How much saturated fat increases LDL-C and thereby CVD risk may depend on the specific type of saturated fatty acid (SFA), as defined by the length of the carbon chain: <6 for short-chain fatty acids (SCFAs), 6–10 for medium-chain triglycerides (MCTs),^[1] and >10 for long-chain triglycerides (LCTs).

Upon entering the small intestine, LCTs stimulate the release of pancreatic lipase and bile, which finish the digestion process and allow LCTs to be absorbed into intestinal cells, packaged into chylomicrons, and excreted into the lymphatic system.^[2] In contrast, MCTs do not stimulate the release of pancreatic lipase and bile;^[3][4] they passively diffuse through the intestinal cells into a portal vein.^[5]

High intakes of LCTs are associated with higher blood lipids and adverse cardiovascular outcomes.^[6] Given their differences in structure and metabolism, MCTs may be more healthful than other SFAs, but what does the research say?

This meta-analysis of 7 randomized controlled trials (364 participants) assessed the effects of MCT oil on blood lipids. The outcomes were LDL-C, HDL-C, total cholesterol, and triglycerides.

The trials lasted at least two weeks and compared MCT oil to another oil or fat. All seven trials reported data on triglycerides and total cholesterol, and six on LDL-C and HDL-C. Three trials were in healthy people, one in people with type 2 diabetes, one in people with mild-to-moderate Alzheimer's disease, and one in people who were Helicobacter pylori positive.

MCT oil increased triglycerides by 0.14 mmol/L (5.41 mg/dL), but did not affect total cholesterol, LDL-C, or HDL-C. In subgroup analyses, MCT oil increased total cholesterol and LDL-C compared to unsaturated fatty acids and slightly lowered LDL-C compared to LCTs.

Using the Cochrane risk-of-bias tool,^[15] the seven trials were classified as “low risk” or having “some concern”.

The big picture: A 2018 meta-analysis found that, compared to diets high in LCTs, diets high in MCTs increased HDL-C, with no significant effect on LDL-C, total cholesterol, or triglycerides.^[16] A 2015 meta-analysis on the effects of MCTs on body composition reported blood lipids as a secondary outcome and found that MCTs did not affect LDL-C, HDL-C, total cholesterol, or triglycerides.^[17]

MCTs are more easily oxidized than LCTs, and so replacing the latter by the former in one’s diet might reduce body weight and body fat percentage.^[18][17] Just adding MCTs to your diet, however, is more likely to promote weight gain by increasing your caloric intake. Furthermore, while MCTs are likely less harmful than LCTs, replacing saturated fats (including MCTs) with unsaturated fats will likely improve your health markers.