Benefits
Improves vitamin A status where intake is low
In a meta-analysis of nine randomized trials, red palm oil raised blood retinol in both children and adults and increased beta-carotene levels. The effect matters most where vitamin A intake is low; it is not evidence that people who already get enough vitamin A gain anything further.
Carotenoid and vitamin E antioxidants
The red colour is carotenoid pigment, and the oil also carries the tocotrienol form of vitamin E. Both act as antioxidants in laboratory terms, and eating them dissolved in fat helps absorption, since carotenoids are taken up poorly without dietary fat.
Unrefined oil keeps what refining removes
Ordinary palm oil is refined, bleached and deodorised, which strips out most of the carotenoids and much of the vitamin E. Red (virgin) palm oil skips that processing, which is the entire difference between the two and the reason the red form is the one studied for vitamin A.
Early work in other clinical settings
Small trials have looked at palm carotenes and tocotrienols for vascular function, and at red palm oil for oxidative-damage markers in hepatitis C related liver disease. These are single small studies on surrogate measures and do not establish a benefit for heart or liver disease.
Mechanism of action
Carotenoid conversion to vitamin A
The body converts alpha- and beta-carotene to retinol in the intestinal wall using the enzyme BCO1. Because that conversion is regulated by need, provitamin A carotenoids supply vitamin A activity without the toxicity risk that comes with high-dose preformed retinol.
The fat matrix aids carotenoid absorption
Carotenoids are fat-soluble and are absorbed poorly from low-fat foods. Delivering them already dissolved in the oil they came from is a plausible reason red palm oil raises blood carotenoid and retinol levels efficiently at fairly modest daily intakes.
Palm vitamin E is tocotrienol-rich
Unlike most edible oils, palm vitamin E is largely tocotrienols rather than tocopherols. Tocotrienols behave differently in membrane antioxidant assays, though most human tocotrienol research uses concentrated extracts rather than the whole oil.
Saturated fat and LDL cholesterol
Roughly half the fatty acids in palm oil are saturated, mainly palmitic acid, which reduces LDL receptor activity and raises LDL cholesterol relative to oils high in unsaturated fat. This is the mechanism behind the cholesterol finding, and it applies to red and refined palm oil alike.
Clinical trials
Meta-analysis of nine randomized controlled trials of red palm oil and vitamin A status (Dong S, Xia H, Wang F, Sun G 2017, Nutrients 9(12):1281, PMID 29186779).
Nine randomized trials in children and adults, largely in settings where vitamin A intake is low.
Red palm oil significantly raised serum retinol in children (p<0.00001) and adults (p=0.002) and increased beta-carotene (p=0.01). Intakes up to about 8 g/day raised retinol, while more than 8 g/day produced no further increase. This is the strongest evidence for the ingredient, and it is about correcting low vitamin A status rather than a general health benefit.
Meta-analysis of controlled clinical trials comparing palm oil with vegetable oils low in saturated fat (Sun Y, Neelakantan N, Wu Y, Lote-Oke R, Pan A, van Dam RM 2015, J Nutr 145(7):1549-1558, PMID 25995283).
Pooled controlled feeding trials in adults comparing dietary fats.
Palm oil raised LDL cholesterol compared with vegetable oils low in saturated fat. Included as the honest counterweight: the carotenoids and vitamin E in red palm oil do not cancel out the effect of its saturated fat. The analysis covers palm oil broadly rather than the unrefined red form specifically.
Supplementation trial delivering beta-carotene through red palm oil in preschool children (Sivan YS, Jayakumar YA, Arumughan C, et al. 2001, J Trop Pediatr 47(2):67-72, PMID 11336137).
Preschool children in a setting with low vitamin A intake.
Beta-carotene delivered as red palm oil improved vitamin A status indicators in young children. A small early trial in a deficient population; it does not speak to well-nourished adults.