The cholesterol lowering effects of foods with plant stanols have been shown in previous studies, with a reduction of 8-17 % in LDL cholesterol [7, 8, 16]. Although the LDL cholesterol response in the present study was low [6.3%] compared to the reduction rates obtained in some meta-analyses, it is supported by other individual studies with similar product, yoghurt [17–19]. The wide variety seen in the LDL cholesterol responses among different studies can be accounted for by the food matrix supplemented with plant stanols, the form of stanol (i.e. free or ester), the dose of stanol, the ingestion of the stanols with or without a meal, the frequency consumption of products with stanols, the background diet, the baseline LDL cholesterol levels, and the subject’s genotype .
The plant stanols were added primarily to fat-based products, such as margarine and spreads, due to their lipophilic nature. After Mensink et al.  demonstrated that the ability of plant stanols as esters to block intestinal cholesterol absorption is not necessarily compromised by a low-fat food matrix, other foods, such as milk, yoghurt, juices, and cereals, have been used to add plant stanols. In addition to the fat content of the food matrix, the solid or liquid format of the carrier food has been suggested to affect the efficacy of plant stanols . Because low-fat dairy products are healthy options, low-fat yoghurt was chosen for supplementation with plant stanols in the present study. Research has shown that low fat products (e.g. milk and yoghurt drinks) containing plant stanols have similar efficacy on serum cholesterol as products with higher fat content [23–26]. To the best of our knowledge, the efficacy of spoonable low-fat yoghurts with plant sterol or stanols as esters in reducing LDL cholesterol has been reported in a limited number of studies [17–21, 27], which showed a broad range for the reduction in serum total cholesterol (-8.7 to -3.3%) and LDL cholesterol (-13.7 to -2.9%) levels. The reduction in total (4.6%) and LDL cholesterol (6.3%) levels obtained in this study were in accordance with those ranges.
Among the previous studies conducted using spoonable low-fat yoghurts supplemented with plant stanols as esters, the highest reduction in LDL cholesterol (13.7%) was shown by Mensink et al. . These previous results suggested a more pronounced effect compared to the 6.3% reduction in LDL cholesterol in our study. However, a few important points need to be considered. First, the study designs were different. Second, the plant stanol dose was 3 g/d in the study by Mensink et al., which is 1.5-times higher than the dose in the present study. Focussing on the dose response of the cholesterol lowering effect of plant stanols, a continuous dose-dependency appears with doses of up to 2 g, and larger doses of up to 3–4 g slightly enhance the effect . Finally, the consumption frequency of low-fat yoghurt was three times per day in the study by Mensink et al., but it was once a day in the present study. The reduction in LDL cholesterol shown in the present study might have been more pronounced if a multiple daily intake model was chosen. On the other hand, the response to the yoghurt single-shot drink was shown to be enhanced when ingested with a meal . The majority of studies have suggested consuming low-fat products with stanol esters with meals. In this study, lunch was chosen for consuming the test products with plant stanols as esters due to the higher fat content of the workplace lunches, which ensures the initiation of bile secretion flow and micelle formation. In contrast to the study by Mensink et al., the reduction levels obtained in the present study were consistent with the results of some other studies [17–19]. A double-blind, crossover trial by Noakes et al.  demonstrated that daily intake of low-fat yoghurt providing 1.8 g of plant stanols reduced LDL cholesterol and total cholesterol by 5% and 3.5%, respectively. In addition, Seppo et al.  reported a reduction in LDL cholesterol of 4.9% and in total cholesterol of 3.8% with low-fat yoghurt including 2 g/d plant stanols. Despite some differences in study designs, the main influential factors were matched with the present study.
The baseline LDL cholesterol level was also suggested to be a confounding variable in response to plant stanols . In the study by Seppo et al. , the cholesterol lowering effect of plant stanols was suggested to be more prominent when the LDL baseline level was ≥135 mg/dl. The baseline LDL cholesterol in the present study was higher than the proposed cut-off values but similar to previous studies [17, 18]. Although the effects of plant stanols appear to be independent of the background diet [7, 29], the composition of diets in the present study might be a barrier to achieving the higher reduction rates for LDL cholesterol. Because total (38% of energy) and saturated fat (12% of energy) content of the diet in the present study were higher compared to dietary intakes in some previous studies . The variation in the response of LDL cholesterol is also explained by genetic factors. Previous studies suggested that the apolipoprotein E genotype may have little effect on the response of LDL to plant sterols and stanols; however, the effects of other polymorphisms have not been shown [12, 15]. The present study suggests that Turkish people as well as European and American populations will benefit from plant stanol intake, regardless of their genetic background.
In addition to the reduction in total and LDL cholesterol, a small and non-significant reduction in apolipoprotein B levels was observed, which is in agreement with an earlier study . In agreement with the results of previous studies [17, 18, 21, 29], changes in many of the parameters of the lipid profile (e.g., HDL, TG, VLDL, apolipoprotein A, apolipoprotein, and lipoprotein-a) were not significant in the present study, whereas the absolute reductions in LDL and total cholesterol levels were almost identical.