New Reasons to Consider NUTRITIONAL LIPIDS
From CLA to phytosterols, research and regulations review their benefits and guide their uses. Interest in an Omega-3 Index grows.
For example, overweight and obesity are growing worldwide problems, and more products are being developed to address weight loss. According to Global Industry Analysts Inc.1, the global weight-control products market may be $46.9 billion by 2015. Conjugated linoleic acid (CLA), a naturally occurring fatty acid found in beef and dairy products, is increasingly being used as a weight-reduction supplement. The CLA isomers c9, t11 and t10, c12 have been demonstrated in animal studies to reduce body fat mass, increase insulin sensitivity, decrease plasma glucose levels and have anti-carcinogenic effects2. As a result of these findings, CLA has been indicated for the use in cancer, diabetes, hypertension, hypercholesterolemia and fat loss.
The assessment of the findings of five human studies included in a recent meta-analysis3 concluded that CLA assists in reducing body fat mass (BFM) and sagittal abdominal diameter (SAD), an abdominal obesity linked with metabolic syndrome. CLA may be beneficial in maintaining changes in BFM. However, minimal effects were noted on BMI, lean body mass (LBM) or body weight. The range of intakes studied were 3.5-4.5g/day for durations of 4 weeks-12 months.
In 28 overweight children, 3g daily of CLA for 6 months significantly decreased BFM and increased LBM compared to placebo. Following 7 months, CLA reduced BFM by 0.5% and total body weight by 0.1%4. In comparison, increases of 1.3 and 0.4%, respectively, were noted in a placebo group. Abdominal body fat was also less in the CLA group.
Health Canada’s Natural Health Product Directorate released a CLA monograph in early 2010 in which the agency allows the following claims on supplements: “May help to support a modest reduction in fat mass” or “May help to support a modest improvement to body composition, when used with a program of reduced intake of dietary calories and increased physical activity.” Required dosages are 3-5g/day5.
However, in response to requests for Article 13 health claims on CLA, the European Food Safety Authority (EFSA) concluded that 14 out of 16 intervention studies in humans did not report a significant effect of CLA on body weight; most of the studies considered were short-term (12 weeks or less); and none of the 3 studies on body weight maintenance after weight loss showed a significant effect of CLA compared to placebo6. On the basis of the data presented, the panel concluded that a cause-and-effect relationship has not been established between CLA intake and maintenance or achievement of a normal body weight.
In spite of mixed reviews from regulatory bodies and the scientific community, research is revealing innovative effects of CLA in asthma and on bone metabolism. A daily dose of 4.5g/day of CLA significantly improved airway hyper-responsiveness and adipokine levels (cytokines produced in fat tissue subjects) in asthmatics7. In mice, CLA showed protective effects on age-associated bone loss, by modulating inflammatory markers and osteoclastogenesis (bone resorption)8. Mice fed a t10c12-CLA diet maintained a significantly higher bone mineral density, accompanied by a decreased production of osteoclastogenic factors in serum.
Competitive Plant Sterols
Another class of novel lipids which has garnered attention over the past two decades is phytosterols (plant sterols). These compounds are chemically similar to cholesterol (which occurs only in animals) and are found widely throughout the plant kingdom. They cannot be synthesized by humans and must be provided in the diet. Their cholesterol-lowering action has been demonstrated for more than 60 years. Plant sterols reduce cholesterol absorption, by competing with cholesterol for absorption into mixed micelles. This action results in less cholesterol returning to the liver and more being excreted9.
Numerous clinical trials in controlled settings have reported daily consumption of 1.5-3g of phytosterols/-stanols from foods can reduce total cholesterol levels by 8-17%. Current recommendations of plant stanols are for 2g/day.
Intakes of plant stanols up to 9g/day produced reductions in LDL cholesterol of 17.4% in a dose-dependent fashion, without affecting antioxidant defenses, in 93 health subjects with slightly raised cholesterol levels10. Subjects were randomly assigned products containing 3, 6 or 9g of plant stanols for 4 weeks. People in the 3g/day group experienced LDL reductions of 7.4%, compared with 11.9 and 17.4% in the 6g and 9g/day groups.
Dairy products represented the initial line of functional foods marketed with phytosterols. More bakery and cereal products, snack foods, prepared foods and beverages are being enriched with phytosterols, and efficacy of effect is being studied. The consumption of a rye bread (9.3g/day fiber), with added plant sterols (2g/day) (active group) or without added plant sterols (control group), was assessed in 68 participants11. In the second phase of the study, the amount of rye bread was doubled, providing 18.6g/day fiber and 4g/day plant sterols. After 2 weeks in the first phase, serum levels of LDL and total cholesterol were decreased by 8.1 and 5.1%, respectively. After the second phase, further reductions of LDL by 10.4% and total cholesterol by 6.5% were noted. Rye bread alone did not decrease cholesterol in the control group.
The U.S. Food and Drug Administration was the first to approve a health claim on the relationship between plant sterol esters and reduced risk of coronary heart disease in 2000. In May 2010, Health Canada approved a similar claim. In the EU, regulations continue to evolve. In July 2009, regulations related to the cholesterol-lowering benefits of phytosterols were extended to 1.5-2.4g from at least 2g. The ruling stated that LDL cholesterol-lowering benefits of between 7-10% can be attained “in 2-3 weeks,” if consumed daily in the form of yellow fat spreads, dairy products, mayonnaise and salad dressings12.
Phytosterol claims are not without controversy. The FDA was accepting comments until February 22, 2011, on proposals that would expand the current claim to allow free esters to be used in bread and cereal, orange juice and low-fat dairy foods and also would require that foods must bear 500mg of phytosterols to be eligible for the claim13. The existing level is 400mg, which has prompted several sterol and stanol suppliers to suggest that under the proposed rule, many products would be forced off the market. The proposed rule change suggests 2g of phytosterols must be consumed per day, which the FDA indicates represented a median between the 1-3g levels found in most intervention studies. NS
1. Global Industry Analysts Inc. February 2011. “Weight Control Products: A Global Strategic Business Report.”
2. Gaullier JM, et al. 2004. Conjugated linoleic acid supplementation for 1 year reduces body fat mass in healthy overweight humans. Amer J Clin Nutr. 79(6):1118–25.
3. Egras AM, et al. 2011. An evidence-based review of fat modifying supplemental weight loss products. J Obesity. DOI: 10.1155/2011/297315.
4. Racine NM, et al. 2010. Effect of conjugated linoleic acid on body fat accretion in overweight or obese children. Amer J Clin Nutr. 91(5):1157-64.
5. Health Canada. Conjugated linoleic acid (CLA) monograph. January 27, 2010. http://tinyurl.com/48chzgd.
6. EFSA panel on dietetic products, nutrition and allergies. 2010. EFSA J. 8(10):1794. www.efsa.europa.eu/efsajournal.htm.
7. MacRedmond R, et al. 2010. Conjugated linoleic acid improves airway hyper-reactivity in overweight mild asthmatics. Clin Exp Allergy. 40:1071-78.
8. Rahman M, et al. 2010. t10c12-CLA maintains higher bone mineral density during aging by modulating osteoclastogenesis and bone marrow adiposity. J Cell Physiol. 2010 Dec 9. DOI: 10.1002/jcp.22578.
9. Plant sterols (phytosterols) in foods. May 2010. Food Directorate. Health Canada. http://tinyurl.com/4j9xa95.
10. Mensink R, et al. 2010. Plant stanols dose-dependently decrease LDL-cholesterol concentrations, but not cholesterol-standardized fat-soluble antioxidant concentrations at intakes up to 9g/d. Amer J Clin. Nutr. 92:24-33.
11. Soderholm PP, et al. 2011. The effect of high-fiber rye bread enriched with nonesterified plant sterols on major serum lipids and apolipoproteins in normocholesterolemic individuals. Nutr. Metab. Cardiovasc. Dis. DOI:10.1016/j.numecd. 2010.09.011.
12. Plant stanols and plant sterols and blood LDL-cholesterol—scientific opinion of the panel on dietetic products, nutrition and allergies. 2009. DOI:10.2903/j.efsa.2009.1175.
13. Food and Drug Administration. 21 CFR Part 101: Food labeling; health claim; phytosterols and risk of coronary heart disease; proposed rule. December 8, 2010. http://edocket.access.gpo.gov/2010/pdf/2010-30386.pdf.
Phytosterols and omega-3s have been shown to support cardiovascular health, among other benefits.
Researchers are looking at the percent of the omega-3 fatty acids EPA (shown here) plus DHA of red blood cells’ fatty acids, as a simple indicator of CHD risk and, also, as a factor in cardiac deaths. More omega-3s lower the risk.
The Omega-3 Index
Cholesterol (total, HDL and LDL) levels in blood serum have been used as indicators of and risk factors for cardiovascular disease risk. Interest is growing in what is called the Omega-3 Index, since a paper was first published on the subject Harris WS and Von Schacky C. 2004. The Omega-3 Index: a new risk factor for death from coronary heart disease?” Prev Med. 39(1):212-20). PubMed now lists some 45 papers on the Omega-3 Index.
The hypothesis is that low intakes, resulting in low blood levels of the omega-3 fatty acids EPA and DHA, are associated with increased risk of death from coronary heart disease. Since the percent of EPA plus DHA of red blood cells’ (RBC) total identified fatty acids reflects long-term intake of these two omega-3s, Harris and Von Schacky proposed that RBC EPA + DHA, now named the Omega-3 Index, be considered an actual risk factor for cardiac death.
The 2004 paper suggested 8% was the optimal target level of the Omega-3 Index, and an undesirable level was proposed as less than 4%, with 4-8% being an intermediate-risk zone. A recent paper (Harris WS. 2010. Curr Cardiol Rep. 12:503–508) notes that a variety of studies since then have provided confirmation of these original target values. It concludes that, one day, Omega-3 Index (like cholesterol levels) may be included in standard risk assessment profiles and that simple, inexpensive steps can be taken to correct omega-3 deficits and reduce cardiovascular disease risk.
To see Von Schacky speaking on the Omega-3 Index, go to http://tinyurl.com/697sacs.
— Claudia D. O’Donnell, Chief Editor