Newsletter 02 2006.pdf - Sight and Life

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SIGHT AND LIFE 20 NEWSLETTER 2/2006 enzymes (the so-called “knock out” mouse) to draw inferences about pathways in carotene metabolism. Geneticist created knock-out animals, deprived of or suppressed regarding one or another receptor. These proved to be strong investigative tools to use in pursuing the role of transporters in carotene uptake. In concluding his talk, Dr Harrison summarized a series of Beltsville laboratory experiments using receptor inhibitors, knock-out mice and their combination, to illustrate a partial dependency of carotene uptake on this class of membrane-associated enzyme as the basis for facilitated cellular uptake of carotenoids in the intestine. Dr Kathleen C Ellwood, of the Center for Food Safety and Applied Nutrition (CFSAN) of the Food and Drug Administration (FDA) of the United States presented the topical theme Reviewing the Scientific Evidence for Health Claims. Dr. Ellwood is assigned to the Division of Nutrition Programs and Labeling, Office of Nutritional Products Labeling and Dietary Supplements of the CFSAN. She provided a lucid exposition of the United States government’s oversight and regulation in the food-labeling area, and participated in a lively and interactive question and answer period thereafter. Need for labeling rules came about with the expansion of knowledge about bioactive substances in foods (of which the various carotenoids are examples). There came an effort by manufacturers of foods and supplements in the United States to transform findings into claims of beneficial effects. This led producers and marketers to seek to make claims about the benefits of consumption of the substances, the food containing the substances or both. To the extent that foods and substances are offered as remedies and therapies, a specific regulatory Kathleen C Ellwood handling comes into play. Dr. Ellwood correctly presented this as a case example of the merger of science with policy. Claim statements for a product are a form of “speech”; within the United States of America, freedom of speech is protected by the First Amendment to the Constitution. Provisions for making claims for health regarding a retail product are now covered by legislation (statutes) and the judicial precedents (case law). The FDA considered disease therapy claims for foods in the 1970s and 1980s, and concluded that food must be treated by the same standards as any drug. Since that era, however, emerging scientific discovery has shown a series of more subtle diet-health relationships including protection and preservation of wellbeing and function. U.S. consumers were interested in seeking the potential benefits from dietary factors, and there was marketing pressure to deliver what the consumer demanded. This led to the passage in 1990 of the Nutrition Labeling and Educational Act, which governs the nature of claims that could be attached to edible products. It was not about treating established disease, i.e. the drug action, but rather about “Health Claims”. The act regulated claims of causal relationships between a food substance and a disease or health-related condition in the general US population or sub-population, in which consumption could reduce their risk. For the Health Claim to be approved the standard was “significant scientific agreement”, that is a strong consensus of a causal relationship. The speaker recounted how manufacturers felt constrained by having to get over such a high bar; they brought suits in court claiming that the Act infringed upon the First Amendment guarantee of freedom of speech. This has led, since 1999, to a secondary level of regulation for labeling, the so-called Qualified Health Claim (QHC). These claims include qualifying language in order to prevent the consumer from being misled. QHCs are applied for relationships such as that relating lycopene or lycopene-containing foods to reduced risk of prostate cancer and similar assertions. The process of evaluation by the FDA for a QHC has a defined set of steps. The first is literature review and selection. Animal studies are not relevant. Insofar as observational studies can indicate association, but not causality, the most relevant literature is considered to be that from intervention trials. The interventions can have outcomes of reduced incidence of disease/condition or favorable modification of a validated modifiable risk factor related to ill health. San Francisco’s famous cable cars.
NEWSLETTER 2/2006 21 SIGHT AND LIFE Prof. Erdman’s collaborators. Once the trial studies are assembled and sorted, those that meet inclusion criteria are rated for quality in terms of design, inclusion/exclusion criteria, balance of population characteristics across groups, verification of compliance with the intervention and appropriateness of statistical analysis. This is done for each study. The CARIG audience was particularly intrigued to learn that any study without a “validated” dietary intake method would be excluded from consideration. For those who know the limitations of dietary method validation/calibration, this seems fraught with arbitrary possibilities. The pre-final step is to rate the overall strength of the body of evidence in terms of type, quality, quantity and studies’ sample size, consistency and replication of findings, and the relevance to the US general population or target subgroups. Finally, the claim can have three degrees of ranking: 1. conclusive; 2. limited; or 3. very limited. The modifications in the FDA procedures derive from the tension among consumers’ desire to preserve health, producers’ and retailers’ desire to exercise free speech, and the government’s duty to protect the citizenry from consumer fraud. Dr. Ellwood’s message had shown that the role of the scientific community lies in how well they design and execute studies on causal relationships between a dietary substance and a beneficial outcome. Prof. John Erdman of the University of Illinois also spoke in the second session of the program with a talk entitled: Tomato, Lycopene and the Risk of Prostate Cancer. He was also awarded this year’s Wilbur O. Atwater Memorial Lecture, sponsored by the United States Department of Agriculture on 4 April, which had the theme of carotenes at its center. His award’s lecture topic was Colors, Critters, and Cancer. As he explained, the colors refer to carotenoid pigments; the critters refer to the selection (limits and possibilities) with different animal models for investigation of carotenoid metabolism and effects; and cancer is specifically prostate cancer. The context is the epidemiological evidence that suggests that tomato consumption is protective against prostate cancer. The world of colorful carotenoids contains over 650 compounds. Phytoene and phytofluene are simple colorless precursor carotenoids. All known members of this family of compounds are initially synthesized in plant tissues; animals cannot form carotenoids. Prof. Erdman reminded his audiences that the ripeness of fruits John Erdman and vegetables is reflected in their carotenoid content. Carotenes contribute to the hues of birds’ feathers and insects’ coloring. Moreover, carotenes are important to aroma compounds in nature that have importance for interspecies signaling. Not all animals handle carotenoids in a uniform fashion. It has been found for instance that, for studies of carotenoid metabolism related to human physiology, gerbils, ferrets and pre-ruminant calves provide the best in likeness to human absorptive systems. They are capable of absorbing the compounds both intact and metabolized. As herbivores, rats and mice are efficient converters of provitamin A carotenoids. They are poor at absorbing intact carotenoids; thus, high feed levels are needed for these rodents to replicate the tissue concentrations achieved in humans. In Prof. Erdman’s view, the armamentarium of animal models for cancer studies with carotenoids includes rats, mice, and again ferrets. The prostate gland and carotenoid-containing foods came together in the observations of vastly different spontaneous incidence rates for prostatic cancer with 70 times greater incidence rates in North American blacks and 50-fold increased rates
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