Additionally, a notable increment in the amount of C18:1 c9 was noted in all tissues except for adipose tissue. Madani et al. (1998) showed that a high-cholesterol diet enhanced fecal steroid excretion, which could be one of the explanations for the significant decrease of C18:1 c9 in adipose tissue in HC (22.7%), this being more marked in HCO (44.2%) probably due to the high content of insoluble fiber of the onion. In the present experimental conditions, a remarkable decrease in stearic acid (C18) in all tissues was shown, with the exception of the adipose tissue, apparently due to its high conversion rate to oleic and linoleic acid. A decrease in C16 was also shown in plasma and liver. It is well-known that some diets affect the novo synthesis of fatty acids and this could be the reason why palmitic and stearic acids decreased in HC and HCO groups. On the other hand, short chain fatty acids are produced by intestinal bacteria (Arora et al., 2011, Cowan et al., 2014 and Macfarlane and Macfarlane, 2003). In the present study it is reasonable to think that the experimental diets may be affecting the metabolic pathways of these microorganisms in the rat's intestine.