Abstract
Basic principles of Japanese dietary reference intakes (DRIs) published in 2005 for n-3 polyunsaturated fatty acids (n-3 fatty acids) are described in detail, and the evidence tables used for their establishment are presented. Since n-3 fatty acids are essential fatty acids and their deficiency leads to dermatitis and growth retardation, their minimal requirement (=lower limit) should be established. However, since only a few case reports of n-3 fatty acid deficiency have been published, it is difficult to establish their minimal requirement. Therefore, the concept of adequate intake (AI), representing the median intake of the Japanese population, was adopted. As most contemporary Japanese do not suffer from dermatitis and growth retardation, the median intake of n-3 fatty acids by age and sex was used as the AI of n-3 fatty acids. As AI is a rather expedient procedure, it is likely that the actual minimal requirement is lower than the AI level. Reports published to date have demonstrated that sufficient intake of n-3 fatty acids can prevent ischemic heart disease. The median intake of n-3 fatty acids by Japanese is much higher than that in the group showing highest intake of n-3 fatty acids among Americans. Thus, intake of n-3 fatty acids equivalent to the median for the Japanese population is considered to adequately decrease the incidence of ischemic heart disease. For Japanese individuals over 18 years of age, the median intake of n-3 fatty acids was set as the lower limit of the tentative dietary goal (DG) for preventing lifestyle-related diseases. The lower limit of DG for individuals over 18 years of age thus became 2.0-2.9g/day. Adverse effects of a higher intake of n-3 fatty acids are also described. Although there have been many reports of increased bleeding time and elevated LDL-cholesterol concentrations, there have been no reports of increased occurrence of clinically adverse bleeding or ischemic heart disease. Therefore, we did not set an upper limit for n-3 fatty acid intake. In the DRIs for 2005, the effects of heavy metals such as mercury and cadmium and chemical environmental pollutants such as dioxins and PCBs present in fish in very small amounts were not considered. However, in this article, evidence tables related to consumption of mercury from fish are presented and the safety of fish intake by pregnant women is discussed.
