recent meta-analysis suggests that no clear relationship exists, and that perhaps previous studies have been confounded by other factors. For example, people who have a higher campesterol level related to a diet high in fruits and nuts may be consuming a Mediterranean-style diet, thus have lower risk because of other lipids or lifestyle factors. Intestinal absorption of cholesterol varies between individuals due to variations in the genes that encode for two proteins. The NPC1L1 protein which sits on the luminal side of the enterocyte is responsible for sterol absorption. Its counterpart, the ABCG5/G8 ATP Binding Cassette protein which also sits on the luminal side of the enterocyte, and on the bile canaliculi side of the hepatocyte, is responsible for sterol efflux. Variations in each of these proteins causes variation in absorption and efflux of dietary and biliary sterols - both cholesterol and plant sterols. Although studies in humans have shown that consumption of phytosterols may reduce LDL levels, evidence to recommend them as a treatment for hypercholesterolemia is insufficient. Larger trials are needed to provide such evidence, and are underway. Animal studies have shown that campesterol and other phytosterols can reduce the size of atherogenic plaques, but no data yet show that consumption of phytosterols results in any clinical benefit such as a reduction in atherosclerosis, heart disease, cardiac events, or mortality. Adverse effects Nutrient levels Excessive supplementation with plant sterols may be associated with reductions in beta-carotene and lycopene levels. Excessive long-term consumption of plant sterols might have a deleterious effect on vitamin E. Increased risk of disease Excessive use of plant sterols has been associated with an increased risk of cardiovascular disease, and genetic conditions that cause extremely elevated levels of some phytosterols, such as sitosterol, are associated with higher risks of cardiovascular disease. However, this is an active area of debate, and no data suggest that modestly elevated levels of campesterol have a negative cardiac impact. References External links ARS GRIN NutritionData Phytosterols