Ketosis After Intake of Coconut Oil and Caprylic Acid-With and Without Glucose: A Cross-Over Study in Healthy Older Adults

Abstract

Introduction: Medium-chain-triglycerides (MCT), formed by fatty acids with a length of 6-12 carbon atoms (C6-C12), constitute about two thirds of coconut oil (Coc). MCT have specific metabolic properties which has led them to be described as ketogenic even in the absence of carbohydrate restriction. This effect has mainly been demonstrated for caprylic acid (C8), which constitutes about 6-8% of coconut oil. Our aim was to quantify ketosis and blood glucose after intake of Coc and C8, with and without glucose intake. Sunflower oil (Suf) was used as control, expected to not break fasting ketosis, nor induce supply-driven ketosis. Method: In a 6-arm cross-over design, 15 healthy volunteers-age 65-73, 53% women-were tested once a week. After a 12-h fast, ketones were measured during 4 h after intake of coffee with cream, in combination with each of the intervention arms in a randomized order: 1. Suf (30 g); 2. C8 (20 g) + Suf (10 g); 3. C8 (20 g) + Suf (10 g) + Glucose (50 g); 4. Coc (30 g); 5. Coc (30 g) + Glucose (50 g); 6. C8 (20 g) + Coc (30 g). The primary outcome was absolute blood levels of the ketone β-hydroxybutyrate, area under the curve (AUC). ANOVA for repeated measures was performed to compare arms. Results: β-hydroxybutyrate, AUC/time (mean ± SD), for arms were 1: 0.18 ± 0.11; 2: 0.45 ± 0.19; 3: 0.28 ± 0.12; 4: 0.22 ± 0.12; 5: 0.08 ± 0.04; 6: 0.45 ± 0.20 (mmol/L). Differences were significant (all p ≤ 0.02), except for arm 2 vs. 6, and 4 vs. 1 & 3. Blood glucose was stable in arm 1, 2, 4, & 6, at levels slightly below baseline (p ≤ 0.05) at all timepoints hours 1-4 after intake. Conclusions: C8 had a higher ketogenic effect than the other components. Coc was not significantly different from Suf, or C8 with glucose. In addition, we report that a 16-h non-carbohydrate window contributed to a mild ketosis, while blood glucose remained stable. Our results suggest that time-restricted feeding regarding carbohydrates may optimize ketosis from intake of MCT. Clinical Trial Registration: The study was registered as a clinical trial on ClinicalTrials.gov, NCT03904433.

Keywords: aged; coconut oil; fasting; glucose; ketogenic diet; ketosis; medium-chain fatty acids; β-hydroxybutyrate.

Copyright © 2020 Norgren, Sindi, Sandebring-Matton, Kåreholt, Daniilidou, Akenine, Nordin, Rosenborg, Ngandu and Kivipelto.

Figures

Figure 1

BHBv concentrations in blood, AUC/time, (mmol/L) during T0–T240 (minutes). Values are absolute and not adjusted for baseline levels. Suf, Sunflower oil (30 g); C8, Caprylic acid (20 g) + Sunflower oil (10 g); C8+Glu, Caprylic acid (20 g) + Sunflower oil (10 g) + Glucose (50 g); Coc, Coconut oil (30 g); Coc+Glu, Coconut oil (30 g) + Glucose (50 g); C8+Coc, Caprylic acid (20 g) + Coconut oil (30 g). BHBv, β-hydroxybutyrate in venous whole blood.

Figure 2

The dynamics of BHBv during T0–T240 (minutes). A descriptive graph based on absolute mean values. The arrow at T0 indicates the start of ingestion of coffee with fatty acids. The circle indicates intake of glucose (arms 3 & 5 only, striped lines), 15 min before the blood test performed immediately before T0. BHBv, β-hydroxybutyrate in venous whole blood.

Figure 3

Individual differences in the ketogenic response to C8. The paths of four subjects in the C8 arm (20 g Caprylic acid + 10 g Sunflower oil), selected to illustrate the big individual differences in BHBv response, and the potentially transient nature of ketosis. BHBv, β-hydroxybutyrate in venous whole blood.

Figure 4

The ratio between the two plasma ketones (BHBp/AcAc), plotted against BHBp. Comparisons of arms including coconut oil vs. caprylic acid (C8) vs. neither or both. For enhanced scaling, one case in arm 2 with a ratio of 11 (0.11/0.01), is excluded from the graph. BHBp, β-hydroxybutyrate in plasma; AcAc, Acetoacetate.

Figure 5

Descriptive dynamics of mean blood glucose during T0–T240 (minutes). T0 represent 12 h fasting values, except for arm 3 & 5 (striped), where glucose was ingested 15 min before the blood test performed immediately before T0, indicated by a circle. The arrow at T0 indicates the start of ingestion of coffee with fatty acids (5 mmol/L = 90 mg/dL).

Figure 6

Distribution of blood glucose levels in the four arms with a 16-h non-carbohydrate window. T0 represents time for start of ingestion of fatty acids, preceded by 12 h fasting. (5 mmol/L = 90 mg/dL).