Abstract

Palm oil (PO) contains approximately 50% saturated fatty acids (44% palmitic acid) and represents one of the most widely utilised vegetable oils in the world. Growing evidence
suggests that palmitic acid may exacerbate metabolic inflammation associated with a range of chronic diseases. The ‘Western diet’, or ‘Western dietary pattern’ is the most common diet in the United Kingdom, suggesting that palmitic acid may make a significant contribution to overall dietary lipid intake. The main objectives of this research were to 1: evaluate the evidence on the role of palm oil and palmitic acid (16:0) on metabolic health and the gut microbiome, 2: assess the awareness of the United Kingdom public of palm oil and palmitic acid; their existence, their prevalence, as well as their potential health effects, 3: analyse the fatty acid composition of common food items, with an emphasis on palmitic acid content and 4: screen a panel of gene expression biomarkers in participants with different levels of dietary palmitic acid intake and assess their potential role in metabolic health.

A systematic review was performed to examine the evidence on the role of palm oil and palmitic acid (16:0) on metabolic health and the gut microbiome. A total of 132 studies are
included in the final review. A total of 251 members of the United Kingdom public completed a questionnaire containing demographic information, details regarding their anthropometry, exercise frequency/intensity, sleeping patterns and dietary habits, as well as their perceptions, behaviours and beliefs towards palm oil and palmitic acid. A total of 62 of these 251 respondents also provided a 4-day food diary. A total of 70 food samples, representing common food groups (vegetable/seed oils, palm-based foods, animal-origin foods, dairy foods, plant based/vegan alternatives, nut/seed-based foods, miscellaneous/snack food items) were analysed for their fatty acid composition. A fatty acid profile of 38 different fatty acids was developed using gas chromatography. A total of 18 participants provided one intravenous blood sample for gene expression analysis, as well as anthropometry and food diary (4-day) data, before being allocated into one of the palmitic acid intake groups (low, medium and high) based on their daily palmitic acid intake.

The outcomes of the review concluded that the majority of studies provide evidence to suggest that palm oil, or more specifically palmitic acid intake, contributes significantly to various chronic diseases associated with metabolic syndrome, such as type 2 diabetes, cardiovascular disease(s), stroke, and nutrition-related cancers. The survey study provided evidence to suggest that palm oil/palmitic acid awareness should be recognised as an important component of health and nutrition literacy. Fatty acid analysis of several food items across multiple food groups highlighted the abundance of palmitic acid within the diet, regardless of dietary inclination. Assessment of mRNA expression provided evidence to suggest that palmitic acid intake is positively associated with an undesirable gene expression profile, although metabolic adaptation(s) may occur above a certain threshold or due to long-term exposure of palmitic acid. Prospective randomized control trials are critical in investigating these suppositions further.