Basic principles of Japanese dietary reference intakes (DRIs) published in 2005 for lipid were briefly described. Among several criteria used for DRIs, adequate intake (AI) and tentative dietary goal (DG) was adopted for the determination of fat intake DRIs. Since n-6 and 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-6 and n-3 fatty acids deficiency have been published, it is difficult to establish their minimal requirement and thus the concept of AI that represents the median intake of the Japanese people was adopted. For DG, since a lower intake of saturated fat increased an incidence of apoplexy (=brain bleeding) and a higher intake increased an incidence of obesity, DG of saturated fat was set as 4.5-7% of total energy intakes. Less than 10% of total energy intakes was set for n-6 fatty acids, since safety of a large amount n-6 fatty acids intakes were not known. Reports published to date demonstrate that sufficient intake of n-3 fatty acids can prevent ischemic heart diseases. The median intake of n-3 fatty acids of the Japanese people is much larger than that in the highest intake group of n-3 fatty acids among the Americans. Thus, for those more than 18 years of age, the median intake of n-3 fatty acids of the Japanese people was set as a lower limit of the tentative dietary goal (DG) for preventing life-style related diseases; the lower limit of DG of those more than 18 years of age becomes 2.0-2.9 g/day. Since a higher intake of cholesterol in Japanese populations increased cancer incidence in women and ischemic heart disease in men, DG of cholesterol was set less than 750 mg/day in man and 600 mg/day in women.
In 2005, Japan Society for Lipid Nutrition conducted a symposium on "the Approach of Dietary Reference Intakes for Japanese, 2005, (DRIJ) to Fatty Acids and Cholesterol". We appreciate that DRIJ drastically increased the upper limits (UL) of cholesterol intakes, and we do not further discuss this issue here. However, the UL of linoleic acid set by DRIJ was 10 energy %. This is calculated to be 22g for 2000kcal-taking people. If the whole linoleic acid is provided from cooking oils, 22g is equal to 50g of usual cooking oils found in Japan. This amount is not practical for Japanese, and almost identical to "no limits". Judging from the comments in the symposium of Dr Osamu Ezaki who chaired the lipid session in DRIJ, the lipid recommendation of DRIJ seems to be considerably influenced by the results of the Nurses' Health Study (NHS) performed in the United States. Its results read that the more linoleic acid, the better after adjustments for many confounding factors. However, Japanese are completely different from the cohort of NHS; Americans' intakes of fish oils have been essentially the lowest of the developed countries for these forty years. It is not appropriate to draw a conclusion about lipid nutrition from the results of cohorts whose marine n-3 fatty acid intakes are extremely low. We need well-planned epidemiological studies in Japan to understand the upper limits of linoleic acid. Until then, it is prudent to keep our linoleic acid intake low, considering the results of some epidemiological studies.
Dietary Reference Intakes (DRI) for Japanese has been established in 2005. The criteria, newly introduced in DRI 2005 instead of previous recommended dietary allowances, may embarrass most of Japanese people, especially in these definitions and nomenclatures expressed in Japanese. In addition, several values in DRI, approved as acceptable distribution ranges or recommendations for fat and fatty acids, may be questionable. Particularly, an adequate intake for n-6 fatty acids, lower limits of tentative dietary goal (DG) for fat and saturated fatty acids, and an upper limit of DG for n-6 fatty acids should be clarified in the future discussion.
The range of intakes, that is, the upper and lower limits of intake, of the fat energy ratio, saturated fatty acids, n-6 series fatty acids, n-3 series fatty acids and cholesterol have been laid down in the Dietary Reference Intakes (DRIs) for Japanese, 2005. However, it is not easy, even for nutrition specialists, such a dietitians who manage daily dietary intakes, to understand the DRIs of lipids, for which there are so many reference values. It would be rather difficult in daily dietary management to control the intake of various lipid-containing foods to satisfy the DRIs of the various components of lipids. Therefore, in this paper, we describe how the DRIs of lipids should be understood from the viewpoint of users, and an example composition of food groups that could be available in the future is shown.
Diacylglycerol oil is an edible oil containing 80%(w/w) or greater diacylglycerol with natural fatty acids, approximately 70% of which is of the 1, 3- diacylglycerol isoform. Diacylglycerol oil has been sold in Japan as a FOSHU (Foods for Specified Health Use) product since 1999 as a cooking oil that gives (1) less postprandial serum triacylglycerol elevation and (2) less body fat accumulation. The energy value of the diacylglycerol oil is practically the same as the ordinary oil containing triacylglycerol. In contrast to triacylglycerol, the main digestive product of diacylglycerol is 1(or 3)-monoacylglycerol which is poorly re-esterified into triacylglycerol in the small intestinal mucosa. The magnitude of postprandial elevations of triglyceride content in chylomicrons has been shown to be markedly smaller after diacylglycerol ingestion compared to triacylglycerol oil with a similar fatty acid composition. Animal studies showed that diacylglycerol consumption increases hepatic enzyme activities for β-oxidation and increases oxygen consumption as compared to triacylglycerol. It has been shown that long-term diacylglycerol consumption prevents the accumulation of body fat and body weight and reduces risk factors for lifestyle-related diseases in humans. The above two claims have been verified not only in subjects with simple obesity but also in those with risks of metabolic syndrome. Through these studies, evidence is being accumulated showing that consumption of diacylglycerol may help reducing the risk of lifestyle-related diseases.
The cooking oil and the margarine containing medium-chain fatty acid (MCFA) have been approved as Foods for Specified Health Use (FOSHU). We introduce recent researches on the nutritional characteristics of MCFA in this review. We conclude that intake of 5-10g of medium-chain triacylglycerols (MCT) suppresses body fat accumulation compared with intake of LCT in Japanese with a high BMI of ≥23 kg/m2. In addition, it is suggested that intake of 14g of medium- and long-chain triacylglycerols (MLCT) containing 1.7 g of MCFA is useful for suppressing body fat accumulation compared with intake of LCT in Japanese individuals. With regard to the mechanism responsible for the suppressive effect on body fat accumulation, we found that the change of serum triacylglycerol of subjects with BMI ≥23 kg/m2 receiving 5-10g of MCT lower than those receiving LCT. Furthermore, intake of MCT at a daily dose of 5-10 g led to higher DIT compared with intake of LCT. Accordingly, the decrease in body weight and body fat weight following MCT intake in subjects with BMI ≥23 kg/m2 might be due largely to the difference in LCT metabolism between these subjects and those with BMI <23 kg/m2. We consider that the difference in BMI greatly affects the oxidation and synthesis of fat in the liver and other tissues, thus explaining the observed difference in the body fat accumulation profile.
CSPHP is a newly developed soy peptide that significantly decreases serum concentrations of total cholesterol and LDL cholesterol. It was made by fortifying soy's widely known serum-cholesterol reducing property by binding enzymatically-decomposed lecithin to hydrolyzed isolated soy protein in the ratio of 80:20 (wt/wt). The two components are considered to be bonded hydrophobically. CSPHP is useful for both normalizing the high cholesterol level of hypercholesterolemia patients and also maintaining serum cholesterol level for healthy humans taking high cholesterol meals. By taking 3 or more grams of CSPHP/day for 3 months consecutively, CSPHP reduced both their total cholesterol and LDL-cholesterol level of the hypercholesterolemia patients. Both cholesterol showed a decrease already at 1 month period by 10.4% and 17.1% (vs. initial, ), respectively. The maximum reduction of the two was 15.0% and 27.7% (p<0.05), respectively, which was seen at the end of the 3 month period. Oral CSPHP of 3g also suppressed the serum total and LDL-cholesterol surge significantly when given to healthy humans receiving high cholesterol diet (2 egg yolks/day). Additionally, by taking 3grams of CSPHP/day in drink form for normocholesterolaemic and mildly hypercholesterolaemic subjects, CSPHP also reduced both their total cholesterol and LDL-cholesterol levels.
Recently, the dramatic increase in expression of allergic disease, which include hey fever, asthma or atopic dermatitis has been social problem. It is well known that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), n-3 polyunsaturated fatty acids, possess anti-inflammatory actions and immunomodulatory activities. Here, we examined the clinical effect of a beverage containing fish oil rich in EPA and DHA on atopic dermatitis. The test beverage was taken by 21 patients with atopic dermatitis, in the volume of 200 ml (containing 1260 mg of EPA and 540 mg of DHA) once per a day for 12 weeks. Except for 3 patients who dropped out, the skin symptoms of 13 patients in 18 patients tended to improve, and overall improvement showed the following scores: marked improvement 5.6%; moderate improvement 38.9%; slight improvement 27.8%; unchanged 16.6%; aggravation 11.1%. These results suggest that the beverage containing EPA and DHA may be useful as an alimentary therapy for atopic dermatitis.
Effects of supplementation of n-3 and n-6 fatty acids on lipid peroxidation and DNA damage of rat tissues are shown. Rats were fed diet containing 5% safflower oil (S) rich in n-6 fatty acids or fish oil (F) rich in n-3 fatty acids for 6 weeks. Lipid peroxidation of erythrocyte membranes and other tissues as assessed by thiobarbituric acid-reactive substances and phospholipid hydroperoxides of both diet groups were not significantly different, whereas lipid peroidation of erythrocyte membranes of F diet group was higher than that of S diet group when they were oxidized under atmospheric conditions. Lipid peroxidaton and vitamin E content of hepatocyteas after intreperitoneal injection of Fe (III) of F diet group were higher and lower, respectively, than those of S diet group, whereas DNA damage of the cells of F diet group was lower than those of S diet group as assessed by 8-hydroxydeoxyguanine and comet assay. In vitro supercoiled DNA damage induced by various oxidants was inhibited by unoxidized polyunsaturated linoleic acid and low density lipoprotein, supporting that polyunsaturated fatty acids suppressed oxidative damage of DNA. The results indicate that supplementation of n-3 fatty acids reduces oxidative damage of DNA as compared with that of n-6 fatty acids.
Docosahexaenoic acid (DHA) is highly concentrated in the nervous system and is rapidly deposited during the brain development in the perinatal and early postnatal period. The depletion and repletion rates of brain DHA were investigated in rodents. The reversibility of the loss of DHA was studied in rodents, which were subjected to a low level of n-3 fatty acids through two generations. The n-3 deficient adult (7wks) rats were provided n-3 adequate diet containing both α-linolenic acid and DHA, and were determined the concentrations of DHA until 8 weeks after diet reversal. Full recovery of the brain DHA wasn't obtained for 8 weeks, although the levels of DHA in the serum and liver were almost repleted within 2 weeks after diet reversal. A consideration of the brain DHA repletion compared with the liver and circulation suggests that transport-related processes may limit the rate of DHA repletion in the nervous system. In the comparison of repletion and depletion rates from weanling (3 wks) and adult mice, the brain DHA recovery from weanling was faster than that of adult mice, but depletion rates in the two age groups were nearly equal. Moreover, the depletion of newborn brain DHA was measured from day 0 of life after exposure to n-3 deficient milk using an artificial rearing system. The brain DHA in n-3 deficient milk group continuously decreased, yielding about 70% decline of n-3 adequate milk group. This result suggests a first-generation model for n-3 deficiency that is similar to the case of human nutrition.
Background: Achieving a low dietary ratio of n-6 to n-3 polyunsaturated fatty acids (PUFA) is clinically relevant for the nutritional management of many patients. Objective: We examined the possibility of creating substantial differences in the n-6 to n-3 PUFA ratio within a typical Japanese diet by developing Model Diet Menus. Methods: We prepared a standard menu called the Model Diet Menu for female subjects aged 18-29. We then developed modified menus using different foods or oils and compared their n-6/n-3 ratios with that of the Model Diet Menu. In Development 1, we replaced all dishes using fish and fish products with meat, creating a "Meat Menu." Next, we replaced all dishes using meat and meat products with fish, creating a "Fish Menu." In Development 2, we replaced vegetable oil with rapeseed oil to produce the "Rapeseed Oil Menu." In another modification, we replaced vegetable oil with perilla oil, creating a "Perilla Oil Menu." In addition, we investigated the differences in n-6/n-3 PUFA ratio produced by changing cooking methods (boiling, grilling, and deep frying) within Japanese, Western, and Chinese cuisine styles. Results: The mean (±SEM) n-6/n-3 PUFA ratio in the Model Diet Menu was 4.55±0.67. In Development 1, the ratios for the Meat Menu and the Fish Menu were 6.18±0.97 and 3.72±1.01, respectively. In Development 2, the ratios for the Rapeseed Oil Menu and the Perilla Oil Menu were 3.71±0.66 and 1.40±0.76, respectively. The n-6/n-3 PUFA ratios of Japanese-style meals were lower than those of Western-style or Chinese-style meals because the amount of oil in the Japanese-style meals was less than that of the Western-style or Chinese-style meals. No differences of n-6/n-3 PUFA ratio between foods prepared by boiling and those prepared by grilling were detected, probably because of the small amount of oil used in cooking. Conclusion: The n-6/n-3 PUFA ratio can be lowered from 4.55±0.69 to 1.29±0.64 by decreasing the amount of oil used for cooking, using an oil rich in n-3 PUFA such as rapeseed oil and perilla seed oil, and substituting fish for meat in the diet.