Researchers in Thailand conducted a review of meta-analyses and systematic reviews to analyse the association of dietary oil intake on cholesterol levels and CVD risk.
The oils included in this study were commonly consumed in Asian countries such as tropical oils (palm, coconut), animal fat (lard), and common vegetable oils (soybean, rice bran).
It is widely known that animal-derived saturated fats contribute to risk factors of cardiovascular disease (CVD), specifically increasing low-density lipoprotein cholesterol (LDL-c) known as the ‘bad’ cholesterol. It is often recommended to reduce intake of such fats and replace with plant-based oils to improve lipid profiles, and thereby reduce CVD risk.
However, plant-based oils like palm and coconut oil are also high in saturated fats, and there is limited evidence on the effect of saturated fats especially from plant oils. Plant-based oils typically help increase high-density lipoprotein cholesterol (HDL-c), the ‘good’ cholesterol.
Palm oil, coconut oil, and lard are classified as saturated fats, while soybean and rice bran oils are classified as polyunsaturated fatty acid (PUFA)-rich oil and monounsaturated fatty acid (MUFA)-rich oil respectively.
The main saturated fatty acid in palm oil is palmitic acid, and lauric and myristic acid in coconut oil.
Because of the high amounts of saturated fats in palm oil and coconut oil, they may also increase LDL-cholesterol and CVD risk.
“Although dietary guidelines generally recommend restricting the intake of animal-derived saturated fats, the health impact of plant-derived saturated fats, which are widely used in Asia, remains inconclusive because both ‘good’ and ‘bad’ cholesterol are elevated following their consumption,” researchers wrote in the journal Nutrients.
This is concerning since palm oil is the most widely used plant-derived saturated fat in many countries, as it is inexpensive and affordable for the majority of the population within developing countries and in the food industry.
This study comprised of nine meta-analyses of randomised controlled trials or observational studies, comparing dietary fat intake with lipid profiles (LDL-c, HDL-c, triglyceride, total cholesterol (TC)).
Those that evaluated oils in the form of dietary supplements or drugs were excluded.
The studies were published between 2009 and 2018, had study durations of 2 to 27 weeks, and populations varied from healthy individuals to patients with CVD risk factors or those diagnosed with CVD.
Studies were from UK, US, Italy, Germany, Iran, Australia and Singapore.
Findings revealed that palm oil significantly increased total cholesterol, LDL-c as well as HDL-c compared to MUFA and PUFA-rich oils.
Coconut oil was also found to significantly increase HDL-c and total cholesterol compared with PUFA-rich oils. It also increased LDL-c although the difference was not significant.
Compared with MUFA- and PUFA-rich oils, lard was associated with increases in LDL-c but it was not significant. Lard significantly increased total cholesterol.
Soybean oil significantly decreased total cholesterol, LDL-c and HDL-c when compared with saturated fats, but there was no difference compared with PUFA-rich oils.
Soybean oil is the second most commonly consumed oil worldwide. “In our analysis, replacement of SF with soybean oil significantly improved all lipid parameters. Substituting soybean oil for lard and butter significantly decreased LDL-c. However, substituting soybean oil for other PUFA-rich oils had no effect on lipid levels.”
Rice bran oil also significantly decreased LDL-c and total cholesterol when compared with PUFA-rich oils and saturated fats. It had no effect on HDL-c.
These findings showed that saturated fats derived from animal (lard) and plant (palm, coconut) sources had different effects on lipid profiles.
Naturally, lard increases LDL-c and total cholesterol, but not HDL-c.
While plant-based saturated fat oils like palm oil and coconut oil increased HDL-c, but also saw LDL-c and total cholesterol increase.
Researchers said further research was needed to understand the effect of consumption of tropical oils compared with other common vegetable oils on the number and size of LDL and HDL particles, CVD incidence, and mortality.
“Future guidelines should therefore address this issue and give specific recommendations.”
“Our study supported the current recommendations to reduce dietary saturated fat intake, particularly animal-derived fat, and to replace this source of fat with foods rich in unsaturated fats from plants to lower the risk of CVD.”
“Tropical Oil Consumption and Cardiovascular Disease: An Umbrella Review of Systematic Reviews and Meta Analyses”
Authors: Chanita Unhapipatpong, et al.