Summary
This systematic review and meta-analysis of observational studies found that individuals with metabolic diseases characterised by lipid metabolism disturbances and obesity exhibit significantly reduced serum carotenoid concentrations compared to normal-weight healthy controls. Total serum carotenoids showed the greatest decrease (−0.28 µmol/l; p<0.001) across seven studies, with reductions observed for most provitamin A and non-provitamin A carotenoids. However, dietary carotenoid intake did not differ significantly between groups, suggesting that low serum carotenoids may reflect a physiological consequence rather than dietary insufficiency in these metabolic conditions.
Regional applicability
The international scope of this meta-analysis provides broadly applicable evidence on carotenoid metabolism in metabolic disease, with implications for United Kingdom clinical practice and dietary guidance. However, observed associations are from observational studies only and cannot establish causality; UK-specific intervention trials examining whether carotenoid supplementation or dietary intake modification improves metabolic outcomes would strengthen local evidence.
Key measures
Serum provitamin A carotenoids (µmol/l), serum non-provitamin A carotenoids (µmol/l), dietary carotenoid intake, serum retinol concentration
Outcomes reported
The review examined associations between serum carotenoids, serum retinoids, and dietary intake in individuals with obesity, overweight, and metabolic diseases (non-alcoholic fatty liver disease, type 2 diabetes, dyslipidaemia, metabolic syndrome) compared to healthy controls. Mean differences in serum carotenoid concentrations and dietary carotenoid intake were quantified via meta-analysis of observational studies.
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