For the first time since the enactment of the National Labeling and Education Act of 1990, the nutrient list on food labels may be expanded to include trans-fatty acids. As the Food and Drug Administration (FDA) continues to consider amending the required nutrients to include trans-fatty acid levels, the Institute of Medicine (IOM) recently released a report that reviews the content and effects of trans-fatty acids (1). The proposed amendment and IOM report raises a concern for me as a nutrition professional and scientist: if we oversimplify the facts about trans-fatty acids,. we are misrepresenting the major foundations of our discipline of dietetics, namely, biochemistry and nutritional and food sciences.
In terms of both structure and function, all trans-fatty acids are not alike (see Figure). If trans-fatty acids are grouped together as one structural entity, as is proposed for labeling by the FDA panel, there exists the possibility for mass confusion and misinformation, especially as we continue to unravel the links of each isomeric structure to physiological effects. With subtle differences in structures, 5ans-fatty acids are likely to have profoundly different physiological functions. For example, structural differences within the class known as conjugated dienoic trans-fatty acids (eg conjugated linoleic acid, CLA) may have profoundly different effects on genomic regulation, metabolic function and physiological outcomes (2). This and other findings regarding the divergent activity of various isomers of conjugated dienoic trans-fatty acids, illustrate the complexity and potential confusion of oversimplifying the nutritional messages concerning trans-fatty acids. While it is proposed that this group of tra ns-fatty acids not be included in the trans-fatty acids required for labeling, this decision is pending.
In terms of CLA, this group of fatty acids is a naturally occurring trans-fat found in foods from ruminant animal sources and a derivative of the fatty acid linoleic acid. The potential benefits and biological activities of this unique group of fatty acids are still being identified. Research concerning the anticarcinogenic effects of CLA has recently been extended to antiatherogenic properties, anti-diabetic properties, enhanced immune response and positive effects on energy partitioning and growth. We expect further research to find even more significant health benefits being derived from GLA. And, in fact, the American Dietetic Association identified CLA as a component contributing to the functional food properties of beef, lamb and dairy products (3). CLA cannot and should not be categorized in the same way as the man-made trans-fats found in baked goods or snack foods
Without more answers about the role of various types of trans-fatty acid isomers in health and disease, are we ready to add further confusion to the public's perception about the potentialiy large and complex role this heterogeneous group of fatty acids may play in our health? If trans-fatty acids are lumped together on a food label, or worse yet, combined with saturated fats, there are many risks to our professional identity, including our integrity as practitioners and scientists. But greater than this, we risk misinforming the public who each of us serves as practitioners, teachers, researchers, mentors and messengers. It is important that consumers make knowledgeable decisions to choose foods based on sound, peer-reviewed, replicable and definitive information. In terms of transfatty acids, it is imperative that the content of trans-fatty acids that are associated with increasing risks for cardiovascular diseases (eg elaidic and translinolelaidic acids) be distinguished from those that do not induce ather osclerotic lesions (eg CLA). Furthermore, the designation of trans-fatty acids as separate entities from saturated fatty acids is crucial for pariaying accurate and correct information to consumers. Is this too complex for the public whom we serve? In light of the alternatives, I think not.
References:
(1.) Institute of Medicine: Food and Nutrition Board. Letter report on dietary reference intakes for trans fatty acids. In: Dietary Reference Intakes for Energy, Carbohydrate, Fiber Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academy of Sciences, 2002.
(2.) Belury MA. Dietary conjugated linoleic acid in health: Physiological effects and mechanisms of action. Annu Rev Nutr. 2002;22:505-531.