This study indicated that liquid oil can generally reduce serum lipids levels when compared with hydrogenated oil. However, changes in serum lipids, except for TG reduction and Apo A enhancement, were not significant when ghee oil group was compared with hydrogenated oil group (serum HDL-C levels had an insignificant increase).
Epidemiological and intervention studies have strongly proposed that hydrogenated fat intake might enhance CVD risk, mainly by adversely affecting serum lipids profile.28
TFAs are produced through the hydrogenation process of liquid vegetable oils. Considerable studies indicate that hydrogenated fat and/or TFAs could increase TC and LDL-C, and decrease HDL-C32
and some studies have shown serum TG elevation;33
however, the responsible mechanisms for these changes are complicated. It has been proposed that the serum lipid-raising effect of hydrogenated fat is due to either delayed LDL-C clearance or enhanced LDL-C production.37
Hayashi et al38
have reported that hydrogenated corn oil raised serum very low density lipoprotein cholesterol and LDL-C through the suppression of hepatic LDL receptor activity in hamsters. Another study also indicated39
that damaging the cholesterol catabolism is more responsible than decreasing its synthesis for higher serum TC seen by intake of high hydrogenated and saturated fat diets. But Kelley et al showed that diet containing cotton seed oil could not modify serum lipids including TC, TG, LDL-C, HDL-C, Apo A and Apo B in comparison with usual diet.40
As Asgari et al found,41
the average TFA contents in hydrogenated oils, liquid cooking and frying liquid oils produced in Iran were 35.2 ± 4.8%, 0.9 ± 0.3%, and 2.6 ± 0.8%, respectively. So, serum lipids modification by liquid oils seems reasonable in this study.
Ghee oil is an important dietary fat in India and other South Asian countries,42
which contains high amounts of SFAs (about 59% of its whole fatty acids). SFAs, except for stearic acid, increase serum TC,44
and therefore, ghee oil, that are high in cholesterol and SFAs, are considered as harmful. On the other hand, ghee is a good source of oleic acid which is capable of protecting LDL-C particles from oxidation and prevents atherosclerosis.45
Furthermore, according to Asgary et al, the average TFA content in ghee produced by Bakhtiari nomads (the kind of ghee that was used in this study) is 8.3 ± 0.7 which is 1.4 times less than the amount of existing TFA in hydrogenated oils.41
Kumar's study indicated that consumption of ghee in the diet even at high intakes does not increase serum lipids. A strong idea was also made to link the consumption of anhydrous milk fat such as ghee with increased risk of heart diseases.47
Kumar's study with experimental animals did not show any linking between ghee consumption to hypercholesterolemia and hyperlipidemia, which are considered to be risk factors for heart diseases. Interestingly, consuming increased levels of ghee reduced serum TC and TG levels.47
However, use of excess intake of ghee as a means for lowering serum TC is not recommended, but the study indicates that there is no reason for apprehension for consuming ghee in the diet, which is an age-old practice that is relished in Indian culinary.47
Mozaffarian et al obtained that substituting 8% of energy intake from TFA with SFA cause to decrease CVD by modifying TC/HDL-C ratio.48
So, it confirms the proper effect of ghee on serum lipid profile.