ID 1517 -
Sprzężony kwas linolowy
PL: Sprzężony kwas linolowy
EN: CLA (Conjugated linoleic acid)
Pdf: conjugated linoleic acid
1. Charakterystyka żywności / składnika
The food that is the subject of the health claim is conjugated linoleic acid (CLA).
CLA refers to a group of positional and geometric isomers of linoleic acid that are characterised by the presence of conjugated dienes. CLA is a natural, but minor, component of fats from ruminant animals present in the human diet primarily in meat and dairy products. In nature, the most abundant isomer is cis-9, trans-11 (c9, t11), whereas in supplement forms CLA is typically sold as an equal mix of the two predominant isomers c9, t11 and t10, c12. Different isomers may have different effects.
The majority of the human intervention studies provided for the scientific substantiation of the health claims have used equimolar combinations of the c9, t11 and t10, c12 isomers, and therefore the Panel assumes that the food, which is the subject of the health claims, is an equimolar mixture of the CLA isomers c9, t11 and t10, c12
The Panel considers that the food constituent, an equimolar mixture of the conjugated linoleic acid (CLA) isomers c9, t11 and t10, c12, which is the subject of the health claims, is sufficiently characterised.
2.3. Zwiększenie wrażliwości na insulinę (ID 1517)
The claimed effect is “insulin sensitivity”. The Panel assumes that the target population is the general population.
In the context of the proposed wording, the Panel assumes that the claimed effect refers to an increase in insulin sensitivity.
The Panel considers that an increase in insulin sensitivity is a beneficial physiological effect.
3.3. Zwiększenie wrażliwości na insulinę (ID 1517)
The references provided in the consolidated list for health claims on CLA included six intervention studies in humans, one animal study (ex vivo) and one in vitro study which were related to the claim (Belury et al., 2003; Moloney et al., 2004, 2007; Riserus et al., 2002; Syvertsen et al., 2007; Smedman and Vessby, 2001; Eyjolfson et al., 2004).
Two double-blind, randomised, control trials (RCTs) were conducted in patients with type 2 diabetes. The study by Belury et al. (2003) did not assess any markers of insulin sensitivity or blood glucose control (but rather changes in body weight and serum leptin) and was therefore not considered pertinent to the claim. In the study by Moloney et al. (2004), 32 subjects with stable, diet-controlled type 2 diabetes were randomly assigned to consume either CLA (3.0 g per day; 50:50 blend of c-9, t-11 CLA and t-10, c-12 CLA) or a control fat mix (blend of palm oil and soya bean oil) for eight weeks. A three-hour 75 g oral glucose-tolerance test was performed at baseline and at the end of the intervention to assess insulin sensitivity. CLA supplementation significantly increased fasting glucose concentrations (by 6.3 %; p<0.05) and reduced insulin sensitivity as measured by the homeostasis model assessment of insulin resistance (HOMA-IR), the quantitative insulin sensitivity check index (QUICKI) and the insulin sensitivity index (ISI) composite. Fasting insulin concentrations did not change significantly between groups.
Two double-blind RCTs were conducted in obese subjects. In the study by Riserus et al. (2002), a total of 60 abdominally obese men with metabolic syndrome were randomised to consume either 3.4 g per day CLA (equimolar isomer mixture) or placebo for 12 weeks. Insulin sensitivity was assessed by means of the euglycaemic-hyperinsulinaemic clamp. A total of 19 subjects per group entered data analysis. The CLA equimolar isomer mixture did not significantly change glucose metabolism, body composition or body weight compared to placebo. In the study by Syvertsen et al. (2007), 118 subjects were randomly assigned to consume either CLA (3.4 g per day, equal amounts of the c9, t11 and t10, c12 isomers) or placebo (4.5 g per day olive oil) for 6 months. Insulin sensitivity was assessed by means of the euglycaemic-hyperinsulinaemic clamp in 41 subjects who completed the study (24 interventions, 17 controls). No significant differences were observed between groups with respect to glucose metabolism, insulin sensitivity or HbA1c during the study.
Two double-blind RCTs were conducted in healthy volunteers. In the study by Smedman and Vessby (2001), 53 healthy men and women aged 23-63 years were randomly assigned to supplementation with CLA (4.2 g per day, equal amounts of the CLA isomers c9, t11 and t10, c12), or the same amount of olive oil, during 12 weeks in a double-blind fashion. No significant differences were observed between the groups in fasting plasma insulin or blood glucose. In the study by Eyjolfson et
al. (2004), 16 young sedentary subjects were randomised to consume 4 g per day of mixed CLA isomers (35.5 % c-9, t-11; 36.8 % t-10, c-12, n=10), or placebo (safflower oil, n=6) for eight weeks. Oral glucose tolerance tests were performed at baseline, at four and at eight weeks of supplementation. The Panel notes the small sample size of the study, and that direct comparisons between changes in the insulin sensitivity index (ISI) between the intervention and control groups were not reported. The Panel considers that no conclusions can be drawn from this study for the scientific substantiation of the claimed effect.
The animal, ex vivo, study showed an effect of c9, t11-CLA supplementation in down-regulating the insulin receptor substrate 1 (IRS1) and GLUT4 mRNA expression, and an increase in insulin- stimulated glucose transport in 3T3-L1 adipocytes compared with linoleic acid (Moloney et al., 2007), whereas the in vitro study reported that the t-10, c-12 CLA isomer promoted NFkappaB activation and subsequent induction of IL-6, which are at least in part responsible for t-10, c-12 CLA-mediated insulin-resistance in mature human adipocytes (Chung et al., 2005). The Panel considers that the evidence provided in animal and in vitro studies is not sufficient to predict the occurrence of an effect of the consumption of an equimolar mixture of the CLA isomers c9, t11 and t10, c12 on the increase in insulin sensitivity in humans.
In weighing the evidence, the Panel took into account that none of the studies from which conclusions could be drawn for the scientific substantiation of the claimed effect observed a CLA-mediated improvement in insulin sensitivity.
The Panel concludes that a cause and effect relationship has not been established between the
consumption of an equimolar mixture of the CLA isomers c9, t11 and t10, c12 and an increase in insulin sensitivity.
Warunki i możliwe ograniczenia stosowania oświadczenia
Up to 3,4 g CLA per day
