The most likely cause is dietary. I say that because in certain rural areas of China where people eat plant based diets, high cholesterol is practically nonexistent. As a matter of fact, their cholesterol levels are very low. In other areas of China, like in big cities where people eat a lot of animal protein and highly processed foods, they have problems with high cholesterol, like we do in the U.S..

For more infromation on this, read "The China Study" by T. Colin Campbell PhD.. The author has studied the effects of nutrition all of his life (he's in his early 70s now) and describes how a plant based diet can prevent diseases of all kinds. And it's all very scientificly based on about 27 years of animal studies plus a 20 year population study of people living in China (which he conducted).