ABSTRACT
Some epidemiologic studies have suggested that ingestion of raw tomatoes or tomato products (which both contain lycopene) is associated with a reduced risk for cardiovascular diseases (CVDs). However, very little is known about the biologic mechanisms through which tomatoes/lycopene could protect against CVDs. Some in vitro studies have suggested that lycopene is a potent antioxidant. Hence, it is thought that antioxidant mechanisms may have important roles in protection against CVD. In addition, in vitro studies have revealed that lycopene can inhibit the activity of 3-hydroxy-3-methylglutaryl-CoA reductase or increase the cellular activity of the low-density lipoprotein receptor, which are key factors in cholesterol metabolism. Therefore, lycopene is thought to act as a hypocholesterolemic factor. Indeed, some human-intervention studies suggested that dietary supplementation with tomatoes or lycopene can result in reductions of low-density lipoprotein-cholesterol (LDL-C) levels in plasma.
Recently, a report revealed that lycopene may affect the activity of lecithin-cholesterol acyltransferase or levels of cholesteryl ester transfer protein and apolipoprotein A. These effects on a metabolic enzyme and constituted factors of high-density lipoprotein-cholesterol (HDL-C) suggest that lycopene could increase blood levels of HDL-C. In agreement with this hypothesis, recent animal and human-intervention studies have suggested that tomato supplementation can increase blood levels of HDL-C significantly without decreasing LDL-C levels. In this review, we summarize the findings of studies that have investigated the relationship between the consumption of tomatoes and/or lycopene and blood levels of HDL-C.
