Pioneer research in the nineteen sixties and seventies indicated that the consumption of fish was associated with a reduced risk for coronary heart disease in Greenland Eskimos. This Eskimo population experienced a low mortality from coronary heart disease despite a diet rich in fat and cholesterol. It was soon suggested that this could be related to the high content of omega-3 fatty acids, typically present in marine foods. These Eskimo studies have triggered a much broader and intensified research on the importance of omega-3 fatty acids and seafood in the human diet. This PhD-study is embedded in that research area and examines in the first place the intake of omega-3 and other fatty acids by the Flemish and Belgian population. In a next step, the question is raised whether seafood is a safe dietary source of these fatty acids and whether the consumption conform with physiological needs induces any toxicological concern. The latter is of importance since the favourable health perception is troubled by information regarding the potential adverse health impact of chemical contaminants in marine foods, occuring naturally or resulting from man-made processes. These conflicting facts form a potential base for an important public health conflict between dietary recommendations on the one hand and toxicological safety assurance on the other hand. A first part of the PhD-thesis presents the results of an intake assessment of individual polyunsaturated fatty acids (PUFAs) in Flemish pre-school children, adolescents, and young women and an intake assessment of vitamin D in Flemish adolescents. The following PUFAs were considered: linoleic acid (LA), a-linolenic acid (LNA), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). First, the results make clear that a lower intake of LA and a higher intake of LNA are necessary to decrease the LA/LNA ratio, since a lower LA/LNA ratio can help in the prevention of some chronic diseases. This can be reached by a higher consumption of LNA rich foods e.g. by replacement of omega-6 (n-6) rich oils by omega-3 (n-3) rich oils such as linseed and rapeseed in food formulations. Second, dietary shifts are necessary to bridge the gap between the intakes and the recommendations of long chain (LC) n-6 and n-3 PUFAs. Regular replacement of meat products rich in saturated fatty acids (SFAs) by poultry meat is a possible solution to increase the AA intake, which was evaluated to be very low for 216 Flemish pre-school children. Moreover, this study suggests that seafood and particularly fatty fish consumption should be stimulated in all subgroups of the population since it is a rich source of LC n-3 PUFAs of which the current intakes are evaluated to be far below the recommendations. Furthermore, increased seafood consumption can lead to higher vitamin D intake and can replace SFA-rich food items. A next part of the thesis focuses on the nutritional-toxicological conflict related to seafood consumption. This conflict arises from the fact that increased consumption of seafood will at the same time increase the intake of environmental contaminants like methyl mercury (MeHg), PCBs, and dioxin-like (dl) compounds (dl PCBs and PCDD/Fs). Therefore, a methodology was developed, including the elaboration of databases and the development of a software module in order to perform a probabilistic assessment of the simultaneous intake of multiple compounds (LC n-3 PUFAs, vitamin D, iodine, (Me)Hg, PCBs, and dioxin-like substances) via seafood consumption. Subsequently, the assessed intakes were evaluated to determine: (1) if nutrient intakes reached the recommendations and (2) if contaminant intakes did not exceed a level of toxicological concern. Two different situations were studied: 1. Starting from the current seafood consumption data of two different subgroups of the Belgian population (adolescents and adults). Based on these consumption data, the simulation results predicted that the studied populations did not reach a sufficiently high intake for the three nutrients under consideration (LC n-3 PUFAs, vitamin D, iodine) taking into account only seafood consumption. Regarding the contaminants, MeHg contamination of seafood on the Belgian market did not seem to be an issue of toxicological concern. In contrast, the tolerable weekly intake for dioxin-like compounds was exceeded in the case of high seafood consumers on the basis of their seafood consumption only. 2. It was investigated whether the Belgian recommendation for LC n-3 PUFAs (i.e. 0.3 % of total energy intake) could be reached through seafood consumption, without exceeding tolerable weekly intakes of MeHg and dioxin-like compounds. Also the contribution of LC n-3 enriched margarines was assessed. The results indicated that the Belgian recommendation for EPA plus DHA can be reached by consuming fatty fish twice a week, or by varying between lean and fatty fish minimally 217 three times a week. It was found that MeHg intake was not an issue of toxicological concern for the Belgian population at this level of seafood consumption. The intake of dioxin-like compounds from seafood only approximated the tolerable weekly intake when consuming fatty fish three times a week or more, being a potential toxicological risk since also other food items contribute to the daily intake of dioxin-like compounds. Use of LC n-3 enriched margarine can further help to increase the LC n-3 PUFA intake, on average by 159 mg/day. To conclude, combination of regular seafood consumption (twice a week), with important contribution of fatty fish species, in combination with regular consumption of LC n-3 enriched margarine can be advised to maximize LC n-3 intake. There is, however, an important limitation related to this study, namely that contaminant intake from other food sources was not taken into account. For MeHg this is not a problem since exposure to MeHg occurs almost exclusively through consumption of seafood. In contrast, consumption of other food items, mainly from animal origin, contributes to the intake of dioxin-like compounds. This is an important fact that has to be taken into account in further research. |
