Scientific Opinion on the substantiation of health claims related to
medium-chain triglycerides and reduction in body weight (ID 643, 677,
1614) pursuant to Article 13(1) of Regulation (EC) No 1924/2006[sup]1[/sup]
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3
European Food Safety Authority (EFSA), Parma, Italy
Słowa kluczowe:
Medium-chain triglycerides
body weight
health claims
long-chain triglycerides
replacement
3. Naukowe uzasadnienia wpływu na zdrowie człowieka - Redukcja masy ciała
The majority of the references provided for the scientific substantiation of the claim reported on the effects of food constituents other than MCTs and/or on health outcomes (e.g. acute or short-term
effects on appetite ratings, energy intake, fat oxidation and/or regulatory hormone concentrations, blood lipids, energy expenditure, and body composition) other than body weight. The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claim.
A total of ten publications reporting on nine human intervention studies which addressed the effects of MCT vs. LCT consumption on body weight were provided (Beermann et al., 2003; Han et al., 2007; Kasai et al., 2003; Krotkiewski, 2001; Nosaka et al., 2003; St-Onge and Jones, 2003; St-Onge et al., 2003a; St-Onge et al., 2003b; Tsuji et al., 2001; Yost and Eckel, 1989). Two publications reported on the same study (St-Onge and Jones, 2003; St-Onge et al., 2003b).
Two of the studies were designed to assess the metabolic effects of replacing LCTs by MCTs, and had a randomised, parallel design, a duration of two and four weeks, and included five and eight subjects per intervention group, respectively (Beermann et al., 2003; Yost and Eckel, 1989). The Panel notes the small sample size of these studies, which may have been inappropriate to assess changes in body weight, and considers that no conclusions can be drawn for the scientific substantiation of the claim.
In a parallel, randomised, double-blind intervention study (Tsuji et al., 2001), the effects on body weight of 10 g/day MCTs were compared to the effects of 10g/day LCTs (blended rapeseed oil and soybean oil) in bread consumed daily at breakfast for 12 weeks in healthy men and women. A total of 100 subjects were randomised but only 78 completed the study and entered data analysis. Dietary counselling was provided to all subjects at the beginning of the study. Compliance with the study diet aiming to maintain energy balance was self-reported. Body weight was measured at weeks 0, 4, 8 and
12. Data from subjects with BMI 23 kg/m2 or <23 kg/m2 were presented separately. Data analyses for the entire study population were not provided. It is unclear whether this sub-group analysis was
planned at recruitment [(BMI 23 kg/m2: n=26 (MCTs), n=30 (LCTs); BMI <23 kg/m2: n=15 (MCTs), n=7 (LCTs)]. The differences in raw data were examined by two-way ANOVA. The significance of differences between the groups for the same period was assessed by unpaired Student’s t-test (two-tailed). It is unclear from the publication whether initial body weight was included as a covariate in the two-way ANOVA, or whether the MCT and LCT groups were
comparable at baseline regarding body weight (mean SEM=75.7 1.9 kg vs. 72.8 1.1 kg). The Panel notes the substantial limitations of the study, and considers that no conclusions can be drawn from it for the scientific substantiation of the claim.
In a randomised, cross-over, controlled feeding intervention (St-Onge et al., 2003a), the effects on body weight of diets rich in either MCTs or LCTs (as olive oil) for periods of four weeks each were assessed in 17 healthy obese women. Diets contained 40 % of energy as fat, 15 % as protein and 45 % as carbohydrates, were designed for body weight maintenance, and all meals were provided to the subjects for the duration of the study under strictly controlled conditions. Of the total amount of fat, 75 % was derived from either beef tallow (LCTs) or a blend of saturated and unsaturated vegetable oils (MCTs). In the MCT diet, 50 % of the total fat was provided by MCT oil, rich in octanoate and decanoate (49 and 50 % of total fatty acids respectively), 10 % by olive oil and 5 % each by butter, coconut oil and flaxseed oil. An unesterified plant sterol/stanol mixture at a level of 22 mg/kg body weight/day was added to the MCT diet to maintain normal cholesterol concentrations. Wash-out periods were of 4-8 weeks to ensure that all women were assessed in the same phase of the menstrual cycle. No significant differences in weight loss between the two study phases were observed
(-0.87 0.16 kg vs. -0.84 0.22 kg during MCT and LCT consumption, respectively). The Panel notes that this study did not show a significant effect of MCTs on body weight at doses of about 55 g/day for four weeks in the context of a diet aiming at energy balance.
In a randomised, cross-over, controlled feeding trial (St-Onge and Jones, 2003; St-Onge et al., 2003b), the effects on body weight of diets rich in either MCTs or LCTs (as olive oil) for periods of four weeks each were assessed in 24 healthy overweight men. Diets contained 40 % of energy as fat, 15 %
as protein and 45 % as carbohydrate, and were designed for body weight maintenance. The diets were identical except for the quality of the fat. The MCT-containing diet contained an oil composed of 64.7 % MCT oil, 12.6 % olive oil, 6.8 % each of canola and flaxseed oil, and 5.8 % coconut oil as the main source of fat (75 % of total fat). The control diet (LCTs) contained 75 % of total fat as olive oil. The MCT oil also contained 3.4 % unesterified stanol/sterol mixture. No significant differences in
weight loss between the two study phases were observed (-1.03 0.25 kg vs.-0.62 0.29 kg during MCT and LCT consumption, respectively). The Panel notes that this study did not show a significant effect of MCTs on body weight at doses of >55 g/day for four weeks in the context of a diet aiming at energy balance.
In a parallel, randomised, double-blind intervention trial (Krotkiewski, 2001), the effects on body weight of MCT vs. LCT supplementation during a very low calorie diet (VLCD) were assessed. Three groups of matched obese women (BMI >30 kg/m2) received an isoenergetic (578.5 kcal) VLCD enriched with MCTs (8.0 g/100g providing 8 kcal/g, n=22) or LCTs (9.9 g/100 g providing 9 kcal/g, n=22), or a low-fat (3.0 g/100 g, n=22) and high-carbohydrate regimen. The diets were administered over four weeks. Body weight significantly decreased in the MCT group compared to the LCT and low-fat group at weeks 1 and 2 of the study, but no significant differences in body weight changes were observed between groups at the end of the study (weeks 3 and 4). The Panel notes that this short-term study did not show a significant effect of MCTs on body weight.
In a parallel, randomised, double-blind intervention trial (Han et al., 2007), the effects on body weight of a test oil with MCTs (extracted from coconut oil, 100 % MCTs with a caprylic acid:capric acid ratio of 2:1) as compared to corn oil (control LCTs), at doses of 18 g/day administered as part of the daily diet were assessed in 40 free-living subjects with type-2 diabetes mellitus living in an urban area of China. Subjects were on treatment with oral antidiabetic medication (sulfonylureas, biguanides or α-glucosidase inhibitors), which were maintained constant during the study. All subjects completed the study and reported being fully compliant with the intervention. Body weight was assessed on days 0, 45 and 90 of the study. Differences between groups at the same time point were assessed using ANOVA, with baseline data as covariate, and Tukey post-hoc tests. Body weight in the MCT group was significantly lower than in the LCT group at days 45 and 90 of the study (p<0.05; p=0.012 for the time-group interaction). Body weight decreased in the MCT group by approximately 1.5 kg, and increased by approximately 0.28 kg in the LCT group. The authors reported that no significant effect of medication use on body weight was detected in either group. However, the Panel notes that this effect was not formally tested in the study, and that the information provided is limited to the type of medication received by each study subject. A significant reduction in energy and fat intake assessed using a three-day weighed food record (first and last week of the study) was also observed in the MCT group compared to the LCT group. The Panel notes that a body weight difference of about -1.7 kg in 12 weeks in favour of MCTs was observed in this study at doses of 18 g/day without imposed energy restriction.
In a parallel, randomised, double-blind intervention trial (Nosaka et al., 2003), the effects on body weight of margarines (14 g/day) containing 5 g of MCTs or an equal amount of LCTs (blended rapeseed oil and soybean oil) consumed with bread at breakfast for 12 weeks were studied. Of the 73 subjects (18 female) recruited and randomised, two dropped out for reasons unrelated to the study, and seven subjects were excluded from data analysis owing to protocol violation. Data analyses were conducted in the population of completers (n=64, n=33 in the MCT group) only. Dietary counselling was provided to all subjects at the beginning of the study. Compliance with the study diet aiming to maintain energy balance was self-reported. Body weight was measured at weeks 0, 4, 8 and 12. A significant reduction in body weight (p<0.05) was observed at week 12 in the MCT group as
compared to the LCT group (mean SD=-4.2 2.8 kg vs.-2.9 2.0 kg) The Panel notes that a weight difference of about -1.3 kg in 12 weeks in favour of MCTs was observed at doses of 5 g/day in the context of an isoenergetic diet, and that differences in body weight between the MCT and LCT groups were only significant at week 12 of the study.
In a parallel, randomised, double-blind intervention trial (Kasai et al., 2003), the effects on body weight of a test bread made with 14 g of cooking oil (obtained by transesterification of 14 % MCTs and 85 % rapeseed oil) with structured medium and long-chain triglycerides (MLCTs) containing 1.7 g MCFAs were compared to the effects of a bread made with LCTs (blended rapeseed oil and soybean oil). Bread or control breads were consumed daily at breakfast for 12 weeks. Of the 93 subjects recruited and randomised, 10 could not consume the specified meal, and one subject dropped out. Data analyses were conducted in the population of completers (n=82, 7 female, n=40 in the MCT group, 4 female) only. Dietary counselling was provided to all subjects at the beginning of the study. Compliance with the study diet aiming to maintain energy balance was self-reported. Body weight was measured at weeks 0, 4, 8 and 12. A significant reduction in body weight (p<0.05) was observed
at weeks 4, 8 and 12 in the MCT group as compared to the LCT group (mean SEM=-2.4 0.2 kg, -
3.5 0.3 kg, -4.5 0.4 kg in the MCT group at weeks 4, 8 and 12 as compared to -1.7 0.2 kg; -2.5 0.3
kg; -3.3 0.4 kg in the LCT group). The Panel notes that a weight difference of about -1.2 kg in 12 weeks in favour of MCTs was observed at doses of 1.7 g/day in the context of an isoenergetic diet, and that differences in body weight between the MCT and LCT groups were already significant at 4 weeks (body weight loss difference of about -0.7 kg in favour of MCTs).
The Panel notes that three human intervention studies of 12 week duration observed a significant effect of MCTs on body weight loss at MCT doses of 1.7-18 g/day in the context of diets aiming at energy balance (Han et al., 2007; Kasai et al., 2003; Nosaka et al., 2003), and that the body weight difference between the MCT and LCT groups (range 1.3-1.7 kg) was rather uniform and apparently independent of the MCT doses used. The Panel also notes that one of the studies already observed a significant effect of MCTs on body weight at four weeks (Kasai et al., 2003) using 1.7 g/day MCTs, whereas no effect of MCTs was reported at the same time point at higher doses (>50 g/day) in the context of isoenergetic (St-Onge and Jones, 2003; St-Onge et al., 2003a; St-Onge et al., 2003b) or energy-restricted (Krotkiewski, 2001) diets in more strictly controlled studies.
A number of possible mechanisms by which MCTs could exert the claimed effect have been proposed, and the evidence for these has been reviewed by Kovacs and Mela (2006). MCTs are readily hydrolysed by lipases in the gastro-intestinal tract, and unlike LCTs are directly absorbed into the portal circulation and transported to the liver for oxidation. The intra-mitrochondrial transport of MCTs does not require carnitine palmitoyltransferase, which possibly accelerates oxidation of MCTs and possibly limits storage within tissues. However, the exact mechanism by which MCTs could have an effect on energy balance is unclear. In animals, there is some evidence that consumption of MCTs may increase satiety, decrease energy intake, and increase energy expenditure, resulting in lower body weight and smaller fat depots compared to isocaloric LCT consumption. However, results from human studies are conflicting. High intakes of MCTs lead to reduced energy intakes in some studies at doses of 18-60 g/day, but no effects on appetite, request for food or changes in any satiety-related hormone have been observed at these intake levels. Similarly, increased energy expenditure following consumption of MCTs at high doses (15-50 g/day) has been observed in the short-term (7 days), whereas results for longer periods of time are inconsistent. No effects of MCTs at lower doses of intake (about 10 g/day) have been observed on any of these variables. The Panel considers that the evidence provided for a mechanism by which MCTs could exert the claimed effect is weak and not convincing.
In weighing the evidence, the Panel took into account that the results from the human intervention studies provided are inconsistent with respect to the effects of MCTs on body weight loss, and that the evidence in support of a mechanism by which MCTs could exert the claimed effect is weak and not convincing.
The Panel concludes that a cause and effect relationship has not been established between the consumption of MCTs and reduction in body weight.
