Scientific Opinion on the substantiation of health claims related to
gamma-linolenic acid and maintenance of joints (ID 494, 637, 1774, 2098),
weight maintenance following weight loss (ID 496), maintenance of
peripheral blood flow (ID 638), maintenance of normal blood pressure
(ID 1771), maintenance of normal blood cholesterol concentrations
(ID 1771) and maintenance of bone (ID 1774) 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:
GLA
Gamma-linolenic acid
blood cholesterol
blood flow
blood pressure
bone
health claims
joints
weight maintenance
1. Charakterystyka żywności / składnika
The food constituent that is the subject of the health claims is gamma-linolenic acid (GLA).
GLA is a n-6 long-chain polyunsaturated fatty acid which is present in small amounts in a variety of foods of both plant and animal origin and which can also be synthesised in the human body from its precursor linoleic acid (LA). GLA is a well recognised nutrient and can be measured in foods by established methods. This evaluation applies to GLA from all sources.
The Panel considers that the food constituent, gamma-linolenic acid, which is the subject of the health claims is sufficiently characterised.
2. Znaczenie oświadczenia dla zdrowia człowieka
2.1. Utrzymanie prawidłowego stanu stawów (ID 494, 637, 1774, 2098)
The claimed effect is “joint health”. The Panel assumes that the target population is the general population.
The Panel assumes that the claimed effect relates to maintenance of normal joints.
The Panel considers that maintenance of normal joints is a beneficial physiological effect.
2.2. Utrzymanie masy ciała po odchudzaniu (ID 496)
The claimed effect is “reduces regaining weight”. The Panel assumes that the target population is overweight subjects in the general population who wish to maintain their body weight after significant weight loss.
Weight control can be interpreted as the contribution to the maintenance a normal body weight after weight loss. In this context, the maintenance of a moderate weight loss in overweight subjects without having achieved a normal body weight is considered a beneficial physiological effect.
The Panel considers that weight maintenance after weight loss is a beneficial physiological effect.
2.3. Utrzymanie prawidłowego krążenia obwodowego (ID 638)
The claimed effect is “maintaining hands and feet in good condition (supportive measure for microcirculation and peripheral nerves)”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect refers to maintenance of a normal peripheral blood flow.
The Panel considers that maintenance of a normal peripheral blood flow is a beneficial physiological effect.
2.4. Utrzymanie prawidłowego ciśnienia tętniczego (ID 1771)
The claimed effect is “vascular health”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect refers to maintenance of normal blood pressure and to maintenance of normal blood cholesterol concentrations. The latter will be assessed in section 2.5.
Blood pressure (BP) is the pressure (per unit area) exerted by circulating blood on the walls of blood
vessels. Elevated BP, by convention 140 mmHg (systolic) and/or 90 mmHg (diastolic), may compromise the normal function of the arteries.
The Panel considers that maintenance of normal blood pressure is a beneficial physiological effect.
2.5. Utrzymanie prawidłowego stężenia cholesterolu we krwi (ID 1771)
The claimed effect is “vascular health”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect refers to maintenance of normal blood pressure and to maintenance of normal blood cholesterol concentrations. The former has been assessed in section 2.4.
Low-density lipoproteins (LDL) carry cholesterol from the liver to peripheral tissues, including the arteries. Elevated LDL-cholesterol, by convention >160 mg/dL, may compromise the normal structure and function of the arteries.
The Panel considers that maintenance of normal blood cholesterol concentrations is a beneficial physiological effect.
2.6. Utrzymanie prawidłowego stanu kości (ID 1774)
The claimed effect is “bone health”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect refers to maintenance of normal bone through the promotion of calcium absorption.
The Panel considers that maintenance of normal bone is a beneficial physiological effect.
3. Naukowe uzasadnienia wpływu na zdrowie człowieka
3.1. Utrzymanie prawidłowego stanu stawów (ID 494, 637, 1774, 2098)
The references provided consisted of one monograph on GLA, two book chapters, nine reports on intervention studies of which seven were double-blind, placebo-controlled trials, one open trial and one controlled trial in patients with rheumatoid arthritis of different severity, 15 reviews of the use of GLA in various medical conditions, and four concerned mechanistic studies of GLA effects ex vivo and in vitro or in animal models of inflammation. The intervention studies were mostly of small sample sizes and did not include healthy controls.
All (but one) human intervention studies, all reviews and the mechanistic studies presented concern therapeutic trials in patients with a clinical diagnosis of acute or chronic rheumatoid arthritis (Belch et al., 1988; Brzeski et al., 1991; Hansen et al., 1983; Jäntti et al., 1989; Leventhal et al., 1993 and 1994; Pullman-Mooar et al., 1990; Zurier et al., 1996; Watson et al., 1993).
Rheumatoid arthritis (RA) is a chronic, symmetric, inflammatory, and destructive autoimmune arthropathy affecting the synovial joints with a prevalence of 0.5 to 2.0 % in the population (Calder and Zurier, 2001). In the studies presented, GLA doses varied between <500 mg /d and 2 g/d and the duration of the intervention was from two weeks to 15 months (Furse et al., 2001; Belch and Hill, 2000; Chilton et al., 1996; Kast, 2001; Pullman-Mooar et al., 1990; Watson et al., 1993) following GLA consumption.
The Panel considers that the evidence provided does not establish that patients with the clinical diagnosis of RA are representative of the general population with regard to the status of joint tissues, or that results obtained in subjects with RA relating to the treatment of symptoms of the disease (e.g. joint pain, joint swelling, joint stiffness, erosion of joint cartilage) can be extrapolated to maintenance of structure and function of joints in the general population.
Administration of GLA-rich oils (2.4 g GLA/d) to healthy volunteers resulted in decreased production of pro-inflammatory cytokines (TNF-α, interleukin-1, interleukin-6) by monocytes (DeLuca et al., 1999), decreased lymphocyte reactivity (Rossetti et al., 1997), and decreased chemotaxis of neutrophils. GLA doses less than 1 g/d did not have an effect on lymphocyte proliferation nor on the production of TNF-α, interleukin-1β, interleukin-2 or interferon-γ (Yaqoob et al., 2000; Wu et al., 1999). These reactions are similar to those measured in patients with RA. However, their clinical significance in healthy subjects with respect to joint health is unknown.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and maintenance of normal joints.
3.2. Utrzymanie masy ciała po odchudzaniu (ID 496)
One double-blind randomised controlled trial on the effects of GLA consumption on weight maintenance after weight loss in obese subjects was provided (Schirmer and Phinney, 2007).
Fifty obese subjects with a recent weight loss of at least 12 kg followed by a 6-month behavioural weight maintenance program were randomised to consume either 5 g/d borage oil (890 mg/d of GLA) or 5 g/d olive oil (controls) for 1 year. The study was terminated after 12 subjects in each group had completed the intervention. Weight regain was significantly greater in the control (8.78 +/- 2.78 kg) than in the GLA (2.17 +/- 1.78 kg) group. Weight regain was significantly lower (1.8 +/- 1.6 kg) in the GLA group than in controls (7.6 +/- 2.1 kg) for the 13 and 17 subjects, respectively, who completed a minimum of 50 weeks in the study. Weight regain did not differ in the remaining 10 GLA and 5 control subjects who were <50 weeks in the study. The Panel notes the small number of subjects
completing the study and the lack of significant effects of the intervention prior to 50 weeks of treatment.
In weighing the evidence, the Panel took into account that only one small study was presented testing the effects of GLA on weight loss without accompanying evidence of a biologically plausible mechanism by which GLA could exert the claimed effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and weight maintenance after weight loss.
3.3. Utrzymanie prawidłowego krążenia obwodowego (ID 638)
A total of 12 references were cited in relation to this claim. One is a monograph on GLA (no authors listed, 2004); two are general reviews on the use of evening primrose and borage oil in rheumatologic conditions (Belch and Hill, 2000) and on the effects of antioxidants in neural and vascular dysfunction in experimental diabetes (Cameron and Cotter, 1999) and one is a general review on diabetic neuropathies (Vinik et al., 2000). The Panel considers that no conclusions can be drawn from these references in relation to the claim.
Four human intervention studies on the effects of GLA were presented. One was related to the symptomatic treatment of Raynaud's phenomenon (Belch et al., 1985); one related to the treatment of peripheral arterial disease (lower limb atherosclerosis, i.e. patients with intermittent claudication) (Leng et al., 1998) , and two were related to the treatment of human diabetic peripheral neuropathy (Jamal et al., 1990; Keen et al., 1993). The Panel considers that the evidence provided does not establish that results obtained in these patient populations can be extrapolated to the general population, and that no conclusions can be drawn from these studies in relation to maintenance of a normal peripheral blood flow.
Four animal studies were also presented on the effects of GLA on nerve conduction and or blood flow in diabetic rodents (Coste et al., 1999; Dines et al., 1995 and 1996; Head et al., 2000). The Panel considers that the evidence provided in the animal studies does not establish the occurrence of an effect of GLA consumption on maintenance of a normal peripheral blood flow in humans.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and maintenance of a normal peripheral blood flow.
3.4. Utrzymanie prawidłowego ciśnienia tętniczego (ID 1771)
No references in relation to this claim were provided on the effects of consumption of GLA on blood pressure.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and maintenance of normal blood pressure.
3.5. Utrzymanie prawidłowego stężenia cholesterolu we krwi (ID 1771)
No references in relation to this claim were provided on the effects of consumption of GLA on blood cholesterol.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and maintenance of normal blood cholesterol concentrations.
3.6. Utrzymanie prawidłowego stanu kości (ID 1774)
Four references were provided to substantiate this claim. None of them addressed the effects of consumption of GLA on either intestinal calcium absorption, bone mineral density or any measures of bone structure and/or function.
The Panel concludes that a cause and effect relationship has not been established between the consumption of GLA and maintenance of normal bone.
Wnioski
On the basis of the data presented, the Panel concludes that:
The food constituent, gamma-linolenic acid, which is the subject of the health claims is sufficiently characterised.
Maintenance of joints (ID 494, 637, 1774, 2098)
The claimed effect is “joint health”. The target population is assumed to be the general population. Maintenance of normal joints is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and maintenance of normal joints.
Weight maintenance after weight loss (ID 496)
The claimed effect is “reduces regaining weight”. The target population is assumed to be overweight subjects in the general population who wish to maintain their body weight after significant weight loss. Weight maintenance after weight loss is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and weight maintenance after weight loss.
Maintenance of peripheral blood flow (ID 638)
The claimed effect is “maintaining hands and feet in good condition (supportive measure for microcirculation and peripheral nerves)”. The target population is assumed to be the general population. Maintenance of a normal peripheral blood flow is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and maintenance of a normal peripheral blood flow.
Maintenance of normal blood pressure (ID 1771)
The claimed effect is “vascular health”. The target population is assumed to be the general population. Maintenance of normal blood pressure is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and maintenance of normal blood pressure.
Maintenance of normal blood cholesterol concentrations (ID 1771)
The claimed effect is “vascular health”. The target population is assumed to be the general population. Maintenance of normal blood cholesterol concentrations is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and maintenance of normal blood cholesterol concentrations.
Maintenance of bone (ID 1774)
The claimed effect is “bone health”. The Panel assumes that the target population is the general population. Maintenance of normal bone is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of GLA and maintenance of normal bone.