La carnitina es un aminoácido que el cuerpo utiliza para convertir la grasa en energía. Normalmente no es considerado un nutriente esencial ya que el cuerpo puede producir todo lo que necesita. Sin embargo, el complemento de carnitina podría mejorar la habilidad de ciertos tejidos para producir energía. Este efecto ha llevado al uso de la carnitina en varias enfermedades musculares así como enfermedades cardíacas.
No existe requerimiento nutricional para el uso de la carnitina. Sin embargo, algunas personas tienen un defecto genético que dificulta la habilidad del cuerpo para producir carnitina. Además, las enfermedades hepáticas, renales o cerebrales podrían inhibir la producción de carnitina. Ciertos medicamentos, especialmente los medicamentos antiataques como el ácido valproico(Depakine) y la fenitoína (Dilantin), podrían reducir los niveles de carnitina; sin embargo, no se ha probado si tomar dosis adicionales de carnitina sería de ayuda. 1 - 11 El tejido muscular cardíaco, debido a sus altos requerimientos de energía, es particularmente vulnerable a la deficiencia de carnitina.Las fuentes alimenticias de carnitina son la carne y los productos lácteos, pero para obtener dosis terapéuticas se necesita un complemento.
Algunos estudios han encontrado evidencia de que un tipo particular de carnitina, el acetil-L-carnitina, podría ser de ayuda en la enfermedad de Alzheimer , 40 - 46 pero los dos más recientes y más grandes estudios no encontraron beneficios. 47,48 Una revisión evaluó los ensayos doble ciego controlados por placebo , publicados y no publicados, y concluyó que la acetil-L-carnitina sólo podría ser de ayuda para la enfermedad de Alzheimer muy ligera. 70
Una enfermedad genética llamada síndrome del cromosoma X frágil puede causar alteraciones en el comportamiento como hiperactividad, junto con retraso mental, autismo y alteraciones en la apariencia. Un estudio preliminar en 17 niños encontró que el acetil-L-carnitina podría ayudar a reducir el comportamiento hiperactivo asociado con esta enfermedad. 51
La carnitina ordinaria se ha mostrado prometedora para el ADHD (trastorno por déficit de atención e hiperactividad)73.
Además, un estudio preliminar sugiere que la carnitina podría ser de utilidad para mejorar el control de los niveles de azúcar en la sangre en las personas con diabetes tipo 2 (aparición en la etapa adulta). 52
Ésta también podría ayudar a prevenir la neuropatía autonómica cardíaca diabética (lesión en los nervios del corazón provocada por la diabetes). 53 Evidencia poco convincente sugiere que la carnitina podría ser capaz de mejorar los niveles de colesterol y triglicéridos, 18 y también ayudar a las personas con degeneración del cerebelo (la estructura del cerebro responsable del movimiento muscular voluntario). 55
Un estudio muy pequeño sugiere que la carnitina podría ser de ayuda para reducir los síntomas del síndrome de fatiga crónica . 56 Un estudio sugiere que la carnitina podría ser valiosa para el tratamiento del hipertiroidismo . 57
La L-carnitina en sus tres formas parece ser bastante segura. Sin embargo, las personas con niveles de tiroides bajos o dudosos deberían evitar el uso de carnitina ya que podría dañar la acción de la hormona tiroidea. 75
Las personas en tratamiento de diálisis no deberían recibir este (o ningún otro complemento) sin supervisión médica.
Las dosis de máxima seguridad para niños pequeños, mujeres embarazadas o en lactancia, así como aquellos con enfermedad renal o hepática grave aún no ha sido establecida.
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