Cholesterol phytosterol quantity

For food applications, stands are synthetically derived from plant sterols. Although the naturally occurring amounts of phytosterols in 30 g of com oil are sufficient to inhibit cholesterol absorption, """ it is not clear whether natural intakes of phytosterols significantly lower plasma LDL-C concentrations. The relatively greater intake of phytosterols by vegetarians may contribute to the lower LDL-C levels commonly observed in this population. It would, however, be nearly impossible for most individuals to obtain more than 1 g of phytosterols from food without iugesting large quantities of food. Com oil is a rich source of phytosterols, yet one would have to consume about 100 g (900 kcal) of com oil per day in order to obtain 1 g/d of phytosterols. 

Presence of phytosterols in oat oil was first reported by Idler et al. in 1953 (128). Oat grain contains 35-60 mg phytosterols/100 g grain (127). Phytosterol content of oat oil varies between 0.19% to 0.32% (125). p-Sitosterol (40-70% of total sterols) is the major phytosterol in oats. A - and A -Avenasterol are the two other phytosterols that present in significant quantities in oats. Campesterol, stigmasterol, A -stigmasten-3p-ol, A -cholesten-3p-ol, and cholesterol were also present in oat grain. 

Coleoptera. The confused flour beetle, Tribollum confusum, was the first phytophagous insect we found that produces an appreciable amount of a sterol other than cholesterol from radiolabeled dietary C28 and C29 phytosterols. We found this insect produced large quantities of 7-dehydrocholesterol, equivalent to as much as 70% of the total tissue sterols isolated (12). It was further determined that cholesterol and 7-dehydrocTfolesterol were in equilibrium in this flour beetle. Another new intermediate, 5,7,24-cholestatrien-3B-ol was identified as an intermediate between desmosterol and 7-dehydrocholesterol (Figure 3). We found very similar pathways of sterol metabolism to exist in the closely related flour beetle, Tribolium castaneum (13). However, another flour beetle, Tenebrio moHtor, nad only about one-third or less of the levels of 7-dehydrocholesterol as the two Tribolium species, but still much higher levels of this sterol than has been found in most species. Fucosterol 24,28-epoxide was also implicated as an intermediate in the synthesis of cholesterol from sitosterol in T. mol i tor (14). 

The composition of major sterols found in several vegetable oils is shown in Table 3.41. The total content of phytosterols in vegetable oils is given in Table 3.42. Usually, vegetable oils contain a mixture of phytosterols and related compounds, which are characteristic of a particular oh. Cholesterol is also a phytosterol as it is found in many vegetable oils, but is usually present at very low levels that have no practical importance in the nutritional balance. Vegetable oils also contain numerous 4,4-dimethylsterols and 4-methylsterols in small quantities. The contents of these compounds and other steroids in maize oil are given in Table 3.43 as an example. 

Cereals contain significant quantities of phytosterols that are known to decrease blood cholesterol. The phytosterols are mainly located in the germ therefore, cereals lose important quantities after milling. 

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