HEALTH NEWS

Study Title:

Plant Sterols May Be Dangerous in High Amounts

Study Abstract

The pathogenesis of aortic valve stenosis (AS) is characterized by the accumulation of LDL-derived cholesterol in the diseased valves. Since LDL particles also contain plant sterols, we investigated whether plant sterols accumulate in aortic valve lesions. Serum samples were collected from 82 patients with severe AS and from 12 control subjects. Aortic valves were obtained from a subpopulation of 21 AS patients undergoing valve surgery and from 10 controls. Serum and valvular total cholesterol and noncholesterol sterols were measured by gas-liquid chromatography. Noncholesterol sterols, including both cholesterol precursors and sterols reflecting cholesterol absorption, were detected in serum samples and aortic valves. The higher the ratios to cholesterol of the cholesterol precursors and absorption markers in serum, the higher their ratios in the stenotic aortic valves (r = 0.74, P < 0.001 for lathosterol and r = 0.88, P < 0.001 for campesterol). The valvular ratio to cholesterol of lathosterol correlated negatively with the aortic valve area (r = –0.47, P = 0.045), suggesting attenuation of cholesterol synthesis with increasing severity of AS. The higher the absorption of cholesterol, the higher the plant sterol contents in stenotic aortic valves. These findings suggest that local accumulation of plant sterols and cholesterol precursors may participate in the pathobiology of aortic valve disease.

From press release:

"Healthy" sterols may pose health risk.

Plant sterols have been touted as an effective way to lower cholesterol and reduce the risk of heart disease. However, a research study in the July JLR has uncovered that these compounds do have their own risks, as they can accumulate in heart valves and lead to stenosis.

Aortic valve stenosis (AS) results from cholesterol accumulation in the valve between the left ventricle and aorta; this impedes the flow of blood and puts extra pressure on the heart. About 2% of individuals over 65 (and over 5% of those over 85) have AS, and as the population ages, it is becoming an increasing problem.

Plant sterols can block the absorption of dietary cholesterol into the body, and as such high vegetable diets and/or plant sterol supplements are often used to alleviate high cholesterol. However, although plant sterols themselves are poorly absorbed, they can enter the body, so Satu Helske and colleagues examined whether plant sterols can also accumulate in aortic valves.

They collected blood samples from 82 patients with severe AS and aortic valves from 21 individuals undergoing valve surgery, along with respective controls. They observed that non-cholesterol sterols, including plant sterols, can accumulate in aortic valves, and at levels that directly related to their blood concentration.

These findings suggest that beneficial plant sterols may end up becoming a risk factor for AS, although the researchers will need to conduct more studies, such as whether dietary sterols and sterol supplements produce different effects.

Study Information

Satu Helske, Tatu Miettinen, Helena Gylling, Mikko Mäyränpää, Jyri Lommi, Heikki Turto, Kalervo Werkkala, Markku Kupari and Petri T. Kovanen.
Accumulation of cholesterol precursors and plant sterols in human stenotic aortic valves.
Journal of Lipid Research
2008 July
Wihuri Research Institute, Helsinki, Finland.