MCT oil

What it is

MCT stands for medium-chain triglycerides, that is, fats made from fatty acids with 6 to 10 carbon atoms. Commercially available are mainly caprylic acid (C8) and capric acid (C10). Classic MCT oil contains both, in one study in a ratio of 55 to 35 percent; pure C8 oil consists of more than 95 percent caprylic acid.

Coconut oil itself is not MCT oil. In a comparative study it contained only 3 percent C8 and 5 percent C10, and its ketone peak reached only 25 percent of that of pure C8.

How it works

Normal long-chain fats are distributed via the lymphatic system and need a transporter to be burned in the mitochondria. Medium-chain fatty acids, by contrast, go via the portal vein directly to the liver and are broken down there quickly. What the liver does not need immediately is turned into ketone bodies such as beta-hydroxybutyrate, which the brain can use as fuel.

This pathway is well measured in humans. In a crossover study with 9 adults, C8 was on average 295 micromoles per liter above control over the day, and the ketone area under the curve was 813 to 870 percent higher. In an 8-hour test with two doses of 10 grams of MCT, ketones rose by 19 percent, blood glucose fell by 12 percent, and insulin remained unchanged.

Interesting for anyone working with intermittent fasting: in the same 8-hour test, an early meal pattern with breakfast but without lunch amplified the ketone effect of MCT more than a late meal pattern without breakfast. The age of the participants and a low-carbohydrate meal, by contrast, did not change the ketone response. MCT can therefore metabolically complement a short fasting phase without the diet having to be fully ketogenic.

The idea behind it: in Alzheimer’s disease, glucose utilization in the brain falls early and in limited regions. Ketones are the brain’s alternative fuel and could bypass this energy deficit. That additional MCT actually brings more ketones into the brain has been shown with PET imaging.

Where MCT has been used for decades

In medicine, MCT is not a new trend. As early as 1967 it was described for the treatment of fat malabsorption, because it is absorbed without the usual fat digestion. In chylothorax, a lymphatic congestion in the chest cavity, an MCT diet is considered the first therapeutic measure. And the MCT ketogenic diet is an established variant of the ketogenic diet in hard-to-treat epilepsy; a 2026 review considers it similarly effective to the classic form, even though equivalence has not been proven.

What the studies show

BENEFIC: 6 months in mild cognitive impairment

People with mild cognitive impairment drank a beverage with 15 grams of MCT twice daily for 6 months (39 participants) or a calorie-matched placebo (44 participants). In the MCT group, free and cued recall, verbal fluency, naming and the number of errors in the Trail Making Test improved significantly. Imaging showed 2.5- to 3.2-fold higher ketone uptake in 9 white matter tracts, and the improvement in processing speed was linked to it.

AC-1202 in Alzheimer’s dementia

152 patients with mild to moderate Alzheimer’s dementia received an MCT preparation or placebo for 90 days. On day 45, the MCT group scored 1.9 points better on the ADAS-Cog cognition test. In patients without the risk gene APOE4 the advantage was larger, 4.77 points on day 45 and 3.36 points on day 90. Side effects, mainly in the gastrointestinal tract, occurred more frequently under MCT.

Two studies in healthy people, two results

In 30 young healthy people, 12 or 18 grams of MCT per day improved performance on Trail Making and digit span after 2 to 3 weeks, but not attention and reaction time. In 80 healthy older people, by contrast, 30 grams per day over 14 days brought no effect at all on cognition or brain activity, even though ketones rose.

Where the data stop

The positive cognition data come almost exclusively from people with mild cognitive impairment or Alzheimer’s disease. The studies are small and short, the authors of the largest meta-analysis see a relevant risk of bias, and the effect appears to be smaller in carriers of APOE4. Whether MCT slows progression to dementia has not been studied. In healthy people, a small positive and a larger negative study stand side by side; that does not support a claim of more focus in everyday life. For sport, a systematic review concludes that MCT oil mostly does not improve performance and does not change substrate utilization; the resulting ketones are apparently hardly used as the main fuel during endurance exercise. The weight effect is small, and the meta-analysis found indications of commercial influence. For an effect against Candida there are only laboratory experiments, no human studies.

Status, approval and legal

In Germany, MCT oil is a food and is sold as an edible fat and dietary supplement; there is no maximum amount. In medicine, MCT fats are used as part of nutritional therapy in fat malabsorption, chylothorax and in the MCT ketogenic diet for epilepsy, there with medical and dietetic supervision. MCT oil is not an approved medicine. It is not on the WADA Prohibited List.

Safety

The most common side effects concern the gut. In a study with 30 grams per day, 75 percent of participants developed diarrhea and 11 percent dropped out because of side effects. A review on sport names 30 grams as a practical upper limit to keep complaints during and after exercise low; in the BENEFIC study, the same amount was split into two servings over 6 months. Almost all cardiovascular and inflammatory markers remained unchanged; only the inflammatory messenger IL-8 rose by 147 percent, and its significance is unclear. In blood lipids, MCT is less conspicuous than often feared: a meta-analysis found no effect on total, LDL and HDL cholesterol, but a small rise in triglycerides of 0.14 millimoles per liter. Compared with oils consisting mainly of unsaturated fatty acids, however, total and LDL cholesterol rose. MCT oil is pure fat and correspondingly energy-dense. The clinical literature lists ketosis, acidosis, that is, overacidification of the blood, and liver cirrhosis as contraindications. Anyone who has diabetes and takes insulin or blood glucose-lowering drugs should discuss a ketosis strategy with a physician beforehand.

Sources

• Vandenberghe et al., Tricaprylin Alone Increases Plasma Ketone Response More Than Coconut Oil or Other MCTs, Current Developments in Nutrition 2017
• Fortier et al., A ketogenic drink improves cognition in mild cognitive impairment: Results of a 6-month RCT, Alzheimers and Dementia 2021
• Roy et al., A ketogenic supplement improves white matter energy supply and processing speed in mild cognitive impairment, Alzheimers and Dementia TRCI 2021
• Avgerinos et al., Medium Chain Triglycerides induce mild ketosis and may improve cognition in Alzheimer disease, Ageing Research Reviews 2020
• Henderson et al., Study of the ketogenic agent AC-1202 in mild to moderate Alzheimer disease, Nutrition and Metabolism 2009
• O Neill et al., The effects of GSK2981710, a medium-chain triglyceride, on cognitive function in healthy older participants, Human Psychopharmacology 2019
• Mumme and Stonehouse, Effects of medium-chain triglycerides on weight loss and body composition, Journal of the Academy of Nutrition and Dietetics 2015
• McKenzie et al., Medium-Chain Triglyceride Oil and Blood Lipids, Journal of Nutrition 2021
• Chapman-Lopez and Koh, MCT Oil Supplementation on Endurance Performance and Substrate Utilization, Journal of Obesity and Metabolic Syndrome 2022
• Pellizzari et al., Medium-chain triglyceride with and without ketogenic diet in drug-resistant epilepsy, Nutritional Neuroscience 2026