Ten-year changes in plasma L-carnitine levels and risk of coronary heart disease

L-Carnitine is abundant in animal source foods, particularly red meat, and circulating L-carnitine may be related to the incidence of coronary heart disease (CHD). We investigated whether long-term changes in plasma L-carnitine over 10 years were associated with the CHD incidence and also examined joint associations of carnitine-rich red meat consumption and L-carnitine changes on the subsequent risk of CHD.

This prospective nested case-control study included 772 healthy women at baseline (386 incident CHD cases and 386 healthy controls). Plasma L-carnitine levels were measured both at the first (1989-90) and second blood collections (2000-02). Incident cases of CHD were prospectively followed from the date of the second blood collection through 2016.

Overall, a greater increase in L-carnitine from the first to the second time point was related to a higher risk of CHD, regardless of the initial L-carnitine levels (relative risk: 1.36 (95% CI 0.999, 1.84) per 1-SD increase). The 10-year changes in L-carnitine were positively associated with red meat consumption over time, and women with higher red meat intake (≥ 36 g/day) and with greater increases in L-carnitine had a 1.86 (95% CI 1.13, 3.09) times increased risk of CHD, as compared to those with lower red meat intake and lesser increases in L-carnitine.

Long-term increases in L-carnitine levels were associated with the subsequent incidence of CHD, especially among women with higher intake of red meat. Our results suggest the importance of atherogenic L-carnitine changes and dietary intakes over time in the prevention of CHD.