Benefits
Effects on LDL and HDL cholesterol
Pooled across 16 trials, coconut oil raised LDL cholesterol by about 10 mg/dL and HDL cholesterol by about 4 mg/dL compared with nontropical vegetable oils. In a 4-week trial in 91 adults aged 50 to 75, 50 g/day raised HDL more than butter or olive oil, while LDL changed no differently than on olive oil and rose on butter. Higher LDL is an established heart risk factor.
Ketone production compared with MCT oil
Coconut oil is often marketed as an MCT source, but in one analyzed oil only 8% of its fat was C8 and C10, the main fats in MCT oil. In healthy older adults, 30 g of coconut oil did not raise blood ketones significantly more than sunflower oil, and in younger adults its ketone peak was about a quarter of pure C8 oil's. The ketone claims belong to MCT and C8 oils.
Lauric acid, monolaurin and bacteria in lab and mouse tests
Monolaurin, a monoglyceride of lauric acid formed in the body in small amounts, killed Staphylococcus aureus in lab tests and improved survival in infected mice. The two coconut oils tested did neither: they showed no bacteria-killing activity in the lab, and mouse survival on them (0 to 16%) was about the same as on saline. No human trial shows that eating coconut oil prevents or treats infection.
Body weight and fullness
Pooled trials found no significant effect of coconut oil on body weight, body fat or waist size compared with nontropical vegetable oils, and a 4-week trial of 50 g/day found no weight difference from butter or olive oil. A review concluded that coconut oil has failed as a weight loss strategy and should not be used to increase fullness or calorie burning.
Brain fuel and cognition
Coconut oil is promoted as brain fuel, but in healthy older adults it raised blood ketones no more than sunflower oil. In a 24-week randomized trial in 120 people with Alzheimer's disease, 30 mL/day gave cognitive scores no different from canola oil. A review that pooled two smaller studies reported better scores, and the brain ketone research on this topic uses MCT oil.
Digestive tolerance
In a 30-day trial of 10 mL/day in capsules taken with meals, no digestive side effects were reported. Larger single servings are another matter: in a ketone study in older adults, one participant dropped out after severe diarrhea following 30 g of coconut oil, and two others reported diarrhea later that day after it.
Mechanism of action
Chain length shapes how the fats are handled
The shorter medium-chain fatty acids, C8 and C10, are largely carried as free fatty acids through the portal vein to the liver, where they are quickly oxidized and turned into ketones. Transport in chylomicrons through the lymph, the route long-chain fats take, increases with chain length toward lauric acid (C12), which behaves more like a long-chain fat than C8 does. Coconut oil is mostly C12 and longer fats, which is why it yields far fewer ketones than MCT oil.
Monolaurin and bacteria in lab tests
Monolaurin, the monoglyceride of lauric acid, is formed in the body in small amounts and kills Staphylococcus aureus in lab tests. Whether eating coconut oil raises monolaurin enough to matter is unproven: in the same study, coconut oil itself killed no bacteria in the lab and gave mice no protection.
Satiety signals (MCT oil data)
In MCT oil studies, people ate less at a later laboratory meal, but pooled across 17 studies there was little evidence of effects on hunger ratings or appetite hormones. In one crossover, peptide YY and leptin rose more after MCT than corn oil, yet the authors concluded these hormones did not explain the lower intake. These studies used MCT oil, and a review concluded coconut oil should not be used to increase satiety.
Clinical trials
Randomized trial in Cambridgeshire, UK, with volunteers recruited through the BBC: 50 g/day of extra virgin coconut oil, extra virgin olive oil or unsalted butter for 4 weeks, worked into the usual diet or taken as a supplement. Primary outcome: change in LDL cholesterol. (Khaw et al. 2018, BMJ Open)
94 adults aged 50 to 75 (67% women) at baseline; 91 completed the 4-week follow-up.
Butter raised LDL cholesterol more than coconut oil (+0.42 mmol/L) or olive oil (+0.38 mmol/L); LDL change did not differ between coconut oil and olive oil. Coconut oil raised HDL cholesterol more than butter (+0.18 mmol/L) or olive oil (+0.16 mmol/L). Weight, waist, fasting glucose and blood pressure did not differ between groups. Four weeks of blood markers, not heart events.
Systematic review with random-effects pooling of clinical trials lasting at least 2 weeks that compared coconut oil with other fats; literature searched through June 2019. (Neelakantan et al. 2020, Circulation)
16 trials; 8 reported body weight, 4 fasting glucose and 5 C-reactive protein.
Compared with nontropical vegetable oils, coconut oil raised LDL cholesterol by 10.47 mg/dL and HDL cholesterol by 4.00 mg/dL, and both effects held after excluding nonrandomized or poor-quality trials. It did not significantly affect markers of blood sugar, inflammation or body fat. The authors concluded that coconut oil results in higher LDL cholesterol than nontropical vegetable oils.
Placebo-controlled trial of 10 mL/day extra virgin coconut oil (ten 1 mL capsules with meals) for 30 days, alone or combined with aerobic exercise training. Outcomes: 24-hour ambulatory blood pressure, blood pressure variability and serum malondialdehyde. (Júnior et al. 2021, Nutrients)
45 adults with stage 1 hypertension in Brazil.
Coconut oil, alone or with exercise training, did not lower blood pressure and had no effect on blood pressure variability or on malondialdehyde, an oxidative stress marker. No adverse effects were reported at 10 mL/day.
Randomized 6-arm crossover after a 12-hour fast: sunflower oil 30 g (control), C8 20 g, C8 plus 50 g glucose, coconut oil 30 g, coconut oil plus glucose, or C8 plus coconut oil, each with coffee and cream; ketones measured for 4 hours. (Norgren et al. 2020, Front Nutr)
15 healthy adults aged 65 to 73 (53% women) in Sweden.
Mean beta-hydroxybutyrate over 4 hours was 0.22 mmol/L after coconut oil, not significantly different from 0.18 after sunflower oil, versus 0.45 after C8. Adding glucose to coconut oil lowered it to 0.08. One participant dropped out after severe diarrhea following the coconut oil arm. A blood marker over 4 hours, not a health outcome.