level strategies to reduce sugar consumption. OBJECTIVE: To examine genetic and environmental influences on variation in FS and NNS intakes in toddlerhood and middle-childhood; and investigate stability and change overtime. METHODS: FS (as % energy intake) and NNS (categorised as non-, low- and high-consumers) were estimated using three-day dietary data at 21-months (n=2,592) with repeated measures in a subsample at 7 years (n=592) from British twins in the Gemini cohort. Longitudinal Cholesky twin models estimated genetic and environmental influences on FS and NNS intakes at both ages. RESULTS: Shared environmental factors strongly influenced both FS and NNS intakes at 21-months (FS: 0.88; 95%CI: 0.86-0.90; NNS: 0.99; 0.99-1) and 7 years (FS: 0.58; 0.45-0.69; NNS: 0.92; 0.86-1), but the effect decreased significantly over time for FS. There was no significant genetic influence on NNS at either age; genetic influence on FS intake increased significantly from toddlerhood (0.09; 0.08-0.11) to middle-childhood (0.33; 0.22-0.47). Small longitudinal correlations indicated greater change than stability in intakes over time for FS (r=0.28, p<.001) and NNS (r=0.35, p<.001), explained predominantly by novel shared environmental influences in middle-childhood and the emergence of novel genetic influence on FS. CONCLUSIONS: Shared environmental factors predominantly shape individual differences in FS and NNS intake during early life. While increasing genetic influence from toddlerhood to middle-childhood reflect growing autonomy in dietary choices for FS intake, variation in NNS intake remained overwhelmingly environmentally driven across both developmental periods. Findings emphasise the need for both age-specific public health interventions and food industry legislation to shape FS and NNS intakes in childhood.