Baseline self-reported supplement category use and two-visit difference in lipoprotein(a): an observational analysis in UK Biobank

BACKGROUND: Circulating Lp(a) is largely genetically determined, but repeated measurements indicate that Lp(a) concentrations may differ within individuals over time. It remains unclear whether self-reported use of common supplement categories is associated with differences between repeated Lp(a) measurements. We aimed to investigate associations between baseline self-reported supplement-category use and two-visit difference in Lp(a), and to explore whether these associations differed by Lp(a) genetic risk. METHODS: We included 12,109 UK Biobank participants with Lp(a) measured at baseline and at the first repeat assessment. Self-reported use of common supplement categories (vitamins A, B, C, D, E, folate, and multi-vitamins) was assessed by questionnaire. The primary outcome was the continuous two-visit difference in log10[Lp(a)], defined as log10[repeat-assessment Lp(a)] minus log10[baseline Lp(a)]. The primary analysis used core behavioral/sociodemographic-adjusted multivariable linear regression. Threshold-category and genetic-risk analyses were secondary and exploratory. RESULTS: Among 12,109 participants with repeated Lp(a) measurements over a median 4.4 years, estimates in the primary core behavioral/sociodemographic-adjusted continuous log-scale model were small and centered near the null, ranging from β = -0.014 to 0.005 log10 units, corresponding to approximately - 3.18% to 1.22% relative difference in the conditional repeat-to-baseline Lp(a) ratio. None met the Bonferroni-corrected threshold. Expanded clinical/genetic adjustment and secondary descriptive screens did not alter the null interpretation. CONCLUSIONS: In this selected repeat-assessment sample, baseline self-reported use of common supplement categories was not associated with two-visit difference in log10[Lp(a)]. Because supplement use was measured only as broad baseline self-reported categories, these findings should not be interpreted as evidence about dose-specific, sustained, or biological effects of vitamin supplementation on Lp(a).