6.5.2 Inhibition of Cholesterol Biosynthesis
Palm oil and its fractions are rich in tocopherols, particularly γ-tocotrienol. These are
natural antioxidants and possess free radical scavenging properties, protecting the
biological cell against oxidative and carcinogenic stress in addition to inhibiting
platelet aggregation and inhibition of endogenous cholesterol biosynthesis (MoralesGonzalez 2018; Sailo et al. 2018; Peh et al. 2016). Elson and Qureshi (1995) studied
the impact of palm oil on cardiovascular disease and cancer and found that
monoterpenes, sesquiterpenes, carotenoids and tocotrienols downregulate
3-hydroxy-3-methylglutaryl coenzyme A reductase activity, thereby decreasing
cholesterol biosynthesis followed by decreased LDL cholesterol. Palm oil is
observed to have a lipid lowering effect possibly because of a high content of
tocotrienols present in palm oil (780–1080 μg/g). Qureshi et al. (1991) conducted
a double-blind, crossover, 8-week study to compare effects of tocotrienol-enriched
fraction of palm oil (200 mg per day) with those of 300 mg corn oil per day on serum
lipids of hypercholesterolemic human subjects. A significant decrease in the serum
total cholesterol (À15%), low density lipoprotein (À8%), thromboxane (À25%) and
platelet aggregation (À16%) was found when the tocotrienol-rich fraction was
administered for 4 weeks to hypercholesterolemic subjects. Serum cholesterol concentrations of seven hypercholesterolemic subjects decreased 31% during the
4-week period.
6.5.3 Prevention of Platelet Aggregation
An important risk factor for cardiovascular disease is the tendency for a thrombus
(clot) to be formed in the blood wall vessel. Kooyenga et al. (1997) studied the
antioxidant properties of α- and γ-tocopherol-enriched fractions of palm oil with
carotid atherosclerosis. Serum lipids, fatty acid peroxides, platelet aggregation and
carotid artery stenosis were measured over a 24-month period in 50 patients with
cerebrovascular disease. The studies revealed apparent carotid atherosclerotic
regression in 8 and progression in 2 of the 25 antioxidant patients, while none of
the control group exhibited regression, and 10 of 25 showed progression (P < 0.01).
Serum α-tocopherol doubled, while tocotrienols were undetectable throughout the
study. Several studies report that saturated fats such as coconut oil and beef fat
increase the blood clotting tendency, whereas unsaturated fats such as fish oils
decrease platelet aggregation. Surprisingly, palm oil is found to have effects similar
to polyunsaturated oils, i.e. it reduced platelet aggregation and decreased blood
clotting. Thromboxane (TxA 2 ) is a powerful platelet aggregating hormone and
also vasoconstrictive substance that promotes clotting; on the other hand, prostacyclin (PGI 2 ) is a hormone which acts as a platelet aggregation inhibitor. The balance
between these local hormones results in linked with the arterial thrombotic tendency.
Research reports have revealed that palm oil diet in animals increases the production
154
S. Sehgal and V. Sharma
Palm oil and its fractions are rich in tocopherols, particularly γ-tocotrienol. These are
natural antioxidants and possess free radical scavenging properties, protecting the
biological cell against oxidative and carcinogenic stress in addition to inhibiting
platelet aggregation and inhibition of endogenous cholesterol biosynthesis (MoralesGonzalez 2018; Sailo et al. 2018; Peh et al. 2016). Elson and Qureshi (1995) studied
the impact of palm oil on cardiovascular disease and cancer and found that
monoterpenes, sesquiterpenes, carotenoids and tocotrienols downregulate
3-hydroxy-3-methylglutaryl coenzyme A reductase activity, thereby decreasing
cholesterol biosynthesis followed by decreased LDL cholesterol. Palm oil is
observed to have a lipid lowering effect possibly because of a high content of
tocotrienols present in palm oil (780–1080 μg/g). Qureshi et al. (1991) conducted
a double-blind, crossover, 8-week study to compare effects of tocotrienol-enriched
fraction of palm oil (200 mg per day) with those of 300 mg corn oil per day on serum
lipids of hypercholesterolemic human subjects. A significant decrease in the serum
total cholesterol (À15%), low density lipoprotein (À8%), thromboxane (À25%) and
platelet aggregation (À16%) was found when the tocotrienol-rich fraction was
administered for 4 weeks to hypercholesterolemic subjects. Serum cholesterol concentrations of seven hypercholesterolemic subjects decreased 31% during the
4-week period.
6.5.3 Prevention of Platelet Aggregation
An important risk factor for cardiovascular disease is the tendency for a thrombus
(clot) to be formed in the blood wall vessel. Kooyenga et al. (1997) studied the
antioxidant properties of α- and γ-tocopherol-enriched fractions of palm oil with
carotid atherosclerosis. Serum lipids, fatty acid peroxides, platelet aggregation and
carotid artery stenosis were measured over a 24-month period in 50 patients with
cerebrovascular disease. The studies revealed apparent carotid atherosclerotic
regression in 8 and progression in 2 of the 25 antioxidant patients, while none of
the control group exhibited regression, and 10 of 25 showed progression (P < 0.01).
Serum α-tocopherol doubled, while tocotrienols were undetectable throughout the
study. Several studies report that saturated fats such as coconut oil and beef fat
increase the blood clotting tendency, whereas unsaturated fats such as fish oils
decrease platelet aggregation. Surprisingly, palm oil is found to have effects similar
to polyunsaturated oils, i.e. it reduced platelet aggregation and decreased blood
clotting. Thromboxane (TxA 2 ) is a powerful platelet aggregating hormone and
also vasoconstrictive substance that promotes clotting; on the other hand, prostacyclin (PGI 2 ) is a hormone which acts as a platelet aggregation inhibitor. The balance
between these local hormones results in linked with the arterial thrombotic tendency.
Research reports have revealed that palm oil diet in animals increases the production
154
S. Sehgal and V. Sharma